Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 162012
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
312 PM CDT Tue May 16 2017

.SHORT TERM...(Tonight through Thursday night)
Issued at 312 PM CDT Tue May 16 2017

The main issue through Wednesday will be gusty winds associated
with the strong pressure gradient due to the deepening low over
the central Plains. Winds this afternoon have generally been
gusting from 20 to 25 kt, and the Lake Wind Advisory will expire
about sunset as mixing decreases. Winds aloft will be notably
stronger Wednesday, averaging 45 kt at 850 mb. Using 12z nam and
gfs data, the Bufkit momentum transfer algorithm indicates gusts
will be at or just below the 35-knot criteria for a Wind Advisory
tomorrow. Since the situation is marginal for a Wind Advisory,
there is time to wait for 00z model data to decide between a Wind
Advisory or Lake Wind Advisory.

Other than the wind, quiet dry weather is expected through
Wednesday. A few late day showers or storms are possible in the
Ozark foothills of se Missouri on Wed, however the models
indicate a strong cap will be in place.

On Wednesday night, most model guidance indicates at least spotty
qpf over our region. There is a small chance of elevated
convection along a narrow axis of high k-indices and unstable
showalter indices. Upper-level support will be weakening as the
strong 500 mb shortwave moves northeast into the Upper Mississippi
Valley. Pops will be kept rather low, mainly in the chance
category. South winds, increasing clouds, and higher dew points
could keep lows at or above 70 in a few spots.

On Thursday, the models indicate a lingering corridor of moisture
across the Lower Ohio Valley, keeping plenty of clouds and maybe
a few showers or storms over our region. Any precip should be
spotty as a 500 mb shortwave ridge develops over our region ahead
of the amplifying 500 mb trough over the Plains.

On Thursday night, precip chances will increase somewhat as a cold
front sags south to the Interstate 64 corridor of southern IL and
southwest IN by morning. Upper-level support will remain weak,
and wind fields will be fairly light. This again makes any
widespread or intense convection unlikely.

.LONG TERM...(Friday through Tuesday)
Issued at 312 PM CDT Tue May 16 2017

Forecast confidence is quite high in a stretch of summer-ish weather
with daily chances of thunderstorms through the weekend. The daily
details of convective potential have yet to be worked out.
Confidence decreases heading into next week, but the overall trends
will be cooler and drier.

The upper flow through the weekend will be southwesterly, but the
ridge will be just east of the area and close enough to allow a back-
door cold front to approach I-64 early Friday. Low-level moisture
will be increasing with surface dewpoints into the upper 60s, and
may pool to the south of the front resulting a good coverage of
thunderstorms over the northern half of the area on Friday.

As a storm system emerges from the Rockies, surface low pressure
will be developing over the southern and central Plains. As the
system lifts north northeast toward the Upper Midwest the front
should lift back to the north of the area, so much of the area may
be dry Friday night.

The models have trended slower with the cold front, but have
maintained their relative biases. The GFS and GEM move it through
the area Sunday, while the ECMWF has it moving through Sunday
afternoon and evening. The slower ECMWF solution has merit given
that the upper flow is nearly parallel to the front, but the GFS and
GEM have a larger/stronger upper trough with westerly flow in its
base helping to push the front through faster. Will continue to
focus the best PoPs and frontal timing on the GFS and GEM and linger
small chance PoPs into Monday in deference to the ECMWF.

The GFS has negative Lifted Index values Friday through the weekend,
so will emphasize TS throughout the period. Certainly cannot rule
out a strong to severe storm in the heat of the day Friday and
Saturday. Depending on the strength/orientation of the upper flow
and the timing of the surface front, a more concentrated period of
strong to severe storms may develop near and just ahead of the front
Sunday.

Surface high pressure should overspread the area Monday, but it may
not dry us out for long. Another storm system will dive southeast
toward the region Monday night into Tuesday. The 12Z models agree
that there will be a system approaching the area, but the timing
varies. Some small PoPs will return to the forecast Monday night and
Tuesday. Not seeing much evidence of instability for the system to
play with, so tried to downplay TS.

&&

&&

.AVIATION...
Issued at 1212 PM CDT Tue May 16 2017

An area of broken cumulus clouds formed across se Missouri late this
morning. Sct to bkn cu will prevail across the entire region this
afternoon, with the least cumulus coverage over sw Indiana and kowb
area. VFR conditions are expected with cloud bases above 4k feet.
Winds will be gusting to 20 to 25 kt from the southwest. The cu will
dissipate with loss of daytime heating around 00z, and winds will
diminish quickly around sunset.

The main story late tonight and Wednesday will be winds. Winds at 2k
feet will be 35 to 40 knots from late tonight through Wed. This will
result in low lvl wind shear early Wed morning. Once daytime heating
mixes the winds down, some gusts to 30 kt are likely by 18z.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Lake Wind Advisory until 7 PM CDT this evening for ILZ075>078-
     080>094.

MO...Lake Wind Advisory until 7 PM CDT this evening for MOZ076-086-
     087-100-107>112-114.

IN...Lake Wind Advisory until 7 PM CDT this evening for INZ081-082-
     085>088.

KY...Lake Wind Advisory until 7 PM CDT this evening for KYZ001>022.

&&

$$

SHORT TERM...MY
LONG TERM...DRS
AVIATION...MY



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