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Area forecast discussion 
National Weather Service Cheyenne Wyoming
921 PM MDT sun Oct 4 2015

issued at 915 PM MDT sun Oct 4 2015

Decided to issue a dense fog advisory for the southern Laramie
range and adjacent foothills (zones 116 and 117). Wydot sensors
from Buford to The Summit show visible of 300-500 getting some
pretty dense fog. Very moist southerly winds will continue
through 12z so not expecting much improvement in conditions
through sunrise. Hrrr shows fog spreading eastward to Cheyenne
through the remainder of the night...thus will likely have to
monitor observation around Cheyenne.


Short term...(this evening through Tuesday night)
issued at 300 PM MDT sun Oct 4 2015

Surface analysis shows a stationary front from near Rapid City
to north of Torrington to near Laramie this afternoon. Widespread
low clouds blanketing southeast Wyoming and Nebraska Panhandle as
upsloping southeast winds continue. A little warmer today over
Saturday with 1 PM reports ranging from the upper 40s/low 50s east
of the Laramie range to the upper 50s out by Rawlins. Water vapor
imagery showing our next low pressure system to impact our area
over Southern California at this time.

Another repeat of fog/stratus tonight as southeasterly winds
continue. Lower level winds do begin to shift more southerly after
12z Monday...then become southwesterly late morning. Thinking that
fog/stratus will break up tomorrow morning instead of hanging in
like the past couple days.

Both GFS and European model (ecmwf) in good agreement with movement of low over
Southern California. Very slow movement tonight and Monday morning
of the low should allow for a mainly dry day across southeast
Wyoming/Nebraska Panhandle. By Monday evening though...we begin to
see upper level diffluence across our western zones and
southwestern Wyoming/western Colorado. Should see showers and
isolated thunderstorms developing out west possibly as early as
late afternoon tomorrow...but more likely Monday evening.

Differences in low movement Tuesday with the GFS further north
with the low. GFS showing low moving into southern Utah. Should
the GFS solution hold true...many areas would see wetting rains
here in southeast Wyoming Tuesday afternoon. Both show the I-80
corridor picking up the best chance for showers. Did maintain or
increase probability of precipitation for Tuesday with this agreement.

Long term...(wednesday through sunday)
issued at 300 PM MDT sun Oct 4 2015

Wednesday...relatively quiet day as the northern stream shortwave
trough aloft moves to our east. Perhaps isolated showers and
thunderstorms near our southern mountains though with limited low
and middle level moisture...dry conditions will prevail.

Thursday...dry and cooler in the wake of a weak cold front that will
stabilize the atmosphere.

Friday...continued dry with limited low and middle level moisture under
northwest flow aloft. Warming trend begins as the airmass moderates.

Saturday/Sunday...warming trend continues as a ridge aloft moves
overhead and then with zonal flow developing on Sunday...inducing
strengthening surface Lee troughing.


Aviation...(for the 00z tafs through 00z Monday evening)
issued at 539 PM MDT sun Oct 4 2015

IFR ceilings are expected to continue at cys through the evening. Kept
MVFR ceilings across the Panhandle through 06z...although brief
periods of IFR will be possible. Ceilings will then begin to lower
after 06z as low level saturation increases. Winds through the
period will be mostly less than 15 kts.


Fire weather...
issued at 300 PM MDT sun Oct 4 2015

Minimal fire weather concerns as a cool and moist airmass remains
over the area. Southeasterly upslope winds will bring low clouds
and fog for many areas east of the Laramie range this afternoon
through Monday morning. Next low pressure system moves into
western Colorado Monday afternoon for increased chances for
showers and thunderstorms late Monday afternoon through Wednesday
morning. Best chances for wetting rains appears to be Tuesday
afternoon through Tuesday evening.


Cys watches/warnings/advisories...
Wyoming...dense fog advisory until 8 am MDT Monday for wyz116-117.



short term...gcc
long term...Rubin
fire weather...gcc

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