Special Weather Statement, NWS Cheyenne, WY

Area Forecast Discussion
National Weather Service Cheyenne WY
1129 AM MDT Tue May 4 2021

.SHORT TERM...(Today through Thursday)
Issued at 306 AM MDT Tue May 4 2021

Cold temperatures observed this morning with several locations in
the mid 20s to around 30. Fog has struggled to form so far, so
decreased the areal coverage of fog with most of it confined to
the southern Laramie Range and adjacent valleys and eastern
plains. Otherwise, Little to no change to the current forecast
today and Wednesday. Models continue to show a broad upper level
disturbance/vort max, embedded in northwest flow aloft, slowly
translating southeast across Montana and Wyoming into Wednesday.
Models continue to show jet support, some low level convergence,
and plenty of low level instability for this time of the year.
Confident that both days will see a good coverage of rain showers
with widely scattered thunderstorms appearing more likely,
especially on Wednesday. A few of these thunderstorms may produce
small hail due to low freezing levels and CAPE values ranging
between 300 to 500 j/kg. Continued to increase POP up to 60
percent with scattered to numerous coverage across portions of
southeast Wyoming and western Nebraska. This activity may also
linger through tonight as the disturbance will still be located
across central Wyoming early Wednesday morning. Based on model
soundings, a little more instability is present for Wednesday, so
expect similar conditions with perhaps a higher coverage of
thunderstorms across southeast Wyoming. High temperatures both
days won't be quite as cool as Monday, but high temperatures will
struggle to reach 50 degrees along/west of the I-25 corridor with
highs likely in the low 60s east of I-25 into western Nebraska.

On Thursday, models finally show the unsettled weather pattern
briefly coming to an end, as a high amplitude upper level ridge
axis moves along the Front Range. Drier conditions are expected
with highs returning to the 60s and 70s across the area. There
will be some boundary layer instability present, which is typical
this time of the year, but the midlevel subsidence associated with
the ridge should minimize daytime convection.

.LONG TERM...(Friday through next Monday)
Issued at 118 AM MDT Tue May 4 2021

Friday...Ridging aloft will produce a dry day, warmer than Thursday
with 700 mb temperatures near 10 Celsius.

Saturday...The flow aloft backs to southwest ahead of the trough
aloft over the northern Rockies. With some mid level moisture, we
will likely see scattered late day showers and thunderstorms along
with cooler temperatures.

Sunday-Monday...Even cooler in the wake of a cold frontal passage,
and with scattered to numerous mainly afternoon and evening showers
and some thunderstorms associated with a passing shortwave trough
aloft.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1121 AM MDT Tue May 4 2021

All TAF sites across southeastern Wyoming and western Nebraska
Panhandle remain at VFR conditions until Wednesday morning. Brief
periods of MVFR are possible due to thunderstorms in the region
but these storms should move quickly thus it was not included in
the TAF. Thunderstorms will move into southeastern Wyoming
starting 20Z producing OVC skies around 3k ft and gusty winds up
to 30kts. For the Nebraska Panhandle, thunderstorms will push
eastward starting 21Z until 03Z with gusty winds up to 25kts along
with OVC skies. After 03Z, skies will remain OVC to BKN with light
winds around 8-10kts.

&&

.FIRE WEATHER...
Issued at 240 AM MDT Tue May 4 2021

No fire weather concerns this week as the current unsettled weather
pattern will likely continue through Wednesday, with chances for
rain showers and thunderstorms along with cooler temperatures and
high relative humidity. A brief warming and drying trend is expected
Thursday and Friday, but cooler temperatures and additional rainfall
appears likely next weekend through early next week across southeast
Wyoming and western Nebraska. Some snow is possible in the
mountains.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

SHORT TERM...TJT
LONG TERM...RUBIN
AVIATION...AW
FIRE WEATHER...TJT

Hazardous Weather Outlook
National Weather Service Cheyenne WY
439 AM MDT Tue May 4 2021

WYZ101>119-051045-
Converse County Lower Elevations-Niobrara County-
North Laramie Range-Ferris/Seminoe/Shirley Mountains-
Shirley Basin-Central Laramie Range and Southwest Platte County-
East Platte County-Goshen County-Central Carbon County-
North Snowy Range Foothills-Southwest Carbon County-
Sierra Madre Range-Upper North Platte River Basin-Snowy Range-
Laramie Valley-South Laramie Range-South Laramie Range Foothills-
Central Laramie County-East Laramie County-
439 AM MDT Tue May 4 2021

This hazardous weather outlook is for portions of east central
Wyoming...south central Wyoming and southeast Wyoming.

.DAY ONE...TODAY AND TONIGHT

Patchy fog, dense at times, will linger this morning in and around
the mountains of southeast Wyoming. Visibilities may be reduced to
one half mile at times.

Isolated afternoon and evening thunderstorms are possible today. A
few thunderstorms may contain small hail and brief heavy rain.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

Widely scattered thunderstorms are possible Wednesday. A few
thunderstorms may contain small hail.

.Spotter information statement...

Spotter activation will not be required.

NEZ002-003-019>021-054-055-095-096-051045-
Dawes County-Box Butte County-Scotts Bluff County-Banner County-
Morrill County-Kimball County-Cheyenne County-
Northern Sioux County-Southern Sioux County-
439 AM MDT Tue May 4 2021

This hazardous weather outlook is for portions of panhandle
Nebraska.

.DAY ONE...TODAY AND TONIGHT

Isolated afternoon and evening thunderstorms are possible today. A
few thunderstorms may contain small hail and brief heavy rain.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

Isolated thunderstorms are possible Wednesday and each day next
weekend.

.Spotter information statement...

Spotter activation will not be required.

Special Weather Statement
National Weather Service Cheyenne WY
143 PM MDT Tue May 4 2021

WYZ106>108-042015-
East Platte County WY-
Central Laramie Range and Southwest Platte County WY-
Goshen County WY-
143 PM MDT Tue May 4 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN GOSHEN AND
SOUTHEASTERN PLATTE COUNTIES UNTIL 215 PM MDT...

At 143 PM MDT, Doppler radar was tracking a strong thunderstorm near
Slater, or 17 miles southeast of Wheatland, moving east at 35 mph.

Wind gusts of 50 to 55 mph will be possible with this storm.

Locations impacted include...
Chugwater and Slater.

This includes Interstate 25 in Wyoming between mile markers 54 and
68.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Cheyenne.

&&

LAT...LON 4173 10465 4175 10465 4173 10466 4175 10491
      4190 10493 4195 10444 4172 10443
TIME...MOT...LOC 1943Z 263DEG 32KT 4182 10481

Hammer

Special Weather Statement
National Weather Service Cheyenne WY
149 PM MDT Tue May 4 2021

WYZ116>119-042015-
South Laramie Range WY-Central Laramie County WY-
South Laramie Range Foothills WY-East Laramie County WY-
149 PM MDT Tue May 4 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN LARAMIE COUNTY UNTIL 215
PM MDT...

At 149 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 11 miles northwest of Hillsdale to 9 miles
southeast of Crystal Lake Campground. Movement was east at 30 mph.

Pea size hail and wind gusts up to 50 mph will be possible with these
storms.

Locations impacted include...
Cheyenne, Pine Bluffs, Burns, South Greeley, Hillsdale, Ranchettes,
Warren AFB, Frontier Park, North Cheyenne, Warren Af Base, Carpenter,
Fox Farm-College and South Greeley High.

This includes the following highways...
 Interstate 25 in Wyoming between mile markers 1 and 27.
 Interstate 80 in Wyoming between mile markers 343 and 402.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Cheyenne.

&&

LAT...LON 4143 10481 4136 10406 4100 10406 4100 10527
TIME...MOT...LOC 1949Z 272DEG 28KT 4135 10461 4104 10510

Hammer