Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 221718
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1118 AM MDT SUN MAY 22 2016

.SHORT TERM...(Today through Tuesday)
Issued at 245 AM MDT Sun May 22 2016

Today...Cold front slowly moving west to east across our counties
this morning with considerably drier low level air in its wake with
dewpoints falling from the 50s to the 30s. By this afternoon, the
cold front will reside across our far eastern counties of the
western Nebraska panhandle with decent low level convergence across
the front. With adequate low and mid level moisture, expecting
isolated thunderstorms to erupt this afternoon across all our
counties with the greatest coverage of scattered thunderstorms near
the baroclinic band and cold front over far eastern Wyoming and
western Nebraska. Progged shear and cape suggests isolated storms
over our far eastern counties from Chadron to Sidney may approach
severe levels with at least small hail and wind gusts to 55 mph,
with more garden variety thunderstorms further west.

Tonight...Drier and more stable air advects in on west low level
winds with thunderstorms ending in the evening.

Monday...Considerable decrease in low and mid level moisture will be
less fuel for thunderstorm formation. However, with enough low level
convergence across our far southeast counties of Wyoming and the
nearby Nebraska panhandle, expect isolated afternoon and evening
thunderstorms mainly south of a line from Laramie to Chadron with
weaker thunderstorms due to minimal shear and instability.

Monday night...Again expect thunderstorms to dissipate mostly in the
evening with clearing skies after midnight.

Tuesday...Southwest flow aloft continues. Will see a slight increase
in low and mid level moisture thus will see a slight increase in
afternoon and evening thunderstorm coverage, especially along and
east of Interstate 25.

.LONG TERM...(Tuesday night through Saturday)
Issued at 325 AM MDT Sun May 22 2016

There is good agreement with the 00Z medium range models indicating
a prolonged period unsettled weather through the extended forecast.
A nearly stationary upper trough from south central Canada through
the Intermountain West and California Tuesday night will swing east
across the Rockies and high plains Wednesday through Thursday.
Another Gulf of Alaska upper low will drop southeast into the
Pacific Northwest...carving out a long wave trough over the western
half of the CONUS by the end of the week.

A fairly active southwest flow aloft will bring periodic shortwaves
across the CWA...with most of the convection diurnally driven.
Instability will be sufficient for widely scattered thunderstorms...
but do not anticipate severe weather at this time. Model QPF progs
between a tenth and a quarter inch most days...with heavier amounts
possible over the plains where low level moisture will be more
prevalent. Mild temperatures Wednesday will cool to below seasonal
normals for the remainder of the week. Daytime high temperatures
above 9000 feet where most of the snowpack remains will hold in
the 40s with nighttime lows falling into the upper 20s and lower
30s. The cooler temperatures should slow the rate of snowmelt from
these higher elevations.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1116 AM MDT Sun May 22 2016

Using latest HRRR guidance for this TAF package. Better chances
for convection today over Saturday. Went with VCTS wording in TAFs
through the evening hours before convections wanes late this
evening.

&&

.FIRE WEATHER...
Issued at 245 AM MDT Sun May 22 2016

No fire weather concerns based on projected winds and humidities.

&&

.HYDROLOGY...
Issued at 245 AM MDT Sun May 22 2016

The Upper North Platte River at Saratoga, Wyoming will rise to
above minor flood stage Sunday night...and Sinclair, Wyoming by
noon Monday. Cooler temperatures today through much of the
upcoming week will slow the rate of mountain snowmelt. High
temperatures above 8000 feet will range from 45 to 55 degrees
with lows from 25 to 35 degrees.

Minor to moderate flooding will continue along the Lower North
Platte River near Fort Laramie, Wyoming...and Henry...Mitchell
and Minatare, Nebraska through the upcoming week. Minor flooding
is also forecast for the Laramie River at Laramie, Wyoming. Basin
averaged amounts from widely scattered showers and thunderstorms
the next several days will average between a tenth and a quarter
inch.

&&

.CYS Watches/Warnings/Advisories...
WY...None.
NE...None.
&&

$$

SHORT TERM...Rubin
LONG TERM...Jamski
AVIATION...GCC
FIRE WEATHER...Rubin
HYDROLOGY...Jamski



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