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 49 50
FXUS65 KCYS 232118

Area Forecast Discussion
National Weather Service Cheyenne WY
318 PM MDT Thu Mar 23 2017

.SHORT TERM...(This evening through Friday)
Issued at 318 PM MDT Thu Mar 23 2017

A very active 18 hours ahead for the region as a strong storm system
spins across the Rockies bringing snow to parts of the area along
with gusty northerly winds, and cooler temperatures. Afternoon
satellite pix depict this system spinning across Utah currently with
KCYS 88D returning showers along with a few wk thunderstorms along
the Pine Ridge in the N panhandle west back towards Rawlins. 20Z SPC
mesoanalysis does show a few pockets of 500-1000 j/kg pooling across
parts of the area, but agree with the latest few SPC outlooks that
point to just mainly general thunderstorms across the region. At the
surface...pressures have been steadily falling all day in along the
front range with a well defined dryline located between Pine Bluffs
and Kimball with 20z Td`s of 12F and 40F, respectively.

Cold front was knocking on the doorstep of the northern zones
this afternoon and will drop south across the CWA through 9 PM.
Recent HRRR output, suggest area of shower and embedded
thunderstorm activity will expand across the eastern plains
through the rest of the evening along and ahead of this cold
front. Snow-levels will fall this evening turning rain to snow,
first over the I-80 summit and eventually into adjacent higher
elevations (above 5000 feet) by around midnight. At the same time,
with the cyclone deepening to the south, north winds will
increase with gusts of 30-45 mph for a time across the eastern
plains. The combination of these strong winds and 3-7 inches of
new snow has prompted the issuance of a Winter Storm Warning
across the southern Laramie Range. Areas from Arlington to Laramie
and in the vicinity of Cheyenne will be well positioned for 2-3
inches of snow late tonight and for the Friday morning commute.
Again the combination of strong winds and these accumulations has
led to the issuance of a Winter Weather Advisory for these areas.

Some question as to just how far east along I-80 snow will be able
to fall especially given just how dynamic this system si, but for
now have kept accumulations Kimball to Sidney to an inch or less
and don`t suspect to see significant impacts there. Evening shifts
will need to watch for the potential of a 3-6 hours of high wind
potential for Kimball-Sidney from 09-15z. The system departs as
quickly as it moves through, allowing for drying conditions by mid
morning Friday and clearing skies through the afternoon. High
temperatures on Friday only to reach the 40s above 5500 feet, with
5 0s for lower elevations. Winds will gradually subside thru
Friday afternoon.

.LONG TERM...(Friday night through Thursday)
Issued at 318 PM MDT Thu Mar 23 2017

As the main upper low moves to our southeast, precipitation will
taper off around Sidney by 6 PM Friday with upper ridging keeping
a short dry pattern in place for Friday night. The weekend leads
off a rather active period of passing upper systems bringing
chances of snow in the higher elevations and mostly rain or a mix
below 6000 ft across the eastern zones. Given that the position
of the passing shortwaves Saturday into Sunday, then again Tuesday
into Wednesday, we don`t tap any deep cold air. Overall impacts
from winter weather this next week doesn`t look overly impressive
with any of these systems. The only thing to pay attention to
initially will be potential for localized higher amounts of new snow
to near 6 inches in the higher elevations of the Snowy Range this
weekend, but that is about it for anything that would approach
significant snowfall accumulations.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 318 PM MDT Thu Mar 23 2017

Scattered showers with isolated thunderstorms being seen across
parts of SE Wyoming this afternoon. Cold front currently along a
line from Rapid City to Douglas to Rock Springs continues to make
steady progress southward and will move south of Cheyenne and
Sidney by early evening. Behind the cold front we will see a cold
rain switching to snow overnight in Wyoming. We epect lowered
ceilings/visbilities across the entire area, but more impactful
down to LIFR for Cheyenne and Laramie late tonight.


Issued at 318 PM MDT Thu Mar 23 2017

We continue with the Red Flag Warning through 6 PM for parts of SE
Wyoming into the southern Nebraska Panhandle due to gusty winds
ahead of an approaching cold front. Admittedly conditions more
marginal for Red Flag Warning criteria across the Nebraska
Panhandle based on current observations, but Sidney is sitting
around 17 percent RH and we expect their winds to come up late
afternoon. With fuels so dry in the Red Flag Warning area, we are not
comfortable dropping the warning over there just yet, but we may
end up cancelling early over there. We have been hitting the
criteria in Cheyenne most of the late morning and afternoon so
far. Friday looks to be cold and wet, with a wetter pattern on tap
for much of the next week.


WY...Winter Storm Warning from 9 PM this evening to 9 AM MDT Friday
     for WYZ116-117.

     Winter Weather Advisory from 9 PM this evening to 9 AM MDT
     Friday for WYZ110-115.

     Red Flag Warning until 6 PM MDT this evening for WYZ310.

     Winter Weather Advisory from midnight tonight to 9 AM MDT Friday
     for WYZ118.

NE...Red Flag Warning until 6 PM MDT this evening for NEZ313.



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