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Area forecast discussion 
National Weather Service Cheyenne Wyoming
1135 PM MDT Tuesday Jul 22 2014

issued at 835 PM MDT Tuesday Jul 22 2014

Regional radars showed isolated strong convection that produced
large hail northwest of Cheyenne earlier this evening has dissipated
as it moved into the southern Nebraska Panhandle. A cluster of
strong to severe thunderstorms was moving southeast along a instability
axis /sbcapes 2000-3000 j/kg/ toward the northern Nebraska Panhandle.
These storms should exit our northern Panhandle zones by midnight.
Another active tstorm cluster over southeast Montana should pass north of
our northern County Warning Area tonight. Updated zones to increase probability of precipitation over the
northern Panhandle and remove them over southeast Wyoming and southern
Nebraska Panhandle.


Short term...(this evening through Thursday night)
issued at 306 PM MDT Tuesday Jul 22 2014

Far less coverage of cumulus compared to the same time Monday which
surely is indicative of the warmer temperatures aloft. Surface moisture has
increased behind last nights weak boundary...with the 50f
isodrosotherm banked up to the Front Range. Am beginning to see some
weak convective development mainly in the vicinity of the northern
Laramie range...and some near the snowy and southern Laramie range
too. Mesoanalysis shows a pretty healthy capping inversion remains
in place...especially over the eastern plains. Expect this cap continue
to erode through the afternoon. The stronger cap will mean deep
convection will be a bit later in developing...which according to
the hrrr will be between 3-6 PM. Laramie County and the southern end
of Goshen/Platte counties look to see the best chance initially.
Will see additional development over northeast Wyoming dive southeast into
far east central Wyoming and the northern Nebraska Panhandle this
evening. It is this area where severe potential will be greatest
with sbcapes of around 2000 j/kg once the cap breaks. This
convection will dissipate by around sunset.

Attention then turns to a better chance for severe thunderstorm
development Wednesday afternoon. Thermodynamic profiles will be more
conducive for thunderstorm development Wednesday as middle-level
heights/temperatures fall with the approach of shortwave energy. This will
mean less of a cap and a likely earlier start to convective
initiation...which should occur over the snowy/Sierra Madre ranges by
midday. Prognosticated sbcapes over the eastern plains climb above 3000 j/kg
Wednesday afternoon and when combined with deep layer shear of 25-30
knots should be sufficient for some convective activity becoming
severe. Storms will spread onto the southeast Wyoming plains
Wednesday afternoon and into the western Nebraska Panhandle during
the evening. Areas over the southern Panhandle may be influenced a
bit too much by the cap...which may limit convective strength there.
Convection again will wane with loss of insolation.

First shortwave pushes through Thursday morning with a trailing
shortwave poised to move through Thursday afternoon. Instability axis
will be flattened and weakened by the initial shortwave. So expect a
less favorable environment for severe thunderstorm potential. Even
so...weak instability parameters will be sufficient for at least
some isolated convective potential. Thursday will be the warmest day
of the period with high temperatures that will again reach 90s at
most location and low triple digits over lower elevations of the
western Nebraska Panhandle.

Long term...(friday through monday)
issued at 306 PM MDT Tuesday Jul 22 2014

High pressure continues to remain dominant over The Four Corners
region but begins to erode to the south over the weekend. Fairly potent
trough of low pressure moves across the southern Canadian provinces
and brings a series of associated cool fronts across the area (the
strongest front will be Sat evening). Upslope flow looks to develop
by Friday afternoon as dew points approach the middle 50s over the Panhandle.
Could see some isolated showers and thunderstorms during this
time frame both Friday and Sat so have kept some slight probability of precipitation in the
forecast. The European model (ecmwf) is more moist than the GFS at this time and generates a
better coverage of storms each afternoon and evening. Temperatures begin to cool
to more seasonable levels in the low to middle 80s for Sunday...but the
ridge begins to build back into the area and temperatures should warm to
the middle 80s by Monday for southeastern Wyoming and near 90 for areas of
the Panhandle as 700 mb temperatures warm to near 15c.


Aviation...(for the 06z tafs through Wednesday evening)
issued at 1131 PM MDT Tuesday Jul 22 2014

VFR conditions will prevail through Wednesday. Increasing moisture
in the middle levels on Wednesday afternoon may result in another round
of showers and thunderstorms affecting the High Plains and klar.
MVFR visible are possible in the areas of heavier rainfall. There is a
slight chance of low ceilings early Wednesday morning across parts of
the High Plains...but there is too much uncertainty with the
location to add low ceilings to any terminal at this time.


Fire weather...
issued at 306 PM MDT Tuesday Jul 22 2014

Winds have held below critical thresholds thus far today...despite
relative humidities that have dropped below 15 percent. Some
isolated showers and thunderstorms are expected to develop over
Laramie County late this afternoon and over extreme east central
Wyoming and the northern Nebraska Panhandle this evening. Wednesday
will provide a better opportunity for afternoon and evening
thunderstorms across the district...some of which could potentially
become severe in locations east of the Laramie range. Drier and
breezier conditions will exist over western Carbon and Converse
counties on Wednesday. Conditions will likely become near critical
in these areas Wednesday. Thursday looks potentially more critical
over western Carbon and Converse counties and will likely need to
issue a headline in time. Afternoon and evening shower and
thunderstorm chances will continue Thursday and Friday mainly for
areas east of the Laramie range.


Cys watches/warnings/advisories...


short term...Hahn
long term...Finch
fire weather...Hahn

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