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Area forecast discussion 
National Weather Service Cheyenne Wyoming
614 am MDT Wednesday Aug 20 2014

Short term...(today through friday)
issued at 350 am MDT Wednesday Aug 20 2014

Initial shortwave trough aloft moves across our counties
early in the day...with a weaker...secondary shortwave trough
approaching our western counties in the late afternoon. Some low
level drying noted in the wake of the morning shortwave trough...
though it appears there will be enough low and middle level moisture
this afternoon to spark isolated to scattered showers and
thunderstorms...most numerous west of Interstate 25.

Tonight...showers and thunderstorms ending in the evening with the
loss of daytime heating and absence of any other lifting mechanisms.

Thursday...southwest flow aloft continues and with adequate low and
middle level moisture in place...will see isolated late day
thunderstorms along and west of a Lusk to Cheyenne line.

Thursday night...weak cold front enters from the north...though with
minimal low and middle level moisture...rain chances will be slim. Late
in the night...will go with isolated showers after midnight east of
a Douglas to Sidney line in low level convergence boundary.

Friday...increased chance for showers and thunderstorms over
Thursday as a negatively tilted shortwave trough aloft propagates
across our western Nebraska counties...with enhanced southeast low
level winds advecting moisture in...and providing mechanical lift to
help generate thunderstorms.

Long term...(friday night through tuesday)
issued at 350 am MDT Wednesday Aug 20 2014

00z medium range guidance are consistent in swinging an upper
trough through the northern rockies over the weekend. This is an early
indication of the seasonal pattern change that will continue over
the next few months. Saturday still looks relatively warm in the
prefrontal air mass...especially over the eastern plains. Models forecast
1000-1500 j/kg ahead of the front Saturday afternoon. The
favorable thermodynamic profile combined with the proximity of rrq
of a jet streak suggests at least the possibility of a few
stronger storms over the plains Saturday afternoon. Of
course...much of this scenario is dependent upon the current
timing of late Saturday and Saturday evening frontal passage. Convection
will turn more showery in the wake of the front Saturday night.
Sunday will be noticeably cooler Post-frontal with highs only
reaching 70s at most locations. Left mostly shower chances along
with isolated thunder mention going for Sunday. This will depend upon
just how much clearing occurs. Temperatures return to more
seasonal values for Monday-Tuesday timeframe. Hard to remove mention of
daily afternoon and evening convection early next week as
persistent southwest flow ejects impossible to time embedded
shortwaves. Precipitation definitely wont be an all day occurrence...but
cant rule out its possibility mainly during the afternoon and
evening hours. The pattern looks to trend drier for the latter
half of next week.


Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 613 am MDT Wednesday Aug 20 2014

The main challenge with the taf forecast focuses on convective
timing both initially this morning and again this afternoon.
Morning radar returns shows a batch of light rain showers lift
northeast across the area. Krwl had dropped to MVFR very briefly
earlier this morning...but have remained VFR since. Have kept VFR
conditions in place everywhere through the period. This initial batch
of showers will exit the area by mid-morning...with another round
of isolated afternoon and evening showers/storms possible. Have added
thunderstorms in the vicinity to most sites to capture this idea this afternoon. This
activity will dissipate between 02-03z.


Fire weather...
issued at 350 am MDT Wednesday Aug 20 2014

Humidities and winds will remain below critical thresholds the
next few days...thus minimal fire weather concerns.


Cys watches/warnings/advisories...


Short term...Rubin
long term...Hahn
fire weather...Rubin

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