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fxus65 kcys 220939 
afdcys

Area forecast discussion
National Weather Service Cheyenne Wyoming
239 am MST Fri Nov 22 2019

Short term...(today - sunday)
issued at 216 am MST Fri Nov 22 2019

A few lingering snow showers & patchy fog will impact areas mainly
along/south of I-80 early this morning. The most persistent fog is
occurring along I-80 between Laramie & Cheyenne. Wydot webcams are
indicating the fog is extremely dense in spots with visibility at/
below one quarter of a mile. A dense fog advisory is in effect til
5 am MST this morning, after which time forecast soundings suggest
considerable low-level drying as winds become more westerly. A bit
of a warming trend commences today with highs mainly in the upper-
30s to around 40. No precipitation is expected after 12-15z.

Warming further on Saturday with 700 mb temperatures climbing to +2 to
+4 deg c, particularly along the Laramie range. There is potential
for highs to get into the lower 50s over the plains. Our attention
then shifts to the potential for strong winds across the southeast
Wyoming wind corridors on Saturday night. The models show a rather
fast moving mid-level short wave tracking across eastern Montana &
the western Dakotas overnight. Surface pressure falls ahead of the
disturbance should lead to 700 mb/850 mb cag to cpr gradients climbing to
between 60-70 meters by 06z Sunday. The GFS suggests a broad swath
of 50-60 knot flow between 700-800 millibars, and lapse rates seem
quite steep for the time of day. High winds are definitely looking
more likely for arl/brx/vdw late Saturday night into early Sunday.
We did consider a watch, but given that we have nearly 2 full days
prior to the onset of the winds, decided to hold off for now. Wind
gusts may even approach warning criteria into the Cheyenne area if
subsidence spreads far enough east on Sunday.

Long term...(monday - thursday)
issued at 216 am MST Fri Nov 22 2019

Monday...as a shortwave trough aloft and cold front move over our
counties, it will be colder with scattered to numerous snow showers
in the moist atmosphere.

Tuesday...even colder with 700 mb temperatures near -10 celsius,
yielding maximum temperatures in the upper 20s and 30s. Chances for
snow will decrease during the day as low and mid level moisture
decreases.

Wednesday...the flow aloft backs to southwest and strengthens, with
temperatures still on the cold side. Looks like orographic snow
showers over our western counties in the moist flow aloft, dry
elsewhere.

Thanksgiving...slightly warmer, though with orographic snow showers
continuing across our western counties in the moist southwest flow
aloft.

&&

Aviation...(for the 06z tafs through late Friday evening)
issued at 1040 PM MST Thu Nov 21 2019

Southeast Wyoming terminals...expect a slow improvement of
conditions through early Friday morning with krwl likely returning
to VFR by 12z. Confidence for klar and kcys is a little lower since
models show this IFR/LIFR stratus deck and even some fog through 15z
Friday morning. Kept LIFR conditions with occasional 1/2 mile in fog
at kcys and gradual improvement at klar to MVFR ceilings around 2500 to
3000 feet above ground level. All terminals should be VFR with light winds by 18z
Friday.

Western Nebraska terminals...expect VFR conditions as the ceilings at
4000-6000 feet gradually dissipate leaving mostly clear skies
tonight. Can not rule out some near IFR ceilings and lower visible at ksny
through 18z Friday as the upper level system ejects eastward just to
the south of western Nebraska through early Friday morning.



&&

Fire weather...
issued at 216 am MST Fri Nov 22 2019

Despite periods of gusty winds, fire weather concerns remain quite
low with relative humidity values generally remaining above 30 percent during the
next several days.

&&

Cys watches/warnings/advisories...
Wyoming...dense fog advisory until 5 am MST early this morning for wyz116-
117.

NE...none.
&&

$$

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