Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 180117

Area Forecast Discussion
National Weather Service Huntsville AL
817 PM CDT Tue Oct 17 2017

.NEAR TERM...(Tonight)
Issued at 817 PM CDT Tue Oct 17 2017

Quiet weather across the region, with high pressure centered over the
Central Appalachians reinforcing the dome of cool and dry air in
place over the Tennessee Valley. A few bands of cirrus were noted on
satellite imagery, but otherwise a clear sky is expected to prevail
overnight. Light northerly flow and the combination of the
clear/calm boundary layer has allowed for good radiational cooling
to take place this evening. In most areas, dewpoints will stay high
enough to keep lows (generally) a degree or two warmer than last
night. Temperatures should fall into the low to mid 40s by early
Wednesday morning -- with a few cool sheltered valleys in DeKalb,
Jackson, Cullman Counties potentially dropping into the upper 30s.

.SHORT TERM...(Wednesday through Thursday Night)
Issued at 236 PM CDT Tue Oct 17 2017

As previously mentioned, the sfc high currently centered across the
OH Valley will shift eastward through Wednesday but remains in place
on Thursday. This will keep rain out of the forecast and provide
light southeasterly winds under clear/mostly clear skies. This
pattern will start to warm temps back up towards seasonal values and
an approaching upper-level ridge will reinforce the warmth on
Thursday. Wednesday will be in the lower 70s with lows in the
low/mid 40s while Thursday will see highs in the low/mid 70s and
overnight lows in the upper 40s.

.LONG TERM...(Friday through Monday)
Issued at 236 PM CDT Tue Oct 17 2017

The upper ridge over the southeast U.S. will begin to break down
over the weekend as the west coast trof exits the Rockies.  The trof
"splits" as it crosses the Plains, with some continued model support
in a southern cutoff low taking shape.  This tends to dampen the QG
forcing overall for the TN valley, with little thermal advection
support either due to limited temperature gradient and decelerating
9-8h flow.  Also, the low level ridge axis will hold tough into
Sunday, with flow remaining anticyclonically curved over north AL
and southern TN.  This may keep our eastern counties rainfree
through Sunday night with plenty of dry air to overcome for
measurable precipitation. Nevertheless, we will maintain low to mid
range chance PoP going starting Sunday and lasting into Monday.  The
greatest chance will be over NW AL. The front slowly drops southeast
and may completely pass through the area until day 8 (Tuesday).  By
then, moisture and upper level support will already have passed well
to the east.  Will follow close to suggested blended temps thru the
period, which will be near or just above seasonal norms Friday and
Saturday, then fall below with the clouds/precip Sunday into Monday.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 620 PM CDT Tue Oct 17 2017

High pressure will remain in control for a quiet TAF period. This
will allow for mostly clear skies...VFR conditions and winds less
than 10 KTs for the next 24 hours.





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