FXUS61 KILN 222355

Area Forecast Discussion
National Weather Service Wilmington OH
755 PM EDT Sat Sep 22 2018

Moisture will overspread a front stalled over the Tennessee
Valley. This will result in periods of rain across southern
portions of the Ohio Valley this weekend. A moist and
southerly flow will return to the Ohio Valley early next week.
This will result in several rounds of showers and thunderstorms
with heavy rain possible through the middle of the week. A
strong cold front will move through the area Wednesday.


Westerly mid level flow with surface high pressure building
across the Great Lakes today. Surface cold front to remain
stalled over the TN Vly. Weak sheared out shortwave to pivot
though the Ohio Valley resulting in isentropic lift over this
front and an area of rain across ILN/s south thru the evening.
After initial s/w pivots through, rain may sag a little south
late this evening.

Late tonight an east-west 8H axis of convergence develops across
Kentucky. This will lead to another chance of enhanced rain late
tonight into Sunday morning. NAM solution appears overdone with
QPF for this period and GFS is too conservative. Have adjusted
pops higher and followed solution closer to ECMWF. Expect cool
lows from the mid 40s northwest where clearing will take place
to the upper 50s south.


On going rain across the far south Sunday where favorable axis
of 8H convergence will exist. Pcpn coverage may diminish/sag
a little south for a temporary period in the aftn as favorable
forcing exits the area. Cool temperature to continue with
highs from the lower 70s northwest where sunshine will be
observed to the upper 60s southeast.

Mid level flow backs southwesterly late Sunday night with
moisture beginning to spread back north. Will spread a chance of
rain back north across ILN/s FA with the highest chances over
the southwest. Have pops ranging from likely south to slight
chance north. Milder temperatures with Sunday nights lows from
the lower 60s south to the mid 50s north.


On the western periphery of a ridge of high pressure, moisture will
continue to increase across the Ohio Valley on Monday. In addition
to increased moisture, models show warm advection and isentropic
lift that would support showers across the CWA. Showers initially
will likely be located across the southern CWA to start the day then
would tend to lift north as the day progresses. Have likely PoPs
across the CWA during this time. Given the expectation for overcast
skies and showers, have leaned toward the lower end of guidance for
high temperatures which favors upper 60s to lower 70s across the CWA.

Monday night into Tuesday morning, presence of a vort max will help
keep showers over the area, and actually could enhance rainfall
amounts. Then, a cold front is forecast to approach late Tuesday
into Tuesday night with showers and thunderstorms. Models suggest
high moisture content, with precipitable water values possibly near
2 inches, along with some shear. However, CAPE is forecast to be on
the low side. So confidence in widespread severe is low, but given
presence of shear and stronger forcing, strong to damaging wind
gusts may be possible especially if higher instability can be
realized. This threat is reflected in the SPC Day4 Outlook. And
given high moisture, heavy rainfall may promote localized flooding.

Confidence on the exact frontal passage is still somewhat uncertain,
but latest trends favor the front moving east through the CWA
Wednesday morning. PoPs lower behind the front as drier air begins
to filter in. A shortwave and reinforcing front follow Thursday
night into early Friday, but with much less moisture to work with it
looks like only a slight chance of showers as these features move
through. While seven days out, right now Saturday appears dry with
high pressure building in.


An embedded disturbance in conjunction with low to mid level
forcing is resulting in widespread light rain along and south of
the Ohio Valley this evening. This may result in some MVFR
conditions at KLUK/KCVG for a couple of hours to the start of
the TAF forecast. Otherwise, this light rain shield is expected
to shift southeast through this evening.

For the overnight hours into the first part of Sunday, another
embedded disturbance will team up with a low level jet to push
moisture back north toward the Ohio River. This will bring
another round of precipitation to KCVG/KLUK with MVFR conditions
once again possible. There will be a sharp cut off to this
precipitation so only a VCSH has been employed at KILN with the
remainder of the other terminals remaining dry with VFR

Another lull is expected in the precipitation as it shifts
east/southeast into Sunday afternoon.

By late Sunday afternoon and into Sunday night, a better
moisture surge is expected from the south as a stronger
disturbance approaches from the southwest. This will eventually
bring showers and at least MVFR conditions to the terminals
Sunday night and continuing into Monday.

Northeast winds around 10 kts will veer to the east at less
than 10 kts Sunday.

OUTLOOK...MVFR ceilings and visibilities likely on Monday.
Thunderstorms possible Monday through Wednesday.




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