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743
FXUS63 KJKL 020345 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1145 PM EDT Mon Jul 1 2024

.KEY MESSAGES...

- Temperatures 5 to 10 degrees below normal will continue through
  tonight, before temperatures warm to near or slightly above
  normal on Tuesday.

- Humidity will increase through midweek and Afternoon heat
  indices may approach 100 in some locations Wednesday through
  Friday

- The potential for showers and thunderstorms returns by Thursday,
  Independence Day, and lasts through the weekend. The highest
  probability of rain is on Thursday and Friday.

&&

.UPDATE...
-- Changed Discussion --
Issued at 1145 PM EDT MON JUL 1 2024

No significant changes to the forecast with just the inclusion of
the latest obs and trends for the T/Td/Sky grids with this update.
These minor adjustments have been sent to the NDFD and web servers
along with a freshening of the zones and SAFs.

UPDATE Issued at 740 PM EDT MON JUL 1 2024

23Z sfc analysis shows pleasant high pressure in place over the
region providing for light northeast winds and mostly clear skies.
Temperatures were 10 to 15 degrees cooler today than yesterday
thanks to this air mass change along with much dry conditions.
Currently, temperatures are running in the mid 70s while dewpoints
are noted in the comfortable upper 40s to lower 50s, most places.
Have updated the forecast mainly to just add in the latest obs and
trends for the T/Td/Sky grids. These minor adjustments have been
sent to the NDFD and web servers.
-- End Changed Discussion --

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 410 PM EDT MON JUL 1 2024

Late this afternoon, an upper level ridge extended from portions
of the Southern Plains/Arklatex region northeast into the mid MS
Valley to Great Lakes regions. Meanwhile, an upper level trough
axis extended from western Canada across MT and portions of the
Northern Rockies into southwest Conus. At the surface, a ridge of
high pressure extended from the Great Lakes to the OH Valley to
Arklatex regions. Behind the front that crossed the region on
Sunday, the high has ushered in a cooler and drier airmass and
only a few passing cirrus were moving across the region at
present. Highs so far today have been 5 to 10 degrees below normal
for early July.

Tonight and Tuesday, the upper level ridge is expected to build
across the Southeastern Conus with the axis of the 500 mb ridge
remaining west of eastern KY. However, the sfc high pressure ridge
will slide to the eastern seaboard through Tuesday evening.
Meanwhile, the trough extending across the western Conus at
present will move east into the upper MS Valley to Plains region
to the south of an upper level low that evolves from Saskatchewan
and into Manitoba to far western Ontario. Tuesday night, the axis
of the ridge will gradually shift to the east of the area as the
upper low reaches the northern Ontario/James Bay vicinity and an
associated shortwave trough reaches the western Great Lakes to mid
MS Valley areas. The cold front associated with this system will
remain well northwest of the area through the short term period.

The high shifting east across the Great Lakes and the OH Valley
region tonight, will lead to another night with low temperatures
on the order of 5 to 10 degrees below normal. As this high moves
further east on Tuesday, return flow will begin to usher a warmer
and more moist airmass into eastern KY. PW is forecast to rise
from present levels of below 0.50 inches to about 0.65 inches in
the southeast to around 1 inch near Lake Cumberland near dawn on
Tuesday per the HREF mean and then further to around 0.9 to 1
inch east and southeast to about 1.3 near Lake Cumberland on
Tuesday evening followed by an increase to 1 to 1.3 inches
areawide by late Tuesday night.

The pattern will favor a moderate ridge/valley temperature split
with afternoon min dewpoints in the upper 40s to low 50s
supporting some lows in eastern and northeastern valleys in the
low 50s with a 49 or so in some of the typical cold spots. Fog
should also form not long after midnight along the larger creeks
and especially portions of the Big Sandy and Kentucky Rivers as
well as lakes in those basins. Temperatures will warm up nearly 10
degrees from what has been observed so far today on Tuesday with
some fair weather cumulus probable by the afternoon as moisture
increases. Any cumulus that develops on Tuesday should dissipate
by sunset on Tuesday evening and with the upper ridge axis working
across the area yet another ridge/valley split should occur with
a lesser magnitude than tonight. Valley fog should again occur,
but may be more confined to right along the rivers.

.LONG TERM...(Wednesday through Monday)
Issued at 446 PM EDT MON JUL 1 2024

Aloft, models continue to show good agreement with main synoptic
features and with the general evolution of the pattern through the
extended. At times, a mean zonal flow will yield to moderately
amplified shortwave disturbances in an overall progressive flow.
Amplitude of eastern Ridge across the eastern CONUS will continue
to dampen under the assault of a series of passing short wave
disturbances. As a result, eastern Kentucky will become
increasingly vulnerable to easterly moving disturbances as the
core track of westerlies sink further south with time. By the end
of the extended, the overall pattern becomes more amplified with
a large, broad mean trough in place across the Northern Tier of
the U.S., with the mean axis extending southward from the Upper
Midwest into the MO/MS river valleys. At the surface, New England
high pressure will drift out into the Atlantic, allowing a surface
frontal system associated with a deep storm system over eastern
Canada to swing southward towards the Ohio River by late Thursday.
This surface front stalls out north of the Ohio River until a
second storm system (low) developing over the Great Plains moves
northeast into the Great Lakes by the weekend. This second system
appears to send the frontal zone a little further south into our
area by the end of the forecast window.

Our sensible weather will generally be warm and muggy through the
period, a very typical summer like pattern. With a frontal zone
in the region during a good part of the extended and an
occasionally passing disturbance aloft, we can expect relative
unsettled and/or stormy weather through the period. Also, with the
lack of strong ridging over the region and the source of our air
more from out of the Deep South, combined with the increase in
average cloud cover and expected shower and thunderstorm activity,
temperatures will be closer to climatology, with daily highs in
the 80s to around 90 versus the low to mid 90s of the past couple
or few weeks. As such, expect heat indices to run slightly lower
than recent weeks, with the most likely day of approaching
afternoon heat indices of 100 degrees being Wednesday. That`s not
to say our weather will not be uncomfortably muggy. With surface
dew points climbing into the upper 60s to mid 70s, there will
definitely be some sticky, summer like weather to experience.

SPC has our area in a marginal risk for severe weather Wednesday.
But not as impressed for the potential on Wednesday as perhaps a
marginal threat across our north Thursday and Friday. Instability
is ample enough, with SBCAPES climbing to between 1500 and 2000
J/kg each afternoon, mainly along and north of the I-64 corridor
Wednesday and across more of the entire forecast area Thu-Fri. But
bulk shear barely registers above 10-20 kts on Wednesday. At
least on Thursday and Friday, while marginal, bulk shear climbs to
between 30 and 35 kts over northern portions of eastern Kentucky.
Thus while some strong storms could not be ruled out Wed, at this
time, Thu/Fri appear to have a better potential for strong to
severe storms, particularly across our northern zones.

WPC has our northern most zones under a marginal threat for
excessive rainfall on Wednesday and the northern half of the
forecast area under a marginal threat on Thursday. However, hydro
threats may be more localized than anticipated. Overall rainfall
totals may be localized with the hit and miss type convection we
typically see in the summer time. On average, QPF forecasts are
still not that impressive, with ensemble probabilistic 24 hour
averages showing only a 30-40 percent chance of a half inch or
more of rainfall during any 24 hour period. Probabilities for an
inch or more average less than 20 percent. In addition, PWATs have
trended down just slightly over the past 24 hours, and storm
motions appear to have increased a bit closer to 20 kts for the
Thursday/Friday time frame - window of highest PoPs and best
change of seeing higher QPF. Freezing levels have remained high,
GTE 15 kft, which is favorable for heavier rainfall amounts. BUt
with everything considered, feel any hydro threats will remain
localized where the strongest thunderstorms develop and move, with
areas that get repeated rounds of rainfall being under the
greatest threat for locally heavy rainfall and minor flooding.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 755 PM EDT MON JUL 1 2024

Surface high pressure will result in VFR conditions prevailing
through the period. The exception will be during the 05 and 13Z
timeframe, where MVFR and IFR, and perhaps locally lower,
reductions are possible in valley fog. This is not expected to
affect any TAF sites, however. Winds will be generally from the
northeast at less than 5 kts through the period.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GREIF
SHORT TERM...JP
LONG TERM...RAY
AVIATION...JP/GREIF