Area Forecast Discussion
Issued by NWS Cheyenne, WY
FXUS65 KCYS 242106
Area Forecast Discussion
National Weather Service Cheyenne WY
306 PM MDT SUN JUL 24 2016
.SHORT TERM...(This evening through Tuesday night)
Issued at 245 PM MDT Sun Jul 24 2016
Tonight...Agree with the Storm Prediction Center day 1 outlook for
marginal to slight risk including Laramie, Wheatland, Cheyenne
and Kimball. Decent low and mid level theta-e ridge axis sets up
in this area with early afternoon surface based CAPES from 1000 to
2000 J/kg and bulk shear from 35 to 45 knots with isolated
thunderstorms already appearing on the radar shortly after noon.
Thinking a few storms will produce hail and gusty winds with
isolated severe storms possible through early evening. Low level
moisture definitely more available with dewpoints up significantly
from yesterday at this time.
Monday...Mid level temperatures warm considerably. Low level
convergence axis sets up in the afternoon across southeast
Wyoming but it will be difficult for thunderstorm initiation with
less low level moisture and warmer temperatures aloft acting as a
capping inversion. Perhaps isolated thunderstorms across far
eastern Wyoming and western Nebraska.
Monday night...Quiet night with clearing skies.
Tuesday...Temperatures aloft cool down and with increased low level
moisture and a low level convergence axis setting up near the
Colorado state line. Will see isolated to widely scattered afternoon
and evening thunderstorms develop.
Tuesday night...Thunderstorms ending in the evening with loss of
daytime heating...then clearing skies.
.LONG TERM...(Wednesday through Sunday)
Issued at 300 PM MDT Sun Jul 24 2016
This afternoon/s model guidance progs the upper high pressure center
to retrograde west across the Four Corners and Great Basin early this
week. West to northwest flow aloft will develop, shunting most of
the subtropical moisture to the south. Upslope east to southeast low
level flow will advect ample moisture across the plains behind a
front that stalls near the Laramie Range late Wednesday. Some upper
level disturbances in the northwest flow will track southeast across
the northern Great Plains with cooler air aloft providing instability
and some low/mid level shear for strong to severe convection Wednesday
and Thursday. Near seasonal temperatures are forecast Wednesday and
Thursday with highs in the 70s and 80s and lows in the 40s and 50s.
Shower/thunderstorm coverage decreases beginning Friday as the upper
ridge shifts east toward the Rockies. This upcoming weekend looks
dry with temperatures warming above normal with highs in the mid
80s to mid 90s and lows in the mid 50s to mid 60s.
.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1143 AM MDT Sun Jul 24 2016
VFR conditions will continue through early afternoon before
isolated to scattered thunderstorms mid to late afternoon across
portions of southeast Wyoming and far southern Nebraska Panhandle.
Prevailing winds will be southeasterly 10-15 kt east of the Laramie
Range and westerly 10-20 kt to the west. VCTS forecast at Cheyenne,
Laramie, Scottsbluff and Sidney between 20Z and 04Z with MVFR to
localized IFR visibilities in heavy rainfall as well as gusty/erratic
outflow winds to 40 kt and small hail. Convection will diminish
later this evening with clearing skies and light winds.
Issued at 236 PM MDT Sun Jul 24 2016
Expect low humidities along and west of Interstate 25 the next
few days with gusty winds in the afternoons and early evenings.
Will need to watch conditions for Monday.