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000
FXUS65 KCYS 031119
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
519 AM MDT Sat Jun 3 2023

.SHORT TERM...(Today - Sunday Night)
Issued at 358 AM MDT Sat Jun 3 2023

A unique & complex forecast scenario will persist over the next 24
to 36 hours w/ an aggressive Rex Block pattern entrenched over the
majority of the western and central CONUS. Early in the period, an
intense (587 dam) 500-hpa ridge will limit the progression of deep
troughing just off the coast of western British Columbia. Although
general upper-level ridging will be present across a large portion
of the area today, numerous weak short wave disturbances are under
cutting the ridge over the central & northern Rockies, and are not
expected to move much over the next 12-24 hours with weak steering
flow in place aloft. As such, showers & thunderstorms will be very
common through Sunday with the greatest coverage favored diurnally
in the presence of afternoon instability. Recent GOES-16/17 WV Sat
imagery indicates an impressive fetch of mid & high level moisture
courtesy of deep southeasterly flow on the back side of the upper-
high over the Midwest. This will support PW values remaining above
climatology, quite significantly in the neighborhood of 0.8 to 1.2
inches especially over the Plains. Potential will exist for robust
convection given persistent theta-e advection present in the lower
levels through much of the forecast period. While some hail cannot
be entirely ruled out as CAPEs approach 500 J/kg, overall buoyancy
profiles are very tall and skinny with very deep saturation, so we
would expect heavy rain and possible flash flooding to be the main
hazard of interest through this evening. As such, a Flood Watch is
still in effect for the entire CWA thru late tonight. Thunderstorm
activity and associated cloud cover should keep temperatures below
seasonal norms for the most part.

.LONG TERM...(Sunday through Friday)
Issued at 358 AM MDT Sat Jun 3 2023

Generally unsettled weather continues in the extended forecast, with
the current Rex Block pattern transitioning towards an Omega Block
like pattern by early to midweek. Daily chances for precipitation
continue with continuous shortwaves pulsing within the flow and
ample moisture advection as PWATs remain well above average. Main
forecast challenges will include daily chances for afternoon
convection and any possible weather impacts expected.

Current model guidance has this blocking pattern setting up over the
central CONUS with an upper level closed low digging southward
across the western seaboard and an additional low stalling out just
north of the Great Lakes. This blocking pattern is expected to limit
movement of the upper level features before becoming nearly
stationary Tuesday night. Although somewhat of a drier pattern as
compared to days prior, several shortwaves digging across the region
remain possible, effectively undercutting the ridge and bringing a
chance for afternoon precipitation almost every day. In addition to
the precipitation, there are slight chances for any storms able to
develop to become stronger with guidance from the SREF convective
probabilities indicating a 35 to 50 percent chance for CAPE values
to exceed 500 J/kg across southeast Wyoming and the Nebraska
Panhandle both Monday night and Tuesday Afternoon. With that being
said, main concerns remain with the constant moisture advection into
the region and PWATs hovering around the 75th percentile under this
pattern as the low pressure pushes southwesterly flow across the
Intermountain West and ultimately the models having a hard time
locking onto a solution with the available moisture across the High
Plains. Will need to monitor trends throughout the week to determine
any possible impacts for the CWA. Nevertheless, should begin to see
a decent warmup, with daytime highs rebounding into the low-70s for
the majority of areas and even into the low-80s for the far northern
zones.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 509 AM MDT Sat Jun 3 2023

Much of the forecast remains on track, with showers and
thunderstorms remaining possible over the next 24 hours. Weak
shortwave disturbances are progged to pulse within the flow with
plenty of moisture advection across the zone to produce precipitation
across the majority of terminals this afternoon and into the
evening hours. Main forecast challenges will include the overall
timing of each storm as it moves across each zone and the
potentials for fog across the Nebraska terminals this morning.
Most of the Nebraska Panhandle sites have struggled to drop into
IFR categories. However, clearing overhead skies, light winds, and
plenty of surface moisture indicates a decent likelihood of fog
to develop, and as a result, maintained TEMPO groups for IFR
conditions for KCDR, KSNY, and KAIA where fog seems more likely.


&&

.FIRE WEATHER...
Issued at 358 AM MDT Sat Jun 3 2023

No fire weather concerns w/ widespread measurable rainfall.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Flood Watch through late tonight for WYZ101>119.

NE...Flood Watch through late tonight for NEZ002-003-019>021-054-055-
     095-096.

&&

$$

SHORT TERM...CLH
LONG TERM...MRD
AVIATION...MRD
FIRE WEATHER...CLH