Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000
FXUS63 KABR 190422
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1122 PM CDT Mon Mar 18 2024

.KEY MESSAGES...

- Sisseton hills downslope winds expected this evening. Peak winds
  of 40 to 50 mph expected in those favored areas.

- One last mild day on Tuesday, with above normal highs in the
  40s and 50s. Elevated fire danger as well.

- Colder than normal temperatures Wed-Sun. Decent chance for
  light (30-90%) snow Thursday. Probability of 2" or more of snow
  ranges from 55-90% over northern and northeastern SD into west
  central MN.

&&

.SHORT TERM /THIS EVENING THROUGH TUESDAY NIGHT/...
Issued at 315 PM CDT Mon Mar 18 2024

Frontal boundary still on track to move southward across the region
tonight, switching winds to a northwest direction. Also still
expecting a period of gusty downslope winds along the Sisseton hills
this evening, generally in the 40 to 50 mph range. Between 00Z and
06Z this evening, 925mb winds from 35 to 45 knots out of the
southwest (switching to west) develops, but ends as the cold front
eventually moves through. Previous forecast had this handled well,
and kept with the trend of downslope enhancement this evening.

Looking at another mild day on Tuesday with 925mb temps ranging from
around +11C across the southwest CWA, to around 0C over the
northeast CWA. Generally looking at 40s and 50s for highs, but with
decent mixing and those mild 925mb temps across the southwest CWA,
we could be flirting with 60 degrees. Current forecast RH values
aren`t quite as low (30-50%) as what we`re seeing this afternoon, so
while fire danger remains elevated on Tuesday, conditions are not
quite as concerning as today.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 315 PM CDT Mon Mar 18 2024

Main concern for the long term is the unsettled weather pattern we
will be dealing with as snow is forecasted to move into the area
Wednesday afternoon/evening into Thursday. Ongoing precipitation
chances, mainly in the form of snow, continues Friday into the
weekend but confidence decreases further out in time due to model
variability. Otherwise, temps will fall to below average midweek
through at least early next week.

Starting out on Wednesday, Clusters are in good agreement with a
+PNA pattern with the Northern Plains in northwest flow aloft. By
Thursday, this ridge breaks down a bit as a positive tilted
shortwave swings down over western Canada, west of a closed low that
settles itself over the Hudson Bay area by the evening time. With
this northwest flow, mid level energy will move downstream of the
ridge and over the Northern Plains late Wednesday through Thursday.
Grand ensemble hints at some slight 700mb/850mb FGEN Thursday,
mainly clipping our northeastern CWA with much of it in ND/MN. This
may help produce some banding effect in this area, causing for
"higher" snow accumulations. The Clusters are coming together better
for QPF but still some slight variations on where the higher end QPF
(0.10+) will end up, whether staying over ND, along our border, or
more south into our CWA. NBM indicates 15-30% pops around and west
of the Missouri River between 18-00Z and 20-60% 00-12Z Thursday. By
Thursday afternoon/evening pops increase 60-90% along the ND/SD
border into MN.

Combining the Clusters, probability of snow>1" Wednesday evening
through Friday morning ranges from 20-95%, highest over the
northern/northeastern CWA. Probability of 2" is 30-45%, again
highest over this same area and prob of 3" is 15% or less. NBM seems
to agree with this as well with 70-90% probability of 1" over this
area. Prob of 2" is 40-90% and prob of 3" is higher compared to
Clusters, up to 85%. However this is 10:1 ratio and this system
could be closer to 14-15:1. WPC indicates this well too as prob of
QPF>0.25" is up to 30% over extreme northeastern SD/western MN. So
medium to high confidence remains on at least 1-3" of snow over this
area.

By the weekend, the overall pattern does transform into a -PNA
pattern with differences on intensity and timing of this trough
between Clusters and this will determine where/when the lee side
surface low develops. Right now, WPC probability of QPF>0.25" is 20-
50% across our CWA on Saturday and up to 70% Sunday with NBM outcome
around the same. Prob WSSI indicates likelihood of at least minor
impacts in travel range from 40-60%. EC meteograms hint at 70-90%
chance of snow at each ASOS sites for now. It is interesting to note
that EFI indicates QPF 0.6-0.7 with a shift of tails of zero Sunday
and for snow a shift of tails of 1 over northern SD and along the
Missouri River.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1120 PM CDT Mon Mar 18 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast through the TAF period. Low level
wind shear is forecast through 08Z with winds near 40kts just
above the surface. While forecast to stay VFR, MVFR ceilings may
near from the north from 15-17Z Tuesday.

&&

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

$$

SHORT TERM...TMT
LONG TERM...MMM
AVIATION...KF


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