Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 141132 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
632 AM CDT Mon Aug 14 2017

.SHORT TERM...(Today through Wednesday Afternoon)
Issued at 351 AM CDT Mon Aug 14 2017

An area of low clouds/fog has expanded out from behind the slow
moving low pressure system that has now migrated into Minnesota.
Will stick with mention of fog for most of the forecast area, with
dense mention for a few locations - but for the most part the
visibility isn`t that bad with a few exceptions at this time. No
headlines planned but will monitor through the rest of the AM hours.

Today we will see a low amplitude ridge build across the northern
plains, with the ridge axis west river this morning, moving across
the CWA today into Minnesota tonight. Isentropic upglide develops in
the wake of ridge axis passage, but we retain a dry east/northeast
low level regime, and NAM/GFS BUFKIT soundings support this will
lead to mainly mid/high clouds and not result in any precipitation
today.

We continue to see a change in airmasses through Monday night with
warm advection at 850/700mb, with some semblance of a 30kt 850mb jet
leading into the CWA. Several CAMs support convection west river due
to diabatic heating Monday, with the suggestion that remnants of
this convection could reach the western CWA during the overnight
hours as well, though MUCAPE values trail off along the western
periphery of the CWA rather dramatically.

Southwest flow aloft becomes more established for Tuesday, with a
plume of higher dewpoint air into south central South Dakota, with a
low tracking towards the northeast CWA with a well defined warm
front between highway 212/interstate 90. These looks to be the focus
for surface based convection potentially for our southern counties,
but more likely we are talking about elevated convection across our
area with a subtle southwest flow shortwave.

A second wave will lift northeast late Tuesday/early Wednesday. PWATs
by this point are approaching 2 inches. Heavy rain instantly becomes
a concern with any convection, and while there isn`t a well defined
low level jet to help focus storms over our area, 700-500mb flow is
generally around 20kts so we can anticipate slow storm motion in
addition to abundant atmospheric moisture.

.LONG TERM...(Wednesday Evening through Sunday)
Issued at 351 AM CDT Mon Aug 14 2017

An area of sfc low pressure and the upper trough will exit to the
east Wednesday night taking any lingering showers with it. Relief
will be short-lived as another sfc low and upper trough shift into
the northern Plains Thu night bringing more showers and
thunderstorms. As that round exits Fri night, upper ridging will
build in for the weekend. Another sfc low Sun night/Monday will
bring additional chances for showers and thunderstorms.

Temperatures will remain slightly cooler than average until the
weekend when highs will jump a bit under the ridge.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
Issued at 631 AM CDT Mon Aug 14 2017

MVFR/IFR conditions in fog and stratus will improve to VFR by 17z
at the latest. KATY will again drop to MVFR/IFR early Tuesday
morning. Otherwise VFR conditions are expected.

&&

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

$$

SHORT TERM...Connelly
LONG TERM...Wise
AVIATION...Wise



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