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Area forecast discussion 
National Weather Service Louisville Kentucky
641 am EDT Tue Sep 30 2014

..updated aviation discussion...

Short term (now through wednesday)...
issued at 245 am EDT Tue Sep 30 2014

The synoptic pattern early this morning features weak ridging aloft
over the Ohio Valley. There were two troughs of note, one compact
trough pushing southeast through the Great Lakes, with another
upstream trough centered over the Central Plains. The Great Lakes
trough will be the main focus of this short term period, as it will
help drive a weak surface front through the region today.

Conditions remain tranquil early this morning as high pressure
remains in control. Have been keeping a close eye on area
observations/webcams as some fog continues to remain a possibility,
mainly across portions of south-central Kentucky where the drier air did
not penetrate Monday afternoon. So far nothing seems to be too
dense in nature, but this may change so we will continue to monitor
through the morning hours.

Otherwise, today will be another pleasant late-September day. The
aforementioned potent pv anomaly/compact trough will push southeast
through Ohio today, driving a weak cold front south from in/Ohio into
Kentucky by late this afternoon. This front will be moisture-starved,
thus do not expect anything more than a few clouds along it. There
is also not much of an airmass change behind the front, so
temperatures should still be rather mild today across all areas.
Given the dry grounds, guidance continues to have a cool bias, thus
will go above the consensus for highs today. This puts temperatures
in the low to mid 80s.

The weak front will completely wash out over the region tonight as
winds go mainly calm with mostly clear skies. Radiational cooling
will lead to temperatures dropping into the low and mid 50s once
again, with some patchy fog once again possible.

Wednesday will feature more of the same as mild temperatures and
sunny skies continue. Highs will top out in the low to mid 80s once
again.

Long term (wednesday night through monday)...
issued at 258 am EDT Tue Sep 30 2014

The warmth of the past week will come to an end during this long
term as a pattern change brings upper trofs into the region from
the northwest Friday morning, Friday night, and Monday.

With the first trof, a surface cold front will cross the region from
west to east Friday. Scattered showers and thunderstorms will be
possible by Thursday afternoon and will become widespread Thursday
night into Friday morning before tapering off from west to east over
the course of the day Friday. Though we will see an increase in the
low level jet Thursday night and there will be some instability
available, sounding progs suggest any storms will be elevated.
Also, the column will be very moist as precipitable water values
rise well above normal for early October. These factors combined
with the climatologically unfavorable time of day of the fropa
indicate that severe storms will be unlikely. Locally heavy rain
will be a possibility, but with as dry as we've been for the past
2-3 weeks, flooding shouldn't be a problem.

For temperatures on Thursday...models have been running too cool
recently with their maxt's, plus we'll be ahead of the approaching
cold front and pattern change, so will go a little warmer than
guidance for high temperatures despite cloud and rain chances. Will
aim for readings solidly in the middle 80s.

Behind the front on Friday, lower 70s for highs look good for most
locations. Friday could be a rather breezy day, with west-northwest winds
gusting to around 25 mph in the afternoon.

High pressure is expected to nose in behind the departing weather
maker, keeping a secondary cool front to our north. Will go with
dry weather for the weekend as a result. Then by Monday the next
upper trof and surface connection will enter the picture and bring
another chance of showers, though this system looks much weaker and
drier than the Thursday night event.

Chose to go on the cool side of guidance this weekend with
persistent upper troffing expected (especially Saturday and
monday). Will go with 60-65 on Saturday and 60s on Sunday, with
70-75 on Monday. The chilliest morning will be Sunday morning as
lows drop into the lower and middle 40s with upper 30s in the usual
cold spots.

&&

Aviation (12z taf update)...
issued at 640 am EDT Tue Sep 30 2014

The main taf concerns will be fog this morning at kbwg, with an
additional chance for fog/low stratus tonight into Wednesday
morning. As expected, kbwg has been bouncing from MVFR to LIFR this
morning, which will likely continue for the next few hours. All
sites will then go VFR for the remainder of the day. Will have to
watch the evolution of low cigs to the north across Indiana as a
weak cold front approaches the region, but these should mix out by
the time they get toward ksdf later this morning.

The weak front will wash out across the region tonight. Depending
on exactly where it lays out, some fog/stratus development will be
possible. For now, will introduce MVFR vsbys to kbwg and klex, but
some low stratus appears possible as well (similar to what is going
on currently in Indiana along the front).

&&

Lmk watches/warnings/advisories...
Kentucky...none.
In...none.
&&

$$

Short term........kjd
long term.........13
aviation..........kjd

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