Severe Thunderstorm Warning 35, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
312 PM MDT Tue Jun 2 2020

.SHORT TERM...(This evening through Wednesday)
Issued at 310 PM MDT Tue Jun 2 2020

A few showers and storms are beginning to form but have gotten a
late start due to cloud cover for much of the day. Because of the
cloudiness, the coverage of these showers and storms should remain
limited through the rest of the afternoon and evening.
Nonetheless, slight chance PoPs were kept through 10-11pm because
there will be increasing moisture and upslope flow especially near
the Cheyenne Ridge which could keep storms going. The rest of the
night will be dry and mild as low temperatures will be 5 to 10
degrees above normal.

West-northwesterly mid to upper level flow will increase across
far northern Colorado on Wednesday with 500 mb winds reaching
near 50 knots by the afternoon. Temperatures will once again be
hot with highs reaching the upper 80s to low 90s across the urban
corridor and plains. A dryline will setup across the eastern
plains by the afternoon roughly along a line from Sterling to
Limon. This boundary may provide enough low level convergence to
generate a few strong to severe storms especially across the
northeast corner of the state. With mixed layer CAPEs as high as
2,500 j/kg and deep layer wind shear around 40 knots, any storms
that develop over Logan, Washington, Sedgwick, and Phillips
Counties will be capable of producing large hail up to the size of golf
balls and damaging wind gusts up to 60 mph. Further west,
isolated non-severe thunderstorms will develop and won't produce
much rainfall but could produce a few wind gusts up to 40 mph.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 310 PM MDT Tue Jun 2 2020

A few storms may still be ongoing over the far eastern plains
Wednesday evening, mainly south and east of I-76, with a few
showers possible in the mountains. Clouds will remain over the
forecast area, helping to keep low temperatures above normal
still.

On Thursday, the upper ridge will move ever so slightly east,
allowing for slightly warmer temperatures and a drier environment.
There won't even be easterly winds into the plains, so overall,
any convection should be high based with strong outflow winds the
bigger threat of storm hazards. Higher CAPE values are expected
over the far northeast corner of the state, so may see a stronger
or possibly severe storm out that way. A ripple in the westerly
flow aloft is expected to push across northern Colorado in the
evening and overnight, so increased PoPs overnight for this.

On Friday, the flow aloft will turn south-southwesterly as a low
off the southern California coasts quickly lifts northeast into
the Great Basin. High pressure sliding down the Great Plains will
once again push in southeasterly winds carrying in more low level
moisture. This combined with the warmer temperatures being
advected in from the more southerly flow will increase theta-e
values across the plains. Subtropical moisture will also move in
from the southerly flow aloft which will increase showers and
storms across the entire forecast area. Timing of this moisture
however is different between the three longer range models. If the
faster GFS is correct, storms will increase Friday evening and
overnight. Stronger winds aloft will increase shear, so Friday
will have the potential for strong to severe storms. If it's later
like the EC or even later like the Canadian, will have to wait for
Saturday.

The upper low will be opening to a trough and moving from the
Great Basin northeast across the Northern Rockies and into Montana
Saturday, though there are timing differences between the models.
GFS remains the fastest, with the EC the middle ground and the CMC
being the slowest. This will move the jet across Colorado sometime
on Saturday, with a surface low deepening along the lee of the
Rockies to increase southerly winds across the plains. The
increase in winds along with dry warm air will increase fire
weather concerns over the areas with dry fuels.

Sunday will be even more of a concern as the southwesterly flow
stays over the area with strong speeds, hot temperatures and dry
conditions. Widespread critical fire weather conditions will
likely spread across most of the forecast area. Will be in
constant touch with land managers for fuels updates.

The upper trough over the Pacific Northwest will then move east to
finally bring the next chance for a cool down and more
precipitation Monday and Tuesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 310 PM MDT Tue Jun 2 2020

Easterly winds will continue this afternoon and then will veer
toward the southeast this evening. A brief shower or storm cannot
be ruled out but looks unlikely at this time. If a shower or storm
were to occur, they could produce wind gusts up to 35 knots.

Winds veer toward drainage tonight and will be weak tomorrow
morning. There is a small chance of a shower or storm during the
late afternoon and evening tomorrow but it will not be large enough
to mention in the TAF at this time. Any shower or storm that does
develop could produce gusty winds.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

SHORT TERM...Danielson
LONG TERM...Kriederman
AVIATION...Danielson

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1118 AM MDT Tue Jun 2 2020

COZ030>051-031730-
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-
1118 AM MDT Tue Jun 2 2020

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

.DAY ONE...This Afternoon and Tonight

Isolated thunderstorms will continue over the eastern plains
through the early afternoon. A few showers and isolated storms may
develop over mountains, foothills, and Lincoln County this
afternoon and evening. These storms are not expected to be severe
but could produce gusty winds up to 40 mph.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Warmer than normal temperatures are expected through the week, and
especially through the weekend. Readings will be 10 to 15 degrees
above normal. Isolated to scattered afternoon and evening showers
and thunderstorms are expected each day through through Friday.
Overall the threat of severe thunderstorms is expected to be low,
though the eastern plains may see stronger storms Wednesday and
Friday and possibly into Saturday, depending on the speed of the
incoming system.

The weekend is looking hot, dry and windy, especially Sunday.
This will increase fire danger.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed today and tonight.

Special Weather Statement
National Weather Service Denver CO
551 PM MDT Tue Jun 2 2020

COZ042>044-030030-
Central and South Weld County CO-Morgan County CO-
Northeast Weld County CO-
551 PM MDT Tue Jun 2 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN WELD AND
NORTHWESTERN MORGAN COUNTIES UNTIL 630 PM MDT...

At 551 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 6 miles south of Panorama Point to 6 miles
northwest of Jackson Reservoir, or along a line extending from 28
miles southwest of Kimball to 22 miles northwest of Fort Morgan.
Movement was east at 12 mph.

Penny size hail and winds in excess of 45 mph will be possible with
these storms.

Locations impacted include...
New Raymer, Jackson Reservoir, Keota, Weldona, Pawnee Buttes and
Goodrich.

LAT...LON 4033 10382 4037 10432 4100 10411 4100 10366
TIME...MOT...LOC 2351Z 266DEG 9KT 4092 10401 4047 10413

SCHLATTER