384
FXUS65 KCYS 280848
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
248 AM MDT Fri Jun 28 2024

.KEY MESSAGES...

- Strong to severe thunderstorms are expected this afternoon as
  a cold front sweeps across the CWA. At this time, the best
  chance for convection appears to be in the southern Nebraska
  panhandle.

- Active week ahead, with a cooling trend possible throughout
  the week due to several passing upper-level troughs.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 247 AM MDT Fri Jun 28 2024

Cold front analyzed across the northern CWA from Alliance to
Wheatland to Casper to a low near Riverton this morning. South
of the front...seeing dewpoints in the 50s across the southern
Panhandle with 40s north.

Looks like a couple of cold fronts impacting the weather today.
The first moves through this morning...turning winds northerly
for a time. A secondary cold front associated with the colder
air moves through around 00Z.

Given what happened yesterday...thunderstorms are in question
today. HRRR and RAP simulated radar only showing isolated to
widely scattered convection this afternoon mainly from Sidney to
Cheyenne. Best instability looks to be south in Colorado today
and this is where the HRRR/RAP simulated radar is showing most
of the convection. MUCAPE in the southern Panhandle up near 1000
J/KG. SPC has a SLight Risk area highlighted for the southern
Panhandle. Not too sure of that happening. Did decrease PoPs for
this afternoon from the previous forecast.

With that secondary front moving through early evening...700mb
temperatures fall from +13 to +14C currently down to +5 to +6C
by Saturday morning. Expecting to see 40s for lows Saturday
morning with afternoon highs in the 70s and low 80s. Mainly dry
Saturday except for our western mountains.

Maybe better chances for storms Sunday as we get low level
moisture advected north into the Panhandle with a low level
south to southeasterly jet of 30-35kts. Much warmer as well
Sunday as the upper ridge builds back over the area.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Issued at 247 AM MDT Fri Jun 28 2024

An active week is expected for southeast Wyoming and western
Nebraska with daily chances for afternoon showers and thunderstorms.
Sunday night into Monday, an upper-level ridge will slowly push to
the east as an upper-level trough digs into the western CONUS.
Southwest flow aloft develops early Monday morning with several
vorticity maxima ejecting out ahead of the incoming trough. 700mb
temperatures will remain in the 14-16C range, leading to high
temperatures on Monday in the mid-80s to mid-90s area wide, with
slightly warmer temperatures across Converse and Niobrara counties.
As the upper-level trough pushes closer to the region, 700mb heights
will begin to tighten, leading to gusty winds across much of the
region west of the Laramie Range. High winds are not likely, but
breezy conditions will be present throughout the day. Precipitation
chances will ingress in the afternoon as surface heating along with
passing vorticity maxima promote convective development. A fairly
typical summertime pattern for the region.

On Tuesday, the upper-level trough pushes through the region as a
secondary trough develops off to the west. This trough will foster
improved chances for convection across the region and dropping 700mb
temperatures back into the upper-single digits. This departing
trough and cooler 700mb temperatures will lead to a slightly cooler
day on Tuesday, with highs int he upper-70s to mid-80s area wide,
rather than widespread 80s and 90s once more. Precipitation chances
will increase for the afternoon, before dropping back off later in
the evening. Similarly for Wednesday, the upper-level trough will
keep 700mb temperatures in the 8-10C range with surface temperatures
slightly warmer across the region in the low-80s to low-90s once
more. Precipitation chances are expected again in the afternoon,
with isolated showers and thunderstorms possible.

Significant model differences are noted for the late-week. Previous
model cycles suggested a strong ridge overhead, leading to a very
warm 4th of July holiday. However, long range models are now
suggesting troughing over the central CONUS, leading to cooler
temperatures and increased precipitation chances. The GFS is much
cooler than the ECMWF at this time, with the GFS dropping 700mb
temperatures into the 3-5C range by Friday morning, while the ECMWF
has 700mb temperatures in the 6-8C range. With the disagreement
between the models, but the general consensus on cooler
temperatures, decreased high temperatures on Thursday a few degrees
to highlight the cooling trend. The GFS suggests a cold front moving
through the region, whereas the ECMWF keeps it further to the
northeast over South Dakota. Therefore, the GFS is wetter for the
4th of July holiday than the ECMWF. Overall, it will still be a warm
day out there, but likely a few degrees cooler than previous days
with colder overnight lows expected at this time. Does not look to
be like the 4th of July last year when it rained all day and
temperatures struggled to reach the 60F mark!

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1112 PM MDT Thu Jun 27 2024

VFR conditions expected next 24 hours with isolated
thunderstorms during the afternoon Friday. All terminals will
see a breezy Friday, as wind gusts of 30-40 knots are expected
for most areas on Friday afternoon.

&&

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

&&

$$

SHORT TERM...GCC
LONG TERM...AM
AVIATION...GCC