Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 240715
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
315 AM EDT Thu Jul 24 2014

.SHORT TERM (Now through Friday)...
Issued at 252 AM EDT Thu Jul 24 2014

Low level moisture trapped under an inversion around 850hPa has
resulted in a low cloud deck this morning.  These clouds are
expected to persist, and may even generate some isolated sprinkles
or light rain showers, through the morning hours.  We should see
more sun this afternoon than this morning, with the clouds
dissipating by this evening. High pressure centered near Lake
Michigan will supply us with north breezes around 10 mph.  The
combination of the clouds and northerly low level flow will keep
temperatures down today, with highs mostly in the middle and upper
70s.

The Lake Michigan high will slide southeastward into the upper Ohio
Valley tonight, giving us a beautiful summer night.  Under mostly
clear skies and just a slight northeast breeze, temperatures will
tumble into the middle and upper 50s (around 60 in metro areas).
Some valley fog may form towards sunrise Friday morning.

On Friday the high will proceed to the mid-Atlantic coast.  As a
result we`ll remain dry but temperatures will be a little warmer
with afternoon readings peaking generally in the 80 to 85 degree
range.

.LONG TERM (Friday Night through Wednesday)...
Issued at 310 AM EDT Thu Jul 24 2014

An unsettled period of weather will be setting up this weekend,
followed by much cooler temperatures once again next week. To start
off the long-term period, models have been trending slower with the
approach of the first wave of weather this weekend, looking to leave
much of the forecast area dry overnight Friday. Even Saturday may
not amount to much as a frontal boundary struggles to approach from
the north. However, shortwaves look to be traversing through the
region over the weekend before a stout Canadian trough dips down
early next week. The question is how much moisture and instability
will be in place well ahead of the approaching frontal boundary to
trigger storms to fire up. The 00Z ECMWF and GFS are in general
agreement and indicating that the better instability and moisture
transport will exist primarily across northern KY and southern IN
for much of the day on Saturday. As the front drops through late
Sunday, greater thunderstorm chances exist for the entire forecast
area, particularly during the day on Sunday ahead of the front and
with daytime heating assisting. With GFS soundings indicating PWATs
exceeding the 75th percentile (according to climatology for this
time of year) on Sunday, could see a good amount of rain out of any
storms that develop.

Lingering lower-level moisture and continued height falls as the
aforementioned upper trough moves on in leaves shower chances in the
forecast on Monday for the northern and eastern two-thirds of the
forecast area. Locations in the Bluegrass region will have higher
chances, thanks to some assistance from orographic lifting. The
clouds will likely be the last to depart, looking to possibly hang
out overhead through early Tuesday. By the middle of next week,
surface high pressure will move in but the upper trough will remain
in place.

Temperatures in the long-term period will be their warmest Saturday
and Saturday night, reaching the upper 80s to lower 90s and the low
70s overnight. These temps are actually near normal for this time of
year but the remainder of the forecast period will be dominated by
below normal temps. Sunday`s highs will still be on the warm side,
but a few degrees cooler than Saturday as clouds and precip keep
them from getting too high. The noticeable airmass change comes on
Monday as highs only reach the mid to upper 70s, struggling to reach
the 80 degree mark in southern KY. Tuesday looks to be the coolest
day with highs in the low to mid 70s and lows in the mid to upper
50s. Wednesday will rebound slightly, but still struggling to reach
80 degrees for highs and lows will be near 60 degrees. Either way,
another set of beautiful mid-summer days ahead!

&&

.AVIATION (06Z TAF Update)...
Issued at 118 AM EDT Thu Jul 24 2014

A somewhat low confidence forecast for this TAF package as we deal
with low stratus -- always a difficult thing to forecast and rather
uncharacteristic for late July.  Climatology shows that central
Kentucky experiences sub-VFR ceilings during the pre-dawn hours in
July only about 10% of the time (1973-2011).

Anyway, low ceilings have indeed developed along the Ohio River
Valley early this morning and are expected to persist for several
hours.  Ceilings should concentrate around the low end of MVFR, but
could slip briefly to high end IFR around dawn.  Visibility should
not be restricted.

The question with this kind of cloud deck is always how quickly it
will lift and/or mix out.  The models are having their usual
disagreements.  At this point will go with a gradual diurnal lifting
of the clouds, reaching VFR by this afternoon though remaining BKN
for much of the day.  Skies should clear out tonight.

Winds have been chaotic over the past several hours as various
synoptic and mesoscale boundaries move through the region.  However,
winds should concentrate out of the NNW for the pre-dawn hours and
NNE during the day today at speeds of 5 to 10 knots.

&&

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

$$

Short Term........13
Long Term.........lg
Aviation..........13




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