815
FXUS63 KJKL 292320 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
720 PM EDT Mon Apr 29 2024

.KEY MESSAGES...

- Showers and thunderstorms arrive from west to east tonight and
  linger into much of Tuesday.

- Dry and trending warmer midweek, with near record highs on
  Thursday.

- Unsettled weather returns for Friday and lingers through the
  weekend.

&&

.UPDATE...
Issued at 715 PM EDT MON APR 29 2024

Cumulus and/or mid level clouds have decreased east of the
western counties. This should allow for a drop in temperatures in
eastern valleys during the evening before temperatures level off
overnight. Hourly grids have been updated to account for this
expected temperature trend and account for recent observation
trends.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 357 PM EDT MON APR 29 2024

We`ve been following this system moving in tonight for quite a while
now. And with each forecast, it looks a little less and a little
less impressive.

A closed low is currently in place across Minnesota and will
continue to shift northward into tonight, weakening only slightly.
This will create a shortwave which should pass through the Ohio
Valley tonight into Tuesday. At the surface, a low pressure system
will be present moving across the Upper Great Lakes overnight. This
system is already occluded and will continue to wrap around itself
into the overnight. A cold front connected to this low will be
orientated from NE to SW, slowly sweeping the Commonwealth
tonight and during the day Thursday. Perhaps it`s because we are
quite a distance away from the parent low, perhaps it`s because
the cold front never quite makes it all the way through the state
before lifting back northward, or perhaps it`s because there isn`t
a large airmass shift with this system...either way, the warm
moist environment in place and passing boundary would support the
potential for thunderstorms, but they just don`t look very strong.
There is very little organization (llvl wind sheer is basically
nill), the sounding is very saturated, and there is very little
CAPE. That being said, a more likely concern with these storms as
they move in is the heavy rain potential. Can`t rule out that some
locations could receive heavy downpours from storms that may lead
to some isolated flooding concerns.

The system should finally exit to our east by Tuesday evening. Light
and somewhat variable surface winds are expected behind this system
overnight, along with dry air advection, helping to clear out the
skies. With this set up, expect cooler temperatures Tuesday night
compared to tonight, and it is possible that some of the deeper
valleys could decouple and drop temperatures fairly quickly. Tried
to include a ridge/valley split in the forecast, though if it
does pan out, may not have gone extreme enough on the differences.

.LONG TERM...(Wednesday through Monday)
Issued at 445 PM EDT MON APR 29 2024

As the long term period begins, a shortwave trough is expected to
extend from VA to the Carolinas and then off the eastern seaboard
with upper level riding extending north from the Gulf of Mexico
into the Lower OH Valley region with a trough extending to the
southwest Conus from an upper level low near the US/Canadian
border. Another upper level low/trough is expected to be
approaching the Pacific Northwest as it moves around ridging over
the Pacific and into the trough. At the surface, a wavy frontal
zone is expected to extend from south of Cape Cod to the mid
Atlantic states to WV and then northwest as a warm front to sfc
low pressure near the western sections of Lake Superior. A cold
front should extend south and then southwest from this system
into the Central Plains and then west into the western Conus. Sfc
high pressure meanwhile should be centered over the TN Valley and
Southern Appalachian region and extend into the Commonwealth as
the period begins.

From Wednesday to Thursday night, the pattern is expected to
amplify at least briefly with upper ridging building into the
Southeastern Conus to eastern Great Lakes region before the axis
shifts east of the Appalachians on Thursday night and should
extend from off the coast of the Carolinas to the mid Atlantic
states to portions of eastern Ontario and into Quebec as the
period begins. Meanwhile, as the axis of the upper ridge moves
east, a shortwave should move from the Rockies to the Plains and
then to the mid and upper MS Valley to OH and TN Valley regions by
late Thursday night as the upper low meanders near the
US/Canadian border from MT and the Dakotas and Saskatchewan and
Alberta border areas. At the same time, the sfc low initially near
Lake Superior is expected to track into Ontario and Quebec to the
Maritimes with the boundary initially north and eastern of
eastern KY lifting north as a warm front. Meanwhile a second sfc
low should develop/organize to the lee of the Rockies in the
CO/KS to OK panhandle region and then trek across the Central
Plains to the Upper MS Valley/western Lake Superior region through
Thursday night. At the same time, sfc high pressure will remain
across the Southern Appalachians to Southeast Conus region and
upper level ridging will usher in a warm and dry airmass. PW is
forecast per 12Z LREF mean to drop to the 0.6 to 0.9 inch range
for Wednesday to Thursday, before rising to 0.8 to 1 inch late
Thursday night.

Friday to Saturday night, the consensus of guidance is for the
next shortwave trough in southwest flow should work across the
Commonwealth on Friday to Friday evening while a cold front works
east across the Commonwealth from Friday through Saturday as the
associated sfc and upper lows track north across northwestern
Ontario and then toward the Hudson and James Bay regions. The 500
mb trough axis should linger south into the Central Conus to MS
Valley regions by late Saturday into Saturday night though this
trough largely pass north of eastern KY to end the weekend as the
flow aloft becomes more westerly. Additional disturbances should
move from the Plains toward the OH and TN Valley region during
that time while a secondary boundary is expected to have dropped
south of the Great Lakes to end the weekend before stalling near
or north of the OH River late in the period. PW should climb to
1.1 to 1.3 per the 12Z LREF mean to begin the weekend before
decreasing to closer to 1 inch to end the weekend.

A warming trend should follow locally as 850 mb temperatures
should climb to the 13C to 15C range or so on Wednesday and then
to the 16C to 18C range on Thursday. Near record highs will be
possible on Thursday in the warm sector ahead of the next
approaching system. The NBM deterministic was near or below the
25th percentile and hedged more toward the warmer 50th percentile.
Some of the warmer valley locations will probably reach 90,
especially in the Big Sandy region and into the KY basin.
Dewpoints in the 50s on average will lead to min rh near or below
30 percent in some instances on Wednesday, while min rh should
reach 25 percent or lower in several areas for Thursday. With
moisture increasing late Thursday night into Friday and continuing
into the weekend with series of passing disturbances along with
the first front moving across eastern KY to begin the weekend
while a second boundary sags toward the OH Valley to end the
period, unsettled weather returns. Chance or higher pops were used
from Friday afternoon to Monday. Chances for showers and some
storms should generally peak each diurnal cycle though the
boundary and upper disturbance passing Friday to Friday evening
along the boundary slowly moving east focus chances later Friday
night into Saturday afternoon.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 715 PM EDT MON APR 29 2024

VFR conditions are currently in place across the region, with
increasing SW flow. However, mid level disturbance and a weak
front are starting to approach the region. This will lead to a
gradual thickening and lowering of clouds from west to east during
the first 12 hours of the period. Showers and scattered
thunderstorms should begin to encroach on more western locations
by the 06Z to 09Z timeframe and gradually spread east into the day
on Tuesday though they may diminish in coverage during that time
as they move east. Some redevelopment could also occur during the
18Z to 00Z period as well. However, most locations should be
affected at least briefly by a shower or a storm at some point
between 08Z and 18Z. Ceilings will slowly diminish from west to
east mainly after 08Z with MVFR shifting east across the region as
the initial area of showers or storms move through. Gradual
improvements back toward VFR should occur late. Chances for
storms were too limited to include even a VCTS at this time. Winds
will average south at 10KT or less before 15Z, before shifting to
west and northwest to end the period at 10KT or less on average.

&&

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

$$

UPDATE...JP
SHORT TERM...JMW
LONG TERM...JP
AVIATION...JP