Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 192340
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
640 PM CDT Sat Jun 19 2021

.UPDATE...
Issued at 640 PM CDT Sat Jun 19 2021

Updated aviation discussion.

&&

.SHORT TERM...(Tonight through Monday night)
Issued at 309 PM CDT Sat Jun 19 2021

The main concern in the near term is the evolution of strong
storms currently to the north of KSTL. They are not currently
moving much at all, but will attempt to move southeast toward our
region, especially as their outflows pool together. They will
encounter less favorable thermodynamics as they reach our area,
and are likely to then back-build to the southwest into the early
evening. We may get a glancing blow from the storms from Mt
Vernon southwest through Pinckneyville and Perryville in the 22Z
to 01Z time frame.

SPC`s mesoanalysis has 1500-2000 J/kg of MLCAPE and 40kts of
effective bulk shear in those areas, so a severe storm is not out
of the question with large hail and damaging winds possible. A
Severe Thunderstorm Watch has been issued to our immediate
northwest, but does not include any portion of our area.

Other than the activity discussed above tonight and Sunday should
be dry throughout the region. Didn`t stray much from the NBM for
lows tonight or highs Sunday. Winds should die off enough to allow
temperatures to drop into the upper 60s to lower 70s for lows
tonight. Southwest winds will kick in Sunday and we may need a
Lake Wind Advisory over portions of the region. Highs should reach
the low to mid 90s and with humidity figured in heat indices may
touch a hundred for an hour or two.

There is quite a bit of variability amongst the 12Z guidance on
the timing of the cold front Sunday night into Monday. The GFS is
the most aggressive and has the front well into the area by 12Z,
while the NAM and ECMWF bring the front to near the Ohio River by
18Z. It appears that the showers and thunderstorms will be focused
during the day Monday, mainly over the south or southeast half of
the area. A few strong storms cannot be ruled out ahead of the
cold front mainly over west Kentucky Monday afternoon, but heavy
rainfall will likely be the greatest concern, also in the south.
Storm total QPF runs from half an inch in the northwest to around 2
inches in the south.

Sunday night will be quite mild with healthy southwest winds and
increasing clouds, some locations may not drop much below 80. The
NBM highs in the middle 80s Monday are likely way too high with
the frontal passage and precipitation. Lows Monday night will drop
into the 50s.

.LONG TERM...(Tuesday through Saturday)
Issued at 309 PM CDT Sat Jun 19 2021

The main concern in the long term portion of the forecast is the
potential for showers and thunderstorms towards the end of the week.
Forecast confidence starts off higher than average with good model
agreement mid week. However, confidence decreases to just average by
the end of the week with greater model variability.

The period will start with a longwave trough axis positioned over
the Mississippi and Ohio Valleys on Tuesday with high pressure in
control at the surface. This will result in dry and much cooler
conditions in the wake of Monday`s frontal passage. The primary
question is how cool? Looking back to earlier this week, the GFS MOS
was way too cool with temperatures, while the warmer ECMWF was spot
on. Fast forward to next week, and we notice that while the ECMWF is
still warmer than the GFS, it`s substantially cooler than it was
earlier this week. So while highs in the 70s across the entire area
seem a bit of a stretch this late in June, upper 70s to lower 80s
offers a good compromise between the initialized NBM and ECMWF MOS.
As an upper level ridge builds east from the Plains and winds become
southerly on the back side of the departing high, highs on Wednesday
should warm well into the 80s.

Forecast models are in general agreement that another longwave
trough will become established from the Great Lakes into the
Mississippi Valley next weekend. Shortwave energy traversing the
base of this trough in combination with an approaching cold front
should result in increasing chances for showers and thunderstorms by
Friday and into the weekend. At this point, exactly when and where
the better chances occur, and if/when the cold front makes it
through the entire area, are both low confidence forecasts at this
point. Of greater confidence is the increase in heat and humidity,
with highs forecast near 90 by Thursday and Friday and dew points
near the 70 degree mark once again.

&&

.AVIATION...
Issued at 640 PM CDT Sat Jun 19 2021

VFR conditions are expected to continue through the next 24 hours.
There is higher confidence than yesterday that evening shower and
tstm activity northwest of the region will stay north, except for
perhaps the northwestern fringe counties. Southerly to south-
southwesterly winds around 5 knots will increase after daybreak Sun
to 13 to 14 knots sustained out of the southwest, gusting AOA 20
knots in the western half of the region by the end of the TAF period.
There will be increasing chances of shower/tstm activity just
beyond the TAF period due to an approaching cold front.

&&

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

$$

SHORT TERM...DRS
LONG TERM...RJP
AVIATION...DB


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