978
FXUS65 KCYS 010211
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
811 PM MDT Fri May 31 2024

.UPDATE...
Issued at 800 PM MDT Fri May 31 2024

Frontal boundary currently stationary across the Laramie Range this
evening with westerly winds at Laramie and south to southeast
winds reported about 10 miles east of the highest foothills of
the Laramie Range. Do not expect this front to eject eastward
until early Saturday morning. With increasing east to southeast
winds over the high plains and current obs showing increasing
dewpoints (moisture advection), added patchy fog to the
forecast. Do not think the fog will be dense, but ceiling of 300
to 800 feet is close enough for fog...especially along the
elevated ridges. Fog or low stratus is forecast to dissipate
quickly Saturday morning as the front lifts northeast as a warm
front...this will set the stage for isolated or widely scattered
severe thunderstorms east of I-25 Saturday afternoon and evening.


&&

.KEY MESSAGES...

- Daily chances for isolated to scattered showers and  thunderstorms
continue through the weekend. A few storms may  have the potential
to become strong to severe each day.

- Warm and dry weather is expected most of next week, aside from  an
uncertain potential for a cold front which could bring some
shower/storm activity on Tuesday or Wednesday.

&&


.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 150 PM MDT Fri May 31 2024

Surface high pressure located over southwest South Dakota this
afternoon creating an easterly surface wind component over the
eastern half of the CWA. Stratus this morning east of the
Laramie Range has been persistent and slow to break up in
southeast low level upslope flow. 1PM temperatures remain quite
cool with upper 50s in the Panhandle and southeast Wyoming
plains east of the Laramie Range. Cheyenne finally broke out
maybe an hour or so ago. Latest SPC Mesoanalyst page showing
quite a bit on CIN across the Panhandle into southeast Wyoming
in these southeast winds and stratus. Where skies are
clearing...current SBCAPE has risen to 500-1000 J/KG across
western Laramie County into southern Platte County. Lack of
surface heating from the low clouds shows SBCAPE not rising too
much through the afternoon with low level CIN returning by 00Z.

Given the persistent stratus...do not think we will see much
this afternoon convection wise. Another late night show possible
as a dry cold front drops into the southeast Wyoming plains as
parent upper shortwave tracks across eastern Montana and western
SOuth Dakota. HRRR and RAP simulated radar showing convection
developing across the northern Nebraska Panhandle towards 06Z
tonight that could become strong to severe for a time through
11Z.

Really questionable on severe convection Saturday as GFS showing
really dry air pushing into the Panhandle. Dryline on the GFS
pushes through the Panhandle by 21Z Saturday. So its not
matching up well with peak heating. Confidence not high on
severe convection Saturday afternoon/evening and the SPC Slight
Risk area. Guess it depends on timing of the dryline moving
eastward. A slower timing would improve severe convection
chances. Later shifts will need to watch the timing of the
dryline push.

As for Sunday...it all depends on the timing of the dryline
push on Saturday. Could see a dry forecast for Sunday...but for
now...kept chance PoPs (30-40 percent) for Sunday afternoon.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 150 PM MDT Fri May 31 2024

The long term looks relatively uneventful with mostly dry and mild
conditions expected throughout next week. Quasi-zonal flow for the
first half of the work week will lead to breezy and windy conditions
across much of the CWA. A strong shortwave trough passing just to
the north of the CWA on Tuesday will lead to the greatest potential
for high winds across the southeast Wyoming wind prones. The GFS has
700 mb wind speeds of 50 to 60 kts, and elevated CAG to CPR 700 mb
height gradients. In-house guidance is also pinging the potential
for high winds around the wind prones. Cannot rule out some slight
precipitation chances with the passage of this shortwave either.
Cooler temperatures can also be expected on Tuesday as the shortwave
ushers in slightly cooler 700 mb air. By Wednesday, ridging begins
to build over western CONUS, leading to a warmer and drier airmass
infiltrating the CWA. Temperatures through Friday will gradually
increase, with most locations seeing highs in the 80s by Friday.
Minimal precipitation chances are expected during this time frame as
subsidence keeps conditions dry.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 505 PM MDT Fri May 31 2024

Another round of showers and thunderstorms are possible near the
KCDR terminal, but the primary aviation concern will be low
ceilings and potentially some fog across the Nebraska terminals
and KCYS. Could see MVFR to near-IFR conditions at KCYS, with
similar conditions at KBFF, KCDR, and KSNY. KAIA looks to drop
into the IFR to near-LIFR conditions overnight as ceilings crash
to 700ft and visibility is reduced to 2SM. Fog and low stratus
should move out of the terminals by 14Z and VFR conditions will
return. Some sites could see an oscillation between SCT010 and
BKN010 leading to frequent changes between good conditions and
poor conditions.

&&

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

&&

$$

UPDATE...TJT
SHORT TERM...GCC
LONG TERM...SF
AVIATION...AM