229
FXUS63 KABR 300813
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
313 AM CDT Mon Sep 30 2024

.KEY MESSAGES...

- Critical fire weather conditions expected through today due to dry
  and windy conditions. Wind gusts of 40 to 45 mph at times, which
  will cause any fires that ignite to spread rapidly and be difficult
  to control. Burning should be avoided.

- Cooler air will be in place for today and Tuesday with
  temperatures around average. Warmer air moves in Wednesday with
  temperatures around 15 degrees above average.

&&

.SHORT TERM /TODAY THROUGH TUESDAY AFTERNOON/...
Issued at 312 AM CDT Mon Sep 30 2024

Southerly winds gusts of 15 to 30 mph continues across the eastern
half of the forecast area early this morning ahead of a cold front.
The front will sweep across the CWA before 18Z, bringing cooler, but
still near to above average temperatures and strong northwesterly
winds. Buffer soundings indicate the highest winds occurring within
an hour or two after the cold frontal passage, with peak gusts of 45
to 50 mph. These winds may occur as far east of Aberdeen. However,
after the initial gust, the winds should subside later this morning
and early afternoon with gusts around 35 to 45 mph at times, mainly
west of the James River valley. Winds appear to slowly diminish late
this afternoon and through the evening hours, with some model
guidance showing no gusts after 0Z.

While temperatures will be cooler today, the airmass post-frontal
remains dry with RH values remaining at or below 25 percent. The dry
conditions and gusty winds will create critical fire weather today
with a Red Flag warning for the entire CWA.

Seasonal temperatures should move into the CWA tonight with 925 mb
temperatures in the single digits above zero C to around 11C. These
readings are normal for this time of year. Low temperatures should
range in the 30 for most locations, with patch frost possible if
winds fully diminish. The probability of lows dropping below 34
degrees is 10 to 35 percent, only in north central SD. Will hold off
on mentioning frost in the grids for now.

Winds begin to increase once again on Tuesday with southwesterly
gusts of 20 to 25 mph possible along and west of the Missouri River.
RH values remain low, or below 20 percent, with elevated fire
weather a concern once again. Later shift may need to issue a fire
weather headline for counties along the Missouri River on Tuesday.

&&

.LONG TERM /TUESDAY EVENING THROUGH SUNDAY/...
Issued at 312 AM CDT Mon Sep 30 2024

The upper-levels have a low pressure over the Hudson Bay and an
associated trough over the Great Lakes, leading to zonal flow over
SD starting Tuesday evening until Thursday evening, when the models
show a ridge starting to build over the Pacific Northwest, pushing
the flow over SD from the northwest. The models keep this flow over
SD till Sunday, however there are some differences in the
positioning of the ridge. The GFS and ECMWF start moving the ridge
over SD Friday evening, while the Canadian model moves it west
Saturday morning. At the same time, the GFS and ECMWF have a
shortwave moving east over ID, which the ECMWF has reaching SD
Saturday evening and the GFS has over SD Sunday morning. By Sunday
evening, the ECMWF has moved the low to the southeast creating
stronger northwest flow, while the GFS moves it to the east creating
zonal flow over SD.

Wednesday morning the models have mid-level moisture over northern
counties in central SD, while areas to the south are dry. This leads
to widespread surface RH values below 30% over central and eastern
SD, as well as values below 20% around/west of the Missouri River
Tuesday evening and Wednesday afternoon. The deterministic models
show a faint signature for strong surface wind, but because of weak
lapse rates, these winds don`t get to the surface. However, the
clusters show strong wind gusts over the Coteau Tuesday evening into
Wednesday morning. The NBM also shows wind gusts greater than 25kts
over the Coteau starting 6z Wednesday until 15z, and in the
afternoon, there are gust over 25kts in Corson and Dewey counties.
Drier surface RH values from previous days and Wednesday, along with
some stronger wind gusts could lead to more critical fire weather
conditions occurring Wednesday.

Continuing past Wednesday, the mid-level moisture spreads across
central and eastern SD Thursday morning and stays there Friday.
Thursday and Friday afternoon, the surface RH values increase, with
areas in northern SD above 40% with some pockets below 40-30%. By
the evening, the ECMWF and Canadian have mid-level dry air over SD,
but there are some disagreements with surface RH as the models shoe
opposite patterns. The ECMWF has RH values below 40% west of the
James River Valley and below 30% west of the Missouri River, and the
Canadian has areas around the Missouri River below 40%, with
widespread values below 30% to the east. Sunday increases surface RH
values, with the ECMWF having values above 40% north of Potter,
Faulk, and Dewey counties, and below 40% to the south. However, the
Canadian is a bit drier with widespread area below 40% with pockets
below 30%. Monday afternoon, the Canadian has surface RH values
below 40% and the ECMWF shows area west of the Coteau below 40% and
west of the James River Valley below 30%. 0.5km winds don`t show
strong winds lining up with strong lapse rates until late Saturday
evening, when the ECMWF shows widespread areas of wind speeds
greater than 30kts over eastern and northern central SD which
continues into Sunday evening. While the other deterministic models
do not show this, the clusters pick up on it, with gusts around 25-
30kt. The NBM also shows wind gusts picking up Saturday morning over
the James River Valley and the Coteau, with widespread gusts over
25kts until Saturday evening.

There is mid-level WAA over SD Tuesday evening into Wednesday,
leading to surface temperatures Wednesday being around 15 degrees
warmer than normal. After that, the models do vary slightly on when
mid-level CAA moves in, as the GFS and Canadian models move CAA into
central SD early Wednesday morning, and the NAM and ECMWF move it in
Wednesday afternoon. This CAA stays over until the GFS and EC moves
in WAA Friday morning, leading to surface temperatures being around
normal Thursday and Friday, The Canadian joins the other models
Saturday morning with the mid-level WAA over SD, causing surface
temperatures to be 10-20 degrees warmer than normal Saturday. The
GFS and ECMWF then moves mid-level CAA over central and eastern SD
late Saturday evening and the Canadian moves the CAA in Sunday
afternoon, leading to surface temperatures Sunday and Monday being
around 5-10 degrees warmer than normal.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1220 AM CDT Mon Sep 30 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail through the TAF period. Breezy/gusty
southerly surface winds early in the period will gradually switch to
the northwest as a strong cold front moves across the region. Low-
level wind shear will also be a concern through the early morning
hours.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning from 11 AM this morning to 8 PM CDT this
     evening for SDZ006>008-011-018>023.

     Red Flag Warning until 8 PM CDT /7 PM MDT/ this evening for
     SDZ003-004-009-015-016-033>035-045-048.

     Wind Advisory until 4 PM CDT /3 PM MDT/ this afternoon for
     SDZ003-015-033-045-048.

     Wind Advisory from 7 AM this morning to 4 PM CDT this afternoon
     for SDZ004-005-009-010-016-017-034>037-051.

     Red Flag Warning from 7 AM this morning to 8 PM CDT this evening
     for SDZ005-010-017-036-037-051.

MN...Red Flag Warning from 11 AM this morning to 8 PM CDT this
     evening for MNZ039-046.

&&

$$

SHORT TERM...SD
LONG TERM...Vernon
AVIATION...SD