Special Weather Statement, NWS Cheyenne, WY

Area Forecast Discussion
National Weather Service Cheyenne WY
520 PM MDT Mon Aug 3 2020

.SHORT TERM...(This evening through Wednesday night)
Issued at 230 PM MDT Mon Aug 3 2020

Forecast concerns deal with continued severe thunderstorm
chances...followed by critical fire weather conditions Tuesday and
Wednesday.

Currently...Pesky frontal boundary remains over the CWA this
afternoon separating moist air to the east from very dry air to
the west. Front currently lays along a line from Red Feather Lakes
to Laramie to just west of Casper this afternoon. Seeing upper 50
Tds across Platte and Goshen Counties with low to mid 30 Tds over
Carbon County...west of the front. Storms beginning to form along
this boundary already this afternoon...moving southeast in the
northwest flow aloft.

Afternoon concerns with severe storms today. Panhandle remains
capped with current convective inhibition vales of 50 to 75 J/KG.
Along the Laramie Range where convection developing on
radar...looking at CAPE near 2000 J/KG. Latest NAM soundings show
we may not break that low level cap in the Panhandle this
afternoon...so severe storms not really a concern in the
Panhandle. What is concerning is southeast Wyoming where that
higher CAPE is in place along with 40kts sfc-6km shear. Hires
guidance continues to show potential for severe storms east of the
front to the Nebraska state line this afternoon...continuing into
mid evening.

Perhaps a better chance for severe thunderstorms Tuesday as
guidance suggesting drier air surging east across the Laramie
Range into the Panhandle Tuesday afternoon. Dryline type feature
could by the lifting feature we have been missing the past several
days. A little less shear tomorrow over today...but still looking
at sfc to 6km shear 30-35kts. SPC does show a Slight Risk area
identified for the southern Panhandle and eastern Laramie County
Tuesday afternoon.

&&

.LONG TERM...(Thursday through Monday)
Issued at 230 PM MDT Mon Aug 3 2020

The upper ridge to the west of the Continental Divide will shift east
across the Front Range and High Plains Wednesday through Thursday.
with winds aloft backing from northwesterly to southwesterly. Periodic
short waves aloft and surges of subtropical moisture (PWAT values above
an inch east of the Laramie Range) will produce scattered afternoon
and evening showers and thunderstorms. Marginal low-mid level shear
and instability may yield a few strong to marginally severe thunderstorms.
Drier and warmer air aloft (PWAT values decreasing by a half inch)
will result in only isolated diurnal convection over the Southeast
WY mountains Friday and Saturday. Above normal temperatures will
prevail with highs in the mid 80s to mid 90s and lows in the 50s
to lower 60s.

&&

.AVIATION...(For the 00Z TAFS through Tuesday afternoon)
Issued at 520 PM MDT Mon Aug 3 2020

Showers and thunderstorms will impact KLAR, KCYS, and maybe KBFF
this evening as a line of thunderstorms currently west of Interstate
25 move east across the eastern plains.  Thunderstorms should weaken
due to high CIN once they reach the western Nebraska panhandle, with
only a few showers expected for KSNY, KAIA, and KCDR.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail, with brief MVFR-
IFR VIS in the heaviest thunderstorms. Activity should subside
between 02z to 04z.

&&

.FIRE WEATHER...
Issued at 230 PM MDT Mon Aug 3 2020

Stalled out cold front continues to lay across southeast Wyoming
along a line from Laramie to Riverton. West of the
front...afternoon humidity continues to be low...while areas east
of the front see almost daily chances for rain and thunderstorms.
Winds begin to get a little stronger Tuesday across Carbon County
(FWZ 303 and 304) where very low humidity continues. Red Flag
Warning has been issued for FWZ 303 and 304 for Tuesday with a
Fire Weather Watch now in effect for Wednesday afternoon. Front
finally begins to move east Thursday with gusty west winds
spreading eastward behind the departing front. Could see more
widespread critical fire weather conditions across southeast
Wyoming as this happens.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning from 11 AM to 8 PM MDT Tuesday for WYZ303-304.

     Fire Weather Watch from Wednesday morning through Wednesday
     evening for WYZ303-304.

NE...None.
&&

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

Hazardous Weather Outlook
National Weather Service Cheyenne WY
406 AM MDT Mon Aug 3 2020

WYZ104-109>114-041015-
Ferris/Seminoe/Shirley Mountains-Central Carbon County-
North Snowy Range Foothills-Southwest Carbon County-
Sierra Madre Range-Upper North Platte River Basin-Snowy Range-
406 AM MDT Mon Aug 3 2020

This hazardous weather outlook is for south central Wyoming.

.DAY ONE...TODAY AND TONIGHT

Isolated to widely scattered afternoon afternoon and early evening
thunderstorms will develop. Severe weather is not expected.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

Minimum humidity will fall below 15 percent with west winds gusting
to 30 mph Tuesday afternoon outside the mountains. Isolated to widely
scattered high based dry thunderstorms will be possible that may
result in additional fire starts. A Fire Weather Watch is in effect
for west and central Carbon County from 11 AM through 8 PM Tuesday.

Widely scattered afternoon thunderstorms will develop Wednesday
and Thursday, with more isolated coverage Friday and Saturday.
Severe weather is not expected.

.Spotter information statement...

Spotter activation will not be required.

NEZ002-003-019>021-054-055-095-096-WYZ101>103-105>108-115>119-
041015-
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-Shirley Basin-
Central Laramie Range and Southwest Platte County-
East Platte County-Goshen County-Laramie Valley-
South Laramie Range-South Laramie Range Foothills-
Central Laramie County-East Laramie County-
406 AM MDT Mon Aug 3 2020

This hazardous weather outlook is for the western Nebraska
Panhandle...east central Wyoming...and southeast Wyoming.

.DAY ONE...TODAY AND TONIGHT

Scattered thunderstorms will develop over the Laramie Range
during the early afternoon and move southeast onto the high
plains during the late afternoon and early evening. Isolated
strong to marginally severe thunderstorms producing hail up
to one inch and wind gusts of 50 to 60 mph will be possible.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

Scattered afternoon and evening thunderstorms will develop
Tuesday through Thursday, becoming more isolated and confined
to the mountains Friday and Saturday. Strong to severe
thunderstorms producing large hail, wind gusts of 60 mph and
locally heavy rain will be possible along and east of the
Interstate 25 corridor Tuesday.

.Spotter information statement...

Spotter activation will not be required.

Special Weather Statement
National Weather Service Cheyenne WY
546 PM MDT Mon Aug 3 2020

WYZ117-118-040030-
Central Laramie County WY-South Laramie Range Foothills WY-
546 PM MDT Mon Aug 3 2020

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL LARAMIE COUNTY UNTIL 630
PM MDT...

At 546 PM MDT, Doppler radar was tracking a strong thunderstorm near
Whitaker, or 21 miles northwest of Cheyenne, moving east at 30 mph.

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

This strong thunderstorm will be near...
  Whitaker around 600 PM MDT.

This includes Interstate 25 in Wyoming between mile markers 23 and
36.

LAT...LON 4140 10506 4148 10505 4155 10455 4119 10458
TIME...MOT...LOC 2346Z 279DEG 26KT 4143 10498

Rubin

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