Area Forecast Discussion
Issued by NWS Paducah, KY

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459
FXUS63 KPAH 240056
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
756 PM CDT Sun Apr 23 2017

.UPDATE...
Issued at 756 PM CDT Sun Apr 23 2017

Updated aviation discussion.

&&

.SHORT TERM...(Tonight through Tuesday night)
Issued at 304 PM CDT Sun Apr 23 2017

Fairly high forecast confidence through Tuesday night.

Closed southeastward tilted low pressure system will work southeast
into Alabama and and Georgia going into Monday. Any potential for
isolated thunderstorm activity within the cold core of the upper low
has moved southward into Tennessee for the rest of the afternoon.

Utilized a combination of the regionally/nationally blended model
guidance, the NAM-WRF, ECMWF, and Canadian (CMCnh) latest
deterministic runs to address the evolution and departure of
precipitation from West Kentucky this afternoon and this evening.

Similar model guidance was used to address the thermal mixing and
gradients in wind, clouds, and moisture for the same time period.

The effective mixing should have helped increase evaporation rates
over Southwest Illinois and Southeast Missouri from the recent
rains. In concert with NWS offices to the north and west of the WFO
PAH forecast area, minimum temperatures tonight will be slightly
lower.

With lowered humidities tomorrow and more insolation (sunshine)
across the forecast area, diurnal temperature ranges of 30 to 35
degrees should be fairly widespread across the area. Similar
temperature ranges should be expected on Tuesday with some
afternoon highs hovering around 80s degrees.

Timing of the leading edge of the precipitation for the well
advertised Wednesday rainfall was pushed to the very western edge of
the WFO PAH forecast area (Southeast Missouri) until late Tuesday
night.

.LONG TERM...(Wednesday through Sunday)
Issued at 304 PM CDT Sun Apr 23 2017

Forecast confidence is fairly high to start out Wednesday into
Thursday, but it decreases heading into next weekend.

A broad trough aloft will be centered over the Rockies for much of
the period. One storm system will lift out of this trough and
toward the Great Lakes Wednesday into Thursday. This will push a
cold front through our region primarily Wednesday night. A line of
thunderstorms is likely to develop along the front or a pre-
frontal trough, and the potential for severe weather is
increasing.

The 12Z models pivot the upper-level storm system northeast
through Missouri in a negative tilt fashion, which should provide
the needed forcing/lift to overcome an impressive elevated mixed
layer that will be present ahead of the front. The one potential
limiting factor will be low-level moisture, which may not allow
for true surface-based convection. That said, will continue to
advertise a severe threat for the entire area, with an emphasis on
southeast Missouri into southern Illinois mainly Wednesday
evening.

The medium range models overall seem to be trending toward the
more amplified GFS solution for next weekend. More energy dives
into the mean trough position and carves out a deep trough/low
over the Four Corners region by Saturday. This will push a warm
front through our area Friday and Friday night, but then should
result in a dry and warm Saturday.

Given the amplified nature of the flow, it may take awhile for
this system to lift out and bring us our next round of
thunderstorms and potentially severe weather, so Sunday may be
warm and dry as well. The GFS-based MEX guidance contiues to
indicate upper 80s at PAH in the warm sector Saturday, and this
will be possible Sunday as well if the system is slow to arrive.
South winds could be quite gusty next weekend as well.

&&

.AVIATION...
Issued at 756 PM CDT Sun Apr 23 2017

Showers and areas of light rain will continue over the far southern
portions of west Kentucky this evening, but they should not impact
KPAH or KOWB. The main issue for the TAFs will be northeasterly
winds gradually diminishing this evening eventually to below 10 kts.
Some lower VFR ceilings may rotate back into the KOWB and KEVV areas
in the morning. An MVFR ceiling is not out of the question at KOWB.

&&

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

$$

SHORT TERM...Smith
LONG TERM...DRS
AVIATION...DRS/DB



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