Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 211548 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1048 AM CDT Sat Oct 21 2017

Issued at 1044 AM CDT Sat Oct 21 2017

Cold front continues to push east this morning and is near the
I-29 corridor currently. Rather breezy and gusty winds behind the
front and have had to increase wind speeds in the forecast a bit.
Also continue to see a band of light rain across central SD. Hi-
res models continue to try to advance this line eastward a bit,
but diminishing while it does so. Made just a few adjustments to
POPs based on current thinking, but main theme is to keep highest
rain chances over central SD today. Current highs appear on track
and not many changes needed as far as temps go.


.SHORT TERM...(Today through Monday Afternoon)
Issued at 314 AM CDT Sat Oct 21 2017

The 500mb map shows a ridge over the east coast, with a trough
stretching from AK down through MT and TX. The axis of the trough
will slide into the western Dakotas this afternoon, and exit into
the MN Sunday morning. Taking a look at the sfc features, a cold
front east of the MBG through PIR and into western Lyman County
continues to shift eastward. The strongest winds are still about a
county behind this boundary, with gusts of 25-35mph currently being
reported from the Bear Creek and Grand River RAWS through Lemmon and
Bowman. These winds will soon be realized across much of central SD.
The cold front will shift east of a line from ABR to HON by 12Z, and
east of the CWA prior to 18Z. West to northwest winds should remain
under advisory criteria, but with a few gusts nearing 40mph west of
the Missouri River (especially 18-22Z). While we do get rid of the
60kt winds at 850mb, we will have better mixing behind the cold
front, up to the 30-40kt winds at 850mb (highest west). The cool
rush of air will keep highs in the mid 50s to low 60s, with the
warmest readings over MN. The early exit of the cold front and
instability should limit thunderstorms to our east and southeastern
counties this morning, before pushing into MN. MUCAPE values do
briefly jump up to around 750j/kg late this morning along the SD/MN

The 500mb trough will form a cut off low over the lower MS valley
Sunday night through Monday, with zonal flow will take hold of SD
and western MN Sunday afternoon. Dry weather should prevail through
Sunday evening. Can`t rule out some light showers early Sunday
morning with the passage of a broad sfc trough, as a low swings
across southern Canada and another 500mb trough moves overhead.
Large high pressure will be building in from the western U.S.
on Monday, behind the sfc trough. Breezy conditions will return.

Both Sunday and Monday afternoon could bring about elevated fire
concerns for areas along and west of the Missouri River. This will
be the area where Rh values will fall below 25 percent, and winds
will be strongest (out of the southwest on Sunday, and out of the
northwest on Monday).

.LONG TERM...(Monday Evening through Friday)
Issued at 314 AM CDT Sat Oct 21 2017

Upper troughing over the northern Plains will shift east on Tuesday.
However, temperatures will see only a brief recovery on Wednesday
before another upper trough moves in for the end of the week. At the
sfc, an arctic high will follow on the heels of a sfc low on
Thursday bringing a blast of cold air that will sink the region 5 to
10 degrees below average Thursday through Saturday. Dry conditions
will mainly prevail until the weekend when another sfc low drops
down from Canada. Coupled with shortwave energy in a deep, broad
upper trough over the central CONUS the region could see more light
rain or snow showers Friday night into Saturday.


.AVIATION...(For the 12Z TAFS through 12Z Sunday Morning)
Issued at 554 AM CDT Sat Oct 21 2017

VFR conditions are expected at all sites except KATY where some
MVFR stratus will push in from the south this morning. A front is
sweeping across the region this morning bringing some showers and
gusty northwest winds behind it.




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