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Area forecast discussion 
National Weather Service Cheyenne Wyoming
318 PM MDT Friday may 22 2015

Short term...(this evening through Sunday night)
issued at 315 PM MDT Friday may 22 2015

Shortwave lifting northeast from northeast Colorado into western
Nebraska now with some clearing noted over eastern Colorado. Rain
and clouds have kept the airmass rather stable over the County Warning Area with
no storms noted so far. A few not out of the question out west for
the rest of the afternoon.

Should see showers become more scattered in nature tonight as the
initial wave lifts northeast and away from the area with a
minimum in coverage later tonight into Sat morning. Main upper
low currently south of Las Vegas Nevada will lift slowly northeast
through Saturday and arrive over northwest Colorado by late Sat
afternoon. Expect yet another round of convection to develop over
much of the County Warning Area Sat afternoon under surface upslope flow overtopped by
diffluent upper flow. Better instability still depicted by models
for a relatively short time Sat afternoon from far southeast Wyoming into the
southern Panhandle with convective available potential energy from about 1000-1500 j/kg. This along
with decent shear may lead to a few stronger storms though
convection may be elevated. Hail would be the main threat.

Fairly widespread rain and showers likely to continue Sat night
into Sunday as the upper low treks slowly northeast across the
County Warning Area. A drier northwest to westerly flow arrives late Sunday which
will decrease shower activity.

Temperatures remaining cool to mild given the clouds and precipitation with maximums
below seasonal norms.

Long term...(monday through friday)
issued at 315 PM MDT Friday may 22 2015

The main concern with this portion of the forecast is the timing
of the upper level waves moving through the region next week.

Monday-Monday night:
the models are in fairly good agreement is showing another weak
potential vorticity anomaly moving through the forecast area
Monday morning. This feature may trigger a few showers as it
passes through. Otherwise...this upper level trough should continue to
lift northeast into northern plains and take the bulk of the showers
east of the forecast area by midday. However...on its heels
another upper level trough is expected to spin into the northern
rockies. Ahead of this feature...there will be some upper level
diffluence which may be enough to initiate a few showers and
thunderstorms mainly west of the Laramie range. Elsewhere...we may
see some sunshine unless we see a stronger surface high build on
the Lee side of the Laramie range. Not real confident this will
occur...but there a few Canadian/Gem ensembles that are depicting
a little stronger surface high than what depicted on the
operational models. If the weaker high develops...we are looking
a little warmer temperatures with highs finally reaching the 60s
for much of the area. On the other hand...if the stronger surface
high plunges into the area...we may see another cloudy and cool
day with highs only reaching the 50s east of the Laramie range.

the models are in fairly good agreement in showing the next upper
level trough developing over the northern rockies and slowly
shifting eastward through the week. This feature will keep our
pattern pretty unsettled through much of the week. As a
result...we will have a good chance of showers and thunderstorms
each day. However...the good news is that this pattern should
favor a bit warmer temperatures compared to what we have seen this
past week.


Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1144 am MDT Friday may 22 2015

The main concern with this taf issuance is the timing of when the
showers will move out of the area this afternoon and low ceilings
again tonight.

Latest radar loop was showing drier air starting to filter into
the Nebraska Panhandle. However...this dry slot was beginning to
fill back in with more light rain during the last couple of volume
scans. We based our taf on potential drying this afternoon...but
we will have to watch radar trends to see if this dry slot can
remain in tact. Otherwise...MVFR ceilings will be the trend this
afternoon with gusty southeast flow. The next concern tonight
will be the potential for lower ceilings filtering back into the
area once again. Meanwhile...the upper level trough begins to move
into western Colorado from the Great Basin. This feature will
induce surface low pressure east of the Colorado Front Range
tomorrow morning. As a result...the surface flow should become
easterly and bring IFR ceilings to much of the area tonight with
the LIFR ceilings possible around cys. These low ceilings should
gradually climb after daybreak...but may hang on through the much
of the morning.


Fire weather...
issued at 315 PM MDT Friday may 22 2015

Widespread wetting rains expected through Saturday evening before
precipitation decreases and becomes more scattered into early next
week. No concerns seen into early next week with fuels moist and
weather conditions non-critical.


issued at 315 PM MDT Friday may 22 2015

Releases from grayrocks and continued runoff from area rainfall
will keep the Laramie river near Fort Laramie at minor flood stage
through the weekend. Rain likely to continue through late Saturday
then activity should decrease and be more scattered in nature into
early next week.


Cys watches/warnings/advisories...


long term...rec

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