Area Forecast Discussion
Issued by NWS Cheyenne, WY

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425
FXUS65 KCYS 290937
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
327 AM MDT Mon May 29 2017

.SHORT TERM...(Today through Wednesday)
Issued at 325 AM MDT Mon May 29 2017

The GOES-R water vapor imagery showed a nearly stationary upper low
spinning north of MN, and a upper ridge situated over the Intermountain
West. Cyclonic/northwest flow aloft prevailed, with a few weak embedded
shortwaves sparking widely scattered showers over portions of WY and
CO. A cold front extended from occluded low south of Hudson Bay Canada
through southeast MN, far southern SD, northeast WY to northwest MT.
Skies were partly cloudy with northwesterly winds less than 10 mph.
Temperatures were in the 30s and 40s.

00Z short range models prog the cyclonic flow aloft to continue through
Tuesday night. The cold front to the north will progress southward across
the CWA this morning. Weak post-frontal upslope flow, moisture convergence
combined with lift from passing shortwave will promote scattered
afternoon convection, especially over the Snowy and south Laramie
ranges. Fairly steep lapse rates, 600-1000 j/kg CAPE, precip water
0.50-0.75", and ~30 kt 0-6 km shear may lead to a few strong tstorms
producing small hail, brief heavy rain, and wind gusts to 45 mph.
Convection will end shortly after sunset. High temperatures today
will be slightly cooler with highs in the 60s to around 70. It will
be breezy over the north and eastern plains with northwest winds
gusting to 20-25 mph.

Tuesday will trend warmer and slightly drier as precip water values
lower between 0.25" and 0.50". Afternoon convective coverage will be
widely scattered and confined to the mountains and foothills of southeast
WY.

Wednesday will be warmest day of the forecast period as the upper ridge
axis aligns north-south west of the Front Range. The flow aloft will
become more westerly. Afternoon convection that develops will be confined
near the CO border and far northeast plains. Highs Wednesday will average
above seasonal normal with 70s to low 80s. South- southwesterly winds
will be breezy over the plains and western Carbon County with gusts
of 20-25 mph.

.LONG TERM...(Wednesday night through Sunday)
Issued at 300 AM MDT Mon May 29 2017

Fairly typical late spring weather seen across the CWA this period
with mild to warm temperatures and chances for afternoon and evening
showers and tstms at times. An upper trough initially along the west
coast will pivot northeast over the northern Rockys Thursday and leave
a low-amplitude upper high over the central Rockys Saturday and Sunday.
Best chance for convection over the CWA looks to be late Thursday and
late Friday as the upper trough clips the area and interacts with late
day instability. Other days some showers and storms not out of the
question but should be isolated and mainly around the mtns. Temperatures
warm Thursday and Friday before trending down some for the weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 300 AM MDT Mon May 29 2017

VFR expected to prevail at all terminals through the period. Some
periods of mainly MVFR vsbys likely in sctd showers and tstms this
afternoon into early this evening over southeast Wyoming from KRWL
to KCYS.

&&

.FIRE WEATHER...
Issued at 233 AM MDT Mon May 29 2017

Fire weather concerns will be minimal this week. There will be isolated
to widely scattered mainly afternoon showers and thunderstorms each
day, especially for the higher terrain. Temperatures will warm to above
normal by the middle of the week. Minimum afternoon humidities will
lower to 15 to 25 percent across southeast Wyoming from Tuesday through
Friday. Wind gusts will average less than 25 mph.

&&

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

$$

SHORT TERM...MAJ
LONG TERM...RE
AVIATION...RE
FIRE WEATHER...MAJ



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