Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 221742 AAC

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1242 PM CDT Sun Oct 22 2017

Issued at 1239 PM CDT Sun Oct 22 2017

Aviation discussion updated below for 18Z TAFs.

UPDATE Issued at 1030 AM CDT Sun Oct 22 2017

Don`t anticipate many changes to the forecast for the rest of the
day. Under mostly sunny skies, temperatures will rise into the 60s
for most areas, although we could see some low 70s over the
southwest CWA. West to southwest breezes will increase this
afternoon as RH values fall into the 20s. Thus, will see elevated
fire danger this afternoon. Main story in the short term will be
tomorrow`s strong winds.


.SHORT TERM...(Today through Tuesday Afternoon)
Issued at 310 AM CDT Sun Oct 22 2017

Starting this morning with 500mb ridges over the southwestern U.S.,
and across the eastern third of the nation, with a trough over the
central U.S. The trough axis overhead early this morning will exit
across MN this afternoon, with the southern end of the trough
lingering over the southeastern states, as a secondary trough slides
across the Dakotas from the northwest tonight. Northwest flow will
then be the rule aloft, as a high amplitude ridge builds over the
western states up through British Columbia. The southern low will
move back into the large trough Monday evening, with the pattern
being a ridge west and trough east Tuesday. As a result, don`t
expect any significant warm ups anytime soon. In fact, today will be
the warmest day in the near term, with highs in the 60s to near 70
degrees. With very dry air in place, relative humidity values will
still drop to 20 to 30 percent. Winds will increase out of the
southwest this afternoon, and become breezy. Corson County will
again experience very high grassland fire danger index values, with
near-critical wind and humidity this afternoon.

A cold front dropping across the region tonight (and 500mb trough
discussed above) will bring only a slight chance of light rain
showers. The main change will be stronger winds, out of the
northwest, on Monday behind the cold front. Expect frequent gusts of
35 to 45 mph, with the lightest winds over western Minnesota. Will
need to look into a possible Wind Advisory for the western half of
the forecast area Monday. Wind advisory criteria is sustained winds
of 30-39mph for at least an hour, and/or gusts to 45mph. Although
temperatures will top out around 60 degrees, relative humidity
values will still fall to 25 to 30 percent mainly west of the
Missouri River. This will result in another day of very high
grassland fire danger index values from Corson through Hand Counties
and west.

High pressure over much of the Pacific Northwest on Monday will be
able to push a ridge across the western half of SD by the end of the
day Tuesday, allowing winds to slowly diminish west. However, breezy
northwest wind are still anticipated.

.LONG TERM...(Tuesday Evening through Saturday)
Issued at 310 AM CDT Sun Oct 22 2017

The last warmer than normal day will occur at the start of the
extended. There is good agreement in the models that a downward
trend in temperatures will begin on Thursday as a deep, broad upper
trough sinks into the Plains. Cold air advection will see 850 mb
temps drop from +16C to -10C between Wed night and Friday morning.
Precip from the upper low will still be present across eastern SD
and west central MN as the caa takes hold. This means areas along
and east of I-29 could see the first measurable snow of the season
Thursday night, possibly up to an inch of accumulation. However,
timing will be a major factor since daytime highs, though much
colder than recent temps and forecast to be below average, will
still be above freezing.

Highs will fall from the 60s on Wednesday to near 40 on Friday.
Temperatures will rebound closer to average by Sunday as the upper
trough shifts to the east.


.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
Issued at 1239 PM CDT Sun Oct 22 2017

VFR conditions will persist through the TAF forecast period.
Strong and gusty northwest surface winds will develop Monday
morning and persist through the day. There looks to be a period of
wind shear overnight at KABR and have included that in the TAF as




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