Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000
FXUS63 KABR 181730 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1230 PM CDT Sat Mar 18 2017

.UPDATE...
Issued at 1226 PM CDT Sat Mar 18 2017

Aviation discussion updated below for 18Z TAFs.

UPDATE Issued at 1057 AM CDT Sat Mar 18 2017

Only minor adjustments this morning to match current trends.

&&

.SHORT TERM...(Today through Monday Afternoon)
Issued at 359 AM CDT Sat Mar 18 2017

Abnormally warm temperatures and breezy conditions will cause fire
weather concerns in central South Dakota today and Sunday.

A surface high pressure currently over the region will drift
eastward today. A strengthening pressure gradient over the western
Dakotas will bring much above normal temperatures, along with breezy
southerly winds. With little to no snow cover in south central and
west of the Missouri River, highs today should climb into the 60s.
The warm temperatures will combine with the gusty winds and dry
airmass to produce high, to very high fire danger. Both winds and RH
values fall short of a fire weather headline.

The tight pressure gradient will translate eastward tonight with
gusty winds expected, mainly over the higher terrain areas of the
Sisseton Hills. Winds could exceed advisory levels on the lee of the
Prairie Coteau. The winds, along with an upper level ridge, will
bring very warm temperatures into the CWA on Sunday. Based on the
GFS and NAM, 850 mb temps will have the potential to reach record
territory for the 12Z Sunday sounding. A trough crossing the
region by the afternoon will certainly mix down the warm temps
with highs likely climbing into the 60s and 70s. The warm
temperatures, along with gusty winds shifting to the northwest
should produce high to very high fire danger once again for the
Missouri River valley.

Temperatures will cool off on Monday as a surface high pressure
builds into the region. Even with a fairly dry airmass, an upper
level shortwave could bring light pcpn over western and south
central South Dakota.

.LONG TERM...(Monday Evening through Friday)
Issued at 359 AM CDT Sat Mar 18 2017

The focus of this extended forecast discussion centers on the large
upper low that is forecast by all three (GFS/ECMWF/Canadian)
deterministic models (two consecutive 00Z runs now) to lift out onto
the plains by Thursday night. While there are a couple of other
smaller, more transient upper waves moving through the undulating
upper level flow pattern, the system maintaining the highest pops in
the extended forecast (for mainly all rain p-type) is set to work
over the region between day 5 and day 6.

As the period opens, surface high pressure has built down over the
region, and the forecast area is under some of the coolest and
driest air of the extended period. By Tuesday night, high pressure
at the surface is retreating off to the east, giving way to a return
flow pattern over the region and a gradual warm up, which then
persists right on into Thursday ahead of the main event. The 00Z
Canadian and GFS output are more pronounced with their large upper
low lifting out moreso in two discernible chunks of low pressure
energy, the first of which brings the most precipitation potential
to this cwa. When the main area of upper level low pressure moves
out of the Rockies, all three GSM`s track places much of the
deformation zone precipitation setting up south and east of this cwa
on Friday. Will continue to monitor how the models refine system
track/timing for this event.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1226 PM CDT Sat Mar 18 2017

Conditions will remain VFR through the TAF forecast period,
although the main concern will be wind shear overnight. A strong
low level jet will develop during the overnight hours, creating
low level wind shear conditions. Have inserted mention of this
into the TAFs.

&&

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

$$

UPDATE...TMT/Connelly
SHORT TERM...SD
LONG TERM...Dorn
AVIATION...TMT



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