Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000
FXUS63 KABR 142330 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
630 PM CDT Thu Mar 14 2024

.KEY MESSAGES...

- Fire Weather Watch in effect over north central South Dakota on
  Friday and elevated fire weather concerns over all of central
  and northeast South Dakota on Saturday. This will be driven by
  existing dry conditions and gusty westerly winds of 25 to 35 mph
  on Friday, which will turn to the northwest on Saturday behind
  a cold front.

&&

.UPDATE...
Issued at 625 PM CDT Thu Mar 14 2024

See updated aviation discussion below.

&&

.SHORT TERM /THIS EVENING THROUGH FRIDAY NIGHT/...
Issued at 142 PM CDT Thu Mar 14 2024

At 1 PM CDT, temperatures range from the upper 40s to the low 50s
east of the Missouri River valley, where it is partly to mostly
sunny. Over the Missouri River valley and points west, temperatures
are warming through the upper 30s to mid 40s, where it is partly to
mostly cloudy. Low level CAA continues on northerly winds, which are
ranging from 15 to 30 mph with some occasional higher gusts, as
surface high pressure to the northwest of the CWA is slowly building
down into the region.

The surface high will build down across the region overnight,
pushing most of the low cloudiness over the northern high plains
south and east. Some of the saturated layer will also be dispatched
by low level dry air advection chasing it from behind. By Friday
morning, the surface high is over South Dakota and working south
away from the region. So, the CWA will go from today`s blustery CAA
winds on the front side of the high pressure to breezy (or worse)
westerly winds of 15 to 25 mph with gusts to 35 mph in WAA on the
back side of the surface high when the pressure gradient once again
tightens between the departing surface high and approaching surface
low pressure progged to be out of western Ontario by the end of the
day Friday. Later Friday night, the cold front attached to this
surface low is forecast to sweep down across the CWA signaling the
end of warm air and the beginning of low level CAA on northerly
winds.

During the period of low level WAA on Friday, temperatures could end
up overachieving, reaching the low 60s out across the central
portion of the state. For now, keeping in step with mid to upper 50s
across this area. While the westerly WAA winds are happening on
Friday, the air advecting in from the west is supposed to be quite
void of low level moisture. HREF output shows there could be about a
3 to 5 hour window of time Friday afternoon when wind gusts will be
at or above 25 mph (60 to 100 percent chance along and north of U.S.
Highway 212) while relative humidity values could be below 20
percent (40 to 80 percent chance throughout and west of the Missouri
River valley) across north central South Dakota. This is Red Flag
Warning criteria when fuels are cured and ready to burn (which we
have). A Fire Weather Watch is in effect for north central South
Dakota for Friday afternoon.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 142 PM CDT Thu Mar 14 2024

Split flow will start off the long term Saturday morning with the
northern stream in a +PNA pattern, consisting of an amplified
ridge/high over the western Conus and a trough/low settled over
parts of MN/WI into Ontario. The southern stream consists of a
cutoff closed low over the Southwest U.S. At the surface, a cold
front (associated with a surface low over ~central Ontario) will
have passed over the CWA with northwest flow at the surface and
aloft. A high pressure system will dominate the area behind the
system through the rest of the weekend. 850mb CAA (-10 to -12/12hr
at 12Z and -2 to -4/12hrs per EC at 00Z) along with pressure rises
of 2-4mb/6hrs (GFS) will lead to gusty winds through the morning
into the afternoon with the latest NBM forecasting gusts of 30-35kts
and diminishing towards the evening as the high moves in. (example:
mixing heights between 750-800mb with top layer speed of 25kts at
KABR/3pm Sat per GFS bufkit sounding)

Clusters agree that this pattern continues through the weekend into
early next week as this ridge becomes broader with the trough moving
in/over the Northeast U.S. The main difference between the ensembles
is the ridge`s height towards Day 5. Towards the end of the long
term (midweek), a low will be moving south over the Hudson Bay area
with the ensembles agreeing on this pattern but differences on where
the low sets up. West of this, a trough plunges south over western
Canada/Pacific Northwest. This will cause for the ridge to flatten
out a bit with either northwest or zonal flow over the CWA as the
ensembles are 50/50 split on this. With this setup, Clusters do not
even introduce a chance of QPF until Thursday as a surface
low/shortwave sets up over the Northern Rockies, pushing southeast.
Still some variability as Cluster 1 (44% EC,13% GEFS,25% CMC) has a
chance of 0.01" over SD where Clusters 2-4 keep the area dry. Friday
Cluster 1 (mainly GEFS) and Cluster 3 (split EC/GEFS) shows this
continuing chance while 2/4 is dry. Latest NBM is only 15-20% pops
over the northern/northwestern CWA for now. Low confidence exists
due to model variation and being several days out.

RH values are a little higher on Saturday ranging in the 30/40%
values with the exception of south central SD, mainly from Stanley,
Jones, and parts of Lyman counties where lowest RH in the upper
20/lower 30% values. This could cause for elevated fire concerns due
to the gusty winds mentioned above. RH values Monday west of the
Missouri river do get down into the mid 20-lower 30% values with
wind gusts of 25mph so in the afternoon. We will keep a close eye on
this through the weekend.

With the passing of the cold front, temps will be "cooler" in the
40s/50s on Saturday. As the high sinks over the area, high temps for
Sunday will actually be around our average, ranging in the 30s/40s
and lows getting down into the mid to upper teens! We will see temps
gradually increase Monday through the middle of next week before
this next system brings cooler air behind it for the end of the week.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 625 PM CDT Thu Mar 14 2024

Terminals KABR,KATY,KPIR,KMBG

MVFR cigs will linger over north central South Dakota, including
KMBG, through the evening hours before lifting to VFR levels
overnight. There are some indications that some MVFR cigs may
develop across far eastern parts of the area late tonight into
Friday morning, including at KATY. Otherwise, VFR conditions will
prevail tonight through the day Friday. West top southwest winds
will increase into the 15 to 30 knot range Friday afternoon.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Fire Weather Watch from Friday afternoon through Friday evening
     for SDZ003>005-009-015.

MN...None.
&&

$$

SHORT TERM...Dorn
LONG TERM...MMM
AVIATION...Parkin


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