Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Cheyenne Wyoming
545 PM MDT Wednesday Aug 20 2014

Short term...(this evening through Friday night)
issued at 330 PM MDT Wednesday Aug 20 2014

Current kcys radar loop shows showers and few thunder showers
developing over the mountains and the Cheyenne Ridge this
afternoon...and slowly moving eastward. Activity has been weak
with only a few isolated lightning strikes. Expect this activity
to continue through into late this afternoon and early this
evening while developing further east into the High Plains of
southeast Wyoming. Expect any thunderstorms to quickly diminish
around sunset.

Thunderstorm coverage will likely be lower on Thursday across most
of the forecast area as warmer air aloft moves into the area and
500mb heights increase through the day. A cold front boundary will
become more noticeable further north across Montana and northern
Wyoming as it slowly drifts southward through the day.
Therefore...expect the best coverage of showers and thunderstorms
to be across the mountains and well north of i80. Can not rule out
a thunder shower or two along the i80 corridor during the evening
hours. Temperatures will remain near normal and generally in the
upper 70s west of the Laramie range and low 80s to low 90s across
the eastern plains.

This persistent weather pattern will begin to change on Friday and
especially this weekend. Models indicate a pretty strong cold
front for this time of the year pushing southward into southeast
Wyoming. This front will stall sometime on Friday and be the main
focus for scattered to numerous showers and thunderstorms as an upper
level trough from western Canada move south and eventually
eastward into Idaho. Lowered maximum and min temperatures Friday and
Friday night and increased pop between 25 to 45 percent across the
High Plains...and near 70 percent over the mountains.

Long term...(saturday through wednesday)
issued at 330 PM MDT Wednesday Aug 20 2014

Both the GFS and European model (ecmwf) bring a shortwave through the area in
southwest wind flow Friday night into Saturday. European model (ecmwf) roughly 12
hours slower than the GFS...but both are in close agreement with
movement of first disturbance...then moving the main trough
through on Saturday/Saturday night. Just about everyone should see
showers/thunderstorms during the day Saturday with best chances
for the Panhandle Saturday night. Main shortwave through the area
by Sunday...with mainly isolated showers over the mountains.

Next cold front looks to move into the area Monday afternoon into
Tuesday. European model (ecmwf) a little colder than GFS in 700mb
temperatures...but not as bad as a few days ago. Probably need to
go colder with this setup. Discrepancy much greater on Tuesday
with the European model (ecmwf) forecasting 700mb temperatures of +4 to +6c and GFS
showing +10 to +12c.


Aviation...(for the 00z tafs through 00z Thursday afternoon)
issued at 539 PM MDT Wednesday Aug 20 2014

Isolated showers and thunderstorms will die off this
evening by around 04z. Gusty winds and small hail possible with
thunderstorms. Outside of thunderstorm activity this evening winds
will be light across southeast Wyoming and Nebraska Panhandle tonight.
Winds will generally remain light through Thursday but some gusts
to 25 miles per hour can be expected Thursday afternoon along and west of the
Laramie range. A few thunderstorms will be possible Thursday
afternoon and early evening.


Fire weather...
issued at 156 PM MDT Wednesday Aug 20 2014

Minimal fire weather concerns into early next week. Subtropical
moisture will remain over the area through the weekend with
showers and thunderstorms possible each day across southeast
Wyoming and western Nebraska. There is a good chance of wetting
rains by Friday and this weekend as thunderstorm coverage will be
higher. Temperatures will trend cooler by late this week and into
this weekend as a strong cold front for this time of the year
moves into the region late on Saturday.


Cys watches/warnings/advisories...


Short term...tjt
long term...claycomb
fire weather...tjt

National Weather Service Glossary of Abbreviations