133
FXUS65 KCYS 081131
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
531 AM MDT Sat Jun 8 2024

.KEY MESSAGES...

- Scattered to numerous showers and thunderstorms are expected
  over the next 24 to 36 hours. A fast moving complex of storms
  may impact the I-80 corridor late this morning through early
  afternoon between Cheyenne and Sidney. Gusty winds are the
  primary concern, although some small to marginally severe hail
  also cannot be ruled out.

- Monday and Tuesday will see the greatest coverage of late day
  showers and thunderstorms, while Wednesday and Thursday will
  be warmer with a general decrease in shower and thunderstorm
  coverage. Showers and thunderstorms look to return again for
  Friday.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 348 AM MDT Sat Jun 8 2024

An active day ahead for a large portion of southeast Wyoming and
the western Nebraska Panhandle as a fast-moving mid level short-
wave tracks along the Wyoming-Colorado state line. Showers and a
few thunderstorms are ongoing across much of the area early this
morning, mainly driven by a broad zone of WAA aloft. Latest high
res/CAM guidance suggests a second round of activity, initiating
in the vicinity of the central/southern Range by mid to late AM,
and moving rapidly eastward along the I-80 corridor through mid/
late afternoon. There are still some questions regarding overall
storm intensity as early morning convection and low clouds could
impact potential destabilization ahead of the second round. Even
so, a small window of opportunity could exist for sufficient SFC
heating to yield 500-100 J/kg CAPE across far southeast WY & the
southern Nebraska Panhandle, roughly along/s of a line from EAN-
IBM. Deep westerly flow aloft should support upwards of 45 knots
of deep layer vertical shear w/ the orientation favoring chances
for organized/bowing line segments capable of producing elevated
wind gusts near severe limits. Forecast soundings suggest a deep
moist layer and resultant tall/skinny CAPE profiles, a potential
limiting factor to the overall hail risk although small hail may
still occur with the strongest cores. Scattered showers & storms
will persist through Sunday on the northeastern periphery of the
building upper-level ridge.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 348 AM MDT Sat Jun 8 2024

Sunday night/Monday...As daytime heating wanes, isolated to widely
scattered showers and thunderstorms will end from west to east
overnight Sunday night. West northwest flow aloft develops on
Monday, and with plenty of low and mid level moisture available,
scattered late day showers and thunderstorms will be on tap again.
Temperatures will be warmer than Sunday with less cloud cover.

Tuesday...Northwest flow aloft remains, though with increasing
heights aloft along with warmer temperatures, and a decrease in low
and mid level moisture, we should see less coverage of late
day showers and thunderstorms. Slightly warmer with more sunshine
expected.

Wednesday...Even warmer as the flow aloft turns westerly, and with
700 mb temperatures near 17 Celsius, maximum temperatures will be in
the mid 80s to lower 90s. Warmer temperatures aloft will increase
the convective inhibition, and with less low and mid level moisture
around, it looks like it will be dry.

Thursday...Similar synoptic pattern as on Wednesday, though low
level winds will become northeast, and with an increase in low and
mid level moisture, we expect to see isolated to widely scattered
late day showers and thunderstorms. Perhaps a few degrees cooler
than Wednesday with upslope winds and more cloud cover.

Friday...Ridging aloft, over our forecast area, begins to break down
as the next shortwave trough aloft approaches, and with surface lee
trough convergence and an increase in atmospheric moisture, we
expect scattered late day showers and thunderstorms.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 520 AM MDT Sat Jun 8 2024

A cold front and weather disturbance will combine with adequate
atmospheric moisture to produce scattered to numerous showers
and thunderstorms this afternoon and evening mainly south of a
Rawlins to Scottsbluff line.

Wyoming TAFS...Ceilings will range from 6000 to 12000 feet at
the terminals, with areas of fog reducing visibilities to
2 miles and ceilings to 1500 feet at Cheyenne after 09Z.
Occasional thunderstorms or thunderstorms in the vicinity will
occur at the terminals from 17Z to 02Z. Winds will gust to
25 knots at Rawlins until 02Z, to 25 knots at Laramie and
Cheyenne from 17Z to 02Z.

Nebraska TAFS...Ceilings will range from 5000 to 10000 feet,
with areas of fog reducing visibilities to 2 miles and ceilings
to 1500 feet after 06Z. Occasional thunderstorms, or
thunderstorms in the vicinity will occur at Alliance,
Scottsbluff and Sidney from 18Z to 03Z. Winds will gust to
22 knots at Scottsbluff and Sidney from 17Z to 03Z.

&&

.HYDROLOGY...
Issued at 254 PM MDT Fri Jun 7 2024

Above normal temperatures have resulted in accelerated mountain
snowmelt across the Rocky Mountains this week. Temperatures in
the Snowy and Sierra Madre Ranges are expected to remain
elevated this weekend, even as a cold front stalls across the
mountains. Flood warnings for snowmelt continue for the Little
Laramie River west of Laramie, and the Encampment River south
of Saratoga, mainly due to minor flooding concerns. Emergency
Managers have reported some flooding in these areas today.
Flood Watches continue for the upper North Platte River valley
and Medicine Bow River near Elk Mountain for potential impacts
this weekend. Current forecasts suggests river levels will peak
later this weekend and remain elevated into early next week due
to some slightly cooler air. However, rainfall in and around the
mountains may become an issue this weekend and could lead to
rapid additional rises in creeks and rivers.

&&

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

&&

$$

SHORT TERM...CLH
LONG TERM...RUBIN
AVIATION...RUBIN
HYDROLOGY...WFOCYS