Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 181154

Area Forecast Discussion
National Weather Service Cheyenne WY
554 AM MDT Tue Oct 18 2016

.SHORT TERM...(Today through Thursday)
Issued at 222 AM MDT Tue Oct 18 2016

Today...Much less windy today with weaker gradients near the
surface. Fast westerly flow aloft continues with the next quickly
moving shortwave aloft moving into western Wyoming this afternoon,
spreading increasing cloudiness and isolated to scattered showers
across our Carbon county, and especially over the Snowy and Sierra
Madre Ranges. NAM and GFS MOS high temperatures close and have

Tonight...Shortwave aloft and its associated cold front and
baroclinic band pass overhead, producing scattered to numerous
showers, including snow showers over the mountains. Will need to
watch for accumulations over the I-80 summit, though fortunately,
the fast movement of the shortwave should limit snowfall

Wednesday...Cool, breezy and unsettled day with isolated to
scattered showers in the cyclonic flow aloft, with precipitation
north of a Rawlins to Kimball line. Relatively cool day and have
compromised between the NAM and GFS MOS maximum temperatures for

Wednesday night...Clearing skies and cold with sub freezing
temperatures areawide.

Thursday...Warming trend begins with brisk northwest flow aloft
overhead and lack of low and mid level moisture. Again, compromised
between the NAM and GFS MOS maximum temperatures.

.LONG TERM...(Thursday night through Monday)
Issued at 222 AM MDT Tue Oct 18 2016

A fairly benign synoptic pattern is setting up this weekend.

The models are in fairly good agreement with showing a weak upper
level ridge dominating the region with above normal temperatures.
Afternoon highs will generally be in the 60s west of the Laramie
Range with 70s east. Conditions will also continue to be dry with
the potential for critical fire weather conditions especially on
Saturday as a shortwave skirts across Northern Montana/Southern
Canada. This shortwave may create more breezy conditions during
the afternoon. The next chance of precipitation appears to be
around the middle of next week as more shortwave energy ejects
from the the trof in the Eastern Pacific.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 544 AM MDT Tue Oct 18 2016

The main concern with this taf issuance is the snow potential
between Laramie and Cheyenne this evening.

Latest water vapor loop was showing lift beginning to increase
across northeast Utah and northwest Colorado in response to the
right entrance region of the upper level jet. This lift is progged
to continue spreading east during the course of the day and move
towards KRWL/KLAR by around 21z. Instability is not too shabby
over this region, so we would not be surprised to see some
scattered rain/snow showers develop this afternoon. However, the
bigger concern appears to be this evening when the mid level
frontal boundary moves through. This boundary may yield to some
bands of snow showers which may be quite intense. We will have to
keep an eye on where these bands may develop later today. If they
develop over the KLAR airport then things may become slick. KCYS
may also see a mixture of rain/snow while the remainder of the
taf sites should see mostly rain.


Issued at 222 AM MDT Tue Oct 18 2016

Minimal concerns through Thursday based on projected
humidities. However, concerns increase again Friday and Saturday
with lowering humidities and gusty winds expected.




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