Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 210542 AAC

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1242 AM CDT THU JUL 21 2016

Issued at 1235 AM CDT THU JUL 21 2016

Aviation discussion updated below for 06Z TAFs.

UPDATE Issued at 909 PM CDT WED JUL 20 2016

A few thunderstorms still occurring across parts of the
northwestern CWA at this time...but expect them to diminish over
the next hour or so with the loss of daylight. No changes made to
winds or temperatures at this time.


.SHORT TERM...(This Evening through Friday Night)
Issued at 308 PM CDT WED JUL 20 2016

The main issues to deal with in the short term are heat/heat
indices, and storm chances. For tnt weak front is expected to
gradually shift southeast across the region.  Looking at recent sat
pix am not seeing anything that would light off over the region
except for perhaps central/northern North Dakota.  So other than a
meager pop for this evening over far western CWA, will go dry. On
Thursday temps should again be hot, perhaps even hotter than today
due to a slight lowering of the dewpoints. Heat indices will again
bump up against warning criteria and therefore will keep warning
going through Thursday.  However, for Thursday night and Friday have
decided to back away from warning across northern CWA. Based on
latest forecast heat indices, can`t justify it, especially over the
northern zones where some drier air will allow for a cooler night
and then not as high of heat index on Friday.  Kept southern CWA in
warning even though an advisory may be enough to cover the
situation, particularly on Friday.  Something for later shifts to
ponder. As for pcpn chances, Friday night is the best opportunity as
a decent front crosses the region, along with falling heights aloft
as mid level trof moves along the US/Canadian border.  H7 temps
remain pretty robust but models are showing convection lighting off
so won`t fight it.  Temperatures of course start off well above
normal, but then trend toward normal by the end of the week.

.LONG TERM...(Saturday through Wednesday)
Issued at 308 PM CDT WED JUL 20 2016

Saturday will be the first day where 80s return to at least part of
the forecast area. The 25C 850MB temps will get knocked down as low
pressure slides across central and eastern SD during the day. This
will be thanks to the 500MB trough that will be moving in from the
Pacific Northwest Friday and shifting across south central Canada
and western ND Saturday afternoon. PW increases to 1.75-2in through
18Z Saturday. Despite the high PW values and MUCAPE values over
1000J/kg, fcst models are very sparse with the precip Saturday. Part
of this is due to the capped atmosphere, with at least the GFS
indicating 700MB temps of 14-15C across all of the forecast area
except along the ND border. While the NAM is not quite as warm, both
agree that the best shear will likely be near or along the ND/SD
border during the afternoon hours. At the same time, an additional
sfc low over western ND at 18Z Saturday is expected to rapidly
deepen to around 999MB over southern Manitoba by 06Z Sunday as the
cold front exits east into MN.

Dry sfc high will slide across SD and west central MN Sunday
afternoon, and shift across MN Monday afternoon-evening. Near sfc
northwest winds will shift out of the south for Monday. Fcst
solutions are in pretty good agreement through Tuesday afternoon
with increasing moisture and temperatures on strengthening southerly
flow. The 00Z run of the ECMWF deepened the next low overhead and
moves it across southern MN Wednesday, while the 12Z run of the GFS
and ECMWF are more consistent in keeping us in between the trough
over MT/WY and high pressure across the Great Lakes region.


.AVIATION...(For the 06Z TAFS through 06Z Thursday Night)
Issued at 1235 AM CDT THU JUL 21 2016

VFR conditions are forecast to prevail through the TAF forecast
period. There is some potential for BR/FG through the overnight
hours, but confidence in occurrence and areal coverage is low so
will leave out of TAFs at this time.


.ABR Watches/Warnings/Advisories...
SD...Excessive Heat Warning until 7 PM CDT /6 PM MDT/ this evening for

     Excessive Heat Warning until 7 PM CDT /6 PM MDT/ Friday for

MN...Excessive Heat Warning until 7 PM CDT this evening for MNZ039-046.



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