Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 222341
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
541 PM MDT Thu Jun 22 2017

.SHORT TERM...(This evening through Saturday Night)
Issued at 147 PM MDT Thu Jun 22 2017

Tonight...Agree with the Storm Prediction Center moving the marginal
and slight risk areas further north this afternoon and evening as
both the NAM and GFS now show the area of thunderstorms developing
further north. Increased POPs a bit this evening and overnight per
the model progs and mentioned a few severe storms possible with
large hail and damaging winds through the evening as CAPES progged
to range from 1000 to 1500 J/kg with shear around 55 knots. Models
keep showers around after midnight over our southeast counties, thus
will do so in the gridded forecasts as well.

Friday...Relatively cool and more stable day, thus no showers or
thunderstorms expected. Stuck close to guidance high temperatures
from the NAM and GFS.

Friday night...A cool and mostly cloud free period with most
temperatures falling into the 40s.

Saturday...A bit warmer based on 700 mb temperatures and
thicknesses. Continued dry in most locations due to stable airmass
in place, though the northern Laramie Range may see isolated
thunderstorms late in the day.

Saturday night...Continued cool and mostly dry with northwest flow
aloft and cool surface high pressure to our east.

.LONG TERM...(Sunday through Thursday)
Issued at 200 PM MDT Thu Jun 22 2017

Fairly quiet pattern Sunday into early next week as a ridge of high
pressure aloft builds eastward across the central Rockies. By
Tuesday on the GFS we note a strong upper low dropping southeast
across Montana bringing a cold front southeastward before going
quasi- stationary across southeast Wyoming on Wednesday. Only
chances being advertised at this time for showers/thunderstorms
will be for Tuesday afternoon across the northern Nebraska
Panhandle and east central Wyoming as a fairly deep layer of dry
air is projected to cut underneath the upper low across the rest
of our area. The ECMWF is less robust with the upper low over
Montana Tuesday into Wednesday, and with a less favorable
placement of the upper jet doesn`t bring a modifying cold front
southward into our area. Ensembles are also less robust on chances
for showers and thunderstorms through the extended next week...so
for now kept PoPs low Tuesday into Wednesday across the northeast.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday afternoon)
Issued at 540 PM MDT Thu Jun 22 2017

In general, VFR conditions are expected to prevail through the TAF
period. A stray shower/thunderstorm cannot be ruled out during the
next few hours, but overall confidence is decreasing as convection
has had a difficult time getting going this afternoon. We opted to
remove the VCTS/VCSH this evening, but will monitor closely. There
may be a brief period of MVFR ceilings with any developing showers
or storms.

&&

.FIRE WEATHER...
Issued at 147 PM MDT Thu Jun 22 2017

Minimal concerns based on projected winds and
humidities.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

$$

SHORT TERM...RUBIN
LONG TERM...JG
AVIATION...CLH
FIRE WEATHER...RUBIN


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