Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 251126
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
526 AM MDT Tue Jul 25 2017

.SHORT TERM...(Today through Wednesday night)
Issued at 130 AM MDT Tue Jul 25 2017

Today...Negatively tilted shortwave trough aloft will slowly
traverse our counties, first spawning scattered showers and
thunderstorms this morning across our western counties, west of a
Douglas to Laramie line, then initiating isolated to scattered
showers and thunderstorms this afternoon, most numerous along and
west of Interstate 25, where deeper moisture will exist. Relatively
high precipitable water values combined with weak steering winds
will produce a few thunderstorms capable of locally heavy rain over
our western counties, while adequate shear and instability may
produce a few storms with small hail and gusty winds along and east
of Interstate 25. Considerably cooler today over our western
counties due to cloud cover and precipitation, with a lesser
cooldown over our eastern counties compared to Monday.

Tonight...Isolated to scattered showers will continue much of the
night with abundant low and mid level moisture and with the
shortwave trough aloft slowly moving overhead.

Wednesday...Despite ridging aloft developing, enough low and mid
level moisture will be present for isolated to scattered showers and
thunderstorms, most numerous west of I-25 where deeper moisture will
lie. Even cooler temperatures due to cloud cover and precipitation,
along with cooling upslope easterly winds.

Wednesday night...Scattered showers and thunderstorms will continue
into the evening west of I-25, with most showers and thunderstorms
dissipating after midnight with loss of daytime heating and limited
lift.

.LONG TERM...(Thursday through Monday)
Issued at 130 AM MDT Tue Jul 25 2017

Upper ridge axis will be almost directly overhead on Thursday. The
remnants of the closed low currently over northern CA will eject
to the NE and across the northern Rockies Thursday afternoon. Subsidence
and warming aloft may tend to put a damper on convection
especially over the Panhandle. A few storms may develop over our
northern counties Thursday afternoon closer to the influence of
the mid level wave mentioned above. Additionally, moist SE
boundary layer flow into the mountains will likely be enough for
widely scattered coverage of storms mainly along and west of I-25.
The mid level shortwave will round the top of the ridge and track
SE over NE on Friday with best chances for storms shifting into
the Panhandle. For Saturday into early next week, guidance still
indicates building heights over the western US which will put our
CWA in weak northwest flow. Seasonable temps with some chances for
afternoon convection each day although exact coverage and
intensity is difficult to nail down in a weakly forced summertime
pattern.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 521 AM MDT Tue Jul 25 2017

Light showers currently just southwest of Carbon County moving to
the NE. Showers will overspread KRWL by 15Z but ceilings should
remain VFR. Elsewhere, expect scattered to numerous showers and
thunderstorms to develop over the mountains by 18Z and spread
eastward into NE by 21-00Z. Generally expect VFR through the early
evening with brief MVFR visibility in heavier showers along with
gusty and erratic winds. Showers will continue into the late
evening hours with stratus developing after 09Z over the plains
which will likely result in MVFR becoming widespread east of the
mountains.

&&

.FIRE WEATHER...
Issued at 130 AM MDT Tue Jul 25 2017

No concerns based on expected winds and humidities.

&&

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

$$

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



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