Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 240447

Area Forecast Discussion
National Weather Service Louisville KY
1247 AM EDT Mon Oct 24 2016

...Updated Aviation Discussion...

.Short Term (Now through Monday Night)...
Issued at 302 PM EDT Sun Oct 23 2016

After a colder than expected start to the day, especially in the
southeast part of the forecast area, sunshine and a southwest breeze
helped warm temperatures back into the lower 70s across the area
today. While the axis of the surface high pressure ridge had moved
far enough southeast to get the area in the return flow overnight,
the low level moisture on the back side of the high ended up being
too little too late to keep temperatures from falling into the 30s
and generating spotty reports of frost.  The Burkesville Mesonet
site even plummeted to 29 - definitely NOT in anyone`s (or any
model guidance`s) expectations.

The surface high drifts southeast and weakens overnight, allowing a
dry cold front to cross the Ohio River before sunrise. While the
pressure gradient ahead of the front will not be strong, it should
be enough to keep southwest winds from dropping off completely,
which will help prevent another extreme temperature drop from
radiational cooling.  Low temperatures will vary across the 40s,
depending mostly upon wind exposure, though a few locations may
remain above 50 - especially in metro Louisville.

With little moisture and virtually no clouds associated with the
cold front, only a temperature drop of around 5 degrees is expected
for daytime highs on Monday - into the mid 60s to around 70.

An elongated surface high stretching from central Canada to eastern
Kentucky will help keep skies clear and winds light enough to allow
temperatures to drop again by Tuesday morning, with another chance
for frost, especially in favored rural locations. Right now it looks
like most thermometer readings by Tuesday morning will be in the
lower 40s, with upper 30s again not out of the picture for the usual
rural cold spots.

.Long Term (Tuesday through Sunday)...
Issued at 302 PM EDT Sun Oct 23 2016

The progressive pattern continues for the extended period, with two
more cold fronts set to move through the Ohio Valley - one late
Wednesday and Thursday, and the second over the weekend.  Both of
these look to be a little more active than the front coming through
tonight, at least bringing clouds and showers, with isolated
thunderstorms not out of the picture. As with the past several
frontal passages, the surface lows associated with these will pass
well to our north, keeping the bulk of the energy with them out of
our area, resulting in mainly relatively light rain for us.

Both of these FROPAs are associated with fast-moving short waves in
northwest flow, While the GFS and EURO have are in good agreement on
the timing and strength of the Wednesday night-Thursday system, they
differ greatly on the weekend weather.  The Euro is slower and
farther south with the surface low for the weaken system, bringing
it through on Sunday rather than faster GFS arrival on Saturday.
This far out, however, confidence is obviously low on any model
solution, so the weak 20s POPs over the weekend will undoubtedly be
fine-tuned over the next several days.

Temperature-wise, highs will be at or a little above seasonal
norms,generally from the mid 60s to lower 70s, with a few outliers
from that range north of the Ohio and along the Tennessee line.  Low
temperatures will vary a bit more, bouncing from the 40s Tuesday
night to the 50s Wednesday night, then back into the 40s Thursday
night before settling to around 50 for the weekend.


.Aviation (06Z TAF Update)...
Issued at 1245 AM EDT Mon Oct 24 2016

A cold front will pass through the region this morning. A low level
jet has developed ahead of the front. AMDAR soundings out of SDF
show winds of 40-45 knots around 1800 feet. This jet should shift
off to the east over the next few hours with winds aloft becoming
lighter. Will continue to carry LLWS for a couple of hours until
this jet does move out.

Otherwise, the only concern for this TAF period will be the wind
shift with the cold front moving through this morning. Winds will
become northerly between 12-15Z. They are not expected to be too
strong behind the front. Winds will slowly swing around to
northeasterly by this evening. Skies will be mostly clear through
the day.


.LMK Watches/Warnings/Advisories...


Short Term........JBS
Long Term.........JBS
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