093
FXUS63 KABR 270809
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
309 AM CDT Fri Sep 27 2024

.KEY MESSAGES...

- Much above average temperatures will continue from today through
Sunday. Increasing winds Sunday into Monday may cause elevated fire
weather concern, mainly west of the James River valley.

- A cold front will move through Monday ushering in cooler air
temperatures, which will help return temperatures closer to normal
for this time of year.

&&

.SHORT TERM /TODAY THROUGH SATURDAY AFTERNOON/...
Issued at 307 AM CDT Fri Sep 27 2024

A cold sliding across the region CWA this morning will bring slightly
cooler, but still much above average temperatures today. 925 mb and
850 mb temps reach +20C, or above the 90th percentile by 0Z
Saturday. Model guidance has warmed some from 24 hours ago with
highs now in the upper 70s, to the mid 80s, or 15 to nearly 20
degrees above average for this time of year.

A surface high pressure over the area tonight should allow
temperatures to drop into the 40s and low 50s. The high pressure
pushes east on Saturday, with return flow developing over the
western Dakotas. Increasing southeasterly winds, along with a dry
airmass may cause elevated fire weather concerns, mainly along and
west of the Missouri River valley. High temperatures on Saturday
will remain abnormally warm with readings in the 80s and low 90s.

&&

.LONG TERM /SATURDAY EVENING THROUGH THURSDAY/...
Issued at 307 AM CDT Fri Sep 27 2024

An upper level shortwave will move east Sunday evening over western
Montana, though models vary the timing and strength of this
shortwave. These differences lead to the jet streak being located
over different areas, with the GFS and Canadian having the jet over
central SD Monday evening and the ECMWF has the jet over ND. The mid-
levels have dry air over SD until Monday afternoon, when a bit of
moisture moves across the state along with CAA. This occurs along a
cold front at the surface, which is connected to an area of lower
pressure under the shortwave. This front drops the max temperatures
from 20-25 degrees above normal on Sunday to 5-10 degrees above
normal Monday and around normal on Tuesday.

The front will also contribute to strong winds Sunday afternoon into
Monday. 0.5km model winds have strong winds and strong lapse rates
over the James River Valley and to the west. The ECMWF ECI table
shows values that are seen when wind advisories are typically issued
over counties west of the Missouri river, while the other areas are
covered in values just below that threshold, signifying strong winds
are likely. The NBM also shows strong winds, with areas west of the
James River Valley receiving gusts above 30kts Sunday morning into
the afternoon, and then spreading out. The strongest winds Monday
morning start southwest of Jones county and spread over central SD,
with large swaths showing gusts over 40kts until Monday evening.
These winds also come with a decrease in relative humidity (RH),
with models showing areas west of the James River Valley less than
40% RH and areas west of the Missouri river between 20-30% RH. These
lower RH and stronger winds will likely lead to increased fire
danger Sunday and Monday.

By Wednesday evening, the upper level jet has moved east out of SD,
creating zonal flow over the state, while another shortwave starts
moving west over the Pacific Northwest. The models vary in the
strength and location of this shortwave, with southwest to northwest
flow Thursday afternoon and evening. As the mid-level dry air moves
out, the GFS and ECMWF start to develop moisture over northern SD
Thursday morning. This helps to increase surface RH in eastern SD
while central SD only sees a slight increase. Mid-level warm air is
advected over SD Wednesday morning and CAA moves in behind it
Wednesday afternoon, which stays over SD for a couple of days. The
WAA warms surface temperatures Wednesday to be about 5-10 degrees
warmer than normal. The CAA that comes in behind it then helps to
cool the surface to around normal for this time of the year Thursday
and Friday.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1213 AM CDT Fri Sep 27 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected through the next 24 hours.

&&

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

$$

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