Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 262323
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
723 PM EDT Sun Oct 26 2014

...Updated Aviation Discussion...

.SHORT TERM (Now through Monday Night)...
Issued at 309 PM EDT Sun Oct 26 2014

Surface high pressure is sliding across our CWA at this hour, and
will continue to push east this evening. Temperatures should top out
in the 70s under a virtually cloudless sky.

Expect a warm front that is currently organizing to our WSW to
gradually lift ENE tonight as the pressure gradient tightens between
a surface high to our east and a low over the central Plains.
Meanwhile, upper flow aloft will transition to southwesterly after
the passage of a shortwave ridge. Basically, this will lead to a
mild overnight as SW low level winds increase behind the frontal
passage, and low clouds associated with the front develop. Look for
lows only near 60 in our SW, however should cool to around 50 NE.
There is some signal for dense fog again across our SW early
tomorrow, however feel the increase in low level wind will actually
be more likely to yield low stratus than fog. Will continue to
monitor.

With the upper level pattern transition from zonal to southwesterly,
near record warmth will be possible for much of the Ohio River
Valley Monday. Will continue to forecast low to mid 80s in a
well-mixed and warm boundary layer, aided by nearly full sun. Will
also watch as SW winds gust between 20-30 mph tomorrow. Luckily,
enough low level moisture return should occur behind the warm front
to limit low RH values and any fire weather concerns.

Will see increasing sky cover ahead of the next weather maker late
Monday night. This will occur as a surface low quickly rides a
baroclinic zone into the Great Lakes and a trailing cold front
begins to push toward the region. Will hold off any measurable rain
chances only to the far NW counties very late Monday night as the
main precipitation will fall on Tuesday (discussed in long term).
Monday night lows will be quite mild in steady SW flow and
increasing clouds. Look for the 60-65 range.

Below are the records for Monday and Monday night.

               Record Max Oct 27        Record Warm Low Oct 28
Louisville        84 (1940)               64 (1991 and 1984)
Lexington         87 (1940)               64 (1984)
Bowling Green     87 (1919)               65 (1984)
Frankfort         89 (1940)               61 (1899)

.LONG TERM (Tuesday through Sunday)...
Issued at 308 PM EDT Sun Oct 26 2014

...Widespread frost and sub-freezing temperatures likely by next
weekend...

In the medium range, deterministic and ensemble guidance continues
to be in agreement with a mid-level trough axis swinging through the
region Tuesday into Wednesday.  This feature will drag a surface
cold front through the region on Tuesday.  Widespread showers and
scattered thunderstorms will accompany the front as it pushes
through.  Current thinking is that the entire region will pick up on
some measurable rainfall.  For that reason, have increased the PoPs
quite a bit for Monday.  While the main dynamical forcing will be
well to our north, model soundings do show a thin ribbon of
instability available Tuesday.  Thus, will continue to mention
scattered thunderstorms in the forecast at this time.  Temperatures
look to remain quite mild ahead of the front with pre-frontal highs
warming into the lower-middle 70s in the central and east with upper
60s to around 70 in the west.  It will be a breezy day out there on
Tuesday as well as the pressure gradient will be up.  Sustained
winds of 15-20 MPH with gusts of 20-25 MPH will be possible.

By Tuesday night, the front will push off to the east with showers
ending from west to east.  The upper trough will lag behind, so
party cloudy skies are likely Tuesday night and into Wednesday.
Lows Tuesday night will cool into the middle-upper 40s...with highs
on Wednesday warming into the upper 50s in the north with lower 60s
in the south.  Cool and partly cloudy conditions are expected on
Thursday with clouds increasing late in the day as another trough to
the west approaches.  Highs will generally warm into the upper 50s
to around 60 with overnight lows in the lower 40s.

For the late week and into the weekend, the models had been showing
some wild swings in the overall upper level pattern.  These wild
swings have abated and the overall guidance is starting to come into
better agreement.  From a hemispheric scale, a large upper level
trough axis is forecast to develop from the Gulf of Alaska down into
the Pacific NW.  As this trough deepens, downstream ridging over the
inter-mountain west and western Plains will increase.  As the Plains
ridge increases, a mid-level trough axis will swing through the Ohio
Valley and then close off across southeastern Canada and then lift
northeastward by late next weekend.  As the wave travels through the
Ohio Valley, it will likely generate plenty of cloud cover and
scattered rain showers on Friday. These will quickly shunt off to
the east Friday night and clearing skies will attempt to move in.

Friday will be a rather cool day with highs in the lower 50s across
southern Indiana and much of north-central/east-central KY.  With
mid-upper 50s being possible across far southern KY.  Much colder
air will filter into the region Friday night.  However, the extent
of low temperatures will depend on how much clearing takes place.
Current projections suggest lows falling into the lower-middle 30s
region wide.  Saturday will be a cool/crisp fall day across the
region with mostly sunny skies.  Despite the good amount of sun,
cold air advection will keep temperatures at bay with highs only
warming into the middle-upper 40s.  Clear skies and light winds will
set the stage for a widespread frost/sub-freezing temperature event
Saturday night with lows bottoming out in the upper 20s to the lower
30s.  Dry and cool conditions will continue into Sunday with highs
only warming into the upper 40s to the lower 50s.

&&

.AVIATION (00Z TAF Update)...
Updated at 720 PM EDT Sun Oct 26 2014

Main challenge is fog/stratus potential as a warm front lifts north
across Kentucky tonight, bringing a very quick return of low-level
moisture (dewpoints south of the front are pushing 60 compared to
30s north) and a stout low-level jet.

Fairly confident that low stratus will impact BWG, and at the very
least ceilings will go solidly into LIFR. Some indication in model
data that fog will develop, but with winds increasing to 25 kt just
1000 feet off the deck, this scenario appears more supportive of
stratus. Will also include LLWS for the low-level jet just above a
very sharp inversion.

Much less confident in the forecast for SDF and LEX as moisture will
be slower to arrive, and by the time it does arrive low-level winds
will be strong enough to lift it into a stratus deck. That said,
with the lesser amount of moisture, will just carry a scattered low
deck. If a ceiling does develop, it would most likely come in at
LIFR. Winds will be close to LLWS especially at SDF, but confidence
is not yet high enough to include it.

Low clouds will dissipate by late morning and early afternoon, with
a strong SW gradient taking over. Gusts to 20-25 kt will be common
across the board during the peak heating of the afternoon.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&

$$

Short Term........BJS
Long Term.........MJ
Aviation..........RAS





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