888
FXUS65 KCYS 132322
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
Issued by National Weather Service Riverton WY
522 PM MDT Tue May 13 2025

.KEY MESSAGES...

- Near record high temperatures expected Tuesday with gusty
  southwest winds in Carbon County.

- The next storm system will bring cooler weather and increased
  chances for PM shower and thunderstorm activity north of
  US-20 on Tuesday evening, and to a broader area Wednesday
  afternoon.

- Gusty westerly winds will return to the area Wednesday into
  Thursday.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 116 PM MDT Tue May 13 2025

A stationary boundary is currently present along the Laramie
Range and into Converse, Niobrara, and Northern Sioux county in
the Panhandle. Late this afternoon and into the evening the
stationary front will begin to push east as it transforms into a
cold front. Our stout dry layer and cloudy to partly cloudy
skies will inhibit any formation of storms this afternoon.
However, these dry conditions and breezy winds do pose an
elevated fire weather condition favoring easier ignition across
our forecast area. Rawlins will be especially gusty from 18 to
21z today. Rawlins and areas west of I-25 in Carbon and Albany
County will see elevated fire weather conditions, mainly along
the I-80 corridor as RH values drop near 15 percent and wind
gusts increase above 25 mph. This evening the cold front looks
to initiate a few storms in our area. SPC currently has a
marginal risk for hail in our northern counties. High-Res
guidance shows MLCAPE values increasing through the evening up
to 600 joules with Bulk shear between 30-40kts and SRH up to 200
m2s2. With weak UH tracks depicted by the HRRR, RFFS, and NAM
Nest the primary threat with these storms will be larger hail
production and gusty winds as the cores drop. Model soundings
show the mid layers saturating and the lower levels remaining
dry decreasing confidence in any major precipitation events.
Between 02z to 06z in the Northern Nebraska Panhandle looks to
be the best time and location for any severe storms if they do
develop. However, given that the bulk shear increases as the
700mb jet increases, storms will move out of our area fairly
quickly or past 04z effective bulk shear looks to be around
60kts ripping any severe storms apart. Past 06z any storms or
showers look to dissipate past then.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Issued at 116 PM MDT Tue May 13 2025

Thursday...Cooler and breezy in the wake of the cold front with
west flow aloft and 700 mb temperatures near 3 Celsius. Looks
like enough low and mid level moisture to produce scattered
afternoon and evening showers and thunderstorms.

Friday...West northwest flow aloft develops and with 700 mb
temperatures near 3 Celsius, maximum temperatures will be in the
60s. A bit less available moisture, so areal coverage of
showers and thunderstorms will be reduced.

Saturday...The flow aloft turns west southwest, and with a
slight increase in mid level temperatures, high temperatures
will show a warming trend. Still enough low and mid level
moisture for scattered afternoon and evening showers and
thunderstorms.

Sunday...Southwest flow aloft develops in advance of the
approaching shortwave trough. With increasing low and mid level
moisture, and lift generated by a passing shortwave trough
aloft, scattered to numerous showers and scattered thunderstorms
will develop, focused along a low level convergence axis and
surface trough along the Wyoming-Nebraska state line.

Monday...The trough aloft moves into Wyoming. Decent low level
upslope and a moist airmass will lead to scattered to numerous
showers and thunderstorms. Cooler temperatures due to increased
cloud cover and precipitation coverage.

Tuesday...As the trough aloft moves into the Northern Plains
states, northwest flow aloft will develop over our forecast
area, helping to decrease precipitation chances. Warmer
temperatures also expected with a rise in 700 mb temperatures.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 522 PM MDT Tue May 13 2025

All terminals to be VFR through 00Z/Thursday. Isolated showers and
thunderstorms are possible until 05Z/Wednesday, generally north of a
KEAN-KBFF line.

Expect gusty south to southwest winds at KLAR and KRWL to decrease
in speed, but persist through the evening hours. To the east of the
Laramie Range into the Nebraska Panhandle, east-northeast wind
swings to the southeast during the evening at all but KCDR.
High-resolution models indicate isolated high-based showers and
thunderstorms developing along and north of the KEAN-KBFF line
between 00Z-02Z/Wednesday. Confidence is not high that these
will directly impact a terminal, so have no mention of
convection with this issuance. Overall, most locations stay dry
with brief and gusty erratic outflow winds the more likely
aviation impact. Any storms and precipitation should clear the
area by 06Z/Wednesday. Clearing and dry conditions then persist
through Wednesday morning. The next round of convection develops
over the mountains of southeast Wyoming early Wednesday afternoon,
becoming more widespread across southern areas late in the
forecast period.

&&

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

&&

$$

SHORT TERM...MM
LONG TERM...RUBIN
AVIATION...WFO-RIW