← Previous June 18, 2024 12:32 PM

FXUS63 KABR 181732

Area Forecast Discussion
National Weather Service Aberdeen SD
1232 PM CDT Tue Jun 18 2024


- A break from the active pattern is anticipated tonight through
  Wednesday. However, it quickly turns more active again by the
  end of the week into the first half of the weekend with a 40-90%
  chance of precipitation with the highest chances Thursday night
  through Saturday.


Issued at 1225 PM CDT Tue Jun 18 2024

Front continues it progression east, with low clouds,
falling/stalling temperatures and a little drizzle/sprinkles in 
its wake. Out ahead of the front we also continue to see light 
showers and a few lightning strikes. CAMS still support convective
development just east of the CWA later this afternoon in that 
80 over 70 degree airmass (which still persists near 
Ortonville/Milbank/Watertown areas at this time). No major changes
of note to the forecast but will continue to watch the far east 
for convective potential until they end up in the post frontal 


Issued at 318 AM CDT Tue Jun 18 2024

As of 3am a strong line of storms ahead of the cold front, 
within an MCS, extends from northwestern MN and southwestward 
through south central SD. Radar rain estimates have been between 2-4 
inches in central SD as the line has trained over the same areas 
around and west of the Mo River. A Flash Flood Warning has been 
issued for parts of Stanley County as Crest Unit Streamflow's values 
have risen up to values of 600cfs/smi! HREF/CAMs indicates the line 
will continue eastward through the morning. With the LLJ and 
northerly moisture surge, ahead of the front, these storms could 
still stay strong for the next couple hours, but looks to become 
more outflow dominant after this. By 18Z, lingering stratiform rain 
will be over our extreme eastern CWA as the line continues into MN. 
Little bit of a difference between CAMs on the exact exit time here. 
A few of the models do show some light straggling precip behind the 
main line, associated with the 850mb front. I left pops under 10% 
for now.

HREF and LREF ensembles indicate southwest flow continuing over the 
CWA with a longwave trough over the western CONUS as the associated 
shortwave tracks over the Northern Plains today and continues 
northeast into Ontario by early Wednesday. Winds aloft continue to 
be strong downwind of this shortwave, ranging from 50-65kts, 
increasing to 60-70kts this evening from central SD through ND by 
00Z Wednesday. By 12Z, the 850mb low will centered over the Northern 
Plains with the ongoing LLJ in place over eastern to southeastern SD 
into the Central Plains. Speeds are between 50-60kts, decreasing mid 
morning or so as it moves east with the low. The surface low is 
forecasted to be over northeastern SD with the cold front draped 
southward through NE. Winds will switch to northwesterly from west 
to east across the CWA with northwest flow into tonight.

GFS indicates 6 hour pressure rises of +9 to +13mb will move in from 
west to east over the CWA with the incoming high today. This will 
bring in CAA (-3 to -15C/12hr. With pressure rises and CAA this will 
help steepen low level lapse rates a bit. We do lose that LLJ so 
850mb winds won't be anything impressive this afternoon but we do 
reach between 20-25kts, at peak heating, at the top of the mixed 
layer, mainly over central SD per RAP soundings. I did blend 
NBM/NBM75 to show for this with gusts up to 35kts in our usual 
Corson and Dewey Counties.

High pressure keeps the area dry this evening into Wednesday. With 
the cooler air from the high, lows will dip down into the 40s to the 
lower 50s. MaxT temps for Wednesday will range only in the upper 60s 
to the lower 70s.

Unsettled weather returns to the area Wednesday evening through the 
end of the week. The longwave trough remains unchanged through 
Friday with a northern shortwave pushing west to east over the 
northern CONUS and over the Northern Plains/southern Canada by the 
weekend. Models agree on this setup, but still some differences 
between the ensembles on intensity and timing of wave. GEFS shows 
this wave deeper and GEPS keeps it more broad. A surface stationary 
front is forecasted to be centered over the Central Plains Wednesday 
into Thursday and lift northward, as a warm front, into Friday 
morning as a lee side low develops. So pretty similar setup to what 
we have been dealing with. CSU does peg our CWA with a 5% chance of 
severe during this time but still to early to nail down details. 
This low will sweep across the CWA Friday into the Saturday time 
frame. Our highest pops (70-90%) will be Thursday night into Friday 
morning. A high will move in behind the low Saturday into Sunday. 
Well into the extended LREF ensembles indicate another shortwave/mid 
low in Canada that will bring a surface front in, from the 
northwest, early next week.

High temps do not look to be anything extreme through the weekend 
Temps will range in the 70s and 80s with warmer air moves back in 
early next week as a ridge moves overhead aloft, with forecasted 
highs in the 80s into the lower 90s.


Issued at 1225 PM CDT Tue Jun 18 2024


A mix of MVFR/IFR CIGS follows a cold front that should pass
through KATY shortly and has already impacted the other CWA
terminals. CIGS will gradually improve through the
evening/overnight as drier air moves in on a northwest wind.