Special Weather Statement, NWS Cheyenne, WY

Area Forecast Discussion
National Weather Service Cheyenne WY
201 PM MDT Fri Aug 2 2024

.KEY MESSAGES...

- Elevated fire weather concerns continue as above average
  temperatures persist across the region through the weekend.

- Isolated thunderstorms are expected Friday PM in east-central
  Wyoming and in the Nebraska panhandle. Storms may produce
  gusty winds over 40 mph, small hail, and lightning.

- Atmospheric moisture content will continue to be plentiful,
  along with daily afternoon and evening shower and thunderstorm
  coverage, helping to produce a cooling trend during the Monday
  through Thursday period.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 139 PM MDT Fri Aug 2 2024

Afternoon visible satellite reveals several developing cumulus
fields over southeast Wyoming today, as well as over the Pine
Ridge area of the Nebraska Panhandle. Surface obs reveal
dewpoints in the low to mid 50s with light easterly upslope flow
in place east of the Laramie range. This, along with light
westerly flow aloft on the order of 15-20 knots in the 500mb
layer, supports weak bulk shear values on the order of around
20-25 knots today. Combined with around 1000 J/kg of MLCAPE,
isolated thunderstorms, some of which could be stronger, are
possible over the next 1-4 hours in southeast Wyoming into the
Panhandle region. CAM guidance supports the idea of high based
thunderstorms given strong inverted V soundings and DCAPE values
upwards of 1500. Gusty outflow winds will be the primary threat
with any stronger cores that can develop. Isolated small hail is
also possible, however this threat will likely be limited by the
rather warm mid-level temperatures and weak shear in place. The
higher-limit of today's threat would be if any clustering of
stronger cells could occur, which may result in a larger
outflow-based complex moving east through the NE panhandle early
this evening. However, nearly all CAM guidance supports the idea
of this threat quickly ending as thunderstorms push farther east
into NE and northeast CO after around 2z. Overnight, expect dry
conditions and generally light breezes out of the west. Forecast
guidance supports a much drier day on Saturday as PWAT values
decline and surface moisture is shunted eastward. With that
being said, temperatures will warm notably on Saturday, around 5
degrees higher than today. While wind speeds will not be high
enough to support Red Flag fire weather products, extremely low
RH values and critical fine fuels will still support wildfire
threats if any new fires start. Forecast confidence is high
throughout the short term with some adjustments made to raise
temperatures from ensemble blends and add some smoke wording to
the forecast through the first 24 hours.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Issued at 139 PM MDT Fri Aug 2 2024

Sunday...Ridging aloft persists, though we will see an increase in
PWs (precipitable water) values with readings increasing to 0.8 to
1.1 inch. This increase in moisture plus strong daytime heating will
promote widely scattered to scattered late day showers and
thunderstorms. Continued hot with 700 mb temperatures near 19
Celsius.

Monday...PWs increase again to the 0.5 to 1.3 inch range, helping to
spark scattered afternoon and evening showers and thunderstorms,
most numerous from the Snowy Range to Southern Laramie Range in the
afternoon. With the increase in clouds and precipitation coverage as
well as 700 mb temperatures lowering to 16 Celsius, maximum
temperatures will drop correspondingly to the upper 80s to mid 90s.

Tuesday-Thursday...West northwest flow aloft continues with abundant
atmospheric moisture content. PWs from 0.7 to 1.6 inches each day.
This abundant moisture, combined with daytime heating and upslope
low level winds will help generate scattered to numerous showers and
scattered thunderstorms each afternoon and evening, with locally
heavy rain possible from the slower moving thunderstorms. 700 mb
temperatures lowering each day, along with expected cloud and
precipitation coverage suggests a cooling trend in temperatures each
day.

Friday...West flow aloft will continue, with upslope southeast winds
helping to maintain the low level moisture in a moisture laden
atmosphere, which will continue to spark scattered to numerous
showers and scattered thunderstorms. Temperatures slightly warmer
than Thursday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1130 AM MDT Fri Aug 2 2024

Northwest flow aloft continues, and with an increase in
atmospheric moisture content, isolated to widely scattered
showers and thunderstorms will develop this afternoon and
evening mainly along and east of Interstate 25.

Wyoming TAFS...Scattered clouds from 10000 to 12000 feet will
prevail through early evening, then skies will be clear.
Thunderstorms will be in the vicinity of Cheyenne from 21Z to
02Z. Winds will gust to 22 knots at the terminals from 21Z to
03Z.

Nebraska TAFS...Scattered to broken clouds from 8000 to
12000 feet will continue through the evening, then skies will
be clear. Thunderstorms will be in the vicinity at the terminals
from 22Z to 03Z, with occasional thunderstorms at Sidney from
23Z to 03Z, producing wind gusts to 35 knots, visibilities to
4 miles and ceilings near 6000 feet. Fog will occur at Sidney
from 09Z to 14Z, reducing visibilities to 3 miles with ceilings
near 1500 feet. Outside of thunderstorms, winds will gust to
25 knots at the terminals until 03Z.

&&

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

&&

SHORT TERM...MAC
LONG TERM...RUBIN
AVIATION...RUBIN

Hazardous Weather Outlook
National Weather Service Cheyenne WY
144 PM MDT Fri Aug 2 2024

NEZ002-003-019>021-054-055-095-096-WYZ101>119-031945-
Dawes County-Box Butte County-Scotts Bluff County-Banner County-
Morrill County-Kimball County-Cheyenne County-
Northern Sioux County-Southern Sioux County-
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-
144 PM MDT Fri Aug 2 2024

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

Isolated showers and thunderstorms will develop in far eastern
Wyoming as well as the Nebraska panhandle. The strongest storms
may be capable of small hail less than 1 inch and wind gusts of 40
mph or greater. Please report any severe weather to the NWS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

Severe thunderstorm activity is unlikely. A few isolated showers
and thunderstorms may develop during the evening by Sunday and
afternoon thunderstorms with a brief heavy rain threat are
possible each afternoon next week.

.Spotter information statement...

Please report any severe weather to the NWS.

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