Scientific Forecaster Discussion
Return to Local Conditions & Forecast
Area forecast discussion
National Weather Service Cheyenne Wyoming
509 am MDT Sat Apr 19 2014
Short term...(today through monday)
Issued at 256 am MDT Sat Apr 19 2014
An upper level disturbance will move over the forecast area this
afternoon...with surface winds veering to the southeast across the
plains and increasing in strength. Dew points will increase into the
upper 30s to low 40s across the plains in this moisture advection
pattern with weak instability prognosticated for the afternoon. High cloud
cover will keep temperatures on the cool side and thus instability will
be low...but the combo of upper support and weak instability will
support a good chance for rain showers with isolated thunderstorms
this afternoon especially for the mountains and nearby plains.
Looks as though areas from the Laramie range to the I-25 corridor
could see the best chance for storms outside the mountains where
NAM paints instability as high as 200 j/kg within the
best...albeit relatively weak...moisture convergence zone. Should
see wetting rains with this activity as precipitable water values
will increase to between one half and three quarters of an inch
through the afternoon. Convection will diminish through the
evening as the upper wave weakens and moves east.
For Sunday...a cold front associated with a shortwave moving across
US/Canadian border will drop south across the eastern plains in the
afternoon. Temperatures will warm into the upper 60s to upper 70s in the
lower elevations ahead of the front...with lifted indice's dropping to around
zero. Timing of the front could favor development of afternoon
showers and a few weak thunderstorms...especially along the Laramie
range and Cheyenne Ridge where low level forcing and instability are
maximized. A weak disturbance moving overhead from the west will
trigger a few thunderstorms over the mountains in the afternoon as well.
Surface high pressure will build in behind the front for Monday with maximum
temperatures expected to be about 5f cooler. Surface winds will veer back to
the south-southeast in the afternoon and so may see a few rain
showers develop within the convergence zone vcty Laramie range. Cooler
surface temperatures and warm air advection aloft due to a building upper ridge from the west
will minimize instability and thus tstorm chances.
Long term...(monday night through friday)
issued at 256 am MDT Sat Apr 19 2014
Pretty strong low pressure system in the extended expected to
bring very strong winds and some precipitation chances to the County warning forecast area. These
are the challenges in the long term.
For Monday night into Tuesday...upper level ridging builds into
the area with 700mb temperatures climbing from +4c Monday
afternoon up to +8c Tuesday afternoon. Looks like a pretty warm
day Tuesday with 80s returning to the Panhandle and upper 60s/low
70s for areas west of the Laramie range.
A strong upper level low pressure system moves into southern
Nevada to northern Utah Tuesday afternoon...then into western
Wyoming Tuesday night. Ahead of this low...700mb winds become
quite strong with the GFS show 50kts at 700mbs Wednesday morning.
700mb Craig to Casper height gradient at 60mtrs Tuesday night and
increases to 70mtrs during the morning Wednesday. Will need to
monitor this for possible wind headlines during this
time frame...at least for our wind prone areas.
Cold front associated with this low looks to move into the area
Wednesday afternoon with 700mb temperatures falling to -6c across
Carbon County Wednesday night. For now...best chances for precipitation
look to be the mountains and areas west of the Laramie range.
Areas east will be impacted by downsloping winds...so kept these
Concerns for wind headlines shifts east into the Panhandle
Wednesday night as GFS 850mb winds increase to 40kts. Should be at
least Wind Advisory criteria out there...continuing into Thursday
Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 506 am MDT Sat Apr 19 2014
Confidence a little higher for thunderstorms to develop across southern
Wyoming and the southern Panhandle this afternoon and evening.
Latest hrrr forecast showing convection developing as early as 18z
and persisting through 00z for kcys and krwl. Followed this
guidance in tafs. Convection could make it to kbff after 00z...but
will hold off for now on thunderstorms.
issued at 256 am MDT Sat Apr 19 2014
Temperatures will be cooler today with higher humidities and less
wind. Chances for wetting rains and isolated thunderstorms will
increase this afternoon and will continue through the evening as a
weather disturbance tracks across the region. Another cold front
will drop south across the area on Sunday and will bring a slight
chance for afternoon showers and thunderstorms...especially for the
mountains and areas near the Colorado border. After a cooler day
Monday...expect warmer and drier conditions for Tuesday with windy
conditions possible for Wednesday.