Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 140756

Area Forecast Discussion
National Weather Service Louisville KY
256 AM EST Tue Nov 14 2017

.Short Term...(Today through Wednesday)
Issued at 255 AM EST Tue Nov 14 2017

Broad surface high pressure currently extends from Quebec
southwestward across the Great Lakes and into the Ohio Valley, but
we still have quite a bit of stratus on the south end of the high
where low-level moisture remains trapped under an inversion between
925-850mb. These clouds have been quite stubborn under weak easterly
low-level flow, a pattern and time of day that does not support
clearing before daybreak. That said, based on pilot reports in the
last few hrs, these clouds are now quite shallow, and we should be
able to see some clearing by mid to late morning, especially across
south-central Kentucky. The last area to break out will be the
Bluegrass region. Not much change to the previous temp forecast for
today, given that clouds were thin enough Monday to still reach or
exceed the forecast highs.

Northern stream shortwave will move east from the Canadian Prairies
across the upper Great Lakes on Wednesday, with its trailing cold
front pushing through the Ohio Valley. Looks like a high-
probability/low-QPF rain event here, with categorical POPs across
the board by Wed afternoon but generally a tenth to a quarter inch
of rain.


.Long Term...(Wednesday night through Monday)
Issued at 255 AM EST Tue Nov 14 2017

Will begin the period with precip tapering off as a cold front
departs cleanly to our south and east. Chance POPs east of I-65 in
the evening may even be generous. High pressure builds in from the
north on Thursday, but temps only modestly below normal under
shortwave ridging aloft.

Still keeping a close eye on a complex and dynamic storm system that
will affect the Ohio Valley Friday into Saturday. Model consensus
has slowed from previous forecasts, and we now see a 12-18 hr
discrepancy in timing between the faster GFS and the slower ECMWF.
This will cut back our Friday POPs to the chance category. We will
have widespread rain at some point Friday night or Saturday,
possibly even Sat night if the Euro verifies, but there is enough
disagreement in the timing that we will cap POPs at likely and
broadbrush at least 2 of the 3 periods.

Severe potential is tricky, given the robust wind fields associated
with this system. Models continue to show more of an anafront
structure with the precip shield mainly behind the cold front. In
addition, the instability ahead of the front is sorely lacking, but
we`ll need to watch this in case fropa occurs closer to the diurnal
instability max. That being said, what we can say with confidence is
that it will be windy both ahead of and behind the cold front.

Dry weather will follow Sunday and Monday, with plenty of question
as to just how cold. Current forecast favors the GFS, which has deep
NW flow into the Ohio Valley and keeps us well below normal. ECMWF
is much less amplified and could be up to 10 degrees warmer (but
still below normal!) if it works out.


.Aviation...(06Z TAF Issuance)
Issued at 1215 AM EST Tue Nov 14 2017

Stratus deck continues across southern Indiana and central Kentucky
with bases between 2500 and 3000 ft. With a easterly to
northeasterly wind continuing through the period, the moisture is
likely to stay trapped in the low levels keeping the stratus broken
to overcast through at least mid/late morning. It`s possible some
improvement could take place in the afternoon, but confidence isn`t
too high as winds will remain e/ne.




Short Term...RAS
Long Term...RAS
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