847
FXUS63 KDDC 181600
AFDDDC

Area Forecast Discussion
National Weather Service Dodge City KS
1100 AM CDT Wed Sep 18 2024

.KEY MESSAGES...

- Marginal Risk (Level 1 of 5) of a severe storm or two east of
  an Ashland to Larned line, however coverage of storms will be
  much less than last night.

- Next major storm system poised for the weekend with increased
  thunderstorm and rainfall potential. Period of greatest
  rainfall potential from Saturday afternoon through Sunday
  morning.

- Strong cold front behind weekend storm system will lead to
  beginning of cooler period with highs in the 70s next week.

&&

.DISCUSSION...
Issued at 400 AM CDT Wed Sep 18 2024

A significant precipitation event, which over-performed quite a bit
from yesterday`s forecast, continued to push slowly east during the
overnight hours. Total rainfall here at NWS DDC was near two inches
as of 08Z (3 AM CDT)! The over-performance of this event across
southwest Kansas was due largely in part to the exit region of a
stronger-than-forecast southern branch jet that nosed squarely
toward southwest Kansas. The widespread coverage of heavy rainfall
will have a bit of an impact on temperatures this afternoon, and we
have pulled back some on afternoon temperatures closer to straight
NBM (instead of 75th to 90th percentile), thus highs will likely be
upper 80s to around 90 most areas, except for the Red Hills in the
mid 90s where less rainfall occurred.

A remnant convergence axis in low level winds this afternoon, mainly
just east of Dodge City, will likely foster redevelopment of
isolated to widely scattered thunderstorms. The Day One SPC Outlook
does have a Marginal Risk (1 of 5) for this activity, however
overall forcing for ascent will be much weaker today other than the
boundary layer convergence. After this afternoon/early evening`s
isolated thunderstorm activity, we will see a break on Thursday in
between system, then eyes turn back to the west for our next storm
system.

Our next storm system over the weekend still looks on track for
potential significant precipitation amounts across portions of the
Central and High Plains. This event will be focused on late Saturday
and Saturday Night, perhaps into early Sunday morning. Global model
ensemble systems GEFS, ECMWF EPS, and Canadian GEPS all show a
strong QPF signal. Meteorological features supporting heavy rainfall
include a slow-moving upper low ejecting northeast out of the Desert
Southwest region into Colorado, a moistening lower troposphere as
strong southerly winds develop to our south ahead of the system,
allowing for development of a mature warm, moist conveyor belt.
Model ensemble consensus (100-member Grand Ensemble means) show a
500mb low/vorticity max center tracking from near Flagstaff, AZ
Saturday morning to around Denver, CO late Saturday Night. Grand
Ensemble mean 850mb height/wind/temperature fields suggest strongest
low level frontogenetic forcing from eastern Colorado into
northwestern Kansas Saturday Night, which would favor areas just
north of our NWS DDC forecast area for widespread 1-2" rainfall.
That being said, appreciable thunderstorms and rainfall will also
occur within the warm conveyor belt airstream itself across our
southwest Kansas region, supporting fairly high probabilities of
0.50" or greater rainfall over a 24-hr period from Saturday
afternoon to Sunday afternoon (~25% over the Red Hills region
increasing northward to ~60% up across Trego-Ellis County). Over the
past couple of runs, the Canadian GEPS ensemble system has been the
farthest south of the three main ensemble systems, really focusing
heavy precipitation squarely on the northern half of our forecast
area between Highway 50 and I-70. The GEPS has 75th percentile 24-hr
QPF of 1.25 to 1.75". The other two ensemble systems keep 75th
percentile 1.5"+ QPF farther north across far northwest Kansas into
southwestern Nebraska.

The next forecast challenge will be temperatures once the strong
cold front pushes south Sunday morning. Latest Grand Ensemble has
50th percentile afternoon temperatures Sunday in the mid 60s across
our northwest counties (Hamilton-Scott) to the lower 80s across the
Red Hills. There remains quite a bit of uncertainty still as 25-75th
percentile range on the Grand Ensemble is 15 to 18F. Next week,
temperatures will be much more on par for late September with highs
generally in the mid to upper 70s early to mid next week with lows
well down into the 50s, and even upper 40s out west closer to
Colorado.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1111 AM CDT Wed Sep 18 2024

Residual MVFR to IFR cigs will continue for KGCK and KDDC as residual
moisture from rain prevails across the terminals. Flight conditions
will improve to VFR later. VFR conditions are expected for the rest
of the terminals and the rest of the pd. Southerly winds around 20
kt with gusts to 30 kt will continue through late afternoon. A fropa
is expected tomorrow with winds switching out of the NW 10-20 kt.

&&

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

&&

$$

DISCUSSION...Umscheid
AVIATION...Sugden