Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 281706 AAA

Area Forecast Discussion...UPDATED
National Weather Service Cheyenne WY
1106 AM MDT WED SEP 28 2016

.SHORT TERM...(Today through Thursday Night)
Issued at 315 AM MDT Wed Sep 28 2016

Blocking pattern in place across the CONUS this week as downstream
upper-low near the Great Lakes is taking its time departing. The
result for us is a very pleasant stretch of dry and seasonably
warm Autumn conditions. Satellite pix early this morning reveal
cloudless skies across much of the intermountain west with a cold
front evident settling south thru central Montana. This as an
upper-level ridge of high pressure amplifies along the Front
Range. Don`t see much change for today aside from increasing clouds
from the southwest as the next upstream shortwave near the Great
Basin begins lifting northeast. Progd H7 temperatures of 8-12C
will yield afternoon highs that will climb well into the 70s for
all lower elevations, with even some low 80s across lowest elevations.

For Thursday, the aforementioned upstream shortwave will continue
lifting northeast into western and central Wyoming by Thursday
night. Preceding moisture will yield more cloud-cover west-east on
Thursday as well as increasing precipitation chances especially in
and near the Snowy, Sierra Madre, and northern Laramie Range.
Temperatures will again be seasonably warm on Thursday as thicker
cloud canopy offsets low-level warm air advection.

.LONG TERM...(Friday through Tuesday)
Issued at 315 AM MDT Wed Sep 28 2016

High pressure weakens and moves east onto the high plains Friday
as an upper level low moves slowly southeast across the Pacific
Northwest through Sunday. As the upper trough moves slowly east
across the Sierra Nevada Sunday a surface low reflection will
likely form up in the lee of the central Rockies moving east
across western Nebraska on Monday. This will bring a strong cold
front east across the forecast area Sunday into Monday with
chances of showers and a few thunderstorms Sunday afternoon into
the overnight hours over the eastern 2/3rds of the forecast area.
As the colder air moves into place late Monday night we transition
precip type to snow showers in the higher elevations west of I-25.
Operational model trends are colder late Monday into Tuesday with
700 mb temps around -5C over much of eastern Wyoming and the
western Nebraska Panhandle 18Z Tuesday...plenty cold enough to see
snow chances increase. For this morning`s forecast will wait and
see if superblend ensembles start to trend closer to latest
operational runs of the GFS and ECMWF for Tuesday...keeping main
chances for measurable snow in the mountains late Monday into
Tuesday with lesser amounts out east onto the lower elevations. If
the models continue to trend colder...this is something we are
going to have to watch closely for the next few days for early
next week for our first real shot at measurable snow for
elevations above 6000 ft.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1101 AM MDT Wed Sep 28 2016

VFR. Clear skies, except for a few high clouds spreading east
toward the Laramie Range late tonight. Generally light east to
southeast surface winds will prevail.


Issued at 315 AM MDT Wed Sep 28 2016

No critical fire conditions expected over the next week. Seasonably
warm conditions to continue in area districts with high temperatures
reaching the 70s most locations through the end of the week.
Afternoon minimum relative humidities will fall into the 20s today
and Thursday, with 30s and 40s for Friday. Will see a slight chance
of precip spread over the mountains, but coverage will be limited.
Better precipitation chances return early next week, with snow levels
falling perhaps to around 6000 feet.


.CYS Watches/Warnings/Advisories...


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