Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 181736 AAA
AFDPAH

Area Forecast Discussion...UPDATED
National Weather Service Paducah KY
1236 PM CDT Sat Mar 18 2017

.UPDATE...
Issued at 1236 PM CDT Sat Mar 18 2017

Updated the AVIATION discussion for the 18Z TAF issuance.

&&

.SHORT TERM...(Today through Monday night)
Issued at 253 AM CDT Sat Mar 18 2017

In the near/immediate term, we have a cold front bearing down on
the FA, and ahead of it, dense fog with vsbys restricted to 1/4
mile or less in many locations, particularly east of the
Mississippi river. Already expanded the inherited Fog Advisory
westward to the river, and at press release, will have to make a
final adjustment for counties behind and still in front of the
cold front/passage. Probs going to extend the duration of the
Advisory, so that headline at the base of this product will likely
change too (expire time), but the nuts/bolts is the Fog will
disperse with Fropa later this morning.

After that, High pressure moves in/overhead and provides a
dry/seasonally nice weekend. With the High shifting east Sunday,
return flow southerlies warm sector us Sunday night. Instability,
especially elevated, climbs and we become outlooked in the SWODY2
(across our north) for a convective chance/thunder. This
continues into/thru the Monday-Monday night period, as a few
hundred J/KG MU Cape in the 0-1KM layer works in ahead of a
developing cold front making passage up the Ohio river valley and
connective to our boundary for a sort of quasi stationary
boundary set up. Where exactly, the models differ, but at this
writing, it looks like a wet/thundery chance Sun night-Mon night,
with boundary passage/shift to the south of the Ky/Tn border by
12Z Tue. Some MU Cape values during this time climb toward/into
the lower 4 digits Monday night, but best forcing mechanisms
appear displaced from the max instability axis, and heavy
rain/lightning appear to be primary hazards during this time
frame for now, with SWODY3 also general thunder outlook only.

.LONG TERM...(Tuesday through Friday)
Issued at 253 AM CDT Sat Mar 18 2017

Low confidence in the extended longevity of pops with limited
moisture. I very much doubt it will rain every single period in the
extended but that`s what the forecast builder again has produced.

Now with that said, on Tuesday a front is expected to stall just
south of the area. If this comes to fruition, then a chance of
rain would be appropriate for that time frame. In contrast, high
pressure at the surface will conflict with/minimize this chance.
So Wednesday has a good chance of being dry for the most part.
After that, ridging aloft starts to build into the area, which
should mitigate rain chances Thursday. So even though the forecast
is advertising rain chances daily and/or nightly we could very
likely see a dry period through the middle of the week. By Friday
another more potent system starts to move into SEMO. However the
brunt of the system should move across the area early Saturday
morning. The instability index readings are not as strong as
previous runs suggested. LI`s stay positive for the most part and
CAPE`s never reach 500 j/kg2. K index values stay at or below 25c.
I left thunder in Friday night due to previous runs. Temperatures
will be slightly below normal with all the cloud cover but much
closer to seasonal than recent.

&&

.AVIATION...
Issued at 1236 PM CDT Sat Mar 18 2017

Other than MVFR cigs (wrap around clouds) this afternoon at
KEVV/KOWB, VFR conditions will prevail through the period due to
high pressure at the surface. Northwesterly winds around 10 knots
with gusts up to 18 knots expected through the afternoon, then
winds becoming variable AOB 5 knots through the rest of the period.

&&

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

$$

AVIATION...JP



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