Area Forecast Discussion
Issued by NWS Cheyenne, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

FXUS65 KCYS 122107

Area Forecast Discussion
National Weather Service Cheyenne WY
307 PM MDT Sat Aug 12 2017

.SHORT TERM...(This evening through Sunday)
Issued at 205 PM MDT Sat Aug 12 2017

Latest visible loop was showing scattered convection continuing
to develop across the forecast area. The strongest storm was in
Box Butte county Nebraska. These storms should mostly track east-
southeast, but there is potential for some right-movers. Latest
water vapor loop was also showing a jet streak moving through
northern Niobrara county. This jet energy was tracking southeast
and should begin to move into the northern Nebraska panhandle
during the next hour or two. This may help intensify the storms in
that region and yield to more supercellular storms and produce
large hail and damaging winds. The threat for tornadoes look
pretty minimal at this time, but with lower lcl`s closer and
southeast low level flow to the Alliance to Sidney line you
cannot rule out a brief one.

Further west, it appears like the instability is quite a bit less
with weak shear in place. However, one cannot rule out the
potential for gusty winds up to 50 mph with the scattered

The convection should begin to diminish early this evening mainly
over Wyoming, but the threat for severe weather will continue in
Nebraska due to better shear.

More scattered convection is expected to develop Sunday, but not
seeing the shear being quite as high as today. The models are
hinting at some subtle shortwaves affecting the region tomorrow
afternoon mainly along the lee side trof. This will be enough to
trigger some more scattered showers and thunderstorms once again.
Some severe storms will cannot be ruled out again considering the
good instability/lapse rates in place. This convection should
begin diminish Sunday evening.

.LONG TERM...(Sunday night through Saturday)
Issued at 205 PM MDT Sat Aug 12 2017

A transition to a drier pattern looks likely after midweek, however
we will have to get through a few more days of storms early in the
week.  An upper trough will dig into the Great Basin on Monday with
southwesterly flow aloft across the region.  The best llvl moisture
will be pushed into western South Dakota, so strong/severe threat
looks to be lower over the CWA.  The main threat will be gusty
downdraft winds with deep boundary layers.  Highs on Monday will
warm back to around normal, the warmest we have seen in over a week.
 Upper trough axis will push into southeast WY by Tuesday with a
weak front backing southward over the plains.  Isolated to scattered
storms will be possible on Tuesday and Wednesday aftns.  The models
are in agreement at showing PW values dropping after midweek under
northwesterly flow aloft in the wake of the upper trough.  Highs
will be slightly below normal Tuesday thru Thursday.&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1139 AM MDT Sat Aug 12 2017

MVFR cigs will continue for the next hour or two at SNY/AIA.
Otherwise VFR conditions will prevail through the taf period.
Scattered showers and thunderstorms will develop between 19-21Z
across much of the region. A few of the storms could be strong to
severe, mainly over the Nebraska Panhandle. Brief heavy rain,
hail, and gusty winds will be possible with the stronger storms.


Issued at 205 PM MDT Sat Aug 12 2017

Fire weather concerns will remain minimal through middle of next
week with mild temperatures and chances for showers and
thunderstorms expected through this time. High pressure looks to
build in from the west later in the week, bringing warmer and
drier conditions back to the region.




FIRE WEATHER...REC is the U.S. government's official web portal to all federal, state and local government web resources and services.