Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 191608 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1108 AM CDT Thu Oct 19 2017

Issued at 1107 AM CDT Thu Oct 19 2017

Forecast is in fine shape so no major changes expected for now.

UPDATE Issued at 617 AM CDT Thu Oct 19 2017

Have issued a special weather statement (SPSABR) this morning for
the two MN forecast zones, Big Stone and Traverse counties,
highlighting the potential for near critical fire weather
conditions this afternoon. Will need to keep an eye on wind/rh
value trends across far northeast South Dakota and west central
MN this afternoon.

See below for an aviation forecast discussion for the 12Z TAFs.


.SHORT TERM...(Today through Saturday Afternoon)
Issued at 332 AM CDT Thu Oct 19 2017

Warm air will surge back north today, as a 500mb ridge builds in
and the sfc ridge continues to exit to our east. Although 850mb
winds will be out of the southwest at 35-40kt over the eastern
third of the forecast area, mixing heights will be limited to
around 900mb. Still expecting some gusts of 20 to near 30kts from
Hamlin and Deuel Counties up through Grant, western Roberts, and
Marshall County. Fire weather wise, the driest conditions will be
west of the Missouri River, with relative humidity values ranging
to 18 to 25 percent.

The 500mb ridge will slide to the eastern U.S. tonight, with south
to southwesterly flow then dominating our weather picture through
Saturday. This will be as the high amplitude 500mb trough currently
off the Pacific Coast pushes onshore Friday morning, and then by 00Z
Sunday sets up from south central central Canada through the western
Dakotas and down through western TX.

The pressure gradient will increase more east of the Missouri River
Friday, with large high pressure over the eastern U.S. and low
pressure nearing from southern Canada and eastern MT. 850mb winds
will jump to 40-60kts, highest again over our eastern counties.
Better mixing is anticipated, tapping into some of these stronger
winds. Wind headlines may be needed as the time nears if stronger
winds are realized. For now, will continue to highlight the
steady winds around 20 mph with gusts of 30 to near 40 mph in the
HWO and other products. Once again, the lowest relative humidity
values of 20-30 percent will be west of the Missouri River.

Precipitation may enter our southeastern counties as early at 06Z
Saturday, tied with 500mb trough. By daybreak Saturday, the cold
front will already stretch from the low over Manitoba through our
western counties. While models do indicate at least clouds,
precipitation will also be possible, with rainfall totals less than
a tenth of an inch. A rumble of thunder will not be out of the
question, as MUCAPE values rise to around 500j/kg. However, by early
afternoon the best instability should be mainly to our east as the
cold front pushes into MN.

.LONG TERM...(Saturday Evening through Wednesday)
Issued at 332 AM CDT Thu Oct 19 2017

The forecast period opens with an upper level shortwave trof over
the cwa. By Sunday, that energy is working over into MN, and the
flow pattern is briefly zonal. From Sunday night through the rest of
the period, while the flow pattern over the CONUS is progged to
become highly amplified, the portion of it over this cwa is either
northwest or north. There really isn`t much in the way of
precipitation chances throughout the period, and the warmest days
(near to above climo normal) appear to be Sunday and Wednesday, with
(near to below climo normal) colder days sandwiched in between.


.AVIATION...(For the 12Z TAFS through 12Z Friday Morning)
Issued at 617 AM CDT Thu Oct 19 2017

VFR conditions should prevail across the area through Thursday
night. Look for the possibility of some low level wind shear in
the 40 to 50 knot range around the 1500-2000 foot (agl) level
Thursday night.




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