Area Forecast Discussion
Issued by NWS Cheyenne, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 40 41 42 43 44 45 46 47 48
000
FXUS65 KCYS 230902
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
302 AM MDT Mon Oct 23 2017

.SHORT TERM...(Today and Tuesday night)
Issued at 330 AM MDT Mon Oct 23 2017

Sharp cold frontal boundary now seen clearly on radar tracking
southward across the Wyoming and Nebraska plains. Winds have
switched to the north behind the front at about 25 mph and this
should finally put an end to the strong westerly winds we have
seen over the past 24 hours. GFS and NAM CAG-CPR gradients
diminish significantly between 3 and 6 AM and already seeing winds
fall below high wind criteria in the wind prone areas. While there
may be a rogue gust to 60 between 4 and 6 this morning, think the
threat of widespread high winds is diminishing and will let the
warning expire on time.

Flow at all levels becomes more NW today as the core of a strong
140kt jet moves over the eastern Panhandle counties. Thus the
threat of strong winds will shift east this afternoon during peak
mixing. Winds from Alliance to Sidney this afternoon will likely
gust between 50 and 55 mph at times, just below high wind
criteria. Forecast soundings from the GFS show deep mixing up to
around 9kft which may be able to tap into 50kt flow around 650mb.
For now, held off on headlines as the GFS has shown a propensity
to over mix the boundary layer.

Heights rise aloft on Tuesday as the jet core shifts east and
ridging builds over the intermountain west. It will still be
breezy over the Panhandle but winds should be much less than
today. Temperatures will remain seasonable with no chance for
precipitation.

.LONG TERM...(Wednesday through Sunday)
Issued at 330 AM MDT Mon Oct 23 2017

Another high wind event looking likely Wednesday ahead of our next
cold front. GFS Craig to Casper 850/700mb gradients increase above
60mtrs as early as 15Z Wednesday. Did increase winds in our wind
prone areas for most of the day Wednesday as confidence growing in
hitting criteria in those locations.

Fairly fast movement of front through southeast Wyoming Wednesday
night into Thursday. ECMWF still the most bullish on QPF/snow
amounts, though both the GFS and the current ECMWF run have
lowered snow amounts considerably. EC showing maybe up to 2 inches
across Carbon County with this event.

Not as cold Friday as previous model runs have indicated. Latest
GFS showing 700mb temperatures only falling to around -10C and EC
around -12C. This is about 10C warmer than 24 hours ago, so maybe
we won`t see those very cold temperatures after all. Still cold
though, with overnight lows in the teens for most locations Friday
morning.

Northwest flow stays with us through the weekend with a slow
warming trend into Sunday. Conditions look to remain dry with this
pattern.


&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued
at 330 AM MDT Mon Oct 23 2017

Cold front making its way through southeast Wyoming and Nebraska
Panhandle this morning could kick off some light showers. Expect
gusty north winds behind the front, especially for our Nebraska
Panhandle airports today. VFR conditions otherwise.

&&

.FIRE WEATHER...
Issued at 226 AM MDT Mon Oct 23 2017

Elevated fire weather conditions will develop over the Nebraska
Panhandle this afternoon. RH values will fall to around 20 percent
and NW winds of 25 to 35 mph with higher gusts are expected.
Cooler temperatures will keep RH values from falling into the
critical range. It will continue to be dry with a warming trend
through Wednesday. Elevated to locally critical fire weather
conditions are possible on Wednesday east of the Laramie Range as
stronger westerly winds overlap areas with RH values between 15
and 20 percent.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until 4 AM MDT early this morning for WYZ110-
     116-117.

NE...None.
&&

$$

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



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