Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 222053

Area Forecast Discussion
National Weather Service Cheyenne WY
253 PM MDT Tue May 22 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 226 PM MDT Tue May 22 2018

Main concern this evening is the convection evolution tonight.
Latest radar loop was showing some convection developing mainly
west of the Laramie Range. However, there is a good cluster of
storms developing along the Pine Ridge. Latest water vapor loop
was showing the low level clouds tracking from southeast to
northwest. Meanwhile, we are starting to see more of the organized
clusters are starting to track north. Based on this trend, we
would expect the convection to mainly track north this afternoon.
However, we would expect things to evolve further east in response
to the influx of the higher thete air (800-700mb). A few of these
storms may be able to become severe this afternoon based on the
good updraft strength and marginal 0-6km shear around 30 to 35
kts. In addition, we are looking at the potential for heavy
rainfall within some of the stronger storms as the storms slowly
develop eastward. The majority of this convection should lift
north over the forecast area overnight.

Another round of convection is expected to develop over the area
tomorrow along and east of the Laramie Range. Shear potential
looks to be a bit more favorable tomorrow, but the best potential
for convection looks to be in the Panhandle as a potential
vorticity anomaly swings through the area.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 226 PM MDT Tue May 22 2018

Warm and mainly dry weather expected across the CWA Friday through
Saturday as an upper ridge shifts east across the area. There
could be a bit of convection both afternoons over the higher mtns
but warmer mid level temps should keep them limited. An upper low
over the western CONUS will then move slowly towards the CWA
Sunday and Monday and will bring an increase in showers and tstms
both days as weak impulses rotate around this low and over the
region. Best coverage looks like it will be on Monday, aided by
some diffluent upper flow northeast of the upper low. It will be
warm both Friday and Saturday then temperatures trending down some
Sunday and Monday.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1152 AM MDT Tue May 22 2018

Main concern on the aviation desk today will be the coverage of
thunderstorms starting 21Z west of Interstate 25 (possibly
affecting Rawlins and Laramie), Cheyenne 21Z-00Z, Scottsbluff,
Alliance and Sidney 00Z-04Z. Right now have a period of MVFR
visibility at all airports except Sidney (where coverage is
expected to be less) during those timeframes. Otherwise, only
other consideration would be lower visibility in fog for Alliance
and Sidney early Wednesday morning, but right now confidence is
not high enough to go below MVFR on visibilities.


Issued at 226 PM MDT Tue May 22 2018

Fire weather concerns will continue to be on the low side during
the next couple of days due to the potential for more convection.
We will have a drying out period on Thursday and Friday which will
cause afternoon humidity values to drop into the teens, but
greenup is expected to persist through the weekend.




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