Winter Storm Warning 8, NWS Cheyenne, WY

Area Forecast Discussion
National Weather Service Cheyenne WY
930 PM MDT Mon Mar 20 2023

.SHORT TERM...(This evening through Tuesday)
Issued at 137 PM MDT Mon Mar 20 2023

High pressure remains locked in across the southeast CONUS, as a
shortwave continues digging southward into Colorado. Current
observations have seen some gusty winds across the I-80 corridor,
and snow shower actively moving from west to east near Laramie and
further eastward into Wheatland. All in all, no major squalls
developed yet today, with only some minor banded snow that
dropped visibilities near the terminals to around 1sm and winds
remaining under criteria. Main concern tonight includes the
continued chance for snow squalls through sunset. HiRes model
guidance is still pushing upwards to 200 to 350 J/kg of CAPE along
the I-25 corridor from Cheyenne to Douglas and the HRRR hinting
at a line of precipitation developing along the boundary as it
pushes to the northeast along the steering flow. 700mb winds also
remain elevated with some gusts near 40 knots, which support snow
squall development. However, confidence remains low at this time
for anything noteworthy. Nevertheless, with the HRRR maintaining
the development of the snow band later tonight, went ahead and
added some POPs to the forecast to account for this model solution
and will need to monitor just after midnight for any snow squall
potentials.

Current observations have seen intermittent snow, primarily from the
banded snow that has moved across the zones, with better coverage
developing overnight. Snow will begin to taper off during the
daytime hours on Tuesday, with a shortwave ridge moving across the
CWA, which will briefly increase daytime highs to the low-40s to low-
50s for most areas east of I-25 and bringing us into near-normal
temperatures. Next potential wind threat in the next 24 hours
include a chance for strong wind across the wind prone areas on I-25
and I-80. Wind threat still appears marginal, with in-house model
guidance keeping the wind gusts just under 50 knots and CAG-CPR
height gradients dropping from 60 meters with earlier model runs
to around 20+ meters. At this time, decided to hold off on
upgrading any watches to warnings and will let the evening crew
take another look.

.LONG TERM...(Wednesday through Monday)
Issued at 137 PM MDT Mon Mar 20 2023

The main concern with this portion of the forecast is the timing
of the various shortwaves moving through the area during the
remainder of the week.

A very active pattern will be setting up over the area through the
week. The models are showing numerous shortwaves pushing through
the jet. The initial shortwave is progged to move towards the
forecast area on Wednesday on the left exit region of the upper
level jet. It appears like the best lift will be focused over the
Sierra Madre range once again with some shadowing possible over
the Snowy Range, due to strong southwest flow. The other concern
to be on the lookout for is a possible stationary boundary
setting up somewhere between Gillette and Douglas. As the
shortwave ejects into the northern Plains on Wednesday into
Wednesday night it may set the stage for some frontogenesis near
the frontal boundary which could affect Converse and Niobrara
counties Wednesday afternoon into Wednesday night. Not confident
on how this will evolve, but certainly something we will need to
keep an eye on.

The next concern is the wind after the passage of the shortwave
Wednesday night into Thursday. The local in-house models are
showing another favorable period for some strong winds mainly for
the wind prone areas. The GFS is the only model that is trending
to keeping a closed surface low tracking through the northern
Wyoming while the GEFS/EPS ensembles and the ECMWF turns this
feature into more of an open wave. We are leaning towards more
towards an open wave solution for now, which may limit the high
wind potential a bit, but it is still certainly something we will
need to see how this pans out. The GFS is also showing some signs
of some elevated instability in the Nebraska panhandle Wednesday
evening before the front moves through Wednesday night which may
result in some rain/snow showers.

The remainder of the week will continue to be quite active with
another disturbance moving through the area on Saturday. This may
bring our next chance of rain/snow showers. Regardless, the
pattern will continue to be quite cool with highs struggling to
get out of the 30s and 40s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 927 PM MDT Mon Mar 20 2023

A round of -SHSN will move from southwest to northeast during the
overnight to early morning hours. This will cause nearly all
terminals to transition from VFR to low-end MVFR/IFR as CIGs and
VIS decrease between approximately 6Z-12Z Tuesday. SE WY terminals
will see the VIS and CIGs reductions 7Z-10Z, and the NE Panhandle
terminals will experience -SHSN between approximately 10Z-13Z
Tuesday morning. Wind gusts are expected to pick up after
daybreak for all terminals, with gusts of 30-35 kts likely after
18Z Tuesday. Winds/gusts should begin to taper off by 0Z
Wednesday for all terminals.

&&

.FIRE WEATHER...
Issued at 137 PM MDT Mon Mar 20 2023

Fire weather concerns will remain minimal throughout the week due to
multiple rounds of precipitation. Rain and snow showers can be
expected Monday through Thursday, with snow accumulations possible.
High winds are possible for the wind prone areas of southeast Wyoming
Tuesday and Wednesday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Watch from 3 AM MDT Tuesday through Tuesday afternoon
     for WYZ106-107-110.

     Winter Weather Advisory until 6 PM MDT Thursday for WYZ112-114.

NE...None.
&&

SHORT TERM...MRD
LONG TERM...REC
AVIATION...BW
FIRE WEATHER...SF