Area Forecast Discussion
Issued by NWS Cheyenne, WY

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490
FXUS65 KCYS 291752
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1152 AM MDT WED JUN 29 2016

.UPDATE...
Issued at 1021 AM MDT Wed Jun 29 2016

Gridded forecasts updated for this afternoon for some minor
adjustments. By late this afternoon, surface and mid level low
pressure will reside over southeast Wyoming with a decent low
level convergence axis setting up along Interstate 25, as seen
on impressive 850 mb and 700 mb theta-e ridge axis. Thus, it
appears the best thunderstorm initiation will occur early this
afternoon along Interstate 25 with storms then moving east
southeast at 10 to 15 mph. Shear and instability quite capable
for some severe storms again with CAPE ranging from 1500-2500
J/kg and 0 to 6 km bulk shear near 50 knots.

&&

.SHORT TERM...(Today through Friday)
Issued at 350 AM MDT Wed Jun 29 2016

Looks like one more day having to deal with some severe convection
as the overall pattern similar to yesterday. Currently a band of
showers and a couple embedded weak storms moving southeast along a
Torrington to Sidney line. These should end over the next few
hours.

Upper high centered around the 4-corners area with NW flow across
the CWA. next impulse in the flow looks to pass across the area
late this afternoon into this evening. CAPES should rise into the
1000-2500 J/kg range east of the mtns this afternoon with easterly
low level upslope flow setting the stage for another round of
strong/severe convection this afternoon and evening. Large hail
and strong winds the main threat again with activity moving
generally southeastward. Should see a decrease in convection
during the evening but some may hang around through tonight helped
by another weak impulse moving down the front side of the upper
high. Meanwhile a cool surface high will drop south out of
central Canada tonight pushing a front against the mtns Thursday.
Cooler temps will move over the plains Thursday and continue
through Friday which will act to reduce instability so severe
storm threat will be much lower. Scattered showers and tstms
remaining in the forecast Thursday and Friday with a monsoonal-
like moisture feed continuing across the region.

.LONG TERM...(Friday night through next Tuesday night)
Issued at 410 AM MDT Wed Jun 29 2016

Showers and thunderstorms will likely continue through Saturday
across the forecast area as subtropical moisture remains in place
and an upper level shortwave slowly moves eastward across the
central and southern Rockys. Nocturnal convection is certainly
possible late friday night as several models show the shortwave
aloft and associated cooler air moving over the area.
However...there are substantial timing difference in model
guidance...but this is expected this time of the year due to the
relatively slow movement of these waves. Later in the
weekend...all models show signs of resolving these timing
differences and show the upper level shortwave east of the
forecast area and gradually accelerating eastward into the central
Great Plains states. This will result in somewhat drier zonal flow
as PW/s lower from 1.0 to 1.5 inches on Friday to between 0.5 to
0.75 inches on Sunday and Monday. With some instability present
and nearly zonal flow...can not completely rule out daily isolated
thunderstorms early next week...but coverage should be
considerably less compared to recent days...especially east of the
Laramie Range. Temperatures will be near or slightly below normal
at the start of the weekend...generally in the mid 70s to mid
80s...but then are expected to gradually modify into early next
week. Highs Tuesday and Wednesday will become very warm or hot
across the area...as temperatures rise between the upper 80s
across the high valleys to the mid/upper 90s over western
Nebraska.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1146 AM MDT Wed Jun 29 2016

No significant change from the 12Z taf issuance. A couple short
range models are indication convection developing over the
southeast WY mountains early afternoon and moving ESE onto the
adjacent valleys and plains by 21Z, including RWL, LAR and CYS.
Confidence not high/coverage more isolated this afternoon, so
maintained VCTS at these aerodromes. Western NE aerodromes may not
see convection form until around 00Z. Potential for strong/gusty
outflow winds and hail east of the Laramie Range where instability
and wind shear will be greater. Convection will come to an end
later this evening.

&&

.FIRE WEATHER...
Issued at 350 AM MDT Wed Jun 29 2016

Fire weather concerns look to be on the low side for the rest of
the week with widely scattered afternoon and evening showers and
storms...especially today through Thursday. Wetting rains expected
in many areas east of the mountains.

&&

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

$$

UPDATE...RUBIN
SHORT TERM...RE
LONG TERM...TJT
AVIATION...MAJ
FIRE WEATHER...RE



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