Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000
FXUS63 KABR 160530 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1230 AM CDT Sat Mar 16 2024

.KEY MESSAGES...

- Cold front will shift winds to northwest tonight, with wind gusts
  of 30 to 40 mph. These winds continue into Saturday.

- Mainly dry through Wednesday night; then a 20-40% chance of
  precipitation mainly Thursday night/Friday.

- Temperatures see-saw between much below normal and much above
  normal in the long term.

&&

.UPDATE...
Issued at 809 PM CDT Fri Mar 15 2024

With wind speeds decreasing and temperatures beginning to cool,
have allowed the Red Flag Warning across north central South
Dakota to expire. No changes made to winds or temperatures at
this time.

&&

.SHORT TERM /THIS EVENING THROUGH SATURDAY NIGHT/...
Issued at 140 PM CDT Fri Mar 15 2024

As of 1PM, high pressure dominates the region with overall clear
skies and temperatures ranging in the 40s to the lower 50s with peak
wind gusts ranging from 20-30 mph per Mesonet. There are a few high
clouds over ND that will move into the area later on.

This high will push east/southeast as an upper level low/trough will
swing southeast across Canada and settle over Ontario/Manitoba
border at 00Z and over central Ontario by 12Z Saturday bringing some
lower clouds along with it. 500mb winds will increase to 70-90kts
out of the northwest over the Northern Plains this evening into the
overnight as a jet streak moves down and around the axis of the
trough, which will help deepen the low a bit. Down at the surface,
the short term and ensemble models agree on its surface low over the
border of Manitoba and Ontario at 00Z and over central Ontario by
12Z, with a positive tilted surface trough extending over the CWA,
southwest of this low. A cold front is expected to swing northwest
to southeast over the CWA tonight through the overnight and out of
the CWA by 12Z. Cams indicate this will mostly be a dry passing,
however, a few show some very light returns possible, mainly over
extreme easter/northeastern SD into west central MN with the front,
but not enough confidence or amounts to put in the forecast for now.

Winds will remain breezy this evening as a stronger pressure
gradient exists from this low over the CAA with still WAA winds
gusting to 30-40kts or so. Overnight, the main indicator of the
frontal passage will be a shift in winds from zonal to northwest as
we go from warm air mixing to cold air mixing with EC indicating CAA
of -7 to -12C/12hrs at 12Z Saturday and only around -1 to -3C/12hrs
by 18Z. Pressure rises of around 2-4mb/6 hrs is forecasted behind
the front as well to help steepen the LLLR. Gusts continue around 30-
40kts but will overtake much of the CWA through Saturday afternoon
then diminishing towards the evening. Looking at some bufkit
soundings, top of the mixed layer for KABR is around 775mb at 24kts,
KMBG at 23kts, and KPIR at 30kts Saturday afternoon, so NBM seems to
have a good handle on this. Northwest flow aloft continues into
Sunday morning as the Northern Plains will be on the axis to
backside of this now broad tilted trough as this surface trough/low
continues southeast. Behind this low, an elongated high pressure
system will sink south and help diminish the winds Saturday night
into early Sunday. Min RH values for Saturday range from the upper
20 percent across south central SD to around 40%. Fire danger should
not be as widespread but will still need to watch across south
central SD, especially with the ongoing increase in winds.

Overnight lows will range in the lower to mid 30s and cooler for
Saturday with highs in the 40s to maybe around 50 across south
central SD. As this high moves south and the Northern Plains on the
south/southeast side of this system , colder temps expected Saturday
night into the lower to mid 20s, which is actually around average
for this time of year but will feel colder after the warmer temps we
have had!

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 140 PM CDT Fri Mar 15 2024

When the period opens Sunday morning, the upper flow pattern is a
highly amplified positive pna pattern (ridge over the west/trof over
the east). By Thursday, ensembles output supports the pattern de-
amplifying to just about zonal, before there is any potential for
western CONUS upper level longwave troffing to materialize.

As the previous forecaster mentioned, when the CWA is under a nearly
meridional cold northerly flow aloft and shortwave impulses work
through in daytime heating, the combination of steep low level lapse
rates and mid-level lift sometimes does promote iso`d/sct`d daytime
"instability" showers. Will let the ensemble process iron out those
potential PoPs details with time. Otherwise, the pattern does look
to be a dry one through pretty much the entire period. Heading into
Day 7 (Friday), both ensembles and deterministic guidance right now
does hint at the potential for some precipitation sometime between
12Z Thursday and 00Z Saturday (~20 to 35% chance). The probability
of temperatures being cold enough to support snow p-type
Thursday/Friday is ~55 to 95%. And right now, the ECMWF Ens system
supports at least one inch of snow accumulation by the end of the
day Friday (30 to 70% chance) over the CWA.

Temperatures are a source of consternation just now. With the
ensemble system`s 60-day temperature bias correction (much above
normal over the past 60 days over the CWA) likely getting in the
way, high temperatures Sunday and then again Wednesday, Thursday and
Friday are probably somewhat poorly reflected in the ensemble-
powered forecast at the moment. The "polar cold front" will be
oscillating back and forth over the region this upcoming week; and
with no snow on the ground, portions of the CWA on the warm air side
of this arctic boundary will be really warm, while the portions of
the CWA that get into the cold air behind the boundary will be
really cold. S.A. table 850hpa thermal anomalies show these sharp
jumps from being 1 to 2 standard deviations below normal to 1 to 2
S.D. above normal and then back down to 1 to 2 S.D. below normal
again.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1228 AM CDT Sat Mar 16 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail across the area overnight and through
the day Saturday. Winds will shift to the northwest late tonight,
then will increase into the 15 to 30 knot range Saturday morning.
The gusty winds will continue through the afternoon before
diminishing during the evening hours.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Fire Weather Watch from this afternoon through this evening for
     SDZ008-011-019>023.

MN...Fire Weather Watch from this afternoon through this evening for
     MNZ039-046.

&&

$$

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


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