Severe Thunderstorm Warning 130, NWS Cheyenne, WY

Area Forecast Discussion
National Weather Service Cheyenne WY
555 PM MDT Wed Aug 5 2020

.SHORT TERM...(This evening through Thursday)
Issued at 330 PM MDT Wed Aug 5 2020

Forecast challenges transitioning from severe thunderstorms this
afternoon...to critical fire weather conditions through the
remainder of the week.

Currently...Trough of low pressure extends along the front range
of eastern Colorado northwestward into Laramie and eventually to
near Riverton this afternoon. Radar has begun to blossom on radar
this afternoon...similar to what the short range guidance has been
showing. Probably better today than over the past several days.
Less shear today and a little more stable over yesterday. RAP
analysis showing SB CAPE of around 1800 J/KG down here near
Cheyenne to around 1000 J/KG up near Douglas. Off to the west over
Carbon County...very dry conditions being observed with Tds in the
low 20s. Red Flag Warnings look to be panning out out that way and
will continue the current afternoon RFWs for today.

Short range guidance showing storms moving out into the Panhandle
towards 00Z. Should we get this rainfall this evening...do believe
we stand a good chance at patchy fog with southeasterly upslope
flow. Did add patchy fog into the forecast for the Panhandle below
4500 feet elevations. SREF hinting at lower conditions out there
towards 12Z as well.

Drier and breezier Thursday with low humidity spreads east. Looks
like surface boundary shifts east to near the Wyoming/Nebraska
state line. GFS 700mb winds west of the Laramie Range
25-30kts...so critical fire weather conditions look to be certain
out west. Continued the Red Flag Warnings for FWZ 303 through 308.
Best chances for any afternoon showers/storms look to be east of
the Laramie Range.

Very dry conditions Friday as westerly winds continue. 850mb
humidity in the Panhandle falls to 12 percent. Did issue a Fire
Weather Watch for zones we currently have in warnings for Friday.
Later shifts may need to add the Summit and points east as we get
closer to Friday.

.LONG TERM...(Saturday through Tuesday)
Issued at 318 AM MDT Wed Aug 5 2020

A broad upper high will hold over much of the southern half of the
country through the period with the westerlies and embedded
shortwaves being lifted to the north along the international
border. Overall this will provide mainly dry and warm weather to
the CWA with just isolated convection possible where weak
shortwaves clip the CWA, right now looking like later Saturday and
again Tuesday. Temperatures will be above seasonal averages with
little day-to-day changes.

&&

.AVIATION...(For the 00Z TAFS through Thursday afternoon)
Issued at 555 PM MDT Wed Aug 5 2020

Widely scattered thunderstorms across the eastern plains of Wyoming
and western Nebraska will gradually diminish in intensity this
evening through 02z, especially for KSNY and KBFF this evening. Will
have to watch for fog or low CIGS tonight in areas that received
decent rainfall across the panhandle of Nebraska. Will keep out of
TAF for now.

HAZARDS/WEATHER TRENDS: Brief MVFR VIS in any thunderstorm activity
this evening until 02z or 03z, then VFR for the rest of tonight and
into early Thursday morning. Low confidence for fog and low stratus
late tonight for the western Nebraska terminals.

&&

.FIRE WEATHER...
Issued at 330 PM MDT Wed Aug 5 2020

Critical fire weather conditions ongoing this afternoon across
Carbon County where Red Flag Warnings are in effect through 8 PM
this evening. Dry/Breezy conditions return Thursday for areas west
of the Laramie Range. Red Flag Warnings in effect for FWZ 303
through 308 Thursday. Conditions expected to continue into Friday
with a Fire Weather Watch in effect Friday afternoon. See a
slight reprieve Friday night into Saturday as a cold front moves
into central Wyoming. This will be short lived though as
breezy/dry conditions return Sunday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...Red Flag Warning until 8 PM MDT this evening for WYZ303>307.

     Red Flag Warning from 11 AM to 8 PM MDT Thursday for WYZ303>308.

     Fire Weather Watch from Friday morning through Friday evening
     for WYZ303>308.

NE...None.
&&

SHORT TERM...GCC
LONG TERM...RE
AVIATION...TJT
FIRE WEATHER...GCC

Hazardous Weather Outlook
National Weather Service Cheyenne WY
417 AM MDT Wed Aug 5 2020

WYZ104-105-109>115-061030-
Ferris/Seminoe/Shirley Mountains-Shirley Basin-
Central Carbon County-North Snowy Range Foothills-
Southwest Carbon County-Sierra Madre Range-
Upper North Platte River Basin-Snowy Range-Laramie Valley-
417 AM MDT Wed Aug 5 2020

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

.DAY ONE...TODAY AND TONIGHT

Isolated afternoon thunderstorms possible. Storms may produce
strong, gusty winds and dry lightning.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

Decreasing thunderstorm potential day by day as the area dries out
under the influence of a ridge. Fire weather conditions will be
the main concern.

.Spotter information statement...

Spotter activation will not be required.

NEZ002-003-019>021-054-055-095-096-WYZ101>103-106>108-116>119-
061030-
Dawes-Box Butte-Scotts Bluff County-Banner County-Morrill-
Kimball County-Cheyenne-North Sioux-South Sioux-
Converse County Lower Elevations-Niobrara County-
North Laramie Range-
Central Laramie Range and Southwest Platte County-
East Platte County-Goshen County-South Laramie Range-
South Laramie Range Foothills-Central Laramie County-
East Laramie County-
417 AM MDT Wed Aug 5 2020

This hazardous weather outlook is for portions of panhandle
Nebraska...western Nebraska...east central Wyoming and southeast
Wyoming.

.DAY ONE...TODAY AND TONIGHT

Widely scattered thunderstorms will develop near and along the
Laramie Range after noon and move eastward into the High Plains
by mid-afternoon, reaching the western Nebraska Panhandle by late
afternoon. Strong to severe thunderstorms producing large hail
and strong gusty winds will be possible along and east of the
Interstate 25 corridor; an isolated tornado cannot be ruled out.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

Scattered afternoon and evening thunderstorms will develop
Thursday; some may be strong to severe. Storms become more
isolated and confined to the mountains Friday and Saturday.

.Spotter information statement...

Spotter activation may be needed this afternoon along and east of
the I-25 corridor.

Special Weather Statement
National Weather Service Cheyenne WY
650 PM MDT Wed Aug 5 2020

NEZ019-096-060130-
Scotts Bluff NE-South Sioux NE-
650 PM MDT Wed Aug 5 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN SCOTTS BLUFF AND
SOUTH CENTRAL SIOUX COUNTIES UNTIL 730 PM MDT...

At 650 PM MDT, Doppler radar was tracking a strong thunderstorm over
Morrill, or 12 miles southeast of Torrington, moving east at 10 mph.

Penny size hail and wind gusts of 50 to 55 mph will be possible with
this storm.

This strong thunderstorm will be near...
  Morrill around 705 PM MDT.

A Severe Thunderstorm Watch remains in effect until 900 PM MDT for
the Panhandle of Nebraska.

LAT...LON 4199 10403 4203 10399 4206 10378 4186 10386
TIME...MOT...LOC 0050Z 284DEG 7KT 4199 10396

Rubin

Special Weather Statement
National Weather Service Cheyenne WY
709 PM MDT Wed Aug 5 2020

WYZ102-060200-
Niobrara County WY-
709 PM MDT Wed Aug 5 2020

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL NIOBRARA COUNTY UNTIL 800
PM MDT...

At 709 PM MDT, Doppler radar was tracking a strong thunderstorm 10
miles east of Lance Creek, or 18 miles north of Lusk. This storm was
nearly stationary.

Penny size hail and wind gusts of 50 to 55 mph will be possible with
this storm.

This storm will remain over mainly rural areas of central Niobrara
County.

LAT...LON 4295 10424 4294 10471 4312 10472 4317 10429
TIME...MOT...LOC 0109Z 161DEG 3KT 4302 10444

Rubin

Special Weather Statement
National Weather Service Cheyenne WY
737 PM MDT Wed Aug 5 2020

NEZ055-060215-
Cheyenne NE-
737 PM MDT Wed Aug 5 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN CHEYENNE COUNTY
UNTIL 815 PM MDT...

At 737 PM MDT, Doppler radar was tracking a strong thunderstorm near
Colton, or 8 miles northeast of Sidney, moving southeast at 10 mph.

Penny size hail and wind gusts up to 50 mph will be possible with
this storm.

This strong thunderstorm will be near...
  Colton around 810 PM MDT.
  Sunol around 815 PM MDT.

This includes Interstate 80 in Nebraska between mile markers 63 and
68.

A Severe Thunderstorm Watch remains in effect until 900 PM MDT for
the Panhandle of Nebraska.

LAT...LON 4124 10296 4129 10290 4124 10261 4104 10288
TIME...MOT...LOC 0137Z 311DEG 8KT 4124 10289

Rubin

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