Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 200915

Area Forecast Discussion
National Weather Service Cheyenne WY
315 AM MDT Tue Jun 20 2017

.SHORT TERM...(Today through Thursday)
Issued at 300 AM MDT Tue Jun 20 2017

Very warm days ahead with highs a good 10-15 degrees above normal.
700 mb temps will rise to around 16-18C both today and Wednesday,
which will mean highs climbing into the mid 80s to mid 90s. With
the warmer temps, it will be easier to reach the convective temp
by this aftn, thus expect more cumulus. Thinking that drier air
aloft will really hinder any storm development, however cannot
rule out an isolated tstm across southeast WY through this evening
with gusty downdraft winds being the main threat. Very similar
pattern for Wednesday with west to northwest boundary layer flow
across much of the CWA as the surface trough will be over the
Nebraska Panhandle. A weak cool front will push across the plains
Thursday morning, with surface winds becoming easterly in areas
near the Colorado Border by the aftn. Along with around 5-10
degrees of cooling, may see slightly better convective chances
along the Colorado border as higher dewpoints/instability try to
advect westward.

.LONG TERM...(Thursday night through Monday)
Issued at 315 AM MDT Tue Jun 20 2017

Active west-northwest flow aloft will bring a couple of shortwave
troughs across the CWA Thursday night through Saturday. Widely
scattered showers/isolated thunderstorms will primarily impact
the high plains during this period. A strong cold front for late
June will push south through the region Friday, with much cooler
temperatures through Saturday. GFS progs highs of 61 and 59 at
Cheyenne on Friday and Saturday, with 71 and 51 degrees, respectively
from the ECMWF. Trended closer to the ECMWF for highs Friday, and
at least 10 degrees warmer than blended MOS for highs Saturday.
Flow aloft will become more northwesterly Sunday and Monday with
upper ridging from the Desert Southwest across the Great Basin.
Below average temperatures Sunday will warm closer to seasonal
normals Monday.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 300 AM MDT Tue Jun 20 2017

VFR. Light winds early this morning will become westerly with
gusts to 20-25 kt for the southeast WY terminals. Variable winds
10 kt or less will prevail at the western NE terminals. Isolated
afternoon convection will be possible in the vicinity of the
mountains, but should not impact KRWL, KLAR or KCYS.


Issued at 240 AM MDT Tue Jun 20 2017

Very warm temperatures will occur through Wednesday, which will cause
minimum afternoon humidity values to drop to 15-20 percent for areas
to the west of the Laramie Range. West winds will also gust to 20-25
mph this afternoon and Wednesday afternoon. However, fuels are still
green and thus fire weather concerns are limited.




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