060
FXUS65 KCYS 141741
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1140 AM MDT Tue May 14 2024

.KEY MESSAGES...

- Scattered to numerous showers and thunderstorms are expected
  today and tonight. Strong wind gusts 55-65 MPH will be the
  primary hazard, especially this afternoon and early evening.

- A cool and unsettled weather pattern will evolve by mid-week
  as the upper low pinches off over the 4 Corners and drifts
  slowly southward through Thursday.

- Significant model disagreement persists with the evolution of
  the large scale pattern from late week through the weekend.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 430 AM MDT Tue May 14 2024

A warm, but unsettled day ahead in the pre-frontal air mass with
700-mb temperatures remaining between +6 and +8 deg C through at
least mid-day before the arrival of low-level CAA. A pretty warm
start with observed readings in the lower 50s across much of the
area early this AM, so it should not take long at all to achieve
daytime highs in the upper 60s & lower 70s F. Scattered/numerous
showers and thunderstorms can be expected across a large part of
the area today, occurring in two distinct waves. The first round
should occur over our northern zones this morning w/ the initial
frontal surge and lead 500-mb vort max. By mid/late afternoon, a
second wave of convection is expected to develop across Carbon &
Albany counties as a more robust mid-level disturbance pushes to
the southeast. Overall, high-res models have been somewhat quiet
over far southeast WY and the southern NE Panhandle with most of
the energy remaining north and west through Wednesday. Expect to
see locally strong (55-65 MPH) wind gusts w/ the strongest storm
activity today given the large, inverted-v profiles & high cloud
bases around 10k feet, LCLs well above the freezing level. Would
expect limited CAPEs to keep hail at bay, but could see a ribbon
of stronger instability wrap into the northern NE Panhandle with
some localized potential for a marginal hail threat. There could
be some organized convective clusters over western areas as deep
layer vertical shear rapidly increases in response to increasing
500-mb flow, further enhancing the strong wind threat. Otherwise
expect a cool, unsettled pattern persisting through Thursday, as
mid-level energy pinches off from the main flow & drifts ever so
slowly to the south across the Four Corners.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Issued at 430 AM MDT Tue May 14 2024

A progressive upper-level pattern is progged to impact the region
this weekend into next week with several troughs moving through with
intermittent ridging aloft. Several differences appear within the
long range models, suggesting an uncertain evolution of the weather
systems. For Friday and Saturday, the GFS suggests a strong, upper-
level trough dragging across the region, while the ECMWF suggests
more zonal flow just north of the CWA. Both long range models are
dry, despite the passage of the trough in the GFS, with little to no
precipitation expected Friday and Saturday. One thing of note in the
GFS is increased winds across the region Saturday as the trough and
700mb low traverse just north of the region and tighten gradients
along the higher elevation. Did keep breezy conditions in the
forecast for Saturday, as the ECMWF also hints at the possibility of
some stronger winds once more. Craig to Casper height gradients do
favor elevated winds Saturday, but these gradients are from the GFS,
so could be a bit inflated if trough and 700mb low do not stay that
far sound. Therefore, kept breezy winds across the region, but
stayed well away from high wind criteria as it does not look likely
at this time. Additionally, 700mb temperatures will be quite warm
Friday, but the GFs suggests a cold front moving through and
dropping temperatures for Saturday. The ECMWF does not have this
cold front and keeps temperatures quite warm both days. Kept
temperatures in the upper-60s to low-80s across the region for both
days, as warm temperatures are favored.

By Sunday and Monday, the GFS and ECMWF begin to come into better
agreement on the upper-level evolution. Both suggest a long wave
trough across the northern CONUS and southern Canada as a ridge
builds and moves northerly in the subtropical jet. Both models
suggest these trough and ridge moving towards each other, but keep
the region in split flow for Monday. The ECMWF suggests that the
split flow will continue for a longer period of time than the GFS,
which suggests that the subtropical ridge will become the dominant
feature by Monday into Tuesday. The ECMWF eventually jumps on the
bus for a stronger subtropical jet, but keeps it much further south,
primarily over the Four Corners Region and portions of Texas and
Oklahoma. With this split flow regime that is suggested in both
models, though for different durations, some isolated showers and
maybe a thunderstorm could develop Monday as weak lift exists within
the split flow regime and 700mb winds favor the development of
upslope flow. Temperatures remain warm, in the 70s and 80s across
the region.

Significant disagreement between the GFS and ECMWF begins again by
Tuesday through the remaining long term forecast. Both models
suggest a long wave trough moving into the CONUS, but the
positioning, tilt, strength, and location all different between the
long range models. Decided to keep low end PoPs, around 30%, for
much of the region Tuesday and Wednesday as showers may develop with
either solution that comes to fruition. This will be something to
continue to monitor to determine if the long range models come into
better agreement.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1140 AM MDT Tue May 14 2024

A cold front will continue to move across southeast Wyoming and
western Nebraska this afternoon through this evening. This front
will eventually stall across the high plains and will bring off/on
rain showers and some thunderstorm activity later this afternoon
through tonight. Thundershowers may linger through sunrise
Wednesday with some locally heavy rainfall possible.

HAZARDS/WEATHER TRENDS: A brief break in the shower and thunderstorm
activity is expected this afternoon before the next few rounds
develop and push east along a surface front.

Although VFR conditions will prevail, gusty winds up to 35 knots are
expected. Will have to watch the intensity of the rainfall late this
afternoon through tonight as multiple bands of showers and
thunderstorms are forecast to develop and push east, likely
impacting all terminals at some point. Timing details are going to
be tricky since this shower activity will move relatively fast
across the area, so added VCSH and VCTS for now. KCDR will be the
first to experience the thunderstorms after 21z today, with most of
the other terminals seeing precip and low CIGS between 00z to 12z
Wednesday. Expect low CIGS and MVFR conditions at all terminals by
11z and 15z early Wednesday morning as the bulk of the cooler
airmass settled over the region.

&&

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

&&

$$

SHORT TERM...CLH
LONG TERM...AM
AVIATION...TT