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FXUS63 KDDC 021048 AFDDDC

Area Forecast Discussion National Weather Service Dodge City KS 548 AM CDT Thu May 2 2024

KEY MESSAGES

- Next storm system Friday Night will carry with it a Marginal Risk (1 out of 5) of severe weather.

- Widespread heavier rainfall forecast than what we have seen with systems in the past couple months -- 75th percentile at around three-quarters inch for much of western Kansas.

- Major storm Monday will bring higher severe weather risk across eastern half of Kansas. If storm slows down any, portions of southwest Kansas may be in play for a fairly high- end severe thunderstorm risk.

SHORT TERM /THROUGH FRIDAY/
Issued at 413 AM CDT Thu May 2 2024

An active weather pattern will continue through this Short Term period ending Friday Night as yet another storm system will build in behind the trough that was moving across the Northern Rockies overnight tonight. A small, rather disorganized mesoscale convective system (MCS) was moving east across northern Kansas, which was finally clearing Ellis County as of 810Z (310 AM CDT). The north winds behind a cold front were drawing cooler air southward overnight with surface observations showing mid to upper 40s across far west central and much of northwest Kansas.

For today, we will see an initial bump in north winds after boundary layer mixing sets in, but wind speeds will gradually decrease through the day as a surface to 850mb high expands its influence across Kansas. Increasing subsidence will lead to an erosion of remaining low cloud by midday/early afternoon which will help boost afternoon temperatures to a high of around 70 north to mid 70s along the Oklahoma border.

Tonight, easterly winds will develop with 850mb winds veering around from northeast to southeast in response to the next jet steak upstream entering the Northern/Central Rockies. Low level Gulf of Mexico moisture will not be too far away given the quick return flow, thus low level moisture advection from the southeast will commence Friday morning. This will likely bring in some low stratus cloud, especially across the southern counties where moisture advection will be highest early in the morning.

Friday, surface winds will pick up in speed once again as a lee trough develops across southeastern Colorado as the upper level jet streak moves across the Wyoming-Colorado region. The increased low level winds will accelerate low level moisture movement back into western Kansas. So, the moisture will be back. Wind shear will be adequate for organized thunderstorms -- which is climatological for early May out here in western Kansas. Instability will be there with cool 500-700mb temperatures (around -15C/+6C), albeit boundary layer warming will not be all that great. The last ingredient, forcing for lift, will be the key ingredient for Friday Night's system...as a strong cold front will be in play with a sharp temperature gradient and very high (and deep) frontogenetic forcing. The 850-700mb frontogenesis may be enhanced due to constructive coupling of the right-entrance region of the northern jet (across Nebraska) and the left-exit region of the southern branch jet across New Mexico into West Texas.

All models have at least modest QPF (0.25" or more) across west central and southwest Kansas Friday Night due to the explained meteorological ingredients in the previous paragraph. The timing will be later in the night for this event, thus the severe weather risk will not be all that great. This does not look like a supercell setup either, as much of the thunderstorm activity across western Kansas will be confined to the strong cold front, thus the most favored mode will be multicell clusters and quasilinear structures.
Early in the event Friday Night, some large hail will certainly be possible, but later in the night, the event will transition more toward a damaging wind risk and locally heavy rainfall. The latest WPC Excessive Rainfall Outlook for Day Two does have a Marginal (5%)
risk across much of Kansas.

QPF amounts: The May 02/01Z run of the latest NBM is showing 25- 75th percentile amounts of None to around 0.25" across far southwest Kansas...around 0.10" to 0.80" across the mid-section of our forecast area (Scott City to Dodge City to Coldwater)...with a similar 25-75th percentile range up around Hays.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
Issued at 413 AM CDT Thu May 2 2024

After Friday Night's wave moves east, Saturday will be another benign day behind the cold front with all models showing single- digit degC 850mb temperatures in the afternoon, which would support highs Saturday only in the 60s. Sunday will be a transition day in between storm systems as a much larger Pacific storm will be taking aim on the Central Plains come Monday. Ahead of this system on Sunday, the southeast wind machine will resume with strongest Sunday afternoon winds out west toward the Colorado line. The latest NBM surface sustained winds of 20 knots out west might not be high enough.

The strong southeast winds will initially be recirculating the remnant cool airmass from Saturday, so there will likely be quite a bit of cloud on Sunday (along with some morning elevated thunderstorm activity...30-40% chance). Sunday Night/Monday Morning will likely be breezy, mild, and humid as lower to mid 60s dewpoints make a run on southwest Kansas ahead of a formidable upper low centered over southwestern Wyoming (per ECMWF). Monday does appear to be a rather classic looking Great Plains severe weather day ahead of a highly impressive looking negative-tilt 500mb trough. The global models show a cyclonic wavebreak scenario as an upstream, cyclonically curved jet digs in behind the ejecting upper low in a highly dynamic manner. This will almost assuredly focus surface cyclogenesis way up into the Dakotas late Monday (00Z Grand Ensemble 50th percentile MSLP of around 988mb around Dickinson, ND). The impressive upper level jet cutting underneath the ejecting low will likely enhance dryline convergence all across the Central Plains leading to numerous severe thunderstorms, including all types of severe weather. Monday is still 5 days out, however the SPC has issued a 15% outlook area including the eastern half of Kansas (just barely outside of our forecast area). Timing of this system is still a major uncertainty, and if we see any slowing down of the Monday storm, then the severe weather risk will have to be pulled back west in future forecast updates.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
Issued at 546 AM CDT Thu May 2 2024

Morning IFR/MVFR flight category due to low stratus cloud will gradually scatter out to VFR by mid-late morning, however north winds will continue through the remainder of the day. Wind speed will be strongest from mid morning through early afternoon before falling to around 12 knots or so by late afternoon/early evening. Winds will veer around to the east tonight but generally be less than 10 knots.

DDC WATCHES/WARNINGS/ADVISORIES
None.

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