069
FXUS65 KCYS 060331
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
931 PM MDT Fri Jul 5 2024

.KEY MESSAGES...

- Near critical to critical fire weather conditions expected on
  Saturday for parts of Carbon and Albany County. A Fire Weather
  Watch remains in effect for those areas due to gusty winds and
  low humidity during the afternoon and early evening.

- Occasional chances for showers and thunderstorms will exist
  over the next several days as a series of weak disturbances
  impact the region. The potential for measurable precipitation
  will remain quite low.

- A few storms may produce small hail and gusty winds on
  Saturday afternoon with a brief surge of pacific moisture, but
  the overall potential for severe storms will remain very low.

- Gradual warming trend expected through next week with limited
  precipitation chances.

&&

.UPDATE...
Issued at 740 PM MDT Fri Jul 5 2024

In a recent update...went ahead and upgraded Fire Weather
Watches for the Laramie Valley and the Upper North Platte River
Valley to Red Flag Warnings. Looks pretty clear cut that these
two fire weather zones are going to hit Saturday afternoon. As
for the other 3 fire weather zones in the watch...decided to
continue just in case there is any last minute updates in fuels
in those zones overnight or Saturday morning. Updates sent.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 230 PM MDT Fri Jul 5 2024

A pleasant day remains firmly in place across the region this
afternoon. Surface temperatures in the 70s to the lower 80s for
the high plains, and the higher terrain remain in the 60s in our
mountain forecast zones. Breezy winds are also present across
the area, with 20-30mph wind gusts being prevalent in our cwa.
Water vapor satellite imagery shows very dry air being present
in the lower levels, but diurnal heating this afternoon has
create an evident swath of fair weather cumulus and cirrocumulus
while taking a look at the current GOES-16 visible satellite
imagery. Wouldn`t be surprised if a sprinkle or two falls in a
few spots before the afternoon is set and done, which could
create an elevated wind gust or two higher than 40mph. Mostly
clear skies are expected tonight along the I-80 corridor,
especially west of the Laramie Range. A passing shortwave
disturbance to our north across eastern MT and the Dakotas will
create an isolated opportunity for a rumble of thunder and a
brief shower overnight into early Saturday morning mainly north
of the North Platte River Valley into the NE Panhandle. This
will allow for pesky clouds to build and stick around, keeping
temperatures elevated overnight in western NE.

The shortwave disturbance will propagate to the east across the
Northern Plains on Saturday. Weak upper level energy from the
Pacific Northwest will combine with moisture, marginal
instability, and modest lapse rates by late Saturday afternoon
and evening. Chances for isolated showers and thunderstorms late
in the day and overnight Saturday will be possible for areas
along and east of the Laramie Range. Before this, daytime highs
will be warm as several areas see upper 70s to middle 80s.
Slightly cooler temperatures will be present for the
Snowy/Sierra Madre mountain ranges for those that are planning
outdoor extracurricular activities. Very dry air will propagate
into our western forecast zones, especially Carbon and Albany
County on Saturday. Fire weather concerns will ramp up as breezy
to gusty winds of 20-30+ mph are favored. A Fire Weather Watch
has been issued to reflect this. Some areas could dip into the
single digits for relative humidity, which will cause flashy
fuels to burn easily and potentially spread quickly thanks in
part to the wind gusts.

The main shortwave trough axis will swing through the cwa by
Sunday, and bring another cold front to the area. This will
cause pleasant conditions as surface High pressure builds into
the area behind the cold FROPA by late Sunday. Daytime highs by
late Sunday afternoon will struggle to eclipse the 70 degree
mark in southeast Wyoming. Lower elevations in western Nebraska
will creep into the lower to middle 70s. Scattered rain showers
and isolated thunderstorms will remain possible through the
evening hours. Unfortunately, a wetting rainfall in excess of
0.10 inches is not favored for many areas where the scattered
rain showers occur across our cwa. Sunday night will see mostly
clear skies. Despite it being the first week of July, we could
see some areas in the low to middle 30s for the highest
elevations in the Snowy and Sierra Madre Mtns by daybreak
Monday. The remaining areas will see 40s to low 50s for morning
lows as we begin the new full week of July.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 230 PM MDT Fri Jul 5 2024

A gradual warming trend and fairly dry conditions will be the
overall theme for next week`s weather. The main synoptic driver will
be the persistent ridge that is currently building near the West
Coast. Ensembles are in reasonably good agreement on this feature
very slowly drifting eastward over the course of the week. Monday
still look several degrees cooler than average for this time of year
in the wake of the last more significant shortwave trough rotating
around the central US. Tuesday should warm back to near or slightly
below average as the ridge slowly expands eastward. For Wednesday,
several ensemble members (mostly ECMWF) have a slower expansion of
the ridge, which would allow the next shortwave riding around the
longwave trough to bring its cold front through the area and briefly
stall the warming trend. Other members (mostly GEFS) build the ridge
in faster, which would shunt this next front off to the east.
Precipitation will be hard to come by in this period with fairly dry
air in the lower atmosphere. Monday might be nearly completely dry,
but precipitable water values should climb closer to climatological
norms for Tuesday and Wednesday. This should allow for some isolated
afternoon convection, mainly over and near the higher terrain. We`ll
have to watch the plains in the ECMWF slower warm-up scenario, as
this would also allow the vort-max aloft to kick off some activity
on Tuesday/Wednesday in the Nebraska panhandle. The GFS and GEFS
generally keep this more towards central and eastern Nebraska.

By Thursday, ensembles are in good agreement that our area will be
firmly under the influence of the ridge. Thus, expect above average
temperatures to return to the forecast, bringing widespread upper
80s to 90s to the area. While essentially all ensemble members are
on board with hot weather returning by Thursday, the GEFS/GFS
solution is a bit more aggressive than the ECMWF and its ensemble.
NAEFS mean 500-mb heights and 700-mb temperatures are already
approaching the 90th percentile of climatology by Friday, more so
for northern and western portions of the forecast area. While it
certainly looks hot, probabilities of record highs are fairly low at
this time, mainly because this is the climatological hottest time of
the year.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 927 PM MDT Fri Jul 5 2024

Northwest flow aloft will continue, with a weather disturbance
Saturday evening helping to produce isolated to widely scattered
showers along and east of Interstate 25.

Scattered to broken clouds from 8000 to 10000 feet will prevail.
Showers will be in the vicinity of Chadron and Alliance from
08Z to 14Z, and also at Cheyenne and the Nebraska Panhandle
terminals Saturday evening. Winds will gust to 25 knots at all
terminals from 14Z to 00Z.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Fire Weather Watch from Saturday afternoon through Saturday
     evening for WYZ422-423-427.
     Red Flag Warning from noon to 8 PM MDT Saturday for WYZ425-428.
NE...None.

&&

$$

UPDATE...GCC
SHORT TERM...BW
LONG TERM...MN
AVIATION...RUBIN