670
FXUS65 KCYS 310140
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
740 PM MDT Thu May 30 2024

.UPDATE...
Issued at 735 PM MDT Thu May 30 2024

Current forecast for tonight and early Friday morning appears on
track, with late night convection picking up between 10 PM and 1
AM. A few of these thunderstorms may become strong to severe
overnight through early Friday morning with large hail the
primary threat. Added fog to the forecast for the I-25/I-80
Junction and areas east of I-25 towards the southwest Nebraska
Panhandle. Expect outflow winds from thunderstorms and
additional moisture advection along the Laramie Range and
Cheyenne Ridge. High resolution models continue to indicate a
possibility of dense fog around sunrise Friday. Added patchy fog
with areas of fog for the southern Laramie Range. If
thunderstorms become too numerous, fog may have a hard time
developing...so left out the mention of dense fog for now.

&&


.KEY MESSAGES...

- Potential for a late night severe thunderstorm event in the
  Nebraska Panhandle late this evening into the early morning
  hours Friday.

- Daily chances for precipitation continue into the weekend
  before turning drier early next week with above average
  temperatures.

- After a weather disturbance produces a slight chance for
  showers and thunderstorms on Sunday, dry and warm weather will
  prevail for Monday through Thursday.

&&


.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 200 PM MDT Thu May 30 2024

Beautiful day ongoing this afternoon with only some upper level
clouds being observed across the CWA. Most of Wyoming under the
influence of surface high pressure...in between a departing
cold front across central Nebraska and an approaching cold front
to the northwest. Surface trough extends from north central
Colorado...north into the west slopes of the Laramie Range and
then northwest into northern Carbon County.

Latest mesoscale guidance continuing to forecast a late show
tonight for convection...focusing on thunderstorms developing
after 06Z. HRRR most aggressive with development and coverage
over Cheyenne and Kimball Counties...possibly into the eastern
half of Laramie County. MUCAPE values near 1000 to 1500 J/KG
over these areas this evening. Did add severe wording into the
southern Panhandle for late this evening into early Friday for
thunderstorms.

Upper shortwave tracks across eastern Montana/northeastern
Wyoming Friday afternoon for another rounds of scattered
afternoon and evening showers/thunderstorms.

Saturday may perhaps be our best chance for severe convection as
a dryline develops across southeast Wyoming and pushes eastward
into western Nebraska. Depending on the timing of this dryline
push...could see supercells developing across the Panhandle
Saturday afternoon. Storm Prediction Center already has a Slight
Risk area identified for the Panhandle Saturday afternoon.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 200 PM MDT Thu May 30 2024

Sunday...A progressive and low amplitude shortwave trough aloft is
progged to move across the forecast area around peak heating.
Although low and mid level moisture looks rather scant, there should
be enough moisture for isolated to widely scattered afternoon
showers and thunderstorms, mainly east of Interstate 25. A bit
warmer than Saturday with 700 mb temperatures near 11 Celsius,
yielding maximum temperatures in the upper 70s west of I-25, with
80s east of I-25.

Monday...Looks like the warmest day of the week with 700 mb
temperatures near 15 Celsius, yielding high temperatures from the
mid 80s to mid 90s. Warm temperatures aloft and limited low and mid
level moisture will likely keep this day dry.

Tuesday...A progressive shortwave trough aloft moves across the
northern Rockies, sending a dry cold front across our counties, and
dropping high temperatures some 5 to 10 degrees.

Wednesday-Thursday...Ridging aloft builds across our forecast area,
producing mostly clear conditions and warm temperatures with 700 mb
temperatures near 14 Celsius on Wednesday and 17 Celsius on
Thursday. Warm temperatures aloft will likely inhibit convective
development.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 501 PM MDT Thu May 30 2024

A complex forecast for all terminals east of the Laramie Range
due to the threat of overnight thunderstorms. KLAR and KRWL
should remain VFR throughout the TAF period, with little concern
for nocturnal convection over these sites. High clouds and
relatively calm winds expected at these terminals.

For remaining terminals (KCYS, KBFF, KCDR, KSNY, KAIA) nocturnal
thunderstorm activity will be a concern for all sites.
Thunderstorm activity expected to begin just after 06Z and
continue through about 13Z. Expect lowering ceilings with these
storms, as well as gusty and erratic winds around any storm that
develops. Behind the storms, could see ceilings dropping
towards the IFR category by sunrise at KCYS and KSNY. Gusty
winds initially at KCYS and KBFF before all winds decrease
overnight, except when thunderstorms are present.

&&

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

&&

$$

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