Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 282031
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
231 PM MDT WED SEP 28 2016

.SHORT TERM...(Tonight through Friday night)
Issued at 230 PM MDT Wed Sep 28 2016

Clear skies over almost the entire CWA this afternoon with just
some cumulus clouds over the higher mtns. These clouds indicative
of a slow increase in moisture advecting from the south ahead of
an upper low over the CA/AZ border area. This low will open and
eject northeastward on Thursday as an upper ridge over the high
plains drifts eastward. This will continue the increase in moisture
so expect to see an increase in cloud cover over mainly southeast
Wy Thursday along with wdly sctd showers and a few storms in the
afternoon. Activity will diminish in the evening then return again
Friday afternoon in a similar pattern. Temperatures remaining
quite mild to warm both days.

.LONG TERM...(Saturday through Wednesday)
Issued at 230 PM MDT Wed Sep 28 2016

12Z medium range models in good agreement with the steady eastward
progression of the shortwave upper ridge through the Great Plains
and large upper low/trough entering the far west Saturday. It will
be warm with highs in the 60s and 70s. Lee surface trough, subtropical
moisture and upper level diffluence will promote convective development,
especially over the mountains Saturday afternoon/evening. Showers
develop over the mountains midday Sunday then spread further east onto
the plains Sunday afternoon/evening. The upper low intensifies over
the Great Basin and lifts northeast into western Wyoming late Monday.
Shear and instability appear a bit more favorable for organized
convection across the eastern Wyoming plains and Nebraska Panhandle
Monday afternoon. A strong cold front sweeps east across the CWA
Monday night, with blustery northwest winds and colder temperatures.
700mb temperatures fall to -5C by Tuesday with snow levels potentially
dropping to 6000 ft. Definitely could see snow showers in the Cheyenne
area at that time, and will be monitoring future model trends. Some
differences appear Wednesday with the ECMWF developing zonal flow
in wake of upper low and the GFS lagging upper level energy to the
west. Opted to keep small chance pops over the mountains and dry
out the plains. Wednesday will be cool with highs in the 40s and 50s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1101 AM MDT Wed Sep 28 2016

VFR. Clear skies, except for a few high clouds spreading east
toward the Laramie Range late tonight. Generally light east to
southeast surface winds will prevail.

&&

.FIRE WEATHER...
Issued at 230 PM MDT Wed Sep 28 2016

Fire weather concerns expected to remain low for the rest of the
week with mild temperatures and sufficiently high min humidities.
A few showers and storms expected around the southeast Wy mtns
Thursday and Friday.

&&

.CYS Watches/Warnings/Advisories...
WY...None.
NE...None.
&&

$$

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



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