Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 211020
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
420 AM MDT Thu Mar 21 2024

.KEY MESSAGES...

1) Strong westerly winds possible this afternoon with southeast
Wyoming wind-prone locations gusting around 50 mph.

2) Critical to near-critical fire weather conditions east of
the Laramie Range this afternoon.

3) Precipitation chances increase towards the end of the week
into this weekend.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 420 AM MDT Thu Mar 21 2024

Latest GOES WV imagery early this morning shows a shortwave over
the PacNW moving into western MT that will continue to progress
southeastward towards our area this afternoon leading gusty
afternoon winds and potential for critical fire weather
conditions in our area. We will see the return of afternoon
highs in the mid-60s to low-70s for one more day this week along
and east of I-25, while areas farther west will be in the 50s.
Stronger winds will develop this afternoon along and east of the
Laramie Range, however high winds are not expected. Local high
wind guidance and environmental parameter space continues to be
on the marginal side, but could still see gusts around 50-55
mph for wind-prone locations. Downsloping winds off the Laramie
Range will lead to dry conditions so kept Td a few degrees below
latest guidance, especially just south of the developing
surface low in east-central WY where westerly flow will be
strongest. However, based on the timing of the shortwave
passage, the stronger winds may not extend into the NE Panhandle
until late in the afternoon, which is also reflected in latest
hi-res guidance. Headed into early this evening, a cold front
will sweep south behind the surface low with gusty north winds,
but also relief from fire weather conditions. Additionally with
the frontal passage, we could see light showers develop late
this afternoon and early this evening, mainly in the vicinity of
the Pine Ridge as well as along the WY/CO border in south-
central WY.

Decided to upgrade a few FWZs in the immediate foothills of the
Laramie Range to Red Flag Warning as these appear to be the most
likely areas to experience the longest duration of critical
fire weather conditions. Remaining areas within a watch could
see brief periods of critical fire weather conditions, but may
not persist for 3 hours during the afternoon. The frontal
passage will arrive sooner for east-central Wyoming with
increasing cloud cover while stronger winds over the Nebraska
Panhandle may not arrive until the late afternoon to early
evening. These are reasons for not making upgrades at this time.

Friday will be 10-20F degrees colder behind the frontal passage,
especially across east-central WY into the northern NE
Panhandle. This front looks to stall over/near the Laramie Range
limiting temperature drops along the I-25 corridor and
especially west of the Laramie Range with Laramie and Rawlins
forecast to reach the low-50s once again. Chances for
precipitation begin to increase Friday night, mainly for the
Sierra Madres and Snowys as a weak leading shortwave looks to
eject out ahead of the larger scale upper level trough moving
towards the western CONUS for this weekend.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Issued at 420 AM MDT Thu Mar 21 2024

An active extended forecast period appears probable with medium-
range deterministic and ensemble forecast guidance continuing to
support deep troughing over the western CONUS through early next
week. Numerous disturbances embedded within the large scale flow
pattern will likely support daily chances for at least scattered
to numerous rain or snow showers across much of southeast WY and
the western NE Panhandle. However, the potential for significant
precipitation amounts appears unlikely given the fragmented mid/
upper level energy. Stronger surface cyclogenesis is expected to
commence over eastern Colorado and the central & southern plains
by late Sunday into Monday, with a robust sub-990-mb surface low
quickly ejecting northeast across eastern KS & NE and eventually
IA & MN. The GFS and ECM are generally in very good agreement w/
this general evolution, with the storm track favoring the higher
precipitation totals just east of the CWA. Temperatures may be a
bit on the warm side to start the forecast period on Saturday as
southwesterly flow aloft persists, though quickly trending lower
through the remainder of the period as the trough deepens. Highs
should be in the 60s for most areas along/e of I-25 on Saturday,
with the NBM spectrum suggesting 30 to 50% probabilities of high
temperatures at or below 32 deg F on Monday.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 612 PM MDT Wed Mar 20 2024

Mostly clear skies will continue through tonight as a low amplitude
upper level ridge axis pushes through the area. A Canadian cold
front will begin moving south into Montana and Wyoming later on
Thursday, mainly resulting in increasing cloudiness and winds after
16z Thursday.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail tonight. Breezy
conditions this evening will become light and variable after 02z.
However, winds will quickly increase after 15z Thursday, especially
across the southeast Wyoming terminals where gusts of 25 to 35 knots
are expected by midday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Fire Weather Watch from noon MDT today through this evening
     for WYZ417-431.
     Red Flag Warning from noon today to 7 PM MDT this evening for
     WYZ418-432-433.
NE...Fire Weather Watch from noon MDT today through this evening
     for NEZ434>437.

&&

$$

SHORT TERM...MB
LONG TERM...CLH
AVIATION...GCC


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