Area Forecast Discussion
Issued by NWS Paducah, KY
FXUS63 KPAH 211139
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
639 AM CDT Thu Aug 21 2014
Issued at 517 AM CDT THU AUG 21 2014
Minor adjustment to account for light showers over Southern
Illinois and departing convection over Southwest Indiana before
daybreak. The 13km RUc and 3km HRRR suggest a subtle channeled
vortiicity intersecting very minor, low amplitude shortwave
centered around the 14-17kft layer on the KVWX VAD wind profile
between 9-10z. Precipitation chances will remain marginal and
suspect subsidence in this layer will serve to speed up clearing
of cloud debris by mid-morning. With this in mind, went slightly
higher with temperatures through early afternoon.
Should clouds linger 1-3 hours longer than expected, may have to
dial back temperatures and heat indexes to the main forecast
package levels for this afternoon.
.SHORT TERM...(Today through Saturday)
Issued at 306 AM CDT THU AUG 21 2014
Strong thunderstorm clusters rolled through northern parts of the
CWA early this morning, producing some very heavy rain and gusty
winds. They were associated a small upper level disturbance that
is moving across parts of southern IL/southwest IN. The only short
term model that seems to have a good handle on this complex is the
HRRR, which continues to take these remnants east/southeast and
out of the EVV Tri State region over the next few hours. There are
a few light showers forming further west in southeast MO which may
be forming due to decent instability and maybe a weak boundary
over that area per the latest LAPS data. Will opt for some
isolated coverage through about 13Z to cover any remaining
activity as this disturbance moves out of the region.
We will see upper heights build today and we should see the mid
level clouds clear during the morning hours, leaving the afternoon
to heat up. Unlike yesterday, when clouds hung out long enough to mess
with temperatures in our northern areas, it appears we should have
enough sunshine today that all locations should reach the low/mid
90s, as 850mb temperatures do not really change too much. The only
issue may be our eastern counties. If clouds to not clear until late
there, the heat advisory may be in jeopardy. Will keep it going
area wide for now due to uncertainties in cloud cover.
The ring of fire pattern will be rather active to our north, as
disturbance rotate around the upper high. Believe that most of the
activity should stay well to our north today, tonight and into
Friday, but the far northern/northeastern counties might need to be
watched just in case outflow boundaries from storms to the north
light up further south than anticipated.
Friday into Saturday, the upper high over the region becomes even
more amplified, as a upper level trough crashes into the Pacific
northwest. The atmosphere really dries out in the low levels and
even aloft as this occurs. This should really shut off any chances
for potential convection. The heat begins to build even more for
Friday and Saturday as low level temps rise a few more degrees,
which should put us into the mid or upper 90s through Saturday.
Night time lows will remain in the mid 70s. This heat, coupled with
high humidity values, should continue to warrant our ongoing heat
advisory, which might even have to be extended.
.LONG TERM...(Saturday night through Wednesday)
Issued at 306 AM CDT THU AUG 21 2014
The main concern during the long term period will be the extended
duration of potentially hazardous heat. A deep layer subtropical
high will be anchored over the Lower Ohio and Mid Mississippi
Valleys late in the weekend into early next week.
As far as the daily details...
Sunday into Monday...the center of the high /850 to 500 mb/ is
forecast to be nearly overhead. The models forecast some
strengthening of the high...with 500 mb heights near 594 dm by
Monday. Heat indices will likely continue to meet or exceed advisory
thresholds...requiring an eventual extension of headlines.
Tuesday into Wednesday...very little change is indicated regarding
the location of the upper ridge. However...the low level anticyclone
is forecast to shift eastward. Due to weaker capping and less
subsidence...there should be a little more cloudiness and isolated
diurnal convection. This moisture may hold daytime highs down a bit.
Issued at 638 AM CDT THU AUG 21 2014
With this issuance attempted to account for lift associated with
minor shortwave moving through the TAF sites before 17z. Added a
brief MVFR ceiling for KEVV and KOWB through 17z, otherwise kept
ceilings near 110 kft AGL as the dominate cloud cover prior to 17.
The ridge should build in quickly this afternoon, diminishing
opaque cloud cover below 12kft agl. There may be some cirrus in
the area, but did not account for it at this time. Minor visbility
restriction was added after 06z Friday for all of the TAF sites,
ranging between 5 and 6 statute miles.
IL...HEAT ADVISORY until 7 PM CDT Saturday FOR ILZ075>078-080>094.
MO...HEAT ADVISORY until 7 PM CDT Saturday FOR MOZ076-086-087-100-
IN...HEAT ADVISORY until 7 PM CDT Saturday FOR INZ081-082-085>088.
KY...HEAT ADVISORY until 7 PM CDT Saturday FOR KYZ001>022.