646 
FXUS63 KABR 240526 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1126 PM CST Tue Jan 23 2024

.KEY MESSAGES...

- Cloudy conditions are expected through the week. Expect periods of 
dense fog and/or drizzle. With nighttime temperatures below 
freezing, any fog or drizzle that occurs will produce slick spots on 
untreated roadways.

- High temperatures trending into the 30s and 40s for the end of the 
week into the weekend. (10-20 degrees above normal) 

- Very low probabilities for precipitation (less than 10%)

&&

.UPDATE...
Issued at 1123 PM CST Tue Jan 23 2024

See updated aviation discussion below.

UPDATE Issued at 905 PM CST Tue Jan 23 2024

Seeing some areas of reduced visibilities in fog across parts of
the CWA, but not any real widespread areas of dense fog. Expect
this will change as we get into the overnight hours, so will leave
the current Dense Fog Advisory in place and monitor for possibly
having to extend it eastward later tonight. No changes made to
winds or temperatures at this time.

&&

.SHORT TERM /THIS EVENING THROUGH WEDNESDAY NIGHT/...
Issued at 147 PM CST Tue Jan 23 2024

High pressure at the sfc and very weak flow aloft will keep the 
status quo going forecast-wise through Wednesday night. Persistent 
low cloud cover, dense fog redevelopment overnight and the 
possibility of very light freezing drizzle will remain across the 
region in the short term. Temperatures are a bit of a question mark. 
Was surprised to see a 10 degree diurnal difference today from the 
James Valley east given the low cloud cover. This was likely due to 
the breezy (10 to 15kt) southerly sfc flow. Not as sold on this 
happening Wednesday anywhere except west river where they may see 
some sunshine briefly during the afternoon. Blended in some NAMNest 
(which has a good handle on the cloud cover) to try to capture this 
thinking in the grids. Looks like everywhere in the cwa will be 
above normal, though, with lows in the 20s and highs creeping into 
the 30s. 

Kept the dense fog advisory in place west of the James into 
Wednesday morning with the expectation that vsby will tank again 
this evening. Will likely need to add an advisory from the James 
Valley to the Coteau tonight, but according to guidance, the quarter 
mile or less vsby may not happen until after midnight.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 147 PM CST Tue Jan 23 2024

The long term consists of persistent clouds along with fog as low 
level moisture hangs around through the end of the week. The main 
challenge with this will be the temperatures and how high and low 
our temps get. Ensembles agree on a trough continuing to push east 
Thursday morning with winds going from zonal to northwest flow on 
the backside of it. At the surface a back door cold front will push 
through. UL ridge moves in behind this through Friday morning, along 
with a surface high. Another trough/sfc trough moves west to east 
late Friday into early Saturday and surface high shifting east. 
Looking well into the extended, a large ridge sets up over the 
western CONUS this weekend as clusters have a good handle on it. 
Next week, models are still in agreement with this large ridge over 
much of the central CONUS by the middle of next week with minor 
differences in amplitude and timing, with UL winds out of the 
southwest. With this setup, overall dry weather expected through the 
weekend into the middle of next week.

850mb temps will warm to +1 to +3C for the end of the week with 
northwest winds and up to +4 to +7 Sunday into Monday. By the middle 
of next week these temps range from 10 to 12C per ensemble mean! 
Looking at bufkit, we probably will not mix that high as several GFS 
bufkit soundings across our CWA really only mix to 900 or slightly 
above into next week. However, this is just GFS. If we lose some of 
this snow pack for next week, mixing levels will be higher, so that 
will be a factor on how warm we get (and we have more sun Saturday 
and onward). 925mb temps are a little different between EC and GFS 
as GFS keeps temps cooler than EC. For example, 925mb temps for 00Z 
Friday are showing -1C to -4C and EC is -2 to +2C across the CWA. By 
Saturday, we really see 925mb temps warming over the central and 
western CWA, ranging from +3 to +5 (model depending). Monday GFS is 
showing +1 to +10 where EC is +1 to +12, so some discrepancies 
continue. 2m temps per mean ensemble (ENS/GEPS/GEFS) for KABR is 
only a few degrees spread in the lower to mid 30s Thursday/Friday. 
The spread increases to over 10 degrees for next week with the 95th 
percentile in the upper 40s Monday-Wednesday. If we can melt most of 
this snow, highs could get into the 50s! It is struggling with lows 
as there is more than a 5 degree spread. NBM is pretty similar 
(little cooler bias) with less of a spread for the end of the week 
(in the 30s) with quite the spread next week (at least 10+ degrees 
spread). For ex, Wednesday could be in the lower 40s to the the 
lower 50s and dewpoints into the 30s. So even with this spread, 
confidence is high on warming temperatures as temps will range 10 to 
20 degrees above normal! The warmest temperatures will lie west of 
the MIssouri River with the mean NBM temps in the 30s/40s end of the 
week and well into the 40s/50s by next week.

So with the warmer air over the colder surfaces and still dealing 
with snow depth. GFS 925mb RH remains in the 90 percentile over the 
CWA through Friday (drier air at 850) before drier air moves in west 
to east on Saturday. NBM cloud cover backs this up as we start to 
see clearing west to east Friday night into early Saturday. With the 
ridge moving in next week, skies look to remain a blend of clouds 
and sun. So for Thursday into Friday, with LL moisture, expect fog 
chances to continue (maybe some drizzle) as wind remain light before 
increasing a bit Friday afternoon. Roads could be slick during the 
overnight hours as temps dip below freezing with any freezing fog 
that occurs.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1123 PM CST Tue Jan 23 2024

Terminals KABR,KATY,KPIR,KMBG

IFR cigs will remain over the majority of the area overnight
through the day Wednesday. Fog will be a concern again tonight as
well, with periods of MVFR vsbys falling to IFR levels overnight 
into Wednesday morning. By midday or so, vsbys in fog will rise 
to MVFR levels. 

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Dense Fog Advisory until 9 AM CST /8 AM MST/ Wednesday for 
     SDZ003>005-009-010-015>017-033>037-045-048-051.

MN...None.
&&

$$

UPDATE...Parkin
SHORT TERM...Wise 
LONG TERM...MMM 
AVIATION...Parkin