Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 180226
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
826 PM MDT Sun Mar 17 2024

.KEY MESSAGES...

- Well above normal temperatures are expected to return this week.

&&

.UPDATE...
Issued at 822 PM MDT Sun Mar 17 2024

Overall, the forecast remains on track at this time. Decreased
overnight temperatures a degree or so in a few locations, but
most of the region looked good. Decreased dewpoints across the
Panhandle as observations were much lower than the forecast
suggested. Clouds remain overhead west and south of I-25 as of
02Z, but will slowly push out of the area over the next several
hours. No precipitation is expected overnight and for the start
of the week. Pleasant weather ahead for southeast Wyoming and
western Nebraska.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 300 PM MDT Sun Mar 17 2024

Satellite analysis shows a stationary closed low spinning over
the Four Corners region and mid level clouds spilling over the
ridge axis and entering northern Wyoming. This cool northern
flow and invading thick mid-level cloudiness is keeping
temperatures from warming too much across the region and with a
cold start this morning, temperatures are struggling to reach
the 40s for much of SE Wyoming, with low 40s in the Nebraska
Panhandle. As the closed low begins to weaken the main upper
level ridge will build across much of the Intermountain West on
Monday. Temperatures are expected to jump some 10 degrees above
normals tomorrow afternoon with widespread 60s across the
Nebraska Panhandle and for locations north of the North Platte
River valley, with mid 50s for locations to the south. Overall a
very nice start to next week.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 300 PM MDT Sun Mar 17 2024

Most of the week ahead is expected to be dominated by warm and
dry weather, but a return of active weather may be on the
horizon heading towards next weekend.

The synoptic pattern through midweek will be characterized by a
Rex Block over the western CONUS as the remnants of last week`s
storm still spins over the desert southwest underneath an
amplifying ridge. Our area will be somewhat on the fringe of the
ridge, with northwest flow just to our east and general
troughing over the east. Thus, expecting a very nice week for
the most part, with 700-mb temperatures Tuesday supporting highs
some 10-15F warmer than average and mostly sunny skies. A weak
shortwave moving through the northwest flow on Tuesday PM is
expected to graze the area with a weak cold front. We could see
some briefly gusty northeasterly winds over the High Plains
behind this. It should be a dry frontal passage though, with the
only lasting impact knocking down temperatures slightly on
Wednesday. For most of Southeast Wyoming, the front may not even
reach the area, leading to similar highs Wednesday as Tuesday.
However, the northern NE panhandle in particular could lose
about 10F off of Tuesday`s highs in the wake of the front.

By Thursday, ensemble guidance shows that the ridge will flatten
out somewhat as the persistent closed low over the southwest gets
swept off to the east. The baroclinic zone and northern branch
of the jet stream will creep back into the northern Rockies
around this time also. The westerlies will also return, bringing
elevated winds back to the wind prone areas, but probabilities
for high wind are fairly low (around 25% at this time). While a
few weak clipper type systems may slide down the Plains
Thursday through Saturday, most guidance has trended in the
direction of a stronger ridge and storm track further east. A
few ensemble members, mainly from the GEFS, bring a surface
front close enough to drop temperatures considerably on Friday
for the High Plains. So again, the northern panhandle is where
there is the lowest confidence in warm temperatures continuing
through Friday and Saturday, but the rest of the area along and
west of I-25 has better confidence in above normal temperatures
continuing through Saturday. These weak systems in the
Thursday-Saturday period may also bring some light precipitation
to the area. Due to timing differences with any of these
systems, shaved PoPs down slightly through this period.

The most interesting piece of the long-term forecast is at the
very tail end of the operational forecast period on Sunday. Most
ensemble members continue to show a broad, strong, and
progressive trough plowing into the west coast this weekend.
Some members also show a strong Colorado low developing east of
the mountains and delivering another shot at snowfall. At this
time, about 30-50% of members show a warning criteria event for
the High Plains, varying by exact location. Other members, plus
the deterministic ECMWF and GFS, show the system staying just
slightly too far north for a big event, putting a dry slot over
the I-80 corridor. This scenario could still deliver a decent
storm to east central Wyoming and the northern NE panhandle
though. Cluster analysis suggests that the main difference is in
the timing of the trough. A faster, more open trough
(represented more by ECMWF ensemble members) generally leads to
an earlier storm occurring mainly Sunday, but less overall
precipitation. A slower trough (represented more by GEFS
members) tends to deliver more precipitation, but more focused
on Monday. Since this is still about a week away, uncertainty is
very high, but this period will be worth monitoring.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 609 PM MDT Sun Mar 17 2024

VFR prevails. Expect continued BKN-to-OVC coverage of low & mid-
level cloud cover from 5-10k feet AGL through the evening & into
the overnight hours, with skies slowly clearing toward sunrise.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.

&&

$$

UPDATE...AM
SHORT TERM...AW
LONG TERM...MN
AVIATION...CLH


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