Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 211705
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1205 PM CDT THU JUL 21 2016

.UPDATE...
Issued at 1205 PM CDT Thu Jul 21 2016

Aviation update.

&&

.SHORT TERM...(Today through Saturday night)
Issued at 302 AM CDT Thu Jul 21 2016

It is becoming more apparent that the biggest heat wave of the
season is about to hit the region as mid level high pressure
remains anchored over the central Plains, and even begins to
expand further east as we get into the weekend. Sfc temps are
expected to rise into the upper half of the 90s by Fri/Sat and
muggy dew points in the mid 70s should persist. Expecting several
consecutive days where the heat index will likely top 105 degrees
for a around 9 straight hours (10 AM - 7 PM). Temps late at night
will cool only into the upper half of the 70s at many locations.
Because of this, plan on upgrading the heat advisory to excessive
heat warning with this package for all except southwest Indiana
and the Pennyrile of western KY, where the excessive heat may take
a little longer to get going. That said, still think that the
warning area may need to be extended east through the entire
forecast area with time. Also, plan to extend all headlines
through Sunday with this forecast package.

As far as storm potential goes, it will be low but not zero.
Forecast thermodynamic soundings suggest modest capping, but H70
temps around -10 C even suggest a few storms may break through the
mid lvl capping/warm layer. SB CAPES 3000-4000 j/kg during heat of
day combined with steep low level lapse rates suggest some
damaging wind potential with any isolated storms that may fire.

.LONG TERM...(Sunday through Wednesday)
Issued at 302 AM CDT Thu Jul 21 2016

The west to east elongated middle and upper ridge axis appears to be
semi-permanent, at least through the middle of next week before
retrograding west late next week.  Was taken by surprise on how
quickly the ridge worked westward this past Sunday into Monday, but
the ECMWF did an excellent job hinting at this almost four days out.

With both the GFS and the ECMWF maintaining the ridge axis through
at least next Wednesday, the heat and humidity should continue at or
above Heat Advisory/Excessive Heat Warning thresholds through at
least next Monday for most of the WFO PAH forecast area.

Given what we have seen the last day or two, pockets of convection
will limit some areas from reaching their maximum potential heat
index values.

At this time, have 30 to 50 percent confidence on PoP coverage over
the WFO PAH forecast area in the extended forecast period. There are
so many variables, from the mesoscale to storm scale level, to even
entertain any high confidence in the PoPs.  There is higher
confidence in temperatures, given the absence of rain.

&&

.AVIATION...
Issued at 1205 PM CDT Thu Jul 21 2016

Isolated convection possible anywhere. But best chance appears to
be NW of a KEVV-KCIR-KPOF line. No mention in the 4 terminal
forecasts at this time. Just CU, and light SSW winds. Will use a
persistence forecast for tonight. Some high clouds possible with
near calm winds and MVFR fog chance. Will monitor the possibility
for convection KEVV/KOWB by early tomorrow. Just an increase in
clouds in the planning part of the forecast for now given rather
low confidence.

&&

.PAH Watches/Warnings/Advisories...
IL...Excessive Heat Warning until 8 PM CDT Sunday for ILZ075>078-
     080>094.

MO...Excessive Heat Warning until 8 PM CDT Sunday for MOZ076-086-087-
     100-107>112-114.

IN...Heat Advisory until 8 PM CDT Sunday for INZ081-082-085>088.

KY...Excessive Heat Warning until 8 PM CDT Sunday for KYZ001>009.

     Heat Advisory until 8 PM CDT Sunday for KYZ010>022.

&&

$$



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