Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 141128 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
628 AM CDT Thu Mar 14 2024

.KEY MESSAGES...

- Very High Grassland Fire Danger over northern South Dakota on
  Friday and all of central and northeast South Dakota on Saturday.
  This will be driven by existing dry conditions and gusty
  westerly winds of 30 to 40 mph on Friday, which will turn to the
  northwest on Saturday behind a cold front.

&&

.UPDATE...
Issued at 624 AM CDT Thu Mar 14 2024

Updated for 12Z Aviation discussion below.

&&

.SHORT TERM /TODAY THROUGH FRIDAY AFTERNOON/...
Issued at 317 AM CDT Thu Mar 14 2024

Fairly quiet conditions across the area early this morning, with
three layers of clouds over or nearing the forecast area. There is
high cirrus invading the southern part of the CWA from the
precipitation/thunderstorms occurring farther south in NE/IA/MO and
the cirrus should continue to push north-northeastward through the
first part of the morning. Moving down to the mid-level clouds,
those have been expanding southwestward over much of the CWA early
this morning as the 700mb northeasterly flow has increased between
the approaching ridge in western ND and the 700mb low in southeast
NE. Those clouds should shift south through the day as the 700mb
ridge slides south across the area. Finally, low clouds and fog are
working their way south-southeast across western/central ND and
should be moving into Corson county in the next hour or two. Have
shown some fog potential in the forecast for this morning for
Corson/Dewey county as those low clouds move in. The question for
today is how far west those low clouds make it through the
afternoon. Models are fairly consistent on them continuing to drop
south along the Missouri River valley through the day under the
northerly winds, but largely staying west of the James River valley
area until evening when 925-850mb winds turn a little NNW. Either
way, with the multiple layers of clouds, today will be mostly
cloudy, with the far northeast part of SD having the best
opportunity for some sun between the multiple layers. One final item
of note. Seeing some hints of very light precip trying to drop into
north central SD from ND late this afternoon into the first part of
the evening. GEFS continues to be the most aggressive with
probabilities of 0.01" QPF, but even then, it`s only around 20-25%
this evening (EC-Ens/GEPS are less than that). The biggest question
mark based on HREF/EC-Ens soundings is the depth of the moisture
(generally at/below 850mb), which supports keeping a largely dry
forecast for now (have 15% PoPs right on border). Temperatures today
will be cooler than yesterday due to the cooler northerly flow, but
highs will still be above normal, primarily east of the Missouri
River, where highs will be in the upper 40s and lower 50s.

A high pressure ridge will drop southeast across the area tonight,
along with a weak 500mb shortwave trough towards daybreak Friday.
That will help push the mid-high clouds out of the area, but could
still see the low clouds lingering into Friday morning. Attention
then turns to the increasing westerly flow ahead of an approaching
cold front for Friday night. With the increasing pressure gradient
and low level winds, expect fire weather conditions to near critical
levels Friday afternoon. For the winds, 850mb winds will increase
into the 30-35kt range over northern SD during the afternoon and
expect mixing to the 800-775mb range. Thus would expect some gusts
towards 30-35kts around peak heating to sunset. There are still some
slight timing differences on when the strongest 850mb winds will
arrive, but it should be in the 21Z-00Z period. With the westerly
flow and a slight turn to the WSW over the Coteau, do expect some
downslope help on the eastern side of the Coteau. Westerly flow,
warm air advection aloft, and deeper mixing, will lead to a warmer
day with highs in the 50s. The abundant low level dry air and warmer
temps will allow RH values to fall into the 20-35% range, with the
lowest values in the MO River Valley. Thus, with the dry fuels, will
be seeing fire weather conditions in the Very High GFDI category for
areas north of SD-20 and potentially to US-212. Over north central
SD, will be nearing Red Flag criteria, especially over Corson
county, so day shift may need to consider a Fire Weather Watch if
forecast remains on track.

&&

.LONG TERM /FRIDAY EVENING THROUGH WEDNESDAY/...
Issued at 317 AM CDT Thu Mar 14 2024

We start the long term Friday night under an upper level trough with
a cold front starting to move through at the surface traveling north-
northwest to south-southeast. The upper level trough stays in place
through the weekend before a ridge begins to build in Monday.

Ensembles are starting to show increasing chances for some light
precip on Thursday but that is 7 days out so details are uncertain.
Otherwise, the long term looks dry.

Friday evening starts our cooler weekend with the first shot of
cooler air. A cold front moves through the region dropping
temperatures at 850mb almost 10 degrees in 12 hours. A second shot
of cooler air moves through Sunday dropping 850mb temps another
almost 10 degrees in 12 hours. This corresponds to slightly below
average temperatures at the surface for Sunday. Stronger WAA spreads
east into the rest of the CWA.

Winds Friday night into Saturday are still looking to gust upwards
of 35 to 40 mph increasing fire weather concerns. Otherwise, we are
looking at just our normal gusts of 20 to 25 mph across the region.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 624 AM CDT Thu Mar 14 2024

Terminals KABR,KATY,KPIR,KMBG

MVFR/IFR ceilings dropping out of ND this morning will be the main
forecast concern. The IFR cloud deck should be reaching KMBG
around the start of the TAF period and based on upstream
webcams/obs, would expect reduced visibilities with fog too. The
northerly winds will continue to push these clouds south into KPIR
and likely KABR later today. Diurnal heating will try to help
raise the ceilings through the day and bring them up to MVFR
values. Expect these clouds to shift eastward tonight and
eventually dissipate towards Friday morning, as drier westerly
winds develop on the back side of a high pressure ridge that moves
through tonight.

&&

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

$$

UPDATE...SRF
SHORT TERM...SRF
LONG TERM...KK
AVIATION...SRF


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