Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 131755 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1155 AM CST Mon Nov 13 2017

.UPDATE...
Issued at 1155 AM CST Mon Nov 13 2017

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

UPDATE Issued at 958 AM CST Mon Nov 13 2017

Adjusted skycover to reflect a faster progression into "sunshine"
today across the cwa. Will continue to monitor low stratus
advection potential into southeast forecast zones by early/mid
afternoon.

UPDATE Issued at 536 AM CST Mon Nov 13 2017

Aviation discussion updated below for the 12Z TAFs.

&&

.SHORT TERM...(Today through Tuesday Afternoon)
Issued at 347 AM CST Mon Nov 13 2017

Currently seeing a shield of mid and high level clouds moving
eastward across the Dakotas. Models picking up on this fairly well
and will watch this move across the area this morning before
clearing out and making way for mostly sunny skies, at least along
and west of the James River. Also seeing a stratus deck developing
to our south across central NE. This looks to be the beginning of
the potential stratus affecting the eastern CWA later this morning
and afternoon, but to what extent is the big question. Models not
doing the greatest with this feature, but after looking at soundings
and lower level RH progs from various hi-res models, it would appear
that some degree of stratus will move into south central SD over the
next several hours, then affect southeast up through east central SD
later in the day. Although, current thinking is that this may be
much more scattered in nature by the time it makes it this far
north. Don`t have a great feel on this though so this is something
that needs to be watched as a thicker stratus will have an effect on
high temperatures. Speaking of temps, they were increased several
degrees across the region today largely based on 925mb temps in
comparison to yesterday and the highs that resulted from that. This
puts the entire CWA mainly in the 50 to 60 degree range.

Tuesday is looking like another mild day with fairly similar, or
even slightly warmer temps at 925mb. Increased highs above
SuperBlend by several degrees, siding more towards MAV values again,
which has been performing well during our recent warm-up. Will have
to examine potential for low clouds and fog late tonight into
Tuesday morning as models are hinting at this. To what extent they
may be overdoing things is still in question. If confidence
increases in there being lower CIGs over the eastern CWA as some hi-
res models suggest, we may need to take another look at highs on
Tuesday.

.LONG TERM...(Tuesday Evening through Sunday)
Issued at 347 AM CST Mon Nov 13 2017

An upper level shortwave trough will be over the Northern Plains at
the beginning of the period. This wave exits by Wednesday morning,
with weak ridging then dominant through the day Thursday. A stronger
and deeper shortwave trough will move through late Thursday night
and Friday, with northwest flow then setting up through the
remainder of the period.

At the surface, a weak frontal boundary will be over the area early
Tuesday evening, then quickly exits to the east overnight. High
pressure settles in Wednesday and Wednesday night, then pushes east
as low pressure digs down the lee of the Rockies. A fairly tight
pressure gradient develops over the area between the two systems,
with windy conditions expected on Thursday. The low and associated
frontal boundary track across the area Thursday night into the day
Friday, and may bring the next chance for precipitation.
Temperatures look warm enough for the precipitation to be mainly
rain, but there could be some snow mixed in late Thursday night and
again Friday evening. Amounts appear to be minimal at this time.
High pressure returns Friday night and remains dominant through the
weekend.

Temperatures will continue to be mild through the extended, with
highs mainly in the 30s and 40s. Thursday will be the warmest day of
the period with the strong southerly winds, with highs in the 40s
and 50s. A few locations across the southwest may even reach the
lower 60s. Overnight lows in the upper teens to lower 30s will be
common through the extended period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 1155 AM CST Mon Nov 13 2017

With the exception of KATY, good VFR is occurring over terminal
airspace right now. KATY may eventually mix out its MVFR stratus
this afternoon and joing the others in VFR flying conditions
heading into this evening. Given the synoptic pattern, time of
year and available low level moisture around tonight into Tuesday
out ahead of an approaching cold frontal passage, there is some
expectation that low (sub-vfr) stratus and/or fog will develop
overnight across the James River valley of northeast South Dakota
over into the upper Red River valley headwaters region of west
central Minnesota. Model soundings and a number of guidance
sources indicate some good radiational cooling conditions setting
up by early this evening across the region. What`s not abundantly
clear at this point is how far to the west these conditions will
develop/spread overnight. At this point, where confidence is high
enough to add mention in the TAFs, have beefed up sub-VFR forecast
conditions at KABR and KATY, and left VFR forecast conditions
going at KPIR and KMBG where adequate surface/low-level moisture
in the nocturnal boundary layer may not be sufficient to produce
any fog or low stratus. Will continue to monitor trends over the
next couple of TAF issuances.

&&

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

$$

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



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