Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Cheyenne Wyoming
529 am MDT Thursday Sep 18 2014
Short term...(today through saturday)
issued at 330 am MDT Thursday Sep 18 2014
Predawn water vapor loop depicted a upper ridge axis from The Four
Corners to the northern Rocky Mountains. Remnant low from Tropical
Depression Odile was drifting northeast across Southeast Arizona. A large
plume of subtropical moisture expanded east across the Southern Plains
and lower MS valley. A stationary surface front from northeast Wyoming
to southwest Kansas separated dew points in the 50s east from 30s west.
Both the hrrr and sref models forecast weak upslope and l0w level
moisture convergence from northwest Kansas into western NE...with
low stratus and patchy fog developing between 3 am and 6 am for
much of the NE Panhandle. The fog and stratus should dissipate by
A blend of the 00z short range model guidance forecasts the upper ridge
to the west to be situated over the Front Range this afternoon and
central/southern Great Plains Friday morning as a upper trough
traverses the northern tier of the nation. A Lee surface trough and
middle level thermal ridge juxtaposed over the County Warning Area will provide and
dry and quite warm afternoon with 700mb temperatures topping out
around 15c. Low elevations can expect highs in the 80s...with 90
to 95 degrees for the plains of eastern Wyoming and western NE. These
readings will flirt with record territory for some locations. South
to southwest winds will be breezy at times...especially for parts
of western NE and south central Wyoming.
The leading edge of Pacific moisture will encroach on south central
Wyoming later tonight as a weak cold front moves into western Wyoming.
Isolated showers/thunderstorms will be possible over western Carbon County.
Friday will be more unsettled as the front advances east through the
County Warning Area...with isolated to scattered showers/tstorms. It will turn cooler
as 700mb temperatures fall to around 11c. Winds will shift to
northwesterly following frontal passage. Convective precipitation will taper
off Friday night with the passage of the upper trough and advection
of drier stable air from the west.
Upper ridge reasserts itself over The Four Corners Saturday. Weak
upslope and instability may trigger a few showers or thunderstorms over
the southern mountains in the afternoon. It will be 5 to 10 degrees
cooler than Friday with 700mb temperatures around 7c. Highs will
be in the 70s to lower 80s lower elevations with 50s and 60s for
the high country. Northeasterly winds will be be breezy at times
during the afternoon across portions of the NE Panhandle.
Long term...(saturday night through wednesday)
issued at 230 am MDT Thursday Sep 18 2014
Saturday night/Sunday...isolated Saturday evening thunderstorms over
the snowy and Sierra Madre ranges...otherwise dry Saturday night.
Next shortwave trough aloft moves over western Utah Sunday afternoon
spreading clouds and showers and isolated thunderstorms across our
southern counties south of a Rawlins to Scottsbluff line.
Monday...shortwave trough prognosticated to traverse across our counties in
the afternoon...spawning scattered to numerous showers and isolated
afternoon and evening thunderstorms...most numerous west of Interstate
Tuesday...as the shortwave trough is prognosticated to move east of our
counties...will see a corresponding decrease in shower and thunderstorm
coverage in the afternoon and evening.
Wednesday...flow aloft becomes southwest in advance of the Great Basin
large scale trough...and with minimal low and middle level moisture...
showers and thunderstorms look isolated at best across our counties.
Aviation...(for the 12z tafs through 12z Friday morning)
issued at 526 am MDT Thursday Sep 18 2014
Nebraska tafs...areas of IFR ceilings and visibilities in low
clouds and fog through 9 am...otherwise VFR prevails. Wind gusts
of 20 to 30 knots late this morning and this afternoon.
Wyoming tafs...VFR prevails. Wind gusts of 20 to 30 knots late
this morning and this afternoon.
issued at 230 am MDT Thursday Sep 18 2014
Warm and dry conditions will continue today with lowest humidities
from 15 to 25 percent during the afternoon. Wind gusts will peak
around 20 miles per hour. Chances for showers and thunderstorms will return
Friday and Friday night as the remnant circulation from Odile moves
across southern Colorado and weak front passes through southeast
Wyoming and western Nebraska. Saturday will be dry and cooler as
high pressure dominates the districts. A slow moving Pacific upper
low and subtropical moisture will result in scattered showers and
thunderstorms Sunday through Tuesday...with slightly cooler than