580
FXUS61 KILN 271053
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
653 AM EDT Fri Sep 27 2024

.SYNOPSIS...
The remnants of Helene will bring rainy and windy conditions to
the region today into this evening. Low pressure will then
linger in the Ohio Valley into early next week keeping
conditions unsettled.

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...
Helene will get pulled northwest and then westwards across
Kentucky today as it transitions into an extratropical low.

Initial area of light rain across the region early in the day is
forecast to diminish a bit after daybreak as a bit of dry slot
precedes the core of the rain with the storm. But then as
Helene makes its closest approach and pivots past the forecast
area this afternoon, a large band of tropical rain will pass
through the region. This may bring a substantial amount of rain,
1 to 3 inches, from the lower Scioto Valley into the Whitewater
Valley with the highest amounts expected across Kentucky
counties and then into the Tri- State. Even though it has been
so dry previously, this amount of rain will likely lead to some
minor flooding as well as some substantial rises on smaller
creeks and streams.

Another concern is the wind which will steadily increase through
the morning as the system approaches and the pressure gradient
tightens. Winds will become rather strong in the afternoon with
most guidance in rather good agreement sweeping a band of high
winds across the area, starting in northeast Kentucky around
midday and then progressing northwest then west across the Tri-
State and lower Miami Valley, exiting eastern Indiana in the
late afternoon/early evening. Once again, the trend has been
towards higher wind speeds and this necessitated an upgrade to a
high wind warning for much of the southern part of the forecast
area. Further north and east, winds will still be gusty and peak
during the afternoon, but they will not be quite as strong. All
indications are that the strongest winds will decrease fairly
quickly from southeast to northwest late in the day heading into
the early evening.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH 6 PM SATURDAY/...
The former tropical system will complete getting absorbed into
an upper low over the lower Ohio Valley tonight. The then
vertically stacked system will meander about western Kentucky
on Saturday. So rain that may still be occurring near and west
of I-75 this evening will diminish, but then showers will spread
back north across the area, mainly during the day. It will be
dreary with a narrow diurnal range. Lows will be in the lower to
mid 60s with highs in the upper 60s to lower 70s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
At 00Z on Saturday evening, vertically stacked cutoff/closed
low will continue to sit and spin over Kentucky, likely centered
near Louisville or just southwest of there. Sandwiched between
two positive height anomalies (one centered over Florida and
adjacent waters, the other in a broad axis from the Desert
Southwest into the northern Great Lakes over top the low), there
just isn`t much impetus to kick the system out. So it will
continue to spin and slowly weaken/fill through Sunday and into
Monday as it wobbles and drifts east/northeast into the ILN
forecast area. The presence of this feature will mean high rain
chances (particularly during the afternoons of each day) amidst
weak forcing and ample low/mid level moisture, and we could
easily see additional rains up to 1/2" from Saturday night into
Monday in a few slowly moving or nearly stationary rain bands on
the north/east side of the upper low where frontogenetical
forcing and diffluence will be maximized. There`s even enough
warming underneath the cold upper low where meager instability
to result in a few storms. Under this damp/cloudy regime,
temperatures will feature a narrow diurnal range with highs in
the 70-75 range and lows only in the lower-mid 60s.

The low finally weakens to the point where it opens up into a slowly
progressive shortwave trough by Monday evening, with some weak
shortwave ridging building into the Ohio Valley in its wake. By that
time, moisture will have become shallow to the point where we can
probably remove rain chances from the forecast, although fast on the
heels of this ridging will be fast shortwave energy moving through
the base of a large/evolving central/eastern Canada longwave trough.
Frontal boundary push with this wave may instigate a few showers
Tuesday afternoon/evening as it shifts through the area, but chances
look quite low as primary forcing/height falls remain north of the
area.

Wednesday begins a period of seemingly quiet/sunny weather with
seasonable temperatures that moderate with time toward the end of
the work week.  High pressure over the area on Wednesday shifts east
turning the flow southerly on Thursday and Friday, allowing the
moderation and continued quiet weather.

&&

.AVIATION /10Z FRIDAY THROUGH TUESDAY/...
Winds will be increasing across all terminals through the day
and peak between 18Z and 00Z. Gusts will be in excess of 40 kt.
There will be a relatively quick decrease in winds between 00Z
and 04Z. Thereafter they will settle in at around 10 kt.

Rain will be fairly persistent through the day which will result
in reduced visibility. Some IFR visibility will be possible with
heavier rainfall in the afternoon. The rain will diminish
towards or a bit after 00Z. IFR ceilings across all but the
Columbus terminals are forecast to lift to MVFR while the
Columbus area will likely lower to MVFR. Those ceiling heights
are then forecast to remain persistent until after 00Z when they
will lift.

OUTLOOK....MVFR to IFR ceilings and visibilities likely Saturday
into Tuesday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...High Wind Warning from noon today to 10 PM EDT this evening
     for OHZ060>063-070>072-077>081.
     Wind Advisory from noon today to 10 PM EDT this evening for
     OHZ042-051>054-064-073-082-088.
KY...High Wind Warning from noon today to 10 PM EDT this evening
     for KYZ089>100.
IN...High Wind Warning from noon today to 10 PM EDT this evening
     for INZ050-058-059-066-073>075-080.

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...Binau
AVIATION...