Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 292215 CCA
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
411 PM MDT Mon May 29 2017

.SHORT TERM...(This evening through Wednesday night)
Issued at 200 PM MDT Mon May 29 2017

Latest water vapor imagery shows a stalled out upper low over the
Great Lakes area. Ridge of high pressure extends from northern
Arizona, through Nevada, up into Idaho and eventually up into
British Columbia this afternoon. CWFA under northerly flow on the
east side of this ridge. Surface analysis showing a weak cold
front extending out of the Great Lakes low extending southwestward
into northern Kansas and eventually into the western nebraska
Panhandle. IR imagery showing some cooling cloud tops this
afternoon over the Laramie Range. Radar showing most of the
convection south of WYoming with cell movement towards the south
southeast at 30-35MPH. Did get a few spits of rain outside a few
minutes ago here at the office, so will continue the low chance
PoPs we have going for this afternoon.

Latest SPC Mesoanalyst Page showing around 500 J/KG of CAPE in the
vicinity of these showers. May not see much today with a
temperature of 58 here at Cheyenne. Latest HRRR guidance shows
best chances for showers and maybe an isolated thunderstorm late
afternoon in the 21-00Z timeframe. After loss of daytime heating,
these showers really die out.

We stay in this pattern as upper low over the Great Lakes barely
moves through Tuesday. So I have to say more of the same tomorrow.
Upper ridge finally moves overhead for Wednesday. At the same
time, we start to see low level southeasterly flow returning east
of the Laramie Range that could aid in afternoon convection.
Followed latest ECMWF guidance that shows a scattered coverage of
showers Wednesday afternoon.

&&

.LONG TERM...(Thursday through Monday)
Issued at 200 PM MDT Mon May 29 2017

Thursday...Looks like the warmest day of the week to start off the
month of June, as a transitory ridge aloft prevails over our
counties. Models indicate enough low and mid level moisture to spark
isolated to scattered showers and thunderstorms in the afternoon
along and west of Interstate 25, with dry weather further east.

Friday...Slow moving trough aloft moves over our counties and with a
surface low expected to develop somewhere over our central or
eastern counties adding to low level convergence, we expect at least
isolated to scattered afternoon and evening showers and
thunderstorms, most numerous along and east of Interstate 25.

Saturday...Weak troughiness aloft prevails and with low level winds
from the east and southeast, drawing in low level moisture, expect
to see at least isolated afternoon and evening showers and
thunderstorms. Slightly Thursday...Looks like the warmest day of
the week to start off the month of June, as a transitory ridge
aloft prevails over our counties. Models indicate enough low and
mid level moisture to spark isolated to scattered showers and
thunderstorms in the afternoon along and west of Interstate 25,
with dry weather further east.

Sunday...Looks slightly drier as the ridge aloft becomes somewhat
more pronounced, limiting instability. Still looks like enough low
and mid level moisture for isolated afternoon and evening showers
and thunderstorms near the higher terrain and mountains due to
differential heating.

Monday...GFS shows the next potent trough aloft moving into Idaho
with diffluent flow aloft over our counties, aiding in lift to
produce isolated to scattered afternoon showers and thunderstorms
along and east of Interstate 25. Likely quite breezy with moderate
surface pressure gradients suggesting decent low level moisture
return from the south.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 409 PM MDT Mon May 29 2017

Wyoming TAFS...VFR, with isolated showers and thunderstorms at
Cheyenne and Laramie through 01Z.

Nebraska TAFS...VFR. Gusts up to 24 knots at Scottsbluff through
01Z.

&&

.FIRE WEATHER...
Issued at 200 PM MDT Mon May 29 2017

Recent rain and ongoing greenup will preclude any fire weather
concerns this upcoming week. Have a cold front along the east
slopes of the Laramie Range this afternoon that will continue to
kick off showers and thunderstorms over the mountains and adjacent
valleys. Slow warming trend through the week as a ridge of high
pressure builds into the area from the west and forces the weak
cold front east. Afternoon humidities look to stay above critical
levels each day with fair to good overnight recoveries.

&&

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

$$

SHORT TERM...GCC
LONG TERM...RUBIN
AVIATION...RUBIN
FIRE WEATHER...GCC


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