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Area forecast discussion 
National Weather Service Cheyenne Wyoming
338 PM MDT Monday Apr 27 2015

Short term...(this evening through Wednesday night)
issued at 300 PM MDT Monday Apr 27 2015

Stratus continues to plague southeast Wyoming locations along and
east of the Laramie range today...with some sunshine peaking
through the clouds across the Panhandle and further west in the
high country as drier air filters into these locations. A few
showers are developing off the higher peaks this afternoon and
expect light showers to become more widely scattered in coverage
through the afternoon as the deformation band remains overhead in
advance of an upper level trough approaching from the northwest.
Northeasterly surface flow will add in an upslope element to the figure much of the activity will originate off
north-northeast facing slopes of terrain features and move to the
northeast. With colder air aloft...expect precipitation type to be snow
in the mountains and would not be surprised to see some snow mix
down into the high valleys and perhaps the Wyoming plains at times
as well. The upper trough will move over the forecast area tonight
and southeast of the area on Tuesday. Should see showers linger
overnight especially from southwest to northeast across the area
underneath middle and upper level forcing and continued upslope flow.
Cant rule out patchy areas of fog overnight as well...first
developing in the high valleys out west as winds lighten and temperatures
cool and then out east within the continued very moist boundary

Tuesday and Wednesday will see increasing temperatures back into the
50s/60s and then 60s/70s respectively as a positively tilted
ridge moves overhead through this time. Dry conditions will
prevail under partly cloudy skies. A shortwave trough moving into
the Pacific northwest Tuesday night and Wednesday will deepen the leeside surface
trough...with winds along and west of the Laramie range increasing
in response. Not expecting any significant wind speeds...but
gusts of 30 to 35 miles per hour are certainly a high likelihood in the wind
prone areas through Wednesday night.

Long term...(thursday through sunday)
issued at 300 PM MDT Monday Apr 27 2015

The weather in the extended period will be quite nice with above
normal temperatures and only slight chances of showers/thunderstorms during the
afternoons and evenings. A shortwave is prognosticated to move across the
Canadian border on Thursday with a weak front pushing over areas to
the east of the Laramie range during the day. The GFS shows some
weak SBCAPE (100-300 j/kg) during the could see isolated
high based storms. Zonal flow aloft will remain in place through
the weekend with 700mb temperatures of 6-8c. This will translate into
highs in the upper 60s and 70s across the plains. The European model (ecmwf)
differs from the GFS in showing a more scattered coverage of afternoon
showers on Friday and especially Sat. Have slight chance probability of precipitation on Sat
afternoon over much of the County Warning Area. A cold front will approach the region
by Sun night and Monday morning with a shortwave moving over the
northern plains. The models are hinting at cooler temperatures by early
next week with upslope developing along with more widespread


Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1152 am MDT Monday Apr 27 2015

IFR ceilings will continue at cys through around 21z...with MVFR and
VFR ceilings elsewhere through the afternoon. With light winds
overnight...fog is expected to develop at cys and lar in the hours
before sunrise on Tuesday. Also included MVFR visible at rwl where
confidence is not as high for fog development. Winds through the
taf period will generally be less than 10-15 kts.


Fire weather...
issued at 243 PM MDT Monday Apr 27 2015

No fire weather concerns this week due to recent wetting rainfall.
Isolated rain showers are expected to continue through tonight as
another weak system approaches from the northwest. Drier
conditions and warmer temperatures will return by midweek with
daytime relative humidities trending lower but remaining above 15
percent through this time. Showers and thunderstorms will return to the
area by late this week as another series of Pacific disturbances
move across the forecast area.


Cys watches/warnings/advisories...


Short term...rjm
long term...zf
fire weather...rjm

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