Special Weather Statement, NWS Denver/Boulder, CO

Area Forecast Discussion
National Weather Service Denver/Boulder CO
245 PM MDT Fri May 18 2018

.SHORT TERM...(This evening through Saturday)
Issued at 211 PM MDT Fri May 18 2018

Stratus deck still hanging on over most of the plains. Dew points
are still in the lower 50s F. Current ACARS soundings are still
showing a decent cap between 675 to 700 mb. Would need to get into
the 71-75 F range to get ride of it. It will no happen. The 19Z
special DNR sounding indicated the freezing level increased 1700
feet from this morning's 12Z observation. The latest Platteville
profiler shows poor shear as well. We no longer expect severe
weather. Will adjust GFE pops and sky cover accordingly for the
rest of this afternoon/early evening. An observer in Breckenridge
is reporting snow with thunder right now. Models keep some upward
vertical velocity over the CWA tonight and much of Saturday. The
latest models are still showing the heavy rain/flooding potential
is still viable, so will keep the flood watch going. Concerning
the watch for snow in the mountains, only the GFS has high
precipitation amount in the high mountains, and the 12Z GFS
decreased those amount significantly from the previous runs. Will
go with an advisory at this time. For temperatures, there is still
a cold front expected late tonight/early Saturday morning
Saturday's highs will be about 10 C cooler on Saturday from
today's highs.

.LONG TERM...(Saturday night through Friday)
Issued at 211 PM MDT Fri May 18 2018

The upper low will shift east of Colorado Saturday night with the
brunt of the heaviest rain ending over the plains after midnight.
There will still be lingering moisture on Sunday morning with a
cloudy start. Some heating and lingering moisture will result in
scattered showers and thunderstorms Sunday afternoon especially
over elevated terrain like the foothills and Palmer Divide.
Overall dry and warmer on Monday and Tuesday with weak ridging
over the area. Another low will develop over the Great Basin
during the next week with continued southwest flow over Colorado.
the low ejects north of Colorado but will still result in enhanced
chances of precip and cooler temperatures towards the end of the
week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 211 PM MDT Fri May 18 2018

The Stratus deck never eroded away. Now there is a decent batch of
Cirrus over the low clouds from alpine convection. The temperatures
has even gone done a few degrees. Will keep cigs at or below BKN-
OVC020 for the foreseeable future. Will get ride of the thunder
and hail as well. More stratiform rain with embedded showers is
expected for DIA from early/mid evening through most of Saturday.

&&

.HYDROLOGY...
Issued at 216 PM MDT Fri May 18 2018

Main concern is with the flood potential across the Front Range
foothills and northeast plains of Colorado for tonight through
Saturday evening. Overall confidence is rather low on exact
locations for flooding but over impact amongst the models appear
to be from Denver northward and especially along and north of the
interstate 76 corridor up towards the Wyoming and Nebraska border
areas. Model qpf is anywhere from 1 to 5 inches, with the GFS
the highest with the a broad swath of 3-5 inches of rain from
Denver east and North. NAM highest qpf has shifted further west
back into Weld county. It will all depend on the exact track of
the low as it moves over Northern Colorado.

.BOU WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Saturday evening for COZ035-036-
038>040-042>045-048>051.

Winter Weather Advisory from 9 PM this evening to 6 PM MDT
Saturday for COZ033-034.

&&

SHORT TERM...RJK
LONG TERM...Entrekin
AVIATION...RJK
HYDROLOGY...Entrekin

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1133 AM MDT Fri May 18 2018

COZ030>051-191745-
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-
1133 AM MDT Fri May 18 2018

...Flood Watch for much of northeast Colorado later this
afternoon through Saturday evening...

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

.DAY ONE...Today and Tonight

Showers and thunderstorms are already developing over the
mountains and high valleys. Numerous showers and thunderstorms
will develop and move eastward across northeast Colorado through
the late afternoon and evening. Some of the storms are expected to
become severe with hail up to 1.5 inches and wind gusts to 60
mph.

Heavy rain and flooding is possible later this afternoon through
Saturday for the foothills and plains of the forecast area. The
high mountains can expected snow later this evening into Saturday
morning.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Moderate to heavy rainfall will be possible primarily north of
line from around Denver to Akron on Saturday, with less intense
rainfall south towards the Palmer Divide. Heavy snow potential
will exist particularly in the mountains of western Larimer and
western Boulder counties where the strongest northeasterly upslope
will occur. In the warmer foothills of Larimer and Boulder
counties, the heavy rainfall will elevate the risk of flooding.

Precipitation will gradually decrease Saturday night as a slow
moving storm system starts to shift to the northeast. It will be
drier on Sunday with a chance of showers and thunderstorms mainly
over the higher terrain by the afternoon hours. Temperatures will
be cooler this weekend, then warm up again early next week with a
chance of afternoon and evening thunderstorms each day.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will be needed after 2 PM today.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
342 PM MDT FRI MAY 18 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0317 PM     HAIL             3 S BOULDER             39.98N 105.25W
05/18/2018  M0.75 INCH       BOULDER            CO   COCORAHS

&&

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Special Weather Statement
National Weather Service Denver CO
528 PM MDT FRI MAY 18 2018

COZ039-040-190015-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield County
CO-
North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe
Counties/East Broomfield County CO-
528 PM MDT FRI MAY 18 2018

...SPECIAL WEATHER STATEMENT...

At 526 PM MDT, Doppler radar was tracking a strong thunderstorm over
northern Lakewood, or 8 miles west of Denver, moving northeast at 20
mph.

Pea to Half inch hail is likely with this storm, along with brief
heavy rainfall.

Locations impacted include...
Western Denver, Lakewood, Thornton, Arvada, Westminster, Broomfield,
Northglenn, Wheat Ridge, Lafayette, eastern Golden, Louisville, Erie,
Federal Heights and Morrison.

LAT...LON 4004 10496 4000 10496 4000 10485 3962 10510
      3962 10516 3967 10519 3968 10515 3971 10514
      3973 10520 4002 10513 4003 10506 4000 10505
      4000 10501 4001 10499 4003 10499
TIME...MOT...LOC 2326Z 204DEG 21KT 3975 10511

SCHLATTER

Special Weather Statement
National Weather Service Denver CO
559 PM MDT FRI MAY 18 2018

COZ041-046-190030-
Elbert/Central and East Douglas Counties Above 6000 Feet CO-
North and Northeast Elbert County Below 6000 Feet/North Lincoln
County CO-
559 PM MDT FRI MAY 18 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN ELBERT COUNTY UNTIL 630
PM MDT...

At 558 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 5 miles northeast of Kiowa to 10 miles north
and west of Simla, or along a line extending from 36 miles southeast
of Denver to 22 miles west of Limon. Movement was northeast at 20
mph.

Pea to Dime size hail and winds in excess of 30 mph will be possible
with these storms.

Locations impacted include...
Kiowa.

LAT...LON 3936 10458 3955 10427 3932 10378 3913 10413
      3913 10419
TIME...MOT...LOC 2358Z 235DEG 19KT 3942 10441 3930 10410

SCHLATTER

Special Weather Statement
National Weather Service Denver CO
613 PM MDT FRI MAY 18 2018

COZ038-190045-
Larimer County Below 6000 Feet/Northwest Weld County CO-
613 PM MDT FRI MAY 18 2018

...SPECIAL WEATHER STATEMENT...

At 613 PM MDT, Doppler radar was tracking a strong thunderstorm 4
miles southwest of Nunn, or 13 miles northeast of Fort Collins,
moving north at 15 mph.

Pea to Half inch hail and winds in excess of 30 mph will be possible
with this storm.

Locations impacted include...
Wellington, Pierce and Nunn.

LAT...LON 4060 10473 4059 10496 4083 10505 4085 10469
TIME...MOT...LOC 0013Z 178DEG 14KT 4068 10485

SCHLATTER