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Area forecast discussion 
National Weather Service Louisville Kentucky
717 PM EDT sun Oct 23 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 (00z taf update)...
issued at 717 PM EDT sun Oct 23 2016

A cool front will cross central Kentucky during the early morning
hours on Monday. Though skies will stay mostly clear, a low level
jet will crank up just ahead of it. There will be enough of a vector
difference between surface winds and winds around 1500-2000 feet to
warrant a mention of low level wind shear with this feature until the front passes

Skies will stay mostly clear through the taf period. Surface winds
from the southwest this evening will switch to the north behind the
front tomorrow.


Lmk watches/warnings/advisories...


Short term........jbs
long term.........Jbs

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