Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 190935
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
335 AM CST Mon Feb 19 2018

.SHORT TERM...(Today through Wednesday night)
Issued at 335 AM CST Mon Feb 19 2018

A warm front will continue to lift north across the area through
the morning, generating scattered showers, and possibly a rumble
of thunder. Gusty SSW winds will continue to push warmer and more
humid air north across the region as well in the wake of the warm
front. Through the day, the CAM`s push best convective chances to
our NW counties from southern IL into southeast MO. Unseasonably
warm highs in the upper 60s in this area, with mid 70s across the
KY Pennyrile.

The best chance of convection through Tuesday will continue to be
across the NW 1/3 to 1/2 of the CWFA in the warm sector ahead of
an approaching cold front, that will be approaching our CWFA by
early Tuesday evening. Another unseasonably warm day Tuesday with
some areas across the KY Pennyrile near the 80F mark, 70s most
areas. Overnight Tuesday, PoPs will increase from west to east,
with the cold front by 12z Wednesday forecast to be pushing across
the Ohio. Much of the axis of heavy rainfall will be along the
850mb front along and behind the surface boundary. High efficiency
is anticipated with PW`s 2+SD`s above the curve for mid February.
We favored slightly higher WPC forecast numbers vs. the blend. We
typically under forecast heavy rain anyway, so we tended slightly
more aggressive. Thunder overall will be widely scattered, not
overly prevalent due to marginal elevated instability. This lack
of deeper convection may keep amounts from getting too carried
away and allow for more steady rates.

For Wednesday night, we may see a second surge of rain, heavy at
times into west KY. Think the GFS is underdone. The ECMWF has been
more consistent with this signal, and now the NAM supports it as
well. The 850mb boundary never really clears the CWFA by far, then
a return SW low level jet sets up into west KY overnight
Wednesday. We went higher than both the blends and WPC for
Wednesday night, utilizing more of the NAM, ECMWF, and slight CMC
incorporation. The GFS is a a persistent outlier pushing activity
farther southeast. Did not discount it completely. But it defies
pattern logic given the deep mid tropospheric SW flow aoa 700mb.

.LONG TERM...(Thursday through Sunday)
Issued at 335 AM CST Mon Feb 19 2018

Another heavy rainfall event appears to be in the offing late this
week into the weekend. This event could be rather prolonged.

Thursday could potentially be the driest day of the week in the wake
of the cold front that passes through on Wednesday. However, the
models are not even in full agreement on this lull in the precip.
The surface front is forecast to stall to our south Thursday,
somewhere across the Tennessee Valley. The 00z ecmwf is not as far
south as most other guidance, and therefore it indicates rain
continuing on Thursday. The forecast will lean toward the drier gfs,
but the persistent moist southwest flow aloft will ensure the drying
trend is short-lived.

The models agree the front will return north to the Ohio Valley and
southern Missouri Thursday night. Widespread rainfall will accompany
the front.

The front is expected to become quasi-stationary somewhere in the
vicinity of the Ohio River and southeast Missouri from Friday
through Saturday. During this period, a strong southwest low level
jet will feed plenty of moisture into and over the frontal boundary.
Surface dew points will be in the lower 60s south of the front.
Marginal instability will result in some convective enhancement of
the precip. The location of the heaviest rainfall axis will depend
on exactly where the front sets up. The front may oscillate back and
forth across the region as indicated by the 00z ecmwf.

A 500 mb shortwave will then eject northeast from the
base of the western trough, triggering a surface low over the
Plains. This surface low will track northeast across Missouri and
Illinois Saturday into Saturday night. A cold front trailing
southwest from the low will bring one last surge of rainfall as it
crosses our region, most likely Saturday night. Before all is said
and done, there is the potential for at least a few more inches of
rain from Thursday through the weekend.

Temperatures will depend on the location of the frontal boundary,
but it appears they will be mainly in the 60s south of the front and
50s to the north of the front.

&&

.AVIATION...
Issued at 623 PM CST Sun Feb 18 2018

Clouds will lower, and quickly, overnight, with MVFR cigs already
on the doorstep/seen on Satellite just upstream. Rain chances
spike late tonight-early tmrw, as warm advection/isentropic
upglide kicks in. Winds will become gusty southerly tmrw, and
cloud bases should gradually improve from MVFR to VFR, although
cigs will likely be maintained well into/thru the planning
period.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&

$$

SHORT TERM...CN
LONG TERM....MY


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