Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 170812

Area Forecast Discussion
National Weather Service Louisville KY
312 AM EST Wed Jan 17 2018

.Short Term...(Today through Thursday)
Issued at 310 AM EST Wed Jan 17 2018

First off, have had a persistent band of radar returns along I-65
near Shepherdsville. Have issued a couple of special weather
statements for light to moderate snow along this band, as traffic
monitoring programs have been showing slow downs in that area.
Trends in radar and satellite products is for that band to weaken.

Otherwise, latest water vapor imagery showing broad upper trough
oriented along the Ohio River Valley this hour. At the surface, have
a 1044 mb high pressure centered over the Central Plains, with a
ridge axis over the region. The trough looks to close off into an
upper low over the Appalachians later today, whereas the surface
high will drop into the lower MS valley through Thursday.

Until southwest winds become more established Thursday, we will have
to deal with very cold temperatures. Cloud cover early this morning,
though it is bringing a few flurries is allowing us to stay just
warm enough, with most locations staying above zero. Sites south of
the cloud shield earlier made it to several degrees below zero. We
should stay under this shield for much of the day, though we may
break out by late afternoon. After that we should stay clear into
Thursday, helping out with our warmup.


.Long Term...(Thursday night through Tuesday)
Issued at 310 AM EST Wed Jan 17 2018

Ridging moves into the Midwest to close out the work week, promising
a continued warming. Will still have to go a little under guidance
for temperatures until we can melt off the snowpack. We may see some
light rain showers Saturday. The southerly flow will pick up further
on Sunday, as our next storm system approaches the region. At this
point, models are focused on the Monday time frame for the best
chances for rains along the associated cold front. We then return to
some near normal temperatures Tuesday.


.Aviation...(06Z TAF Issuance)
Issued at 1255 AM EST Wed Jan 17 2018

A period of MVFR is likely overnight and Wednesday morning, with a
broad area of stratus over the lower Ohio Valley. Flurries are also
ongoing and are expected to continue, and an occasional light snow
shower is possible as well. The highest/deepest low-level RH looks
to be around 12z at SDF and perhaps between SDF/LEX from 12-15z, so
we may see some light snow showers around that time.

As surface ridging slowly builds east tomorrow and the low-level
inversion weakens, MVFR clouds are expected to scatter out from west
to east. HNB will see an improvement first, with prevailing VFR
after 12z. Right now, have SDF/BWG scattering out by mid to late
morning, with LEX improving during the afternoon. Confidence is only
medium on this timing, however.




Short Term...RJS
Long Term...RJS
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