Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 211753
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
1253 PM EST Thu Feb 21 2019

.SYNOPSIS...
High pressure will move into the Ohio Valley today, keeping
generally dry conditions over the region through Friday
afternoon. Going into the weekend, as a mid level ridge moves
east of the area, precipitation will begin to spread into the
region from the south. The greatest chance for rain will be on
Saturday, in advance of a strong cold front moving east through
the area. Strong winds are expected behind the front on Sunday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY/...
High clouds will continue to work into the Ohio Valley from the
southwest through the remainder of the day and eventually
become overcast tonight and Friday. Until they thicken however,
temperatures will be slightly warmer and range from the low 40s
to upper 40s this afternoon. West wind over the northern half
of the CWA is running around 5-10 mph but is lighter and a bit
more variable over the southern CWA.

CAM models have held back any light precip nosing into the
southern CWA from the southwest tonight, and being that this
would be coming from a mid deck and lowering, the drier lower
atmosphere should win out. Felt comfortable with the solution
that was further south, though a sprinkle could not be ruled out
entirely over KY counties outside of metro Cincy area
overnight.

Temperatures tonight will range from mid 20s in the north to mid
30s in the south under cloudy skies.

&&

.SHORT TERM /FRIDAY/...
Dry conditions are expected again into Friday afternoon. Some
changes will be occurring to the overall weather pattern on
Friday, with a general amplification of the mid-level features
over the country -- the ridging extending from south of Bermuda
into the Ohio Valley, and a deep trough developing in the
intermountain west. The surface pattern will not be adjusting
too quickly over the Ohio Valley, with cool easterly flow
remaining in place through the whole day on Friday. However, a
sharp warm front at 850mb is forecast to move north into the
area on Friday afternoon, bringing the next round of showers to
the region -- as well as extensive cloud cover associated with
the moisture transport just off the surface.

With little change to the near-surface pattern on Friday,
temperatures will be kept very similar to values forecast for
today -- with the temperature gradient slightly relaxed, this
allows for lower to upper 40s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
For Friday night, a low level jet will begin to organize to our
southeast. As this takes place, low level moisture convergence
will increase across our southern zones. It now looks like the
process of pcpn moving northward into the norther zones may be
slowed some per consensus model solutions, so the highest PoPs
now relegated along and south of the Ohio River. Lows will range
from the lower 30s north to the lower 40s south.

The weather pattern will become very interesting as we head
into Saturday and Sunday as a potent low pressure system takes
aim at the Great Lakes and the Ohio Valley.

Mid level energy will be ejecting from the southwest U.S. into
the southern Plains on Saturday. At the surface, the associated
surface low will begin to deepen with time as it moves northeast
toward the middle Mississippi Valley. Back farther east, a warm
front will develop to our south, and with continued moist
ascent with the aforementioned low level jet, pcpn will continue
spread north and increase in coverage as the front lifts north.
We could see a few elevated thunderstorms by afternoon,
especially across the west. There continues to be a renewed
concerned for flooding since it remains very wet across the
region. With pwats increasing through the period (perhaps as
high as 1.50 inches by Saturday evening), that concern is
justified. At this time, the best chance for prolonged pcpn,
with moderate to heavy rain as pcpn transitions over to a
convective nature, seems poised for locations along and south of
the Ohio River Saturday and Saturday evening. For the remainder
of the region, showers and embedded thunderstorms are expected,
but the greatest amounts should occur with frontal passage
Saturday night, with amounts being limited due to the expected
quick nature of the pcpn as it moves east. Overall, locations
along and south of the Ohio River may receive another 1 to 2
inches of rain, with locally higher amounts due to showers and
embedded thunderstorms. Will mention this in the HWO.

The next concern will be the potential for a QLCS to form
either in a region of a prefrontal convergent low level trough
axis or along the cold front itself Saturday night. A very
strong south/southwest low level jet between 70 knots and 80
knots is forecast. In addition, at least some instability is
expected for a few thunderstorms, especially west. Even so,
these features are notorious for still producing damaging wind
gusts with little or no thunder given the convective nature of
the showers and the transfer of strong winds aloft with
associated downdrafts. With that being said, SPC has placed some
of our Kentucky counties in a slight risk for severe storms,
with the remainder of the region in a marginal risk. Will be
mentioning damaging wind gust potential in the HWO. It should be
noted that there is a threat for isolated "spin up" tornadoes
in this pattern. However, will refrain the mention at this time
until the picture becomes clearer.

Finally, the forecast pressure drop of the low pressure as it
heads northeast into the Great Lakes on Sunday is of concern.
The latest 00Z EPS suggests the low may deepen between 970 mb
and 980 mb. The deepening low, of course, will result in a
strong wind field in the low levels. with most operational
models showing 50 to 60 knots in the wake of the low at 850 mb.
In the CAA pattern, momentum transfer may bring a portion of
these winds to the surface. Overall, the EPS suggests a high
likelihood of a Wind Advisory across the entire region (wind
gusts between 46 mph and 57 mph). It also suggests at least a
chance of reaching High Wind Warning criteria in terms of gusts
(>= 58 mph) for parts of the area, particularly west central
Ohio, the Whitewater/Miami Valleys, and parts of central Ohio.
Have continued to bump up the winds, sustained and gusts, as
confidence continues to increase. Will also make mention of this
in the HWO.

Pcpn is forecast to quickly come to an end in the drier, CAA
pattern behind the front on Sunday. There should be considerable
post- frontal stratocumulus clouds, especially north. As for
temperatures, they will warm into the 50s to the lower 60s ahead
of the cold front, then slowly fall on Sunday. Temperatures
will range from the mid 30s northwest to the mid 40s southeast
by Sunday evening.

For Sunday night into Monday, as the potent low pulls farther
away into Canada, winds will gradually decrease as surface high
pressure builds into the region from the northwest. After lows
in the 20s, highs on Monday will range from the mid 30s north to
the mid 40s south.

Models are struggling on the timing, placement, and strength of
the next weather system for the Tuesday/Wednesday time frame.
It now looks like Tuesday will remain dry with pcpn perhaps
returning Tuesday night into Wednesday. Will continue with a
chance of rain or snow during this period.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
VFR conditions will prevail as a cirrus deck moves in and
thickens tonight and through the day Friday. West wind this
afternoon 6-8kt over DAY ILN and CMH/LCK will lighten and go
more variable tonight. These winds will shift east-northeast
and then increase to 6-8 kt Friday morning.

OUTLOOK...MVFR conditions are possible from Friday night through
Sunday. There will be a chance of thunderstorms on Saturday
night. Strong winds are expected on Sunday.

&&

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

&&

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



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