Area Forecast Discussion
Issued by NWS Nashville, TN

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FXUS64 KOHX 241014

Area Forecast Discussion
National Weather Service Nashville TN
414 AM CST Tue Jan 24 2017

(Today thru Thu Night)

Will mention patchy fog across the Cumberland Plateau Region where
it has formed, in some locations locally dense, and will mention
across southwestern portions of mid state were slow erosions of
cloud coverage is occuring. Otherwise, expect continued decreasing
cloudiness from the SW to NE thru the remainder of the morning
hrs, with skies becoming moclr by late afternoon across the
entire mid state. This due to upper level ridging influences
building across the mid state thru at least midnight tonight.
This will result in afternoon high temps spanning the 50s, still
a few degrees above seasonal normal values. a weak sfc cold frontal
passage will approach the mid state region late tonight and push
thru the mid state on Wed. With S to SW sfc flow expected,
resulting in moisture pooling ahead of this frontal passage,
temps tonight will be significantly warm, actually at or even
a few degrees below seasonal high temps for this time of year,
spanning the mid to upper 40s, lower 40s Cumberland Plateau
Region. In reference to frontal movement, this is a little slower
progression than expected at this time last night, and with a
more pronounced swly flow pattern aloft that could support weak
multiple weak shortwave disturbance passages in this flow aloft,
consensus model consensus as taken a significant change from this
time yesterday also with now showing iso to sct light shwrs being
possible across the entire mid state by Wed afternoon, with even
numerous light shwrs during the early evening hrs on Wed night
across far eastern portions of the Cumberland Plateau Region.

Most of the moisture will be ushered east of the mid state by
late Wed night, but really what this weak cold sfc frontal passage
mentioned above will bring is a significant CAA pattern resulting
in lows Wed night spanning the mid 30s, and with highs on Thu now
actually a few degrees below seasonal normal values, spanning the
40s. Enough moisture may still be around across the Upper
Cumberland Region to support a light rain/snow mix late and thru
the morning hrs on Thu. No significant wintry accumulations are
expected at this time. This will turn to a slight chance of rain
shwrs by Thu afternoon as temps warm, and as also influences of
broad upper level troughing across the Ohio Valley Region
continues to move southward into at least northern portions of
the mid state. This will eventually result in the Upper Cumberland
Region once again possibly experiencing some iso light rain/snow
shwrs during the evening hrs with a change over to all snow after
midnight. Just like Wed night, no significant wintry mix or snow
accumulations are expected at this time for Thu night. The reason
there will be a complete change over to all snow is that sfc
ridging influences based across the Rockies will become even more
entrenched across our region, with lows on Thu night seasonal,
below freezing, spanning the mid to upper 20s.


(Fri thru Mon)

An upper trough will deepen across the region through the weekend,
dropping temperatures down to normal late January levels, and
perhaps slightly below normal for a couple of days. Models show a
few weak impulses coming down into the trough Friday and Saturday,
and a fairly strong impulse on Sunday. This impulse will bring a
reinforcing shot of cold air along with a chance for rain and snow.
Models vary with moisture, but the GFS shows enough post frontal
moisture to keep a chance for snow showers Sunday night into Monday
morning, especially for the Upper Cumberland / Plateau. By late
Monday, the upper trough will relax and a more zonal flow will
begin to develop.




Mostly MVFR cigs behind yesterday`s system for Middle TN, however
the exception will be KCSV. Almost all of the hi-res guidance is
suggesting the current IFR vis at KCSV will get worse overnight
and last through 15Z -- even with a good breeze still going on. As
the winds relax a little around midnight, look for LIFR to VLIFR
conditions to settle in over KCSV.

Winds will continue to blow out of the NW for the next couple of
hours then relax after midnight. A little southeasterly breeze
will pick back up Tuesday afternoon as a weak surface ridge move
east of the region.


Nashville      56  47  65  37  45 /   0  10  40  40  10
Clarksville    55  48  63  35  42 /   0  10  20  10  10
Crossville     51  43  58  34  40 /   0  10  40  60  20
Columbia       56  47  63  36  45 /   0  10  40  40  10
Lawrenceburg   56  46  62  36  46 /   0  10  40  40  10
Waverly        56  48  63  34  42 /   0  10  20  10  10





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