Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 171526 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1026 AM CDT Wed May 17 2017

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


.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 12Z TAFS through 12Z Thursday Morning)
Issued at 615 AM CDT Wed May 17 2017

MVFR cigs are expected to expand across much of the region this
morning as showers edge closer. Meanwhile, KATY will probably
experience IFR cigs for a time before some improvement this
afternoon. The best chances for any rain will be at KPIR/KATY.




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