547
FXUS63 KDDC 031049
AFDDDC

Area Forecast Discussion
National Weather Service Dodge City KS
549 AM CDT Fri May 3 2024

.KEY MESSAGES...

- Bimodal severe weather risk with initial supercell/large hail
  risk early-mid this evening and squall line/damaging wind
  risk later on tonight with the cold front.

- Many areas likely to see much needed rain with widespread one-
  half inch or greater rainfall expected.

- Severe weather outbreak, including tornadoes, appearing more
  concerning across the Central Plains, including portions of
  southwest and south central Kansas.

- Critical fire weather risk west of the dryline is also a
  concern Monday afternoon, primarily west of Highway 283.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 400 AM CDT Fri May 3 2024

The main forecast challenge will be in the Tonight period with
respect to severe weather risk and how much/where heaviest rainfall
will occur.

Overnight water vapor loop showed the first northern branch jet
streak lifting northeast out of the Northern Plains into the Upper
Great Lakes region with the next upstream jet streak entering the
Northern Rockies. The lower troposphere was beginning to feel the
influence of the next jet approaching with low level winds
continuing to slowly veer around from the northeast to the east
overnight. Observations were showing lower to mid 50s dewpoints not
too far south of our forecast area across western Oklahoma and the
Texas Panhandle. This increasing moist upslope low level flow
pattern was manifesting as low stratus development per Nighttime
Microphysics RGB satellite loop. As low level winds continue to veer
to the southeast, moisture advection will increase into southwest
Kansas today. As this is happening, our upstream jet streak will be
rounding the base of the shortwave trough as it moves east across
Wyoming later today.

Low level cold frontogenesis will ramp up in earnest late this
afternoon and this evening across northeast Colorado and southwest
Nebraska. South of the front, a 998-1000mb surface low will be
across southeastern Colorado. Increased lee trough/dryline
convergence near this surface low will foster development of surface-
based thunderstorms across southeast Colorado ahead of the cold
front. There is a high degree of confidence in convective initiation
as just about all convection-allowing models (CAMs) show development
in the 21-24Z time frame late today. HREF mean SBCAPE in the 1000-
1300 J/kg and favorable looking hodographs with rather well-shaped
clockwise curvature in the 0-3km layer support supercell structures
with the surface low/dryline initiation across southeast Colorado.
There is a fairly solid clustering of 50+ J/kg 2-5km AGL Updraft
Helicity from Baca and Prowers County, CO into our western counties
of Hamilton-Stanton and points east toward Scott-Finney-Haskell
County by 01Z (8pm CDT) or so. Any supercells will be capable of
golf ball to perhaps 2-inch diameter hail stones as the primary
risk. As the cold front approaches west central KS later tonight,
additional storms will form with the mode being more linear in
nature with the greatest severe risk being 55 to 70 mph wind gusts.
The initial supercell(s), should they form as forecast, may wipe out
some (or most?) of the CAPE which complicates the severe weather
risk later on tonight with the main cold front. Regardless, low
level moisture will continue to advect northward toward the front
late tonight with very strong low level winds ahead of and behind
the front with intense cold frontogenesis. The magnitude of
convergence/frontogenesis is expected to result in numerous showers
and thunderstorms. Most models now have a rather large area of one-
half to one inch of rain, and given the forcing for ascent and other
aforementioned meteorological reasons, it is hard to argue with this
aggressive QPF.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 400 AM CDT Fri May 3 2024

Monday continues to be the most hazardous looking weather day in the
Long Term period as a very impressive cyclonically-curved jet streak
enters the Great Plains. The exit region of this jet will aim
squarely on Nebraska and Kansas with the mid level and surface
cyclones undergoing robust development through the day Monday. We
will likely see both severe weather and fire weather risk late
Monday. There remains high uncertainty in where exactly the dryline
and/or mid level cold front will be positioned by the time
convection initiates Monday afternoon. The ECMWF, no surprise, is
the farthest west of the three main global spectral deterministic
models with the dryline/dry intrusion front feature somewhere
near/west of Pratt by "go" time. The EC has mid 60s dewpoints
driving north into south central Kansas with a classic looking
vertical wind shear profile very  much on the supercell end of the
spectrum. Monday`s main question will be how long mode can be
supercell. The shape/orientation of the upper level jet almost
orthogonal to the orientation of the dryline/dry intrusion front is
an important pattern recognition component to consider as many
historical Great Plains tornado outbreaks have a similar type of
upper level jet pattern with a large warm/moist sector out ahead of
it.

On the other side of the dryline, the development of drought
conditions and stunted green-up so far this spring west of Highway
283 will likely yield Critical Fire Weather risk as afternoon
relative humidity is likely to fall below, if not well below 15% on
a strong southwest wind 20 to 35 mph.

Monday`s storm will be the last severe weather risk across
southwest/south central Kansas for the foreseeable future as the end
of the Long Term period and beyond will be characterized by
anomalous high surface pressure, cooler temperature, and drier air
as the North America pattern becomes one of ridge in the west and
trough in the east through at least 13 May. The latest ECMWF and
GEFS Ensemble systems are in rather remarkable agreement at Day 10
regarding this cooler/drier/essentially non-existent severe wx
pattern as we head deeper into the middle-third of May.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 543 AM CDT Fri May 3 2024

Stratus cloud continued to expand across southwest Kansas at the
onset of this TAF period, however ceilings were comfortably
above 3000 feet (MVFR threshold). Ceiling is forecast to fall to
below 3000 feet at LBL before scattering out later in the
morning. Numerous thunderstorms will impact all terminals later
tonight as a strong cold front pushes south across western
Kansas late in this TAF period.

&&

.DDC WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...Umscheid
LONG TERM...Umscheid
AVIATION...Umscheid