-- Discussion containing changed information from previous version are highlighted. --
202
FXUS65 KCYS 050113
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
713 PM MDT Tue Jun 4 2024

.KEY MESSAGES...

- High Wind Warnings remain in effect for a large part of
  southeast Wyoming until Wednesday afternoon. Wind gusts 60-65
  MPH are expected, especially overnight into early Wednesday
  morning.

- A significant warming trend is expected through mid to late
  week, with widespread highs in the 80s and lower 90s on
  Thursday and Friday.

- Increasing chances for showers and thunderstorms late in the
  week through the weekend. Strong to severe storms cannot be
  ruled out.

&&

.UPDATE...
-- Changed Discussion --
Issued at 713 PM MDT Tue Jun 4 2024

No major changes to the forecast this evening. High Wind
Warnings remain on track, with a lull ongoing across much of the
area. Winds will begin to pick up again overnight and through
the morning and afternoon hours tomorrow. Made some slight
changes to dewpoint, as they were a little lower than current
conditions suggest. Overall, tomorrow will be a warm and windy
day across the region.
-- End Changed Discussion --

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 219 PM MDT Tue Jun 4 2024

Strong winds are expected to persist across much of southeast WY
through at least mid-day Wednesday. Occasional wind gusts around
55 to 60 MPH have been observed over the past several hours over
areas mainly along/west of the Laramie Range, but have generally
seen a lull in the strongest wind speeds given the weakening low
level gradients in the wake of the first fropa. 700 millibar CAG
to CPR gradients are expected to quickly ramp up to 60-70 meters
by 03-06z tonight, in response to strong pressure falls ahead of
the next frontal passage. H7-H8 flow peaks near 60-65 knots over
the southeast Wyoming wind corridors (also spilling into central
and eastern Laramie County) at 12z Wednesday. Forecast soundings
for Cheyenne suggest a very steep near-surface lapse rates along
with a sharp, well-pronounced mountain top inversion which would
suggest strong potential for mountain waves overnight into early
Wednesday morning, especially closer to sunrise. Have gone ahead
and upgraded the High Wind Watch to a Warning for Cheyenne. High
Wind Warnings for remaining zones are in excellent shape through
Wednesday. Winds should begin to slowly diminish after Noon Wed.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 219 PM MDT Tue Jun 4 2024

Thursday and Friday will be the warmest days of the extended
forecast, with afternoon high temperatures being in the 80s and 90s
for the lower terrain and high plains. This is approximately 10-15
degrees above normal for the first week of June. 700mb temperatures
on Thursday and Friday for portions of southeast WY will be
approximately +15C to +18C. With dry conditions being favored for
the weather forecast both days combined with surface high pressure,
KLAR and KRWL could approach record high temperatures of the upper
80s. The mountain elevations of the Snowy and Sierra Madre should
see 60s, which should be pleasant weather for those that are
planning outdoor recreation. Northwest flow at H5/H3 will be the
persistent upper level steering flow pattern, due to the upper level
ridge axis being firmly entrenched across the Great Basin area.
Isolated showers and a possible thunderstorms are expected to pop up
by late Friday afternoon east of the Laramie Range and the Nebraska
Panhandle.

Not much has changed regarding the forecast for the weekend. We will
continue to be under the influence of northwest flow aloft.
Although, our cwa will be near the periphery of a passing shortwave
trough, and subsequent cold front. Daytime highs are likely to be
approximately 10 degrees cooler for most of the cwa on Saturday and
Sunday, but the warmer temperatures aloft may mix down for portions
of Carbon County, keeping those areas in the upper 70s to lower 80s.
This is in response to 700mb temperatures hovering near +10C for
most locations in the region, which is approximately +4C to +8C
cooler than the previous couple of days. We will have much more
moisture being present for the weekend however. Bulk shear, modest
lapse rates, PWATs being near or above 0.75-1.0 inches, surface
convergence should all play their part for afternoon diurnal
convection. This could be the first of several days of thunderstorm
activity in a row, which would bring some much appreciated moisture
to drought stricken areas of the cwa. Model guidance has the upper
level ridge become flattened by Sunday as a progressive longwave
trough intensifies further upstream across the Pacific NW. Strong to
potentially even severe thunderstorms may be favored on Sunday
afternoon and evening if model guidance remains consistent in the
coming days.

The only change for early next week is that deterministic model
guidance is favoring a much cooler solution for daytime highs on
Monday. The GFS is the most aggressive, with keeping daytime highs
in the 40s and 50s behind a strong cold front and pesky cloud cover
sticking around. The Euro and Canadian model are not as aggressive,
but still on the cooler side of daytime highs as 50s and 60s are
favored. Ensemble members are not showing as much of a daytime high
shift between Sunday and Monday, so have gone with a conservative
approach to temperature changes. The showers and thunderstorm
potential continues for weather impacts on Monday into Tuesday,
before we begin to warm back up by the middle of next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 546 PM MDT Tue Jun 4 2024

VFR conditions expected across area terminals through the
forecast period. West winds gusting around 30-35 kt continue for
southeast WY terminals early this evening. Winds will drop off
temporarily this evening before increasing once again early
Wednesday morning through much of the afternoon. Mountain wave
activity could support brief periods of 50 kt wind gusts,
especially near daybreak Wednesday. For NE panhandle terminals,
gusty northwest winds around 30 kt are expected for much of
Wednesday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until noon MDT Wednesday for WYZ104.
     High Wind Warning until 6 PM MDT Wednesday for WYZ106-109-110-
     115>117.
     High Wind Warning from midnight tonight to noon MDT Wednesday
     for WYZ118.
NE...None.

&&

$$

UPDATE...AM
SHORT TERM...CLH
LONG TERM...BW
AVIATION...MB