Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 281850
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
150 PM CDT Fri Apr 28 2017

.SHORT TERM...(Tonight through Sunday night)
Issued at 126 PM CDT Fri Apr 28 2017

A warm front is lifting north across the region. This front will
be both the immediate and short term focus for convection.
Currently, surface based CAPES were starting to appear in southern
Ky and the SEMO Bootheel, or, along/just south of the boundary,
where surface dew points have risen into the mid 60s. North of the
boundary, parcel lift is elevasted, with dew points from the mid
50s to low 60s. Helicity values along the boundary are high, but
with scarce surface based instability, and still some capping to
erode, activity on radar has been more isolated to scattered, and
more to our west, where first couple of warnings have been issued.
Will continue to monitor closely as warm front lifts north, and we
warm sector. Latest SWOMCD outlooks 50 percent probs for watch box
this pm, so they are literally `watching` as well.

Tonight, better organization/better upper dynamics come into play,
so should see better storm coverage, even in the warm sector. Alot
then depends on where boundary sets up, and there is still some
model difference between across our northern counties, or, to our
north entirely. Either way, activity should be most vibrant along
and in vicinity of boundary, with heaviest rains focused in that
vicinity. Highest qpf thus expected across our north and west,
with least qpf across our south/east, where convective activity
will be most isolated/marginalized.

Saturday, as advertised, looks like a pause, with reignition late
Saturday into Saturday night. Sunday still looks active and as we
transition to cold front and it`s passage, into Sunday night, pcpn
ending west to east. Continued SLGT risk Sat pm-night and Sun pm-
night as well.

Per collab with LMK, expanded FFA to the south and east to mesh
with southern In and northcentral Ky. Ran for entire event.
Amounts will be highest further south and west, but this will line
up best with IND/LMK.

.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
period.

&&

.AVIATION...
Issued at 126 PM CDT Fri Apr 28 2017

Warm front passing this pm, will result in MVFR CIGS, which are
already showing up at KCGI and KPAH. This should expand further
northward and eastward with time, as warm front lifts. Convective
chances are ramping up with peak heating, but have to overcome cap
and slow to rise surface based instablity (mostly elevated).
Better activity will organize tonight, with deeper layered shear
and instability. Anticipate lowering CIGS and altogether
deteriorating conditions overnight. May see IFR CIGS/VSBYS in
thunder late/during the planning period, and even after
convective chances wane toward expiration time, may see lingering
low MVFR are marginal IFR cigs persisting.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Flash Flood Watch from 7 PM CDT this evening through late Sunday
     night for ILZ075>078-080>094.

MO...Flash Flood Watch from 7 PM CDT this evening through late Sunday
     night for MOZ076-086-087-100-107>112-114.

IN...Flash Flood Watch from 7 PM CDT this evening through late Sunday
     night for INZ081-082-085>088.

KY...Flash Flood Watch from 7 PM CDT this evening through late Sunday
     night for KYZ001>005-014-018-019.

&&

$$


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