719
FXUS65 KCYS 170536
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1136 PM MDT Tue Jul 16 2024

.KEY MESSAGES...

- Widely scattered storms possible this afternoon. Increasing
  moisture Wednesday will support strong to possibly severe
  thunderstorms Wednesday afternoon. Daily chances for
  precipitation continue through the rest of the week.

- Warm mid-week before cooling trend begins for the weekend.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 230 PM MDT Tue Jul 16 2024

Latest radar scans showing isolated thunderstorms over the CWA
at 2 PM this afternoon. Cells are moving from north to south in
northwest flow. Latest RAP mesoanalysis showing around 500 J/KG
surface based CAPE. Cells don`t appear to have much vertical
growth . Still considerable lightning being observed with these
isolated storms...so we will continue to monitor.

Current PWATs over southeast Wyoming are quite dry...GFS showing
.6 to .8 inches over southeast Wyoming and .9 inches over the
Panhandle. Latest HRRR/RAP simulated radar shows convection
decreasing significantly after 01Z or so. SBCAPE does not
increase significantly through the late afternoon...so severe
storms are not a concern for the rest of the day.

Better chances Wednesday as low level winds shift easterly this
evening and draw low level moisture north from western Kansas.
Later shifts will need to be on the lookout for low stratus in
the Panhandle Wednesday morning for aviation forecasts. PWATS
increase to 1.27 inches in the Panhandle Wednesday afternoon to
near .9 inches here at Cheyenne. NAM/SREF/GFS showing pretty
widespread QPF over areas east of the Laramie Range Wednesday
afternoon. The outlier is the ECMWF that keeps the more
widespread QPF south in Boulder`s CWA. Afternoon MUCAPE in the
Panhandle up near 1500 J/KG. So could see a few severe storms
out that way.

Look for another round of showers and storms Thursday as low
level moisture remains in place through the day. Though less
than what we see Wednesday.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 335 AM MDT Tue Jul 16 2024

Upper-level ridging will develop once again over the western
CONUS Thursday through most of the long term forecast. This
ridge is progged to bring warmer temperatures to southeast
Wyoming and western Nebraska once again, but should be cooler
than this previous weekend. 700mb temperatures will only
increase to the 15C mark under the ridge on Thursday leading to
surface temperatures in the mid-80s to mid-90s. This ridge will
remain overhead for Friday as well, with a 500mb high centered
over the Four Corners region and advecting in monsoonal
moisture. Precipitable water will surge well over an inch for
portions of the Panhandle with closer to an inch over southeast
Wyoming. With several vorticity maxima traversing through the
ridge, precipitation looks likely both Thursday and Friday
evening, with Friday having the better chance for wider-spread
precipitation. As a result of the additional precipitation and
cloud cover expected for Friday, temperatures will be cooler in
the low-80s to low-90s across the region.

Saturday and Sunday both look cooler as the upper-level ridge
retrogrades slightly back to the west and colder air floods down
from Canada. Northerly to northwesterly flow aloft will remain for
both days, leading to the potential for precipitation chances in the
afternoons. A large fetch of northerly winds will be present from
southern Canada to northern Arizona, further promoting the cooler
temperatures. Temperatures on Saturday are expected to be in the
low- to upper-80s, with upper-70s to mid-80s expected Sunday. Kept
PoPs fairly low for these two days, between 20 and 30%, as afternoon
showers and storms will be difficult to track down at this time. The
cooler temperatures look to remain through the early week as the
strong northerly flow aloft remains.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1136 PM MDT Tue Jul 16 2024

Light easterly winds overnight will help pull in more moisture
ahead of Wednesday. This will lead to a slight chance for IFR
CIGs at KSNY and KAIA between about 11z and 15z. The probability
is too low to add as a prevailing group, but hinted at the
possibility with FEW clouds below 1000 ft.

Showers and thunderstorms will develop quickly Wednesday afternoon
around 19z, and continue to around 02 to 03z. All terminals will
have the potential to see nearby lightning, gusty winds, and brief
MVFR to IFR VIS in locally heavy rainfall, but confidence is too low
to go beyond VCTS at this time.

&&

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

&&

$$

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