Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 242159

Area Forecast Discussion
National Weather Service Cheyenne WY
359 PM MDT Mon Jul 24 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 359 PM MDT Mon Jul 24 2017

A line of thunderstorms has developed in portions of Kimball
County and much of Cheyenne County ahead of a sfc trough where
SBcapes are around 1000 J/kg. Further west, weaker and shallower
convection has sprinkled much of southeast Wyoming south of
Converse/Niobrara Counties where instability values are much less.
Expect to see these trends continue eastward through the evening
as a weak shortwave moves overhead. A much stronger shortwave
embedded in a deeper plume of subtropical moisture will approach
from the southwest Tuesday morning, moving over our forecast area
through the day. A rather robust cold front will accompany this
wave moving southeast across the area through the day, with some
meager instability resolved ahead of the front by the models. PW`s
will increase to between 1" and 1.5", therefore expect to see a
broader coverage of showers and thunderstorms develop through the
day. With deep layer moisture on the rise, could see heavy rain
and even some small hail out of the more vigorous storms. However,
not expecting widespread strong activity due to the meager
instability. Rather gusty west-northwest winds will follow the
front with gusts in excess of 40mph, and could enhance any
downdraft winds from thunderstorms. A secondary front pushing
south overnight looks to keep shower potential ongoing through
Wednesday morning, with stratus likely to develop during the early
morning hours. The stratus is progged to burn off during the mid-
morning hours but conditions should remain relatively stable in
the cooler post-frontal environment through the day. The best
chance for storms Wednesday afternoon will be west of I-25.

.LONG TERM...(Wednesday night through Sunday)
Issued at 359 PM MDT Mon Jul 24 2017

Upper-level ridging is expected to remain centered across the Four
Corners region through most of the extended period. This will give
way to an active westerly flow aloft over the area on the northern
fringe of the aforementioned ridge, with several weak disturbances
traversing the flow. Occasional shots of monsoonal moisture should
yield daily chances for convection, although the exact location as
well as coverage/intensity is indiscernible right now. The overall
pattern will be typical of late July, so temperatures are expected
to be a bit closer to seasonal norms w/ highs generally in the 80s
or lower 90s.|


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1222 PM MDT Mon Jul 24 2017

VFR prevails. Skies will become SCT-BKN this afternoon and evening
with ceilings around 10-15k feet AGL. Isolated thunderstorms are a
possibility between 22z-01z, particularly over the southeastern WY
terminals and KSNY. Our confidence in thunderstorm development for
today is low, but the primary aviation concern should be gusty and
erratic surface winds with any convection.


Issued at 359 PM MDT Mon Jul 24 2017

Hot, dry, and breezy conditions prevail across the district this
afternoon. Humidities have dropped as low as 9 percent across the
Wyoming plains with low to mid teens in the Nebraska Panhandle.
Winds overall are generally light, but a few spots west of I-25
are gusting 20 to 25 mph. With a continued increase in cloud cover
through the afternoon, expect conditions to improve. Isolated
thunderstorms remain a possibility through this evening for much
of the district, but the chances for wetting rains are low. A
plume of subtropical will move up from the southwest on Tuesday
bringing a better coverage of showers and thunderstorms along
with increased chances for wetting rains. A strong cold front will
push northwest to southeast through the area from the late morning
through afternoon on Tuesday as well, with gusty northwest winds
in the wake of the front. Humidities should remain 25 percent or
higher through this time.




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