Area Forecast Discussion
Issued by NWS Cheyenne, WY

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218
FXUS65 KCYS 190111
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
711 PM MDT MON JUL 18 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 335 PM MDT Mon Jul 18 2016

The primary focus of this forecast deals with trying to pin down
timing, strength and coverage of thunderstorms later this
afternoon/evening. Latest satellite pix depict shortwave energy
rotating northeast around the periphery of strong high located
ovr the central plains. Convection has been fairly subdued thus
far, likely struggling to overcome 0-6 km shear that has been not
quite strong enough. This will be changing as these storms push
into a much more favorable environment across the western Nebraska
Panhandle over the next several hours. 21Z SPC mesoanalysis shows
SBCAPES in excess of 3000 j/kg with a cap that continues to erode
with the approach of the upstream shortwave. Expect additional
development/intensification as these storms roll into the
panhandle this evening. Favorable supercell composite along with
deep layer shear suggest that storms will be discrete initially
and merge into a multicell linear structure this evening. Large
hail, damaging winds and very heavy rain will be the primary
hazards. Speaking of heavy rain, contemplated a flash flood watch
for the panhandle, but storms have been moving at a fast enough
clip to hold off and 12z model output did not lend to certainty.
Will keep heavy rain mention in the forecast and will continue to
monitor. This activity will move east of the area by around 8 PM
or so.

Heights will continue building on Tuesday as the upper high
strengthens across the central plains. This will produce very hot
temperatures especially for elevations below 5000 feet. Expect
Chadron/Alliance to be close to, if not reach triple digits.
Can`t rule out an isolated shower or rogue thunderstorm Tuesday
afternoon/evening, but coverage/strength would be limited.

Temperatures will warm a few degrees for Wednesday, which will
likely be the hottest day of the week. Low 100s will certainly be
in the cards for northern Nebraska Panhandle locations. Warm
mid-level temperatures will cap the eastern plains. However, will
likely begin seeing a surge of monsoonal moisture into the
southeast Wyoming mountains by Wednesday afternoon.

.LONG TERM...(Wednesday night through Monday)
Issued at 335 PM MDT Mon Jul 18 2016

The large upper high centered over the southern plains mid-week
will shift westward into the desert southwest over the weekend
then hold over that area into early next week. Monsoonal moisture
initially moving across the region will keep chances for mainly
late day convection going through Friday then diminish over the
weekend as the upper flow turns more westerly then northwesterly
over the weekend and cuts off the moist flow. A decent shortwave
may enhance convection again Sunday before drying again on Monday.
Rather hot temperatures expected through Friday before lowering
closer to seasonal averages over the weekend as thicknesses lower
some in response to shortwave energy moving across south-central
Canada.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 711 PM MDT Mon Jul 18 2016

Scattered showers and thunderstorms will continue across the
southern Nebraska panhandle through 03Z, with MVFR vsbys in
moderate rain and gusty erratic winds the main impacts to the
terminals. Breezy west-southwest winds will occur for Tuesday,
with more of an isolated threat for showers and storms in the
afternoon.

&&

.FIRE WEATHER...
Issued at 335 PM MDT Mon Jul 18 2016

A typical late July pattern ongoing with a very hot week ahead
for lower elevations of SE Wyoming and W Nebraska. These areas
will see scattered shower and thunderstorm activity this
afternoon/evening, some of which could become severe containing
large hail and damaging winds. Otherwise, will see the first push
of monsoonal moisture into the southeast Wyoming mountains ramping
up this week. This will produce better chance for moisture for
mountain locations. Minimum humidity values will drop below 15
percent this week, but wind gusts will remain below critical
thresholds of 25 mph.

&&

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

$$

SHORT TERM...CAH
LONG TERM...RE
AVIATION...RJM
FIRE WEATHER...CAH



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