Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 240532 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1232 AM CDT Mon Jul 24 2017

Issued at 904 PM CDT Sun Jul 23 2017

There`a a low pressure system (currently moving into se Montana/ne
Wyoming) approaching the region from the west. Short-range CAMs
suggest some weak convection may be working into the far western
forecast zones by 12Z Monday, with small chances steadily
spreading east during the day. Introduced some small pops to
address this potential. No other changes planned at this time.
Updates are out.

UPDATE Issued at 643 PM CDT Sun Jul 23 2017

See below for an aviation forecast discussion for the 00Z TAFs.


.SHORT TERM...(This Evening through Monday Afternoon)
Issued at 321 PM CDT Sun Jul 23 2017

Scattered to broken cigs remain over the eastern CWA this afternoon
under the western side of a surface high. This high will remain
dominant over the area into tonight, so expect the clouds to
dissipate with the loss of daytime heating later this evening. The
high gets pushed east on Monday ahead of an approaching low pressure
system. The front associated with this system will reach the western
part of the state Monday afternoon, with just a small chance for a
shower or thunderstorm ahead of the front over the far western CWA
late in the afternoon.

Low temperatures tonight will be range from the upper 50s east to
the mid 60s west. Warmer air will filter in ahead of the approaching
low on Monday, with highs ranging from the mid 80s east to around
100 degrees along and west of the Missouri River.

.LONG TERM...(Monday Evening through Sunday)
Issued at 321 PM CDT Sun Jul 23 2017

Monday Night: +50kt low level jet will set up overhead, with a
southwest orientation. Best area of low level convergence migrates
from central to northeast counties before exiting the area in the
early morning. Additionally, CAPE values peak early before migrating
out of the area. Divergence ahead of a 90kt jet max will reside
overhead, before migrating east placing us under the right exit
region. The net result looks unfavorable for nocturnal convection,
while temperatures will remain mild overnight. We will also see a
surge of higher humidity air into the area.

Tuesday: A surface front undercuts this mild mid level air. Flow
becomes southwesterly ahead of the front, and as such have increased
temperatures across the southern/eastern periphery of the CWA over
blended guidance. Understandably there is some uncertainty as to how
deep we can mix given the recent wet soils and active crops - not
something we have had much experience with this summer. Despite
this, mixing to 850/700mb range where temperatures are +26/+15C
respectively yields a range of temperatures in the mid/upper 90s to
mid 100s. On the north side of the front, temperatures will be more
subdued, though above average with favorable mixing in northwest
winds, and lower humidity. As for convection chances, will maintain
blended guidance POPs although with the understanding that there is
a strong cap in place.

Tuesday night: The surface boundary has stalled across our south and
eastern CWA border, and the upper jet migrates east so we are under
neutral flow, with a right entrance region moving towards the area.
A 500mb wave is migrating east across southern Canada at that time,
but there also appears to be a weak area of vorticity associated
with the southwest monsoon rounding the upper high. The low level
jet has migrated southeast of the CWA but other elements are in
place for elevated convection. Guidance is fairly consistent at
developing convection along the front. Chances continue into
Wednesday however the fetch of 700/500mb moisture migrates to the
south by mid day.

For the rest of the forecast, there was no need to deviate from
blended guidance. Upper flow becomes generally unsupportive for
widespread precipitation, though there is a weak signal for some low
POPs Friday. Temperatures will be close to average.


.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
Issued at 1230 AM CDT Mon Jul 24 2017

Good VFR is expected over all four terminals over the next 24
hours. Also, there could be an isolated or widely scattered shower
or thunderstorm around in the vicinity at KPIR and KMBG in the




LONG TERM...Connelly
AVIATION...TDK is the U.S. government's official web portal to all federal, state and local government web resources and services.