Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 280831

Area Forecast Discussion
National Weather Service Paducah KY
331 AM CDT Fri Apr 28 2017

.SHORT TERM...(Today through Sunday night)
Issued at 249 AM CDT Fri Apr 28 2017

Well, this is still looking to be quite an active period in many
respects. Confidence is high that many ingredients will come
together to support both multiple rounds of heavy rainfall and
intense thunderstorms...beginning later this afternoon and
lasting right through Sunday...esp in our far west/nw counties. A
bit of good news is that it appears much of the southeast half of
the forecast area may see a pretty good break in the precip during
the day Saturday into Saturday night.

The biggest forecast issue lies with where exactly the heaviest
rain and most widespread thunderstorm activity will occur...esp
later today and tonight. There remains considerable spread in the
model guidance on where certain boundaries will set up and hence
where the most widespread activity will be focused. 00Z NAM
continues to be one of the farther north solutions, and wants to
take the warm front up north of the area. This would take the
higher QPF up into central IL/northern MO. Meanwhile, the
operational GFS and to a greater extent the ECMWF suggest another
secondary boundary down closer to the TN border overnight, which
would focus more intense convection/heavy rain down over our CWA.
The models have been fairly stubborn lately with these trends,
making it more difficult to ascertain a good solution. A
compromise of solutions may be the best option for now.

As stated earlier, dynamics/moisture transport/mid lvl lapse
rates/strong shear values all point to both very heavy rainfall
and intense/severe convection in locations where the convection
focuses. As such, SPC has continued with a slight to enhanced
risk of severe storms from later this afternoon right through the
weekend over many locations. Large hail looks to be on of the
biggest concerns, but damaging wind gusts and isolated tornado
risk also appears to be on the table.

In any event, most locations in the current Flash Flood Watch area
should eventually get into a heavy precip/strong to severe
thunderstorm environment by the 2nd half of the weekend as the
main upper trof and associated cold front slowly work there way
east. Therefore, plan no changes this time to the watch area. Will
mention within the product, however, that much of Saturday into
Saturday night could be rainfree southern/eastern portions of the
watch as most model data suggest much of wrn Ky and the southern
tip of IL will get into a drier warm sector regime. Could even
get a decent amount of afternoon sunshine over western KY. Along
with the breezy south flow, should see temps at least into the mid

.LONG TERM...(Monday through Thursday)
Issued at 249 AM CDT Fri Apr 28 2017

In addition to the regionally initialized model guidance, the
deterministic ECMWF and GFS model suites were comparable in the
PoP/Weather solutions for next week.

The signal for northeastward ejection of the closed low to the Great
Lakes on Monday and a tight west-northwest flow in its wake into
Tuesday remains similar to yesterday`s model runs. In addition,  the
signal for a short, but intense zone of rainfall on Wednesday
remains consistent. The only caveat is that there is a slight
difference in the southwest to northeast east axis of the
precipitation. The GFS is further south, closer to an inverted
trough in the Lower Mississippi on Wednesday, while the ECMWF has
the inverted trough over Texas, extending further north into the
Middle Mississippi and Ohio Valleys. The regionally model guidance
initialization seems to blend these different solutions and provides
a good compromise for rain chances next week.

Both the ECMWF and GFS take upstream shortwaves originating from
western Canada and sharpen the zonal flow into a sharp trough over
the WFO PAH forecast area next Thursday, effectively ending
precipitation chances for the remainder of the week.

Overall have good confidence on the timing of the weather system
next Wednesday and Thursday. Have much lower confidence that there
will be any lingering precipitation chances beyond next Thursday, so
kept the forecast dry for the remainder of the extended forecast


Issued at 1148 PM CDT Thu Apr 27 2017

VFR conditions at all sites through the first half of the period,
then possible MVFR cigs/vsbys along with SHRA/TSRA in the last
half of the period as a warm front lifts northward across the
region. Variable winds AOB 10 knots early will swing around to the
south by with speeds increasing after 12Z with sustained values
of 10-15 knots and gusts eventually up to 20 knots.


IL...Flash Flood Watch from this evening through late Sunday night
     for ILZ075>078-080>094.

MO...Flash Flood Watch from this evening through late Sunday night
     for MOZ076-086-087-100-107>112-114.

KY...Flash Flood Watch from this evening through late Sunday night
     for KYZ001>005.



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