Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 171742 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1242 PM CDT Wed May 17 2017

.UPDATE...
Issued at 1236 PM CDT Wed May 17 2017

Aviation discussion updated below for 18Z TAFs.

UPDATE Issued at 1019 AM CDT Wed May 17 2017

Continue to watch progression of low pressure across the plains as
rainfall continues moving northward. Adjusted POPs a bit based on
latest hi-res guidance and current radar imagery. This basically
led to increasing chances across the southeast CWA while lowering
POPs a bit across the northern edge of the system. Still expecting
the majority of rainfall to occur over the eastern/southeastern
CWA through the day and overnight hours, with an area also
trailing back into the southwest CWA. Made some minor changes to
highs for today, which will feature cool temperatures with highs
in the upper 50s to around 60 degrees. Cloudy skies and a brisk
north to northeast wind will make it feel rather cool out there
today.

&&

.SHORT TERM...(Today through Friday Afternoon)
Issued at 305 AM CDT Wed May 17 2017

Dry north/northeast winds and a little farther south and east
placement of upper level forcing has resulted in a downscaling of
POPs and QPF with the system this morning and today. That said, the
SREF mean QPF for Watertown is still around an inch so still looking
at some spots to get a deep soaking. Widespread cloud cover and weak
cold advection means highs will be just a few degrees off current
readings. Did not deviate from the previous forecast in that
respect. Winds will also come up with mixed winds in the 20-30kt
range, as the central pressure falls to 991mb over northwest Iowa,
with a 2026mb high over south-central Canada.

This high pressure continues to sink south Thursday, and despite the
associated partial clearing, cold advection means that temperatures
will again struggle to reach low 60s Thursday. Guidance lows for
some locations are in the 30s, so will continue to watch for the
potential for frost though timing means everything as we will also
see a low lifting from the south, with isentropic upglide resulting
in increased mid/high cloud cover hopefully saving us from dropping
too close to the freezing mark.

Ceilings slowly lower Thursday night into Friday from south to
north, though with the high center so close to the CWA, soundings
suggest we retain a dry near surface layer. Timing on the advance
northwards of moisture means that what limited daytime heating
combined with just enough of a warm layer, we can keep surface
precipitation as only rain.

.LONG TERM...(Friday Evening through Tuesday)
Issued at 305 AM CDT Wed May 17 2017

It appears that a pattern change will occur during the long term.
The recent west conus trof/east conus ridge mid level pattern should
do a reversal, and resemble more of a positive PNA pattern. But
first, we will have to deal with an upper low shearing across the
region Friday through Saturday.  This is probably the forecast areas
best shot at decent measurable pcpn during the period. Stability
progs indicate little if any chance for severe weather. The latter
half of the weekend still looks mainly dry, but developing northwest
flow aloft will likely lead to scattered showers next week as sfc
diabatic heating works with cool temps aloft to produce pcpn.
Temperatures start off the period below normal, but then trend
quickly to near normal, and remain that way through the vast
majority of the period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1236 PM CDT Wed May 17 2017

-SHRA will continue to affect KABR and KATY through the
 afternoon, and linger over KATY into the evening hours. Further
 west, dry conditions expected at KMBG and VCSH will do for KPIR.
 CIGs will generally be MVFR from KABR to KPIR, with IFR
 conditions at KATY. Over KMBG, more VFR CIGs expected with just
 SCT MVFR. VSBY may be MVFR at times over KATY in areas of SHRA
 later this afternoon and evening. CIGs will gradually improve
 from west to east this evening through Thursday morning.

&&

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

$$

UPDATE...TMT
SHORT TERM...Connelly
LONG TERM...TDK
AVIATION...TMT



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