Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 292312

Area Forecast Discussion
National Weather Service Huntsville AL
612 PM CDT Thu Sep 29 2016

For 00Z TAFs.


 (Issued 237 PM CDT Thu Sep 29 2016)
The 19z IR/visible satellite imagery indicated that the upper low at
500 millibars was rotating counterclockwise across central Kentucky.
Quite a bit of broken to overcast low clouds were shifting south-
southeast around the periphery of the upper low toward the forecast
area. Expect that at least a broken deck of low clouds will continue
to remain across the forecast area tonight. This cloud cover may
be enough to keep temps at or slightly above guidance numbers

The short term models continue to slowly lift the upper low slightly
northward with time on Friday and expect that any light precip should
remain generally north of the forecast area. The orientation of the
upper low to the north of the region and high pressure across the
southeast should result in a continued northwest low level flow
through Sunday. Will slowly increase temps with time as per GFS/ECMWF
temp guidance through Sunday. The mid to upper level ridge axis will
remain across the region through Wednesday. The models are indicating
that a surface cold front will move eastward with time between
Tuesday and Wednesday into the mid Mississippi through Ohio Valley
region by 00z Thursday.

The models disagree involving whether the cold front will maintain
its intensity against the upper through surface ridge that will shift
east of the region by Thursday. For now, will follow closer to the
GFS solution of keeping conditions dry across the region on Thursday,
compared to the wetter solution of the ECMWF model. Went with a
compromise involving temps between the warmer GFS and cooler ECMWF
temp guidance through the extended forecast periods.



For 00Z TAFs: The upper level low is centered near Louisville, KY and
along the west side winds remain out of the N/NW. Upstream
observations indicate slightly better surface moisture over KY/IL/TN
will continue south into the area tonight increasing dewpoints into
the lower 50s. Models and satellite imagery indicate that we will see
some clearing in the BKN/OVC deck after 02Z this evening, which will
allow temps to fall into the low to mid 50s.

There is some uncertainty in the guidance but if the skies remain
clear tonight, we could see fog develop tonight. Did not go nearly as
low as some guidance suggests for Vsby/CIGS (IFR) due to the
uncertainty. But will monitor trends tonight and adjust the TAFs if
it does look like fog is more certain. Expect mainly VFR conditions
with a continued BKN/OVC AOA 4,000ft for Friday.





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