Watertown, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

062
FXUS63 KABR 221103
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
503 AM CST Sun Dec 22 2024

.KEY MESSAGES...

- There is a low (15-25%) chance of a light wintry mix of
precipitation, including rain and freezing rain over north central
South Dakota this afternoon, as well as freezing rain or snow over
northeastern SD into west central MN this evening.

- Temperatures will run around 5 to 20 degrees above normal through
next Sunday.

&&

.UPDATE...
Issued at 503 AM CST Sun Dec 22 2024

Aviation discussion updated below in accordance with the 12Z TAFs.

&&

.SHORT TERM /TODAY THROUGH MONDAY AFTERNOON/...
Issued at 234 AM CST Sun Dec 22 2024

Main story in the short term forecast is the potential for some
light precipitation this afternoon caused by an upper level
shortwave. Hi-res guidance is hesitant to bring anything into the
ABR area, and instead keeps the best chances up in North Dakota.
Some lingering ensemble chances over north central and northeastern
South Dakota and western Minnesota in addition to a few CAMs still
resolving precipitation over the area have led to keeping some areas
of slight chance PoPs in the north Sunday evening through night.

In terms of precipitation type, soundings indicate that rain and
freezing rain are the most likely type over north central South
Dakota, while snow and freezing rain become the dominant types as
the system progresses eastward. Everything is dependent on both
surface temperature and mid-level moisture through the event.
Soundings are a little unclear on the latter, but generally suggest
that moisture aloft needed for saturation of the DGZ will not be
present at the beginning of the event but will increase over
northeastern South Dakota as the event continues. In terms of
surface temperatures, warm air advection will keep temperatures
above freezing over central South Dakota, but the same cannot be
said for the northeastern part of the forecast area. Freezing line
for high temps at the surface looks to set up in a line northwest
to southeast across McPherson, Edmunds, Brown, and Spink counties.
To summarize, at some point during the event (likely ~0Z), a switch
from supercooled water to ice nuclei will occur, and precipitation
types will change from rain and freezing rain to snow and freezing
rain. Regardless of what type precipitation ends up at, QPF values
are expected to be low, only a couple hundredths of liquid
equivalent at the most.

On Monday, high pressure to the north begins to build into the area.
Light northerly winds switch to southerly through the day Monday.
Cloud cover over the northeastern forecast area will limit highs to
the 20s over northeastern South Dakota and western Minnesota, while
relatively clearer skies over central South Dakota will support
highs in the 30s to low 40s.

&&

.LONG TERM /MONDAY EVENING THROUGH SATURDAY/...
Issued at 234 AM CST Sun Dec 22 2024

Above normal temperatures will continue through the long term
forecast. While mainly dry weather will continue, we do have a
couple mentions of light precipitation Thursday night on. There is
only a 15-25% chance of a wintry mix over our far southeastern
counties Thursday night, and then over our eastern counties Friday
night through Saturday.

As for the overall weather pattern, we`ll be starting out at 00Z
Tuesday with a 500mb ridge over the Dakotas and western MN. This
will be short lived as a shortwave trough over western MT/western WY
moves overhead Tuesday into Tuesday evening. Another ridge will
quickly slide across the Central to Northern Plains Tuesday night
into Wednesday morning. A change to this oscillating pattern will
come Wednesday as a 500mb low over the 4-corners of the interior
southwestern U.S. shifts east on Thursday into Thursday evening,
across the Central to Southern Plains states. There continues to be
some discrepancies between models on how far north-northeast the low
tracks. The operational models bring the surface low anywhere from
eastern SD to southwestern MO by 18Z Friday. That`s nearly a 475
mile difference. As expected, this leads to significant variability
and low confidence in specifics, like cloud cover and any chances of
precipitation, which could be on the increase in later forecasts. As
a result, there will be several changes to the forecast for this
period. The 00Z Ensemble EC guidance is clustering more to
precipitation chances on Saturday, and the GFS looks to be trending
the same way. The slight chance (15-25% chance) of precipitation
over eastern SD/west central MN looks reasonable at this time.
Still, the overall trend steady to increasing high and low
temperatures will continue through at least Friday, on the order of
5 to 20 degrees.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 503 AM CST Sun Dec 22 2024

Terminals KABR,KATY,KPIR,KMBG

The next system is expected to move across North Dakota this
afternoon into this evening, with the potential to drop a wintry mix
of precipitation over the northernmost parts of central and
northeastern South Dakota. Probability of precipitation for KMBG and
KABR is less than 30%, so have opted to leave and mention of -RA, -
FZRA, or -SN out of the TAFs.

MVFR cloud deck will move in overnight, with ceilings potentially
dropping to IFR at times. Model guidance does have a signal for some
patchy fog at KMBG/KABR/KATY tomorrow morning, but there is still
some uncratinty. Winds may be strong enough to keep visibilities up,
but will be a bit lighter in the James Valley, so have put a mention
of BR accompanied by 6SM visibilities in the KABR TAF.

&&

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

$$

UPDATE...BC
SHORT TERM...BC
LONG TERM...KF
AVIATION...BC