Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 270927

Area Forecast Discussion
National Weather Service Cheyenne WY
327 AM MDT Sat May 27 2017

.SHORT TERM...(Today through Monday)
Issued at 325 AM MDT Sat May 27 2017

GOES-R water vapor imagery depicted a positively-tilted trough axis
from ND across southeast MT, western WY into northern UT/NV. A
distinct shortwave was rotating southeastward across southwest WY.
A way stationary surface front extended east-west from the Midwest
across the central Plains and Rockies to the southern Great Basin.
A strong southerly low-level jet and forcing from energy aloft
maintained strong convection over northern KS. Regional radars
detected scattered showers moving northeast from northwest CO into
southeast WY and far western NE. Some patchy fog formed overnight
over portions of far southeast WY and the western NE Panhandle.
Temperatures were in the 30s and 40s, with westerly winds 5-15 mph.

The upper trough will shift to the east across the CWA today and
into the plains this evening. Cyclonic flow aloft and a few weak
disturbances rotating through the trough will maintain a cool and
showery pattern today. Isolated afternoon thunderstorms are also
possible with low-mid level lapse rates near 7 deg C/km and CAPE
values 200-500 j/kg. Strong convection is not expected though with
weak shear and instability. High temperatures today will average
10-15 degrees below seasonal normals with mid 50s-mid 60s.
Northwesterly winds will be breezy through the day with gusts to
30 mph. Showers will end this evening with subsident and more
stable air mass in the wake of upper trough passage.

Sunday will trend somewhat drier with a northwest flow aloft on
the anticyclonic side of the western CONUS upper ridge. It will
be breezy across the plains with northwest winds gusting to 25
mph. Another embedded shortwave interacting with weak moisture
convergence will favor widely scattered afternoon convection
over the mountains and far north/northeast plains. High
temperatures Sunday will be 5-10 degrees warmer with mid 60s-low

Little change Monday with the upper ridge still to the west and
cyclonic flow aloft from the influence of a upper low north of
Lake Superior. A upper level disturbance and slightly more
unstable environment suggests higher convective coverage over
southeast WY, especially the mountains and foothills. High
temperatures Monday will be a few degrees warmer.

.LONG TERM...(Monday night through Friday)
Issued at 245 AM MDT Sat May 27 2017

An upper ridge over the western CONUS will move slowly east across
the area during the early to middle part of next week and over the
plains states by Friday. At the surface, a cool high pressure area
will settle southward out of Canada into the northern and central
plains by Weds then shift east Thursday and Friday. Mainly dry and
mild conditions are expected over the CWA Monday night and Tuesday,
though a few showers may occur near the Colorado border. Daily
chances for showers and tstms then return for Weds through Friday
as impulses lift northeast across the region and interact with
some increased instability. Warmer temperatures and better moisture
return will result from lee troughing over the high plains.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 225 AM MDT Sat May 27 2017

Some lingering showers early in the period mainly over the Neb
Panhandle. Sctd IFR cigs early in the period but improving during
the morning. Sctd showers and a few tstms again later this morning
through the afternoon.


Issued at 225 AM MDT Sat May 27 2017

The cool and showery weather will continue today. Isolated afternoon
thunderstorms are also forecast, however strong storms are not
expected. Somewhat drier and milder weather returns Sunday and Monday,
with widely scattered afternoon thunderstorms, mainly over the higher
terrain of southeast Wyoming. Minimum humidities of 40 to 50 percent
today will decrease to 30 to 35 percent Sunday and Monday.




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