High Wind in Wyoming, December 10 to 11, 2024

Area Forecast Discussion
National Weather Service Cheyenne WY
231 PM MST Tue Dec 10 2024

.KEY MESSAGES...

- High Wind Warnings issued for the southeast Wyoming wind prone
  locations Tuesday afternoon until Wednesday evening. Wind
  gusts up to 65 MPH possible.

- Isolated snow showers in the NE panhandle and east-central
  Wyoming may result in a coating to an inch of snow on Tuesday
  afternoon and evening.

- Seasonably cool temperatures are expected to persist through
  the remainder of the week into the weekend.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 219 PM MST Tue Dec 10 2024

Yet another surface cold front is progged to push through the CWA
later this afternoon and through the evening hours. Unlike Monday's
front, this front will likely have a little less precipitation
associated with it. Hi-Res guidance like the HRRR shows sparse
coverage of snow showers this afternoon ahead of the front. Behind
the front, some light stratiform precipitation will be possible,
mainly for the northern zones and into the Nebraska panhandle.
Current visible satellite imagery shows a large swath of stratus
clouds to the north, moving into Converse and Niobrara
Counties. Ground observations from northeast Wyoming show light
snow falling across these areas as well. Stratiform
precipitation will likely make its way into the northern zones
late this afternoon and continue through the evening hours.
Snow accumulations will be minimal, anywhere from a dusting to
an inch in these areas.

High Wind Warnings still look on track for the southeast Wyoming
wind prones. This gradient driven wind event is the result of the
incoming cold front which will produce a surface trough east of the
Laramie Range, and a strong surface high over the Colorado Rockies.
This scenario will set the stage for a strong MSLP gradient over the
CWA, leading to high winds. Winds aloft will max out around 55 kts
with strong subsidence, so these winds will likely make it down to
the surface. High winds will continue through the day Wednesday, but
gradually weaken through the afternoon as a weak upper-level
ridge over the Great Basin shifts further east. This will cause
MSLP gradients over the CWA to relax a bit, but remain elevated
enough to still cause blustery conditions over the wind prones
Wednesday night. Aside from winds, expect warmer conditions on
Wednesday as the exiting upper-level trough ushers in warmer 700
mb temperatures.

Uneventful weather is expected for the day Thursday. Winds by
Thursday will ease, but clouds will increase throughout the day
ahead of an incoming shortwave. Precipitation is not expected,
however some snow showers may begin to move into the mountains
overnight. Despite the cloud cover, most locations can expect to see
slightly above average high temperatures in the 40s.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 219 PM MST Tue Dec 10 2024

A more active synoptic weather pattern will take over late this week
into early next week, but it remains unclear whether this will
translate to any snowfall for our area.

Model guidance is in fairly good agreement showing the next
shortwave trough passing through the area from west to east around
Friday. While the upper level presentation of this system looks
decent, and with a favorable track for precipitation, a secondary
upper level low positioned just to the north of the main along with
very limited column moisture will prevent widespread snowfall.
Westerly flow will still produce some snow showers in the mountains
Friday, but probabilities of Advisory criteria (6+") are less than
50% at this time. Elsewhere, expect something similar to the last
few events with a few light snow showers or flurries scattered about
but minimal impacts. This system will knock down temperatures a
touch, with near average high temperatures expected on Friday and
breezy to windy conditions returning to the wind prone areas. This
could be a marginal high wind event for the I-80 wind prone areas,
but probabilities of criteria gusts is about 40% or less at this
time.

Temperatures will warm up again for Saturday to perhaps 5-10F above
average. This ridge aloft looks fairly transient, with another
stronger upper level trough on its tail for the Sunday/Monday time
period. Sunday's high temperatures have considerable uncertainty
depending on the timing of the frontal passage. Ensembles are split
into two camps, with the GEFS and ECMWF ensemble systems showing
distinct separation. The GEFS mean shows a faster, weaker trough
that passes through Sunday, leading to much colder highs on Sunday,
light mountain snow, and widespread strong winds. This scenario
would also warm up faster on the tail end, with moderating
temperatures by Monday. A majority of ECMWF ensemble members fall
into a slower, stronger cluster that would deliver another mild day
for Sunday, followed by much colder conditions on Monday and a
better chance for widespread light to moderate snowfall. Even though
the high end precipitation amounts are not too impressive (ensemble
90th percentile is in the 0.1" to 0.25" QPF range for the plains),
strong winds on the backside of a departing cyclone could increase
the relative impact in this scenario. With little insight into which
scenario will be favored, opted to make minimal changes from the NBM
consensus.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1036 AM MST Tue Dec 10 2024

Another round of light snow developing this afternoon and
evening may bring periods of MVFR to IFR conditions to the NE
panhandle terminals, but confidence is fairly low. Otherwise,
expect gusty northwest winds across the board today, with gusts
lingering into the overnight in Wyoming. LLWS may develop
tonight at KCYS and KLAR.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until 5 PM MST Wednesday for WYZ106.
     High Wind Warning until 5 PM MST Wednesday for WYZ110-116-117.
NE...None.

&&

SHORT TERM...SF
LONG TERM...MN
AVIATION...MN

Hazardous Weather Outlook
National Weather Service Cheyenne WY
139 PM MST Tue Dec 10 2024

NEZ002-003-019>021-054-055-095-096-WYZ101>105-107>109-111>115-118-
119-112045-
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-East Platte County-Goshen County-
Central Carbon County-Southwest Carbon County-Sierra Madre Range-
Upper North Platte River Basin-Snowy Range-Laramie Valley-
Central Laramie County-East Laramie County-
139 PM MST Tue Dec 10 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

Some light snow possible this afternoon and overnight. Minor
accumulations possible in the Nebraska panhandle and Converse and
Niobrara Counties.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

The probability for widespread hazardous weather is low. Gusty
winds and dry weather are expected for the remainder of the week.

.Spotter information statement...

Please report any new snow to the NWS.

WYZ106-110-116-117-112045-
Central Laramie Range and Southwest Platte County-
North Snowy Range Foothills-South Laramie Range-
South Laramie Range Foothills-
139 PM MST Tue Dec 10 2024

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

High Wind Warnings are in effect for the southeast Wyoming wind
prones. Wind gusts up to 65 MPH possible.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

High winds continue into the day Wednesday with gusts up to 65 MPH
possible.

.Spotter information statement...

Please report any new snow to the NWS.