901
FXUS63 KABR 022151 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
451 PM CDT Tue Jul 2 2024

.KEY MESSAGES...

- There is a Marginal Risk (level 1 of 5) for severe weather
  Wednesday afternoon and evening across west and central South
  Dakota. The main threats with the stronger storms will be large hail
  and strong wind gusts.

- The active weather pattern of showers and thunderstorms persists
  for the Fourth of July into Friday.

&&

.UPDATE...
Issued at 450 PM CDT Tue Jul 2 2024

Added some pops to the forecast until sunset as diurnally driven
showers and thunderstorms are spreading across central SD and
toward the James Valley.

&&

.SHORT TERM /THIS EVENING THROUGH WEDNESDAY NIGHT/...
Issued at 258 PM CDT Tue Jul 2 2024

Some light showers/weak thunderstorms have crept into the western
CWA but will dissipate rapidly with loss of heating. Westerly winds
will also decouple. Focus shifts towards convection potential for
tomorrow afternoon. Return flow around weak surface high pressure,
with an approaching weak shortwave, will result in a weakly unstable
atmosphere with skinny CAPE, high bases and 35 to 50kts of
westerly/northwesterly unidirectional shear. Thus, the potential for
hail and winds with these relatively fast moving cells. Instability
and shear drop off rapidly overnight with a second wave coming in
during the morning in the west. The main issue with the second
round, while PWATs aren`t anything anomalous, is the low shear and
skinny shallow CAPE suggesting the potential for slow moving/weak
storms with warm rain cloud processes.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 258 PM CDT Tue Jul 2 2024

Fourth of July looks to be pretty wet as ensembles agree on the
shortwave`s axis over western SD/WY and southward into western NE
starting out at 12Z Thursday. Down at the surface, the center of the
Colorado low is forecasted to be positioned over NE/KS border with a
surface trough back over the central and northern Rockies. Another
area of low pressure will be centered over Manitoba as well.
Moisture will be ongoing from Wednesday/Wednesday night with pops
ranging from 60-90% from 12-18Z and 70-90% through 00Z Friday. This
means high confidence on widespread coverage of rain showers as this
will be a slow moving system. By Thursday evening, the center of the
low will be over MO/IL border with the northern low over northern
MN.

NAEFS really do not show anything out of the ordinary in terms of
PWAT as its running around average for this time of year (1-1.25").
GEFS plumes` mean 24 hr QPF, ending Friday at 12Z, ranges from 0.62"
at KABR and around 1" at KATY with lesser amounts across central SD.
Latest NBM prob of 0.50" ending 12Z July 5 ranges from 35% (just
east of the Mo River) up to 55% (Milbank to Watertown.) WPC is more
aggressive with the moisture with values between 0.50" up to 1.50+"
with the highest totals over our southeastern CWA for the same time
period. Due to this, there is a slight risk (15%) for excessive
rainfall in this area for Day 3. EFI does indicate QPF of 0.5-0.7
with a shift of tails of 1 over the CWA. Instability remains low as
MUCAPE values are 600j/kg and below along with weak mid level lapse
rates. There may be just enough for a few brief general storms at
times on Thursday (35-55% Prob of thunder per NBM).

Both of these systems come together and occlude ~over MN Friday as
moisture continues to linger on the western side of this low, mainly
James River Valley and eastward (20-35% pops). MUCape increases to
1000-1500 j/kg east of the Mo Friday afternoon and evening providing
a chance for thunderstorms.

For Saturday, the occluded low is forecasted to be over MI as a weak
shortwave will move over the Northern Plains, from the northwest,
within a larger longwave trough as the mid level ridge over the
western CONUS becomes quite amplified by early Sunday. Either a
trough or weak front will accompany this shortwave Saturday as it
pushes southeast over the Northern Plains through early Sunday.
Highest pops of 20-45% look to be Saturday afternoon and evening
with the best chance of rain over northeastern SD into west central
MN. By early next week, a +PNA pattern continues with the Northern
Plains in ongoing northwest flow aloft with this ridge starting to
push a little east by midweek.

Temperatures will be 10-15 degrees below average on Thursday with
highs only in the upper 60s to the lower/mid 70s. Friday`s temps
will rebound a bit in the mid to upper 70s to around 80. Highs will
range in the mid/upper 70s an 80s for the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1215 PM CDT Tue Jul 2 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions for all terminals. Breezy west to northwest winds
will decouple this evening.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...Wise
SHORT TERM...Connelly
LONG TERM...MMM
AVIATION...Connelly