High Wind in Wyoming, March 1 to 3, 2024

Area Forecast Discussion
National Weather Service Cheyenne WY
1034 PM MST Fri Mar 1 2024

.KEY MESSAGES...

- Widespread wind gusts 55-65 MPH are expected across southeast
  Wyoming on Saturday. After a brief early evening lull, a
  significant bora event will be possible along and east of the
  Laramie Range during the overnight hours into early Sunday
  morning.

- Critical fire weather conditions are expected across much of
  southeast Wyoming and western Nebraska on Saturday afternoon
  with minimum RH values near 15 percent and frequent wind gusts
  well in excess of 35 MPH, perhaps as strong as 55-60 MPH
  closer to the Laramie Range.

- Winter Storm Warnings have been issued for the Snowy and
  Sierra Madre mountain ranges from 5 PM Saturday through 5 AM
  MST Monday.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 316 PM MST Fri Mar 1 2024

An extremely active 24 to 48 hours ahead for southeast Wyoming &
the western Nebraska Panhandle w/ potential for numerous weather
impacts from multiple hazards including widespread strong winds,
critical fire weather conditions, and heavy mountain snow. Winds
have remained elevated across Carbon County this afternoon, with
the peak gust reaching 62 MPH at KRWL at 1252 PM MST. Winds will
decrease in intensity during the evening & overnight in response
to weakening low-level gradients. Unfortunately, this break will
be fairly short lived as SW-NE oriented MSLP gradients will very
likely increase markedly between 12z and 18z Saturday as intense
cyclogenesis takes place across northeast Wyoming into southeast
Montana in response to a highly energetic, negatively tilted mid
and upper-level trough digging across the northwestern CONUS. As
this occurs, a belt of 45 to 55 knot 700 to 800 millibar flow is
expected to spread across southeast Wyoming. Impressive downward
omega/deep subsidence will persist in association with a 120+ kt
250-millibar jet, and models suggest deep mixing with very steep
low-level lapse rates and 50+ knots available to mix across much
of our Wyoming zones. The latest MAV for RWL/DGW/LAR all suggest
30+ knot sustained winds after 18z Saturday, usually a very good
indicator of 60+ MPH gust potential. Deterministic GFS output is
also suggesting widespread 30+ knot surface winds, so confidence
is rapidly increasing in a potentially widespread episode of 55-
65 MPH gusts over much of southeast Wyoming during the late AM &
afternoon hours on Saturday. NBM 50th %ile values for most areas
along and west of I-25 suggest wind gusts 45-55 knots. While the
main potential for strong winds should end between 00-03z across
Carbon and Albany counties with the loss of daytime heating/low-
level mixing, a substantial bora is expected during the evening/
overnight over the Laramie Range & adjacent I-25 corridor w/ the
intense cold air advection and impressive subsidence, along with
a robust mountain-wave signal across the entirety of the Laramie
Range. In-house RF model guidance suggests high probabilities of
58+ MPH gust exceedance at several lower-elevation sites outside
of the wind corridors. This supports the issuance of a High Wind
Watch for all zones along and west of I-25, with the easternmost
zones (Douglas, Wheatland, Cheyenne) extending through the night
into Sunday morning for the bora threat.

In addition to the threat for strong wind gusts, conditions will
remain very dry with afternoon RH values as low as 15 percent in
the afternoon. In the past week, we have seen a number of grass-
fires across the region which have managed to spread rather fast
in multiple instances. Given this concern, we have opted for the
issuance of a Red Flag Warning for our western Nebraska zones as
well as the Laramie Range Foothills and adjacent high plains for
Saturday 10 AM to 6 PM. Fuels are considered non-critical in FWZ
419 due to mountain snow pack, but southern portions of the zone
immediately adjacent to FWZ 430 (a fire occurred here today) may
still be conducive to large fire growth. Given the situation, we
did include this zone as well w/ the focus on southern Platte Co
for the enhanced fire danger.

Finally, the very robust upper-level jet & favorable orographics
will create an optimal environment for very heavy mountain snow-
fall from Saturday evening through Monday morning. Accumulations
of 1 to 2 feet look to be a good bet for both the Snowy & Sierra
Madre Range, with local amounts near 3 feet possible. Have opted
to upgrade the Winter Storm Watch to a Warning with this package
given the high confidence level. Could eventually see a need for
Advisories for some areas along/west of the Laramie Range w/ the
potential for localized amounts 2-4 inches, but this should stay
primarily focused in the high country.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 436 AM MST Fri Mar 1 2024

Monday...Blustery, windy and cold with cyclonic flow aloft and
tight low and mid level gradients. With enough moisture and
cyclonic flow aloft, slight chances for light snow will
continue. 700 mb temperatures near -10 Celsius will yield
maximum temperatures from near 30 degrees west of I-25, to the
mid 30s to mid 40s east of I-25.

Tuesday...Expect a slow warming trend as the flow aloft turns west,
helping a surface lee trough to develop. 700 mb temperatures rebound
to -13 Celsius, helping maximum temperatures to reach the mid 30s
west of I-25, with 40s further east.

Wednesday...The slow warming trend continues as the flow aloft backs
to southwest and 700 mb temperatures rebound to -7 Celsius. Looks
like a chance for orographic snow showers for the Snowy and Sierra
Madre ranges.

Thursday...Somewhat moist zonal flow aloft continues, producing a
chance of snow. Temperatures remain about the same as those from
Wednesday based on 700 mb temperatures near -9 Celsius.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1033 PM MST Fri Mar 1 2024

KRWL and KLAR will see winds gradually increase in magnitude tonight
and into the day Saturday. Winds will be the primary aviation
concern during the day Saturday. Nebraska terminals could see gusts
up to 30 kts and Wyoming terminals could see gusts over 45 kts. A
cold front will begin to move into the area during the afternoon,
bringing increased clouds as well as snow. Snow will mainly
affect southeast Wyoming terminals during the afternoon and
into the evening hours. IFR conditions expected in falling snow
due to reduced visibility.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning from 10 AM to 6 PM MST Saturday for WYZ419-
     430>433.
     High Wind Watch from Saturday morning through Sunday morning
     for WYZ101-106-107-116>118.
     High Wind Watch from 8 AM MST Saturday through Saturday
     evening for WYZ104-105-109>111-113-115.
     Winter Storm Warning from 5 PM Saturday to 5 AM MST Monday for
     WYZ112-114.
NE...Red Flag Warning from 10 AM to 6 PM MST Saturday for
     NEZ434>437.

&&

SHORT TERM...CLH
LONG TERM...RUBIN
AVIATION...SF