Winter Storm Watch 13, NWS Denver/Boulder, CO

141 
WWUS45 KBOU 180113
WSWBOU

URGENT - WINTER WEATHER MESSAGE
National Weather Service Denver/Boulder CO
713 PM MDT Wed May 17 2017

...HEAVY SNOW EXPECTED FOR THE MOUNTAINS AND NORTHERN FRONT RANGE
FOOTHILLS THROUGH FRIDAY...

.A strong spring storm will drop south across the Great Basin
tonight and Thursday. It then moves slowly east across Colorado 
Thursday night through Friday evening. Significant snow is 
expected with this storm if it continues on the current forecasted
track. If the storm track moves further north, then the Southern 
Front Range Foothills may receive much less snowfall.

This storm is expected to bring rain and possibly snow to the
Urban Corridor including the Denver Metro area. The coldest air
and best chance for snow is expected to be Thursday night and
Friday for the Denver area. Significant snow for the Denver area
is possible.

COZ033-034-180915-
/O.CON.KBOU.WS.W.0011.000000T0000Z-170520T0000Z/
South and East Jackson/Larimer/North and Northeast Grand/
Northwest Boulder Counties Above 9000 Feet-
South and Southeast Grand/West Central and Southwest Boulder/
Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet-
713 PM MDT Wed May 17 2017

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 6 PM MDT FRIDAY...

* TIMING...snow will become widespread tonight and is expected to
  to continue through Friday afternoon. 

* SNOW ACCUMULATIONS...12 to 24 inches of snow expected with up 
  to 36 inches on favored east slopes, including Rocky Mountain 
  National Park. 

* WIND/VISIBILITY...Visibility will fall below a quarter mile in 
  heavy snow. 

* IMPACTS...Roads will become snow and slush covered. Wet snow 
  may accumulate on leafed out trees, resulting in broken tree 
  limbs and power outages. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning for heavy snow means severe winter weather
conditions are expected or occurring. Significant amounts of snow
are forecast that will make travel dangerous. Only travel in an
emergency. If you must travel...keep an extra flashlight...
food...and water in your vehicle in case of an emergency.

&&

$$

COZ036-180915-
/O.CON.KBOU.WS.W.0011.170518T0600Z-170520T0000Z/
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet-
713 PM MDT Wed May 17 2017

...WINTER STORM WARNING REMAINS IN EFFECT FROM MIDNIGHT TONIGHT
TO 6 PM MDT FRIDAY...

* TIMING...Rain is expected to change to tonight as cold air 
  moves into the area. Snow is expected to continue through Friday
  afternoon before it dissipates. 

* SNOW ACCUMULATIONS...12 to 24 inches.

* WIND/VISIBILITY...Visibility will fall below a quarter mile in 
  heavy snow. 

* IMPACTS...Roads will likely become snow and slush covered. Wet 
  snow may accumulate on leafed out trees, resulting in broken 
  tree limbs and power outages. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning for heavy snow means severe winter weather
conditions are expected or occurring. Significant amounts of snow
are forecast that will make travel dangerous. Only travel in an
emergency. If you must travel...keep an extra flashlight...
food...and water in your vehicle in case of an emergency.

&&

$$

COZ035-180915-
/O.CON.KBOU.WS.W.0011.170518T0600Z-170520T0000Z/
Larimer and Boulder Counties Between 6000 and 9000 Feet-
713 PM MDT Wed May 17 2017

...WINTER STORM WARNING REMAINS IN EFFECT FROM MIDNIGHT TONIGHT
TO 6 PM MDT FRIDAY...

* TIMING...Rain is expected to change to snow tonight as cold air
  moves into the area. Snow is expected to continue through 
  Friday afternoon before it dissipates. 

* SNOW ACCUMULATIONS...12 to 24 inches of snow with up to 36 
  inches on favored east slopes. 

* WIND/VISIBILITY...Visibility will fall below a quarter mile in 
  heavy snow. 

* IMPACTS...Roads will likely become snow and slush covered. Wet 
  snow may accumulate on leafed out trees, resulting in broken 
  tree limbs and power outages. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning for heavy snow means severe winter weather
conditions are expected or occurring. Significant amounts of snow
are forecast that will make travel dangerous. Only travel in an
emergency. If you must travel...keep an extra flashlight...
food...and water in your vehicle in case of an emergency.

&&

$$

COZ038>041-180915-
/O.CON.KBOU.WS.A.0013.170519T0000Z-170520T0000Z/
Larimer County Below 6000 Feet/Northwest Weld County-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield
County-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County-
Elbert/Central and East Douglas Counties Above 6000 Feet-
713 PM MDT Wed May 17 2017

...WINTER STORM WATCH REMAINS IN EFFECT FROM THURSDAY EVENING
THROUGH FRIDAY AFTERNOON...

* TIMING...Rain could change to snow early Thursday evening and 
  continue into Friday afternoon. 

* SNOW ACCUMULATIONS...Up to 12 inches possible with the highest 
  amounts near the foothills and over the Palmer Ridge. 

* WIND/VISIBILITY...Visibility could fall below a quarter mile 
  in heavy snow. 

* IMPACTS...Roads could become snow and slush covered. Wet snow 
  may accumulate on leafed out trees, resulting in broken tree 
  limbs and power outages. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Watch means there is a potential for significant
snow...sleet...or ice accumulations that may impact travel.
Continue to monitor the latest forecasts.

&&

$$

640 
WWUS45 KBOU 180919
WSWBOU

URGENT - WINTER WEATHER MESSAGE
National Weather Service Denver/Boulder CO
319 AM MDT Thu May 18 2017

...HEAVY SNOW FOR THE MOUNTAINS AND NORTHERN FRONT RANGE 
FOOTHILLS THROUGH FRIDAY...POSSIBLY SPREADING DOWN TO THE I-25
CORRIDOR...

.A strong spring storm will drop south across the Great Basin
today and tonight, and then move slowly east across Colorado 
Friday. Significant snow will fall across the Front Range
Mountains and Foothills, accumulating into the feet of snow.

In lower elevations including the I-25 Corridor, rain may be 
mixed with snow this morning near the Wyoming border and from 
Denver into the Palmer Divide. Temperatures will turn colder 
tonight into early Friday morning with rain mixing with and 
changing over to snow. Snow accumulation on fully leafed out trees
may result in broken tree limbs and scattered power outages. 

COZ034-036-181800-
/O.CON.KBOU.WS.W.0011.000000T0000Z-170520T0000Z/
South and Southeast Grand/West Central and Southwest Boulder/
Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet-
Including the cities of Berthoud Pass, Breckenridge, 
East Slopes Mosquito Range, East Slopes Southern Gore Range, 
Eisenhower Tunnel, Indian Peaks, Kenosha Mountains, Mount Evans, 
Williams Fork Mountains, Winter Park, Bailey, Central City, 
Evergreen, Georgetown, Idaho Springs, and Westcreek
319 AM MDT Thu May 18 2017

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 6 PM MDT FRIDAY...

* TIMING...Snow will continue into Friday. The snow will be heavy
  at times today and tonight with snowfall rates up to 2 inches 
  per hour on the eastern facing slopes of the Front Range. Snow 
  will gradually taper off in intensity by Friday afternoon. 

* SNOW ACCUMULATIONS...12 to 24 inches.

* WIND/VISIBILITY...Visibility will fall below a quarter mile in
  heavy snow. 

* IMPACTS...Travel will be hazardous and slow at times due to snow
  and slush covered roads. Wet snow may accumulate on leafed out 
  trees, resulting in broken tree limbs and power outages. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning for heavy snow means severe winter weather
conditions are expected or occurring. Significant amounts of snow
are forecast that will make travel dangerous. Only travel in an
emergency. If you must travel...keep an extra flashlight...
food...and water in your vehicle in case of an emergency.

&&

$$

COZ033-035-181800-
/O.CON.KBOU.WS.W.0011.000000T0000Z-170520T0000Z/
South and East Jackson/Larimer/North and Northeast Grand/
Northwest Boulder Counties Above 9000 Feet-
Larimer and Boulder Counties Between 6000 and 9000 Feet-
Including the cities of Cameron Pass, 
Laramie and Medicine Bow Mountains, Rabbit Ears Range, 
Rocky Mountain National Park, Willow Creek Pass, Estes Park, 
Glendevey, Nederland, and Red Feather Lakes
319 AM MDT Thu May 18 2017

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 6 PM MDT FRIDAY...

* TIMING...Heavy snow will fall today and tonight, with snowfall
  rates up to 2 inches or more per hour on east facing slopes of 
  the Front Range. Snow will gradually taper off in intensity by 
  Friday afternoon.
 
* SNOW ACCUMULATIONS...16 to 30 inches, with 3 feet or more on
  east facing slopes.

* WIND/VISIBILITY...Visibility will fall below a quarter mile in 
  heavy snow. 

* IMPACTS...Travel will be difficult if not impossible on some
  roads due to the depth of snow. Wet snow may also accumulate on
  leafed out trees, resulting in broken tree limbs and power 
  outages. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning for heavy snow means severe winter weather
conditions are expected or occurring. Significant amounts of snow
are forecast that will make travel dangerous. Only travel in an
emergency. If you must travel...keep an extra flashlight...
food...and water in your vehicle in case of an emergency.

&&

$$

COZ037-181800-
/O.NEW.KBOU.WW.Y.0022.170518T0919Z-170519T0000Z/
Central and Southeast Park County-
Including the cities of Fairplay, Hartsel, Lake George, 
and South Park
319 AM MDT Thu May 18 2017

...WINTER WEATHER ADVISORY IN EFFECT UNTIL 6 PM MDT THIS
EVENING...

The National Weather Service in Denver has issued a Winter
Weather Advisory for snow, which is in effect until 6 PM MDT this
evening. 

* TIMING...Snow, heavy at times, will continue today. The snow is
  expected to decrease in intensity late this afternoon or early
  evening. 

* SNOW ACCUMULATIONS...4 to 9 inches through early afternoon, 
  with storm totals of 6 to 12 inches. 

* WIND/VISIBILITY...Visibility will fall to a quarter mile or less
  during periods of heavy snow.
 
* IMPACTS...Travel will be hazardous and slow at times due to snow
  and slush covered roads. Wet snow may accumulate on leafed out
  trees, resulting in broken tree limbs and power outages. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Weather Advisory for snow means that periods of snow 
will cause primarily travel difficulties. Be prepared for snow 
covered roads and limited visibilities...and use caution while 
driving.

&&

$$

COZ038>041-181800-
/O.CON.KBOU.WS.A.0013.170519T0000Z-170520T0000Z/
Larimer County Below 6000 Feet/Northwest Weld County-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield
County-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County-
Elbert/Central and East Douglas Counties Above 6000 Feet-
Including the cities of Fort Collins, Hereford, Loveland, Nunn, 
Arvada, Boulder, Golden, Lakewood, Longmont, Aurora, Brighton, 
City of Denver, Denver International Airport, Highlands Ranch, 
Littleton, Parker, Castle Rock, Elbert, Fondis, Kiowa, 
and Larkspur
319 AM MDT Thu May 18 2017

...WINTER STORM WATCH REMAINS IN EFFECT FROM THIS EVENING THROUGH
FRIDAY AFTERNOON...

* TIMING...Rain will be mixed with snow at times this morning near
  the Wyoming border and from the Denver metro area south to the
  Palmer Divide. Rain will likely mix with or change over to all
  snow tonight and then continue into Friday as even colder air
  arrives. 

* SNOW ACCUMULATIONS...2 to 6 inches most likely, but up to 12
  inches still possible near the foothills and over the Palmer 
  Divide.

* WIND/VISIBILITY...Visibility could fall below a quarter mile 
  in heavy snow. 

* IMPACTS...Wet snow may accumulate on leafed out trees, resulting
  in broken tree limbs and power outages. Some slush and snow
  accumulation will be possible on roads mainly near the Palmer
  Divide and Wyoming border, with slick and hazardous travel 
  conditions.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Watch means there is a potential for significant
snow accumulations that may impact travel and produce power
outages. Continue to monitor the latest forecasts.

&&

$$

911 
WWUS45 KBOU 181620
WSWBOU

URGENT - WINTER WEATHER MESSAGE
National Weather Service Denver/Boulder CO
1020 AM MDT Thu May 18 2017

...HEAVY SNOW CONTINUE IN THE MOUNTAINS...NORTHERN FRONT RANGE 
FOOTHILLS AND WESTERN PORTIONS OF THE I-25 CORRIDOR...

.A strong and slow moving spring storm will continue to drop 
heavy snowfall over portions of north central and northeast
Colorado today through Friday morning. Snowfall will be especially
heavy in the Front Range foothills where snowfall rates of 2 to 3
inches per hour are likely.

In lower elevations, areas west of I-25 will also experience
periods of moderate to heavy snowfall through Friday morning with 
snowfall rates of 1 to 2 inches per hour at times. East of the
I-25...snowfall rates and accumulations will be less and much of
what falls on paved surfaces today will either be slush or melt.
However tonight, precipitation will turn to all snow within the
I25 corridor and even farther out on the plains. Snowfall will
likely be heaviest near the foothills and on the Palmer Divide
creating hazardous driving conditions. The wet, heavy snowfall 
will likely cause significant tree damage and create scattered 
power outages. Snowfall should gradually taper off late on Friday
starting in areas south of I-70. Most if not all snow 
accumulation in the area should end Friday night. 


COZ038>041-190030-
/O.UPG.KBOU.WS.A.0013.170519T0000Z-170520T0000Z/
/O.EXB.KBOU.WS.W.0011.000000T0000Z-170519T2100Z/
Larimer County Below 6000 Feet/Northwest Weld County-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield
County-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County-
Elbert/Central and East Douglas Counties Above 6000 Feet-
Including the cities of Fort Collins, Hereford, Loveland, Nunn, 
Arvada, Boulder, Golden, Lakewood, Longmont, Aurora, Brighton, 
City of Denver, Denver International Airport, Highlands Ranch, 
Littleton, Parker, Castle Rock, Elbert, Fondis, Kiowa, 
and Larkspur
1020 AM MDT Thu May 18 2017

...WINTER STORM WARNING IN EFFECT UNTIL 3 PM MDT FRIDAY...

The National Weather Service in Denver has issued a Winter Storm
Warning for heavy snow, which is in effect until 3 PM MDT Friday.
The Winter Storm Watch is no longer in effect. 

* TIMING...Snowfall moderate to heavy at times...especially in
  areas west of Interstate 25 and on the higher terrain of the
  Palmer Divide through Friday morning. The rain and snow mix
  roughly east of I-25 Denver should change over to all snow by
  late this afternoon with the arrival of colder air. Snowfall in
  this area could be moderate to heavy this time in the evening.  
 
* SNOW ACCUMULATIONS...2 to 6 inches likely, with 8 to 12 inches
  near the foothills and possibly near 15 inches on the Palmer 
  Divide.
  

* WIND/VISIBILITY...Visibility could fall below a quarter mile 
  in heavy snow. 

* IMPACTS...Wet snow may accumulate on leafed out trees, 
  resulting in broken tree limbs and power outages. Some slush 
  and snow accumulation will be possible on roads mainly near 
  the Palmer Divide and Wyoming border, with slick and hazardous 
  travel conditions. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning for heavy snow means severe winter weather
conditions are expected or occurring. Significant amounts of snow
are forecast that will make travel very low and hazardous. If you
must travel...keep an extra flashlight... food...and water in 
your vehicle in case of an emergency.

&&

$$

COZ034-036-190030-
/O.CON.KBOU.WS.W.0011.000000T0000Z-170520T0000Z/
South and Southeast Grand/West Central and Southwest Boulder/
Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet-
Including the cities of Berthoud Pass, Breckenridge, 
East Slopes Mosquito Range, East Slopes Southern Gore Range, 
Eisenhower Tunnel, Indian Peaks, Kenosha Mountains, Mount Evans, 
Williams Fork Mountains, Winter Park, Bailey, Central City, 
Evergreen, Georgetown, Idaho Springs, and Westcreek
1020 AM MDT Thu May 18 2017

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 6 PM MDT FRIDAY...

* TIMING...Moderate to heavy snowfall will continue through Friday
  Heaviest snowfall will shift to the northern foothills later
  today. Snowfall rates of 2 to 3 inches per hour are likely at
  times on east facing slopes. Snow will gradually taper off in 
  intensity by Friday afternoon.
 
* SNOW ACCUMULATIONS...18 to 35 inches.

* WIND/VISIBILITY...Visibility will fall below a quarter mile in 
  heavy snow. 

* IMPACTS...Travel will be hazardous and slow at times due to 
  snow and slush covered roads. Wet snow may accumulate on 
  leafed out trees, resulting in broken tree limbs and power 
  outages. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning for heavy snow means severe winter weather
conditions are expected or occurring. Significant amounts of snow
are forecast that will make travel dangerous. Only travel in an
emergency. If you must travel...keep an extra flashlight...
food...and water in your vehicle in case of an emergency.

&&

$$

COZ033-035-190030-
/O.CON.KBOU.WS.W.0011.000000T0000Z-170520T0000Z/
South and East Jackson/Larimer/North and Northeast Grand/
Northwest Boulder Counties Above 9000 Feet-
Larimer and Boulder Counties Between 6000 and 9000 Feet-
Including the cities of Cameron Pass, 
Laramie and Medicine Bow Mountains, Rabbit Ears Range, 
Rocky Mountain National Park, Willow Creek Pass, Estes Park, 
Glendevey, Nederland, and Red Feather Lakes
1020 AM MDT Thu May 18 2017

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 6 PM MDT FRIDAY...

* TIMING...Heavy snowfall will continue today and tonight, with
  snowfall rates to around 2 inches per hour on east facing slopes
  of the Front Range mountains. Snow should gradually taper off 
  in intensity by Friday afternoon. 

* SNOW ACCUMULATIONS...18 to 30 inches, with locally up to 40
  inches on east facing slopes above 9500 feet. 

* WIND/VISIBILITY...Visibility will fall below a quarter mile in 
  heavy snow. 

* IMPACTS...Travel will be difficult if not impossible on high
  country roads due to the depth of snow. The wet, heavy snow
  accumulating on leafed out trees will likely result in numerous
  broken tree limbs and power outages. Auto accidents may also
  create serious slow downs and even temporary road closures.


PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Warning for heavy snow means severe winter weather
conditions are expected or occurring. Significant amounts of snow
are forecast that will make travel dangerous. Only travel in an
emergency. If you must travel...keep an extra flashlight...
food...and water in your vehicle in case of an emergency.

&&

$$

COZ032-190030-
/O.EXB.KBOU.WW.Y.0022.000000T0000Z-170519T1200Z/
Grand and Summit Counties Below 9000 Feet-
Including the cities of Dillon, Fraser, Granby, Grand Lake, 
Hot Sulphur Springs, and Kremmling
1020 AM MDT Thu May 18 2017

...WINTER WEATHER ADVISORY IN EFFECT UNTIL 6 AM MDT FRIDAY...

The National Weather Service in Denver has issued a Winter
Weather Advisory for snow, which is in effect until 6 AM MDT 
Friday. 

* TIMING...Snowfall, moderate at times, will continue through this
  evening. Expect snowfall to decrease in intensity early 
  evening. 

* SNOW ACCUMULATIONS...5 to 9 inches...heaviest near the mountain
  slopes. 
 
* WIND/VISIBILITY...Visibility will fall to a quarter mile or 
  less during periods of heavy snow. 

* IMPACTS...Travel will be very difficult and slow at times due 
  to snow and slush covered roads. Wet snow may accumulate on 
  leafed out trees, resulting in broken tree limbs and power 
  outages. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Weather Advisory for snow means that periods of snow
will cause primarily travel difficulties. Be prepared for snow
covered roads and limited visibilities...and use caution while
driving.

&&

$$

COZ037-190030-
/O.EXT.KBOU.WW.Y.0022.000000T0000Z-170519T1200Z/
Central and Southeast Park County-
Including the cities of Fairplay, Hartsel, Lake George, 
and South Park
1020 AM MDT Thu May 18 2017

...WINTER WEATHER ADVISORY NOW IN EFFECT UNTIL 6 AM MDT FRIDAY...

* TIMING...Snowfall, moderate at times, will continue through late
  this afternoon. Expect snowfall to decrease in intensity during
  the evening. 

* SNOW ACCUMULATIONS...3 to 7 inches...the heavier amounts in
  northern and western Park county. 
 
* WIND/VISIBILITY...Visibility will fall to a quarter mile or 
  less during periods of heavy snow. 

* IMPACTS...Travel will be very difficult and slow at times due to
  snow and slush covered roads. Wet snow may accumulate on leafed
  out trees, resulting in broken tree limbs and power outages. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Weather Advisory for snow means that periods of snow
will cause primarily travel difficulties. Be prepared for snow
covered roads and limited visibilities...and use caution while
driving.

&&

$$
Baker

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1002 AM MDT Wed May 17 2017

.UPDATE...
Issued at 940 AM MDT Wed May 17 2017

Current satellite imagery showing next system spinning over ID
with moisture increasing over western CO. For this afternoon on
the plains short term models show a push of NE winds beginning
around 22z that will converge along a line north and east of DIA
and form thunderstorms by the late afternoon. Model soundings have
some decent BL CAPE and QG ascent over the NE plains. Deep layer
shear is only in the 50s so do not expect severe...however small
hail and gusty winds with showers will be possible along and NE of
a line from Greeley to Limon through the late afternoon and
evening hours. Still expect the cold front to drop down from the
NW by evening hours bringing more stable...stratiform rain to the
mountains and foothills. Models are showing some lift ahead of the
front that could bring some non-severe storms to the urban
corridor by the evening hours but at this time anticipating more
showers than thunder. Increased pops on the plains for the
convection...otherwise forecast is on track.

Still looking at a potent spring storm to impact the mountains
and foothills starting this evening and continuing through Friday.
Rain is expected to change over to snow around midnight tonight
for the foothills. Amounts are still coming together with
forecast trends but expect at least a foot possible over the
foothills with more along east-facing slopes.

&&

.SHORT TERM...(Today and tonight)
Issued at 400 AM MDT Wed May 17 2017

Upper low over southwest Kansas still responsible for continued
showers over the northeast plains, although the areal extent of
showers continues to diminish. Still a fair amount of mid level
clouds further back towards the Front Range but this will also
shift east towards sunrise.

Attention then turns to even stronger system which is located over
Northern Idaho and Oregon this morning, and will be dropping
southeastward into Utah tonight. Model tracks are fairly
consistent at least through tonight, although the NAM is a bit
further North with this feature. Increasing QG ascent expected
from late this afternoon over the mountains and spreading over
much of northern Colorado tonight as the low approaches Colorado.
The associated cold front already moving through Northern Utah
with good pressure rise behind it. This front will sweep across
Northern colorado mountains this afternoon and then over the urban
corridor late afternoon with increasing northwest winds. Winds
will then switch northeast this evening over the front range as
surface low pressure intensifies across southeast Colorado.

Rain showers and isolated thunderstorms will become more
widespread by later this evening and overnight with deepening
upslope flow and modest QG ascent. Focus area for tonight will be
locations from Denver Northward and especially in the foothills of
Boulder and Larimer counties. As cold air filters in, snow levels
will be dropping through the night to around 7000 ft over the
foothills. Will be upgrading the watches to warnings for the
mountains and northern foothills (also see long term discussion
below). Confidence not as high for Southern Front Range foothills
especially if the 700mb low circulation ends up further North,
like the latest NAM is showing. So will keep zone 36 in a watch
for now.

.LONG TERM...(Thursday through Tuesday)
Issued at 400 AM MDT Wed May 17 2017

The upper low over Utah on Thursday morning will swing into
Colorado through the day. Overall, models have slowed their
progression with the system, as well as gotten slightly stronger.
This trend will result in warmer temperatures across the eastern
plains, and possibly into the urban corridor, with higher snow
levels than the previous forecast. Trying to key into where the
700 mb low will end up, as this will have a big impact on areas
around and south of I-70. The GFS is keeping it further south
which will bring good easterly upslope flow up through 300 mb
across most of the forecast area. The NAM is further north with
the 700mb low which is causing a drying effect along and south of
I70. This is the reason for keeping a Winter Storm Watch over the
southern foothills where confidence is lower.

Have upgraded the remaining Watches to Winter Storm Warnings as
moisture surges up from the Gulf of Mexico to combine with the
Pacific moisture, good upward QG motion, unseasonably cold
temperatures and deep upslope flow combine together through
Friday. With the low slowing its progression, dynamics will be
able to continue to produce appreciable amounts of precipitation
across most of the area. Models have anywhere from 2 to 6 inches
of liquid falling over the Front Range mountains and foothills,
with a half inch to 6 inches of liquid for the plains - the NAM
being the driest along and south of I70 due to its 700mb low
position. All models have placed their highest amounts over
Larimer County, with 3-6 inches common. This will result in
impressive snowfall amounts, even if possible convection is
doubling the amounts. Half that amount of liquid will still
produce impressive snowfall amounts, especially for the second
half of May. One interesting thing is however, the models are only
showing PWs of near half an inch along the foothills and urban
corridor, quite a lot less than the storm a little over a week
ago. Snowfall rates over the mountains will likely be 1-2 inches
per hour through the day, making travel difficult. Some concern on
the deep convection expected over the Great Plains Thursday, may
rob some moisture and disrupt the flow into the low. Snow levels
are expected to start around 8000-9000 Thursday with lowering from
northwest to southeast through the day and night. Dynamic cooling
with the falling precipitation may be able to lower these levels
farther, however for now, see snow levels getting down to about
5500 feet by Friday morning. Will keep most of the plains rain,
with some rain/snow mix and some light accumulations up to a
couple inches in the western urban corridor and Palmer Divide
seeing an inch or two more. Good soaking rains will be expected
over elevations below this. High temperatures this day will be 20
to 30 degrees colder than normal for this time of year. Winds will
be northeasterly upslope through the day, with speeds of 10 to 25
mph, aiding in snowfall over the Front Range high terrain.

The system will continue to slowly move northeast across the area
Friday with high temperatures a few degrees colder than Thursday.
Confidence is low on where the heavier precipitation will be due
to the differences in the track and speeds of the system in the
models. However precip will continue across the area likely
through the afternoon and into the early evening, before a sharp
decrease is seen. With the models slowing the departure of the
system, this may effect low temperatures Friday night and into
Saturday morning, but still expecting at or below freezing along
the urban corridor, with slightly warmer temperatures further
east.

Saturday, a few showers may still remain in northwesterly flow
over the mountains, but drying otherwise. Temperatures will
increase about 10 degrees under clearing skies.

A weak shortwave in westerly flow Sunday will bring warmer
temperatures along with scattered showers and thunderstorms. Flow
will then turn northerly as a trough drops out of Canada, for
slightly cooler temperatures and an increase in showers Monday and
Tuesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 940 AM MDT Wed May 17 2017

Winds will continue from the SW before transitioning to the west
by 17z. Winds will veer around to the north by 22z then around to
the NE with a push in the afternoon. Some area convection will be
possible but expect storms to stay out of APA and DIA with a
slight chance affecting BJC later this afternoon. Cold front
moving into are late this evening with some light rain possible
between 00 and 04z. Ceilings will become IFR by 05z with
increasing moisture push and increasing rain intensity behind
front.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from late tonight through Friday afternoon
for COZ036.

Winter Storm Warning from midnight tonight to 6 PM MDT Friday
for COZ035.

Winter Storm Warning from 6 PM this evening to 6 PM MDT Friday
for COZ033-034.

&&

UPDATE...Bowen
SHORT TERM...Entrekin
LONG TERM...Kriederman
AVIATION...Bowen

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
429 AM MDT Wed May 17 2017

COZ030>051-181030-
Jackson County Below 9000 Feet-
West Jackson and West Grand Counties Above 9000 Feet-
Grand and Summit Counties Below 9000 Feet-
South and East Jackson/Larimer/North and Northeast Grand/
Northwest Boulder Counties Above 9000 Feet-
South and Southeast Grand/West Central and Southwest Boulder/
Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet-
Central and Southeast Park County-
Larimer County Below 6000 Feet/Northwest Weld County-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield
County-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County-
Elbert/Central and East Douglas Counties Above 6000 Feet-
Northeast Weld County-Central and South Weld County-Morgan County-
Central and East Adams and Arapahoe Counties-
North and Northeast Elbert County Below 6000 Feet/North Lincoln
County-
Southeast Elbert County Below 6000 Feet/South Lincoln County-
Logan County-Washington County-Sedgwick County-Phillips County-
429 AM MDT Wed May 17 2017

...Potent Late Spring Storm headed towards Northern Colorado...

This hazardous weather outlook is for northeast and north central
Colorado.

.DAY ONE...Today and Tonight

Scattered showers and thunderstorms will develop over the
mountains this afternoon and spread over the plains during the
afternoon and evening. A cold front and approaching storm system
will result in rain showers becoming widespread over the plains by
by late evening and overnight.  Snow will increase over the
mountains and Northern Foothills tonight with the snow level
lowering to around 7000 feet by Thursday morning. Snowfall tonight
will range from 3 to 9 inches, highest amounts along the
Continental Divide and higher east slopes.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Significant snowfall is expected over the mountains and high
foothills Thursday through Friday, especially near Rocky Mountain
National Park. Snowfall totals could be upwards of 1 to 3 feet by
Friday evening. This will cause snowpacked roads, and some
possible broken tree branches and power outages from heavy
snowload. Travel may become quite difficult with forecasted
snowfall amounts, especially over smaller less traveled roads. At
lower elevations, mainly below 6000 feet, widespread rain is
expected. A few thunderstorms are possible over the far eastern
plains during the day. Snow may lower to around 5500 feet by
Friday morning with up to 3 inches of wet slushy snow. This system
will bring temperatures that are 20 to 30 degrees below normal
for mid to late May. Temperatures will be just above freezing
Thursday night over the plains, with at or below freezing
temperatures expected Friday night along the urban corridor.

Expect warmer and drier conditions Saturday through Monday, with
another system coming out of Canada for a wetter and cooler
Tuesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today or tonight.