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FXUS63 KDDC 031501 AFDDDC

Area Forecast Discussion National Weather Service Dodge City KS 1001 AM CDT Fri May 3 2024

Updated Aviation/Key Messages

KEY MESSAGES

- Much needed rainfall expected across much of southwest Kansas Friday night and early Saturday. Some strong to marginally severe thunderstorms are possible.

- North winds and cooler air Saturday.

- Severe thunderstorms are expected in Kansas Monday, with the risk of hail and tornadoes east of US 283 Monday afternoon and evening.

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. HRRR 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 /18Z TAFS THROUGH 18Z SATURDAY/
Issued at 1001 AM CDT Fri May 3 2024

VFR is expected to continue at all airports through at least 00z Sat. Broken mid level clouds will prevail through Friday afternoon with increasing S/SE winds, gusting to near 25 kts.
A strong cold front is scheduled to sweep through the airports in the 06-09z Sat time range, accompanied by an abrupt, strong northerly wind shift, gusting to near 30 kts. Numerous rain showers and thunderstorms are expected to accompany frontal passage. Confidence was high enough to include convective TEMPO groups in this 18z set of TAFs for all airports, in this 06-09z range. Outflow winds from the strongest storms may approach 50 kts. Rain showers are expected to diminish from NW to SE through 12z Sat, with widespread MVFR stratus ceilings through Saturday morning.

DDC WATCHES/WARNINGS/ADVISORIES
None.

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