Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 270937

Area Forecast Discussion
National Weather Service Cheyenne WY
337 AM MDT TUE SEP 27 2016

.SHORT TERM...(Today through Thursday)
Issued at 247 AM MDT Tue Sep 27 2016

Today...Another picture perfect early autumn day with ridging aloft
keeping it warm and dry. Warmer than yesterday based on thickness
changes and 700 mb temperatures near 10 Celsius.

Tonight...Clear and mild in this warm airmass.

Wednesday...Ridging aloft moves overhead and with low level winds
becoming upslope (easterly), and 700 mb temperatures cooling to
near 8 Celsius, temperatures will be slightly cooler.

Wednesday night...Continued mild with increasing high level

Thursday...Flow aloft becomes southwest with a weak shortwave moving
across Wyoming. Surface trough runs north to south across our
western counties and with a slight increase in low and mid level
moisture, will see isolated showers and thunderstorms over the
mountains, specifically our Northern Laramie, Snowy and Sierra Madre
ranges. Temperatures still mild with 700 mb temperatures near 10

.LONG TERM...(Thursday night through Monday)
Issued at 247 AM MDT Tue Sep 27 2016

The main concern with this portion of the forecast is the track
of the upper level trof this weekend into next week.

Thursday night-Saturday:
Models are in pretty good agreement in showing the upper level
ridge pushing east into the plains while the upper level trof in
the pacific northwest begins to break the pattern down across the
Rockies. Before the trof enters the picture we should be looking
at mild temperatures with only a few isolated showers/thunderstorms
mainly in the higher terrain.

There is still some uncertainty on how this upper level trof will
amplify over the Rockies, but the latest NAEFS/GEFS ensembles are
not showing any signs of this being a significant trof. In fact,
most of the energy is progged to lift into the Northern Plains
which should keep most of colder air bottled up in Montana and the
Northern Plains next week. Until then, it will continue to remain
warm through most of the weekend with highs in the 60s west of the
I-25 corridor and 70s east. The models are showing a fairly strong
piece of energy moving through the trof and affecting our forecast
area on Sunday. This day looks to be our best shot of
precipitation at this time. However, we will keep our
precipitation chances fairly low at this time until confidence
increases with the timing of this shortwave energy. After this
shortwave and frontal boundary moves through, it could become
quite windy on Monday with the potential for critical fire weather
conditions. Then cooler temperatures will be moving into the area
Monday night and Tuesday with highs dropping about 10 to 15
degrees with afternoon highs only reaching the 50s west of I-25
and 60s east.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1134 PM MDT Mon Sep 26 2016

No real concerns during this TAF issuance. Wind speeds will
generally be 10kts or less from the northwest, and VFR conditions
will be the rule.


Issued at 247 AM MDT Tue Sep 27 2016

Minimal concerns based on projected humidities and winds, staying
above critical thresholds.


.CYS Watches/Warnings/Advisories...


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