Area Forecast Discussion
Issued by NWS Aberdeen, SD

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000
FXUS63 KABR 141738 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1138 AM CST Tue Nov 14 2017

.UPDATE...
Issued at 1129 AM CST Tue Nov 14 2017

Did scrape a few degrees off of high temperatures today across
northeast South Dakota and west central Minnesota where fog and/or
low stratus will likely stick around for a better part of the day
and keep things from warming up. Speaking of fog, areal coverage
of "light fog" is still holding in a number of places, but areal
coverage of "dense fog" is diminishing, so planning to let the
dense fog advisory expire at its currently scheduled time of 18Z.

See below for an aviation forecast discussion for the 18Z TAFs.

UPDATE Issued at 850 AM CST Tue Nov 14 2017

Leaving forecast gridded elements as is for now, except for wx
and hazard grids, and will see how long it takes to eliminate
fog/stratus today (mainly high temperature potential impact).
Extended coverage and time length of dense fog mention this
morning to 18Z. Fog still expanding westward (to KPIR now) and
webcams throughout the eastern half of the Missouri River valley
indicate at least "areas of" coverage of dense fog is probable out
there (supported by area surface obs and satellite imagery).
Updates are out.

UPDATE Issued at 528 AM CST Tue Nov 14 2017

See updated aviation discussion below.

&&

.SHORT TERM...(Today through Thursday Afternoon)
Issued at 410 AM CST Tue Nov 14 2017

Dense fog will continue to be the main concern today. ABR and ATY
remain around 1/4SM visibility. With the high clouds slowly
exiting to our southeast, we`ll begin to see again the actual
extent of fog on the nighttime microphysics GOES-16 satellite
imagery. The Dense Fog Advisory remains in effect, and may need to
be extended in time over our eastern counties. Morning fog east
of the Missouri River will slowly exit east, as a cold front
sweeps across the region and into MN this afternoon. While cooler
air will slide in behind this boundary, a secondary cold front
sinking across late tonight will really bring the cooler air.
850mb temperatures will fall to around -5C along the ND/SD border
by daybreak Wednesday. There will only be a slight chance of
precipitation this evening along the North Dakota and South Dakota
border. Couldn`t rule out a slight chance, given several forecast
models starting to converge on the idea, as a shortwave trough
pushes across ND.

Highs Wednesday will be in the 30s, with a few low to mid 40s over
our southwestern counties. Cool Canadian high pressure will build a
ridge overhead Wednesday afternoon and evening. Behind the exiting
sfc ridge, southeasterly winds of 25 to 35 mph, and gusts as high as
40 to 45 mph will be possible Thursday.

.LONG TERM...(Thursday Evening through Monday)
Issued at 410 AM CST Tue Nov 14 2017

Upper level ridging will be exiting the region at the beginning of
the extended period, with a shortwave trough approaching from the
west. This trough will track across the region late Thursday night
through the day Friday. Northwest flow then becomes dominant until
another shortwave trough approaches at the very tail end of the
period.

At the surface, an elongated low pressure system will be just west
of the CWA Thursday evening. The frontal boundary with this system
looks to track across the CWA overnight Thursday into early Friday
morning, bringing a chance of precipitation to the area. The timing
of the precipitation looks to be between midnight and noon on
Friday, but may linger across the east into Friday evening. For the
most part, temperatures will be warm enough for the precipitation to
be rain, but may see a little snow mix in across the north early
Friday morning and across the east Friday evening. High pressure
moves back in beginning late Friday night, remaining dominant
through the weekend. The high slides east on Monday as low pressure
approaches, but remains just off to the west through Monday night.

Friday will be the warmest day of the period, with highs mainly in
the 40s. Will then see a bit of a cool down with highs in the 30s to
mid 40s Saturday and Sunday before slightly warmer air returns with
highs in the upper 30s to lower 50s on Monday. Warm overnight lows
in the 30s Thursday night will trend back to lows in the teens and
20s through the remainder of the period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 1129 AM CST Tue Nov 14 2017

VFR conditions in place at KPIR and KMBG with cold front just
about to sweep through that (central South Dakota) region of the
state. Further east, KABR/KATY are in the soup (LIFR), and it`s
expected that they will remain so for at least the next 6 hours
(KABR), and possibly longer (KATY) before any improvement will be
had. There is a cold front moving through the region, and if
daytime heating/mixing doesn`t get things back to "better-than-
IFR", the cold frontal passage is expected to later this
evening/overnight. There could also be a quick shot of light rain
or some sprinkles later this evening/overnight as the main area of
low pressure aloft moves through. If confidence/areal coverage
increases over the next 3 to 6 hours, there may be some light
precip mention added to the TAFs.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Dense Fog Advisory until noon CST today for SDZ005>008-010-011-
     016>023-034>037.

MN...Dense Fog Advisory until noon CST today for MNZ039-046.

&&

$$

UPDATE...Dorn
SHORT TERM...KF
LONG TERM...Parkin
AVIATION...Dorn



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