Area Forecast Discussion
Issued by NWS Paducah, KY

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549
FXUS63 KPAH 181750
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1150 AM CST Sat Nov 18 2017

.UPDATE...
Issued at 1150 AM CST Sat Nov 18 2017

Line of convection increasing, including lightning activity, and
progressing rapidly into/across the NW part of the FA...a bit
ahead of schedule. Expect near severe to severe wind gusts along
and ahead of line with an overall increase in risk of damaging
winds (primary threat)with bowing line segments possible as low
level wind max mixes downward with stronger storms. The severe
threat will rapidly end with the passage of the cold front.

Updated Aviation discussion for 18Z TAF Issuance.

&&

.SHORT TERM...(Today through Monday night)
Issued at 149 AM CST Sat Nov 18 2017

Not much going on across the CWFA at this time. Just gusty south
winds and unseasonably mild temperatures. Radar is free of precip.
That may change as weak support aloft may kick off a few showers,
perhaps isolated thunder. Prior models and PoP forecasts were
certainly overdone for up to this point.

For today, the forecast is basically the same. Surface low
pressure should be near KSTL at 12z and head quickly northeast to
NW Indiana by 18z and then Ohio by 00z. Cold front will push
rapidly across the CWFA from our west counties around 17z,
reaching central sections by 20z, then departing our east counties
by 22/23z. Unseasonably mild temps ahead of the front, then
falling temperatures behind it through the afternoon. Convective
allowing models show an uptick in the strength of convection
especially from 18 to 22z, based on members that make up the HREF.
Likely to categorical PoPs today for showers and storms as the
front moves through.

SPC raised the outlook to a level 2 (slight risk) for severe
today over the eastern 2/3 of the CWFA. We do not see much that is
different in the data overall from the previous couple of days.
The one thing that might increase the probabilities of locally
damaging wind gusts is higher low level jet wind speeds farther
west toward fropa. Either way, still looks like that is the main
hazard with linear segments, should parameters come together.
And, the convective allowing models have that "look" in their
reflectivity progs.

As far as the Wind Advisory goes, will end it at 00z across the
west 1/2 of the area, then 03z east. Also, probably not at Wind
Advisory criteria levels until closer to the arrival of, and for
a few hours right behind the front. But, it`s not worth changing
the start time.

Other than a slight chance of a few lingering showers far east
this evening, dry and colder overnight. High pressure will result
in dry, chilly weather Sunday, then temperatures will rebound
a bit on Monday as return flow sets up west of the surface high
moving on to the east of our area. The dry weather will continue.

.LONG TERM...(Tuesday through Friday)
Issued at 149 AM CST Sat Nov 18 2017

The longwave pattern aloft over the CONUS is forecast by the medium
range models to amplify, with a persistent mid level ridge over the
southwestern states and a dominant longwave trof over the eastern
half of the country. Within this pattern there will be impulses of
shortwave energy, notably one on Tue. This feature will have a
surface cold front associated with it, followed by an area of high
surface pressure. Model indications are there will not be enough
moist return flow to tap into for deep moist convection, so a dry
fropa is anticipated Tue afternoon/evening for us.

Some models, namely the GFS, depict a stacked low may form over the
Gulf of Mexico by Thu. This could increase the surface pressure
gradient over the PAH forecast area a bit on Wed, but by only a few
knots. Otherwise, dry northwesterly flow aloft (and possibly short-
lived drier ridging in the GFS solution) will dominate through Day
7. Surface winds should finally turn back to southwesterly by then.

As a result, temps will start out at near seasonable averages Tue,
then plummet midweek, with highs dropping at least ten degrees (into
the 40s) and lows dipping into the lower 30s and the upper half of
the 20s. This will be followed by a rebound to near seasonable
averages by Fri (Day 7).

&&

.AVIATION...
Issued at 1150 AM CST Sat Nov 18 2017

Line of storms will progress rapidly SE across the FA this
afternoon impacting KCGI in next hour and KPAH around 19Z and KEVV
19-20Z and KOWB around 20-21Z. Gradients wind gusts ahead of the
line could easily average around 30kts with storm associated wind
gusts AOA 40 knots possible. MVFR Cigs will dominate this
afternoon with temporarly restricted visibilities mainly as line
of storm passes. The winds should diminish from 00z- 06z and
continue from the NW. Skies will clear tonight.


&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory until 6 PM CST this evening for ILZ075-080-081-084-
     085-088-089-092-093.

     Wind Advisory until 9 PM CST this evening for ILZ076>078-082-083-
     086-087-090-091-094.

MO...Wind Advisory until 6 PM CST this evening for MOZ076-086-087-100-
     107>112-114.

IN...Wind Advisory until 9 PM CST this evening for INZ081-082-085>088.

KY...Wind Advisory until 6 PM CST this evening for KYZ001>004.

     Wind Advisory until 9 PM CST this evening for KYZ005>022.

&&

$$

UPDATE...Shanklin



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