Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 181117
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
517 AM MDT Sat Mar 18 2017

.SHORT TERM...(Today through Monday)
Issued at 228 AM MDT Sat Mar 18 2017

Today...Picture perfect Chamber of Commerce type day today with
ridging aloft and temperatures climbing into the upper 60s to near
80 degrees at lower elevations. Plenty of sunshine also expected.

Tonight...Another relatively mild overnight with decent low level
mixing...winds and warm airmass in place. Low temperatures above
freezing at lower elevations.

Sunday...Flow aloft becomes westerly and strengthens, inducing even
more downslope warming east of the mountains, with high temperatures
near or slightly warmer than Saturday highs. With increased low
level gradients and mid level winds, it will be breezy to locally
windy compared to today.

Sunday night...A cold front sags southward across our eastern
plains, perhaps up to the Laramie Range, with a few showers possible
after midnight north of a Douglas to Alliance line. Not as mild as
Saturday night in the cooler airmass.

Monday...Definitely cooler in the wake of the cold frontal passage,
though still mild for the first day of spring. For high
temperatures, compromised between the NAM and GFS MOS maximums.
Looks like enough low and mid level moisture for isolated to
scattered showers, most numerous north of a Douglas to Alliance line
where moisture will be deeper.

.LONG TERM...(Monday Night through Friday)
Issued at 228 AM MDT Sat Mar 18 2017

Minor shortwave traverses the area early Tuesday bringing a chance
of snow showers, with a quasi-stationary front just clipping the
northeastern 1/3rd of the forecast area. Models depict upper ridging
across SE Wyoming and western Nebraska through midweek with
unseasonably warm temperatures in the 60s and 70s east of the
Laramie Range, then we see an upper trough moving across late week
bringing down a cooler airmass Friday into Saturday with increasing
chances for showers. Some differences being depicted between the GFS
and ECMWF the late week with the ECMWF farther south with the main
upper low although not tapping deep cold air into our area, whereas
the GFS is showing a deepening low to our east bringing a colder
airmass southward across Wyoming and Nebraska by Friday. For now we
will stick with the ensemble blend for temperatures and
precipitation chances for late week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 517 AM MDT Sat Mar 18 2017

VFR category expected across SE WY and the wrn NE Panhandle
through 12Z Sunday. It will be breezy by afternoon across the
southern Panhandle and SE WY today, but nothing out of the
ordinary.

&&

.FIRE WEATHER...
Issued at 228 AM MDT Sat Mar 18 2017

Borderline criteria today for critical conditions across fire
weather zones 310 through 313 based on projected minimum
humidities from 15 to 20 percent and wind gusts of 20 to 25 mph.
In coordination with offices in Boulder and North Platte, we have
opted to issue a Red Flag Warning for Sunday afternoon for zones
310 through 313 as humidities will fall below 15 percent with wind
gusts in excess of 25 mph. Fortunately, humidities will increase
early next week, alleviating fire weather concerns.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning from 11 AM to 7 PM MDT Sunday for WYZ310.

NE...Red Flag Warning from 11 AM to 7 PM MDT Sunday for NEZ311>313.

&&

$$

SHORT TERM...SML
LONG TERM...ZF
AVIATION...JG
FIRE WEATHER...SML
HYDROLOGY...ZF



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