Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 291050
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
650 AM EDT Mon May 29 2017

.SYNOPSIS...
A slightly drier air mass is in place in the middle Ohio Valley
behind a cold front. Another weak front will move through the
area tonight, which could bring a few showers or thunderstorms.
Upper level low pressure will remain in place over the northern
Great Lakes through the middle of the week, with seasonable
conditions over the Ohio Valley.

&&

.NEAR TERM /THROUGH TONIGHT/...
It is not easy to say exactly where the surface trough/front is
located early this morning, as there is little definition to
the wind shift. Dewpoints probably tell the story the best, with
a drop from the lower 60s to upper 50s, but even this is not
especially well defined. Regardless, there are clear signs of a
drier air mass advecting into the region, which will be the
biggest change in the weather from yesterday to today -- similar
temperatures, but less humidity and clearer skies.

With the drier air in place, model soundings show much deeper
mixing today, perhaps to around 5kft-6kft. Wind flow, however,
is not very strong -- limiting gust potential today to maybe
around 20 knots. The low-end chances for precipitation this
evening will be discussed in the Short Term AFD section below.

&&

.SHORT TERM /TUESDAY/...
The dominant feature in the large-scale weather pattern early
this week will be the upper low centered north of Lake Superior.
On the southern periphery of this low, pseudo-zonal flow is
expected over the ILN CWA, but with some intrusion of very weak
shortwave forcing at times. One such instance will occur this
evening, with a very weak vorticity maxima moving east through
the CWA between 00Z and 06Z. Looking at winds and theta-e, there
is also evidence of a weak front at 925mb-850mb. This is not an
especially strong amount of forcing, and the air mass it will be
interacting with is fairly dry. At most, soundings are
developing SBCAPE values of around 500 J/kg -- shallow and
high-based. Thus, not seeing a reason (at least this far out in
the forecast process) to increase PoPs above the 20-30 percent
chances currently in the forecast. These chances will end after
06Z as the weak trough moves onward to the east.

Owing to the slight decrease in 925mb-850mb temperatures,
temperatures are likely to drop slightly from Monday to Tuesday,
even though it will be another day with a reasonable amount of
insolation and mixing. With 850mb temperatures falling by 2-3
degrees C, the Max T forecast will show a 3-5 degree F drop
from Monday to Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
The center of an upper level closed low over Ontario will continue to
elongate and rotate northeast Tuesday night into Wednesday. A couple
of embedded disturbances rotating around the base of this low across
our region, coupled with a weak cold front/trof axis, requires
keeping low chance PoPs going during this period. The weak front
should exit the eastern CWFA by Wednesday evening when the threat
for pcpn should come to an end. After lows in the lower to mid 50s
Wednesday morning, highs on Wednesday will range from the lower to
mid 70s.

As the main mid level trough axis shifts east Wednesday night,
confluent flow in the mid levels will result in surface high
pressure building into the Ohio Valley. Skies will clear and winds
will become light to calm. It will likely be the coolest low
temperatures of the extended given radiational cooling. Lows will
drop into the upper 40s to the lower 50s.

We will try to squeeze out a dry day on Thursday. However, return
moist flow around departing high and a pseudo warm front approaching
the region from the west may bring clouds and a low chance of
showers and thunderstorms to our far western CWFA by Thursday
evening. Highs on Thursday will range from the mid 70s north to near
80 south.

Long range models are in decent agreement as we head into the first
part of the weekend, but then diverge as we go into next week.
Another upper level closed low is forecast to dig southeast into
southeast Canada and the northern Great Lakes Friday into Saturday.
As this occurs, a cold front will slowly push south across the Great
Lakes, and then it may get hung up somewhere across our area on
Saturday. Chances of showers and thunderstorms will increase on
Friday with the highest chances likely coming Friday night into
Saturday morning.

The remainder of the extended, as stated, becomes muddled as models
can not agree if upper level closed low will push off to our east or
additional energy will dig southward from south central Canada into
the Great Lakes. Have broad brushed the forecast during this period
as front may be slow to depart to our east/southeast. Thus, kept at
least a chance of showers and thunderstorms across the south, but
did allow the far north to dry out. High temperatures will remain in
the 70s for the weekend.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Some areas of fog and stratus have developed this morning,
primarily affecting the CVG/LUK/ILN airports. A range of MVFR to
LIFR conditions can be expected for another hour or two, before
these conditions improve by mid-morning. Once this has occurred,
VFR conditions are expected through the rest of the day, with
just some high/mid clouds and perhaps a few cumulus.

There may be a chance for a few scattered showers or
thunderstorms this evening, but confidence is too low to
include in the TAFs as of now. A VCSH will be used at TDAY.

OUTLOOK...Thunderstorms will be possible on Friday.

&&

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

&&

$$
SYNOPSIS...Hatzos
NEAR TERM...Hatzos
SHORT TERM...Hatzos
LONG TERM...Hickman
AVIATION...Hatzos



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