Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 241815 CCA
AFDCYS

Area Forecast Discussion...Corrected Aviation
National Weather Service Cheyenne WY
1151 AM MDT SUN JUL 24 2016

.SHORT TERM...(Today through Tuesday)
Issued at 240 AM MDT Sun Jul 24 2016

Weak upper level shortwave moving overhead through sunrise will
interact with midlvl subtropical moisture and result in isolated
showers, mainly across the plains.  Models continue to show
southeasterly winds developing to the east of the Laramie Range by
midday with some llvl moisture advection.   The 00z model runs show
higher dewpoints, better instability, and better convective chances
from the southern Laramie Range eastward in areas near Interstate
80.  This is also supported by latest runs of the HRRR.  Bumped up
pops to around 30 percent across Laramie county. The combination of
good instability (CAPE around 1500 J/kg) and bulk shear (45-50 kts)
could result in stronger storms so added the mention of small
hail/gusty winds.   SPC has a marginal risk from the southern
Laramie Range eastward into Laramie county.  Temps today will be the
coolest through the short term.

Heights will rise some by Monday and Tuesday with the upper ridge
centered just south of the CWA (across SW Colorado).  Lee
trough/dryline will be located just east of the Laramie Range during
the aftn.  Instability is high to the east of this feature. However,
it is rather capped with CIN values of 50-100 J/kg.  Kept slight
chance pops confined to the Nebraska Panhandle but it remains to be
seen how much convective initiation can occur. Another marginal
risk is depicted from SPC. Sfc trough will be right along the
eastern edge of the CWA by Tuesday with limited instability/tstms.
Temps will rise to slightly above normal by Tuesday.

.LONG TERM...(Tuesday night through Saturday)
Issued at 220 AM MDT Sun Jul 24 2016

Medium to long range models continue to show the center of the
upper level high pressure retrograding westward into the Great
Basin region for next week. Northwest flow aloft will develop
across Wyoming and Nebraska by Wednesday and Thursday with
temperatures lowering closer to normal for this time of the year.
Although the high will block subtropical moisture from advecting
northward into the forecast area...upslope easterly flow will be
common by the middle of next week with model sounding showing a
good supply of low to midlevel moisture behind a surface cold
front. In addition...several shortwave disturbances embedded in
the northwest flow will move southeast out of Canada and will
likely result in some cooler air aloft and added instability and
jet dynamics. Will need to monitor the potential for strong to
severe thunderstorms on Wednesday and even more-so on Thursday due
to increased instability and 0-6 bulk shear. There are some
differences in timing of this cold front...with the ECMWF and GEM
a full 24 hours quicker with the front across southeast Wyoming
late on Wednesday. The GFS shows this front stalling across the
Dakotas for a while before it progresses southward into the
forecast area for Thursday. So not as confident with Wednesday
severe potential compared to Thursday...which appears more likely
at this time. Temperatures will remain in the 80`s to 90`s during
the day Wednesday...and then likely trend lower by late in the
week with highs in the mid 70`s to mid 80`s expected by Friday
behind the cold front.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1143 AM MDT Sun Jul 24 2016

VFR conditions will continue through early afternoon before
isolated to scattered thunderstorms mid to late afternoon across
portions of southeast Wyoming and far southern Nebraska Panhandle.
Prevailing winds will be southeasterly 10-15 kt east of the Laramie
Range and westerly 10-20 kt to the west. VCTS forecast at Cheyenne,
Laramie, Scottsbluff and Sidney between 20Z and 04Z with MVFR to
localized IFR visibilities in heavy rainfall as well as
gusty/erratic outflow winds to 40 kt and small hail. Convection will
diminish later this evening with clearing skies and light winds.

&&

.FIRE WEATHER...
Issued at 220 AM MDT Sun Jul 24 2016

Minimal fire weather concerns through Tuesday.  Minimum humidity
values will fall to 10-20 percent each afternoon for areas to the
west of the Laramie Range.  However, wind gusts will stay mostly
below 20 mph and thus no fire weather threat is anticipated.
Isolated thunderstorms will be possible across areas to the east of
the Laramie Range, however the chance of wetting rains will be
small.

&&

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

$$

SHORT TERM...ZF
LONG TERM...TJT
AVIATION...MAJ
FIRE WEATHER...ZF


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