Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 312049

Area Forecast Discussion
National Weather Service Cheyenne WY
249 PM MDT WED AUG 31 2016

.SHORT TERM...(This evening through Friday night)
Issued at 249 PM MDT Wed Aug 31 2016

Quiet across the CWA so far with most convection confined around
a small circulation center evident near the Colorado/NW Kansas
border. Main difficulties with the forecast will be late
night/early morning low clouds and fog over the plains next couple
days as moisture continues to move across the area on healthy
southeasterly winds. Moisture field is better today so would
expect to see fairly widespread low clouds...though breeziness
may limit fog.

Mainly dry weather across the area Thursday as an upper high holds
across the region. This high will slip east over the plains
Thursday night and Friday and allow for weak impulses to move
across the area in swly expect to see an uptick in
convection Friday...aided by a surface trough that will set up over
the high plains.  Continued warm through Friday.

.LONG TERM...(Saturday through Wednesday)
Issued at 249 PM MDT Wed Aug 31 2016

Southwest flow aloft will stregthen this weekend ahead of a broad
upper level trough moving across the Pac NW and into the northern
and central Rockys by early next week. Models in fairly good
agreement...showing the cold front moving across the area and
stalling near the Colorado border on Sunday. Jet energy aloft will
continue to increase on Saturday...with a good chance of scattered
showers and isolated thunderstorms across the mountains and
eastern plains. Breezy winds are expected in the afternoon west of
the Laramie Range where southwest winds are expected. Winds will
become light out of the south or southeast east of the front
across the plains...but gusty winds associated with thunderstorm
activity are possible. Can not rule out some additional showers
and a few thunderstorms late Saturday night and Sunday as a 85 to
90 knot jet max moves northeast over the area...which may provide
enough lift for some nocturnal convection Saturday night along
with some activity lingering through the day on Sunday...even
though the post-frontal environment will be more stable. Similar
weather is expected on Monday as the trough axis moves into
Wyoming with some stronger storms possible across the plains of
western Nebraska. Temperatures will trend a few degrees lower each
day from Saturday through Monday. However...areas further south
near the Colorado border will be closer to the stalled frontal
boundary...with high temperatures a few degrees warmer from
Cheyenne to Sidney Nebraska.

For Tuesday and Wednesday...there is significant model
disagreement with the ECMWF showing the trough axis digging
southward before moving across the area...resulting in increasing
coverage of showers/thunderstorms and cooler temperatures across
most of the area. The GFS is much more progressive...showing the
trough axis already moving into the Great Lakes region. The
majority of the ensembles...including the GFS ensembles...favor
the ECMWF solution. Did not make many changes to the extended
portion of the forecast...and kept cooler than normal temperatures
and POP between 20 to 30 percent. Once this trough exits the
area...believe the upper level flow will become more zonal by the
middle of next week as a strong storm system moves towards the
U.S./Canada border.


.AVIATION...(For the 18Z TAFS through Thursday morning)

VFR conditions are expected today with breezy southeast winds across
southeast Wyoming and western Nebraska. There is a 20 percent chance
of thunderstorms from KCYS eastward to KSNY...otherwise dry
conditions are expected at other terminals.  Did not add VCTS to
KCYS nor KSNY this afternoon due to low confidence...but will
monitor conditions through this afternoon.  Low CIGS and fog may
return to the eastern plains late tonight with IFR conditions
possible along and east of Interstate 25.


Issued at 249 PM MDT Wed Aug 31 2016

Some elevated fire weather concerns are possible over far western
and northern areas Thursday afternoon...and somewhat more
widespread Friday winds increase in those areas.
Breezy to windy over the plains the next couple days but min
humidities remaining above critical thresholds.


.CYS Watches/Warnings/Advisories...


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