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-- Discussion containing changed information from previous version are highlighted. --
839
FXUS61 KILN 241048
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
648 AM EDT Tue Apr 24 2018

.SYNOPSIS...
An upper level low pressure system will push slowly east across
Tennessee and Kentucky today, bringing rain showers to the
region. High pressure and drier conditions will return for mid
week. Cooler than normal high temperatures will persist through
the end of the week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Upper level low pressure can easily be seen rotating over
southwestern Kentucky this morning on water vapor. Through the
day today temperatures will stay mostly in the 50s as widespread
cloud cover and rain helps to keep the diurnal range suppressed.
The main story for today will be the precipitation. Most of the
day will be wet as PWATs stay around 1.00" (or near the 90th
percentile for this time of year). Lift will come from the upper
level low as it meanders east. An upper level jet streak on the
east side of the low will modulate today and quickly strengthen
as the upper level low starts to get absorbed back into the
main flow. This strengthening jet will place the ILN forecast
area in a LFQ. This will allow for ongoing precipitation
currently in Kentucky to slowly progress northeast and grow in
coverage as the jet streak strengthens. The jet streak (as well
as coupled low level convergence) will slowly push northeast
allowing the primary band of precipitation to progress
northeast. As the jet streak pivots northeast and the primary
band moves over CMH, holes in the precip shield will likely
start to occur somewhere across our southwest.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
This evening as the upper level jet streak pushes east a
deformation band over Indiana will slowly progress east as
well. Models struggle here on how quickly the deformation band
looses cohesion. The reason for this is how the mid level low
begins to open up. The latest runs of the ECMWF and GFS actually
hold the low together until it moves over the east coast and
gets absorbed back into the main flow. This would in general
imply the deformation band holding together longer. For now,
have trended the TAFs this direction. Behind the deformation
band, precipitation will come to a quick wind.

During the day Wednesday an upper level disturbance will be
swinging east across northern Michigan allowing a cold front to
wash through the area Wednesday afternoon. The frontal passage
will be precipitation free as mid and upper level dry air
plunges south. High temperatures Wednesday will remain below
normal for this time of year or around 60 degrees.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
A mid level short wave will move across the Tennessee Valley
Wednesday night into Thursday. The better forcing associated with
this will remain to our south while a weak surface ridge will be in
place across our area. This will provide for dry but continued
cooler than normal conditions on Thursday with highs mainly in the
lower 60s. A sheared out trough axis will then push quickly east
across the region on Friday, resulting in a chance of showers. Highs
on Friday will be in the low to mid 60s.

High pressure will then build into the region at the surface and
aloft through the weekend with dry conditions expected into early
next week. Highs on Saturday will again be in the low to mid 60s.
Temperatures will then start to moderate in a developing WAA
pattern. Highs on Sunday will be in the mid to upper 60s, warming to
highs in the low to mid 70s by Monday.

&&

.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
VFR conditions continue across the TAF sites this morning with
precipitation moving in from the south. Upper level low pressure
will slowly progress east-northeast this morning with the upper
level jet strengthening over eastern Ohio. This has allowed for
precipitation across our area to quickly start to fill in. The
forecast remains largely unchanged this morning as high res
models continue to show precipitation near KCMH/ KLCK expanding
(due to the strengthening upper level jet and low level
convergence) with precipitation across our southwest weakening
this afternoon (due to dry air entrainment). This means that
there will likely be a decrease in coverage around KCVG/ KLUK
this afternoon while showers continue everywhere else. As the
precipitation expands this morning ceilings will slowly fall
into MVFR.

This evening the mid level low will progress east with a
deformation band pulling east across the TAF sites as well. The
extent spatially and temporally of this band is uncertain as the
mid level low looks to open up. This will trend towards the
deformation band starting to weaken as it heads east. Given the
latest trends on the high res models though the general thought
is that the deformation band will likely hold together through
the TAF sites (this matches the GFS and ECMWF keeping the low
closed further east). Borderline IFR/ MVFR ceilings will then be
possible overnight. High res guidance continues to highlight
KDAY/ KCVG/ and KILN going to possible IFR with KCMH/ KLCK being
to far east.

Wednesday morning as winds turn from the north precipitation
will quickly come to an end with the ceilings recovering.

OUTLOOK...MVFR ceilings possible Friday night.
-- End Changed Discussion --

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.

&&

$$
SYNOPSIS...Haines/Sites
NEAR TERM...Haines
SHORT TERM...Haines/Sites
LONG TERM...JGL
AVIATION...Haines