Severe Thunderstorm Warning 109, NWS Cheyenne, WY

Area Forecast Discussion
National Weather Service Cheyenne WY
605 PM MDT Mon Jul 20 2020

.SHORT TERM...(This evening through Tuesday)
Issued at 206 PM MDT Mon Jul 20 2020

Latest GOES-E satellite imagery shows pockets of convection this
afternoon along the Laramie Range and portions of Converse County.
Blended much of the POP/QPF this afternoon towards the HRRR and
NAMNEST as model solutions appear to initialize well to the
current conditions. Expect further development of showers and
thunderstorms further eastward as an embedded elevated shortwave
moves through today. Some storms will be on the strong to severe
side with best chances out in NE. Wind shear remains a bit lacking
this afternoon as values generally between 20 and 35 kts leading
to limited storm growth and longevity that will likely limit our
severe warned storms till later this afternoon and evening to
just a few storms if that. MLCAPE values from 1000 J/kg across
Laramie Range to 3000 J/kg across portions of Cheyenne County NE.
Some CIN remains along the WY/NE border that may require the
outflow from the storm over central Laramie Range to provide the
initial lift prior to shortwave arrival.

Otherwise, a less heat-stricken day across the region with
temperatures falling into the slight-below-normal range as KCYS
and other sites are just now reaching past the 80 degree mark.
Another chance for showers and thunderstorms, strongest across
southeastern Wyoming on Tuesday as frontal boundary begins to
eject.

.LONG TERM...(Tuesday night through Monday)
Issued at 206 PM MDT Mon Jul 20 2020

Pockets of moisture advection as monsoonal flow begins to impact
the American West and Southwest with almost near daily chances of
precipitation. Some storms may be on the strong side given an
above-normal stretch of days ahead. Upper 80s and 90s daytime
temperatures expected by the beginning of the Dog Days of Summer
through the weekend though additional moisture may add a bit of
what we may try to consider a muggy-humid feeling for WY and NE.

Biggest concern still remains the passage of mid-layer shortwave
with a deeper digging by the GFS vs the EURO into CO that sets up
the deeper monsoonal rich atmospheric river into the CWA. 12z runs
are coming into some bit of agreement though QPF amounts have some
stark difference in terms of coverage and amount that will require
some tracking over model cycles as better sampling of system as it
comes onshore.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 541 PM MDT Mon Jul 20 2020

All sites from Wyoming to the Nebraska Panhandle remain in VFR. An
extreme moist layer will hover through the KCYS site which may
lower visibility temporary; overcast skies are included in the
KCYS TAF along with thunderstorms until 01Z. Isolated
thunderstorms will move across our area from the northwest but
will likely affect KBFF and KAIA until 01Z. Cloud ceilings for
most sites will trend between SCT and BKN under 5k ft. Next
discussion could indicate MVFR conditions for KCYS due to
overcast skies and low level moisture.

&&

.FIRE WEATHER...
Issued at 133 PM MDT Mon Jul 20 2020

Portions of Carbon County area of main concern for elevated fire
weather risk this week. Periods of light rain and gusty winds
possible with showers and thunderstorms. Possibility remains for
lightning fire starts in the western forecast area where min RH
values will remain from the low teens into low 20 percents this
week coupled with temps into the 80s and 90s. East of the Laramie
Range, fire weather concerns are lessen as min RH values will
generally remain above 20 percent.

&&

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

SHORT TERM...WM
LONG TERM...WM
AVIATION...AW
FIRE WEATHER...WM

Hazardous Weather Outlook
National Weather Service Cheyenne WY
127 PM MDT Mon Jul 20 2020

NEZ002-003-019>021-054-055-095-096-WYZ101-102-107-108-118-119-
211930-
Dawes-Box Butte-Scotts Bluff County-Banner County-Morrill-
Kimball County-Cheyenne-North Sioux-South Sioux-
Converse County Lower Elevations-Niobrara County-
East Platte County-Goshen County-Central Laramie County-
East Laramie County-
127 PM MDT Mon Jul 20 2020

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

Isolated to scattered strong to severe thunderstorms possible.
Damaging winds and large hail main threats in strongest storms.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

Recurring chances for afternoon and evening strong to severe
thunderstorms this week. Damaging winds and large hail possible
threats in strongest storms.

.Spotter information statement...

Spotters are encouraged to report any hail and thunderstorm wind
damage to the Cheyenne, Wyoming National Weather Service.

WYZ103>106-109>117-211930-
North Laramie Range-Ferris/Seminoe/Shirley Mountains-
Shirley Basin-Central Laramie Range and Southwest Platte 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-
127 PM MDT Mon Jul 20 2020

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

Non-severe thunderstorms possible this week. Frequent lightning,
gusty winds, and small hail possible.

.Spotter information statement...

Spotter activation will not be needed.

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