Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 131504 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1004 AM CDT Wed Mar 13 2024

.KEY MESSAGES...

- Rainfall chances have decreased for Today into Thursday morning,
with a 20% chance of rain over northeast South Dakota today, then a
15-30% chance of rain for areas south of US-212 tonight.

- Gusty west to northwest winds of 25 to 35 mph on Friday and
Saturday will lead to an elevated fire weather concern.

- Temperatures will cool down into the 30s for Sunday, which is near
to slightly below normal for mid March.

&&

.UPDATE...
Issued at 1003 AM CDT Wed Mar 13 2024

No changes planned to the today period forecast.

UPDATE Issued at 604 AM CDT Wed Mar 13 2024

Updated for 12Z Aviation Discussion below.

&&

.SHORT TERM /TODAY THROUGH THURSDAY AFTERNOON/...
Issued at 304 AM CDT Wed Mar 13 2024

Abundant mid-upper level moisture continues to stream northeast
across the area early this morning, which is leading to mid-high
level clouds over much of the region. This moisture and clouds are
associated with the southwesterly flow on the east side of the upper
trough axis that is located from western MT to UT and northern AZ.
Under the clouds, 2am temperatures are in the upper 30s to lower
40s, with the coolest areas associated with pockets of thinner
clouds or brief clearing. The upper trough will gain a positive tilt
with time, as the northern part of the upper trough axis shifts to
to Lake Winnipeg by 00Z Friday.

In the last 12-24hrs, there has been a shift in the precipitation
chances farther to the southeast, tied to the upper level
shortwave/forcing rounding and exiting the base of the upper trough
in northern AZ and tracking more through NE/KS versus farther to the
north. Thus, the resultant surface low that develops in lee of the
central/southern Rockies today into tonight is farther south and
even more elongated as it moves into MO on Thursday. So as mentioned
above, the primary potential for rain has shifted farther south and
thus our PoPs have followed suit. Lowered PoPs about 20-25% for
tonight into Thursday morning (down to 15-30% south of US-212), with
the PoPs down below 15% heading into Thursday. The primary focus for
the rain now appears to be into northern NE and into IA. With that
lowering in PoPs, it doesn`t mean that no precipitation is expected,
as CAMs do have some slight precip pivoting into the southern areas
tonight, but amounts look to be a hundredth or two at the most (due
to the low level dry air).

There are two other opportunities for precipitation in the short
term. First for today over northeast SD, where there may be enough
700-500mb moisture with weak warm air advection to lead to some
light rain showers. Already have some 7-12kft clouds in place as
seen in the nighttime microphysics RGB between the high cirrus.
Accounted for this with 10-20% PoPs, with a mention of light rain or
sprinkles through much of today. The primary question mark will be
the ample dry air below 700mb from the HREF members and global
ensemble members and how much that will lead to evaporation of the
falling precipitation. CAM solutions tend to believe that will
really limit the measurable potential, but the EC-Ens does have a
decent number of members producing at least a few hundredths around
KABR. The second item of note is the potential for a secondary wave
of precipitation dropping south out of ND on Thursday (associated
with increasing 850-750mb moisture under northeasterly flow). Most
CAMs have this diminishing as it nears SD and runs into the existing
dry low level air, so have kept PoPs below 10%. Otherwise on
Thursday, mid level dry air drops southeast across the area as a
ridge axis quickly moves in.

Finally, do want to mention the winds for the short term, due to the
dry fuels in place. North to northeast winds will pickup through the
day today as the weak surface low currently in central SD drops to
the southeast and merges with the developing low in the lee of the
Rockies. Gusts will generally be around or below 20kts, but will
need to watch the northeast part of SD late this afternoon, as gusts
could end up being up around 25kts or a touch higher. It will all
depend on how quickly the low level winds ramp up before diurnal
heating is lost. The north-northeast winds will persist into
Thursday, with gusts in the 20-25kt range. Thus, with the dry fuels,
the Grassland Fire Danger values will be in the High category for
today into Thursday. The lowest RH values will be today, especially
over northeast SD and into west-central MN, where minimum RH values
will be in the upper 20s to mid 30s. Will highlight this in the fire
weather discussion/forecast.

&&

.LONG TERM /THURSDAY EVENING THROUGH TUESDAY/...
Issued at 304 AM CDT Wed Mar 13 2024

An upper level trough continues to dominate the long term as a
shortwave treks across the region Friday followed by a deeper trough
on Saturday with several lows embedded in the trough. During the day
Monday a ridge starts to make its way into the area lasting through
the end of the period.

Precipitation chances are slim to none. The EC is trying to show
some light pops for our western areas on Sunday, but no other models
have precip at this time.

Friday will see a slight bump up in temperatures due to some WAA
ahead of the shortwave before a strong push of CAA enters the region
Saturday. Another push comes in Sunday to drop temperatures even
more. Some of our western counties will get a little bit of an early
warm up Monday before a stronger push of WAA comes through on
Tuesday with the ridge to bring our temperatures back up to above
average. We look to remain in a WAA pattern through the end of the
period.

Friday and Saturday look to be the windiest days in the period as the
shortwave moves through first and then we get a cold front Saturday
with strong CAA. The probability of gusts of more than 40 mph on
Friday is 50 to 90% for Corson and parts of Dewey county along with
the Leola Hills and the eastern side of the Coteau. Probabilities on
Saturday increase to 70 to 98% on Saturday across the entire CWA.
Fire weather could become a concern Saturday if relative humidities
fall a little, depending on the dryness of fuels after the midweek
precip.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 604 AM CDT Wed Mar 13 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail at the TAF sites through the period.
The may be a rain shower or two at KABR/KATY today, but confidence
wasn`t high enough to include as a VCSH and any shower is not
expected to reduce visibility below VFR.

&&

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

$$

UPDATE...Dorn
SHORT TERM...SRF
LONG TERM...KK
AVIATION...SRF


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