Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 181743 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1243 PM CDT Mon Mar 18 2024

.KEY MESSAGES...

- Very high fire danger the result from a combination of winds and
  low afternoon humidity (20 to 30%). Peak winds are expected in
  the late afternoon north of Highway 212 in the 30 to 40 mph
  range.

- Sisseton hills downslope winds also expected late this afternoon
  through the early overnight hours. Peak winds of 40 to 50 mph
  expected in those favored areas.

- Additional fire weather concerns are the result of a cold frontal
  passage this evening/overnight, shifting winds from west to
  northwest with more widespread gusts of 20 to 35 mph.

- Colder than normal temperatures Wed-Sun. Decent chance for light
  snow Thursday. High probabilities of at least an inch over the
  northeast quarter of the state.

&&

.UPDATE...
Issued at 1234 PM CDT Mon Mar 18 2024

Aviation discussion updated below for the 18Z TAFs.

UPDATE Issued at 1041 AM CDT Mon Mar 18 2024

Lowered sky cover a bit based on current satellite trends, and may
have to lower things even more. Main concern this afternoon is the
very high fire danger. Many areas will be borderline Red Flag
conditions, so will be keeping a close eye on this. Temperatures
still stuck in the teens and 20s for most areas, but with
southwest winds kicking in and strong warm air advection this
afternoon, still expecting 40s and 50s for highs across the
region, with portions of central/north central SD flirting with 60
degrees.

&&

.SHORT TERM /TODAY THROUGH TUESDAY AFTERNOON/...
Issued at 318 AM CDT Mon Mar 18 2024

Low clouds and some lingering flurries persisting early this morning
but continue on a southwards trajectory as high pressure is slow to
build overhead. Guidance depiction of surface high pressure center
is still supposed to move relatively rapidly across central South
Dakota early, with a southwest component resulting in efficiently
mixing out our cold air, and the gradient rapidly tightens after 15Z
to about 10mb from northwest to southeast across the state. That
said, a strong warm advection signal will result in a somewhat
inhibiting of stronger winds mixing down from aloft. CAMS ensembles
probabilities of exceeding 25mph is nearly 100 percent after 4pm
north of Highway 212, though the 25th percentile remains below Red
Flag criteria though 8pm. Thereafter, much more spread with the
passage of a cold front, which is a wrinkle to contend with if we do
see any fires develop since the potential for an increase in speeds
will also coincide with a wind shift. Overall, guidance is
supporting peak gusts of 35 to 40mph along the higher terrain across
northwest counties and the Leola hills during that transition
period. Additionally, the warm advection signal and southwest wind
component will translate into Coteau downslope winds, also on the
order of 40 to 50mph. As for temperatures, will see upper 50s/low
60s out west while the warm advection push happening late in the day
(an maybe not until tonight) will mean highs only in the 40s for
Minnesota and far northeast South Dakota. CAMS ensembles minimum
relative humidity is again in the 20 to 30 percent range, with the
25th percentiles remaining above 20 percent. As such, its another
potential fire weather day that doesn`t quite meet the strict
definition for Red Flag mainly due to humidity.

Winds will keep temperatures from dropping off too much overnight,
however a second, backdoor front will draw Canadian air back the
Dakotas Tuesday, in all probability stalling temperatures thanks to
stratus and/or daytime heating strato cumulus.  Could see some
flurries in the northeast as well. Mixed winds Tuesday are also in
the 20 to 30kt range in a cold air advection regime.

&&

.LONG TERM /TUESDAY EVENING THROUGH SUNDAY/...
Issued at 318 AM CDT Mon Mar 18 2024

The persistent mid-level block over the western CONUS looks to
breakdown during the long term, but not until the upcoming weekend.
Before then, the main system to be dealt with moves through on
Thursday. There has been pretty good model agreement/consistency
over the last few model cycles, and thus forecast confidence is
moderate to high. Over the northeast quarter of the state various
ensemble data suggests high probs of an inch or greater snowfall in
24hrs. Bump up to 3 inches and probs become negligible. The official
forecast for now stand at 1-3 inches for the system. After Thursday,
the forecast becomes muddled and unclear at best. The one thing that
does appear as if it will occur is a pattern change to some sort of
troffing aloft over the western CONUS. How the energy is handled
within that trof is the issue, and the models are not very
complimentary. As one would expect, forecast confidence really wanes
toward the end of the forecast period. Of some assurance is that
temperatures will likely average out below average for the vast
majority of the forecast.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1234 PM CDT Mon Mar 18 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast through the TAF period. Will be
watching potential for MVFR CIGs to slide southward into northeast
SD Tuesday morning, but unclear whether or not BKN or OVC
conditions affect KATY prior to 18Z. For now have introduced a SCT
mention. Will also be dealing with low-level wind shear (LLWS)
this evening/overnight and have inserted mention of this for the
TAF sites. Southwest surface winds this afternoon will become
northwest through the evening/overnight.

&&

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

$$

UPDATE...TMT
SHORT TERM...Connelly
LONG TERM...TDK
AVIATION...TMT


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