Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 120641
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
141 AM CDT Sat Jul 12 2014

.SHORT TERM...(Today through Monday night)
Issued at 131 AM CDT SAT JUL 12 2014

Our airmass will heat up and soup up over the next 24-48 hours.
This will allow a diurnal flare of pops, esp as some energy in the
upper levels drops down from the north, i.e. our northern counties
will see the pops today-tmrw. Pops will be small, however, at
least this weekend, with little to drive them beyond the heat/humidity
and small ptn of energy aloft that dips down and touches our nrn
counties.

Sunday night-Monday offer heightened pop chances, as a cold front
drops down in a broader troffing action that takes place over the
upper Midwest. Offering this feature, with upper level energy as
well as fropa, will enhance storm probability and strength, and
thus we are in a slgt risk SVR for this time frame (Sun night-
Monday). Pops for now look to peak in the likely cat.

The 00z GFS has the front making passage by 00Z Tuesday, which
would imply a dry Mon night. But given it`s the first or one of
the first ensemble members to model that, we`ll retain a chance
cat pop (hedging lower than allblends) til this is more
consistently modeled.

Given fropa, the weekend heat should be relieved with fropa
offering a cool back to the 80s/60s by Monday-Monday night.

.LONG TERM...(Tuesday through Friday)
Issued at 259 PM CDT FRI JUL 11 2014

A marked cooldown is anticipated in the long term. A
climatologically rare...deep upper level low will descend as far
south as the Great Lakes region on Tuesday. The 12z ecmwf indicates
a central height of 555 dm over Lower Michigan at 18z Tuesday. 850
mb temps will fall into the single digits during the middle of the
week as far south as the Ohio River...and possibly to the Tennessee
Valley. 850 mb temps will be as low as 3 standard deviations lower
than climatology over Missouri on Tuesday evening...and 2 to 3 sd
from climatology over a wide area for a few days.

As far as the daily details...
The timing of the cold front varies considerably from model to
model. The models may not be helpful in this case...since the
influence of convective systems will probably determine the
effective frontal position. A realistic scenario not depicted by any
global model is that a convective complex will cross our region
Sunday night...effectively relocating the frontal boundary to our
south by Monday. The 12z ecmwf is the slowest model...taking the
cold front across the Lower Ohio Valley late Monday night.

The forecast will continue to indicate 50 to 60 percent pops Monday
into Monday night due to the proximity of the frontal boundary. The
potential for strong to severe convection will be heavily influenced
by the presence of any convective systems early Monday. If the
atmosphere is not raked over early Monday...there is some potential
for severe weather later in the day into the night. Temps will of
course depend on outflow boundaries and convective activity.

The forecast is more clear cut the rest of the week. A
climatologically rare blast of cool air will arrive Tuesday and last
through most of the week. The cooler ecmwf guidance has been quite
consistent...and performed very well during the early month cool air
intrusion. Therefore...will trend toward this guidance as opposed to
the warmer gfs guidance and the all blend. The coverage of
cloudiness will be a factor with temps. There may end up being quite
a bit of diurnal cumulus given steep lapse rates and deep cyclonic
flow around the Great Lakes low.

By the end of the week...the models indicate residual upper
troughing lingering down into the Lower Ohio Valley. The 12z ecmwf
and 12z gfs ensemble mean show a surface warm front lifting north
across Tennessee...with some qpf reaching into western KY. Will keep
the forecast dry after collaboration with neighboring offices and a
look at the dry 12z gfs.

&&

.AVIATION...
Issued at 131 AM CDT SAT JUL 12 2014

A warm front will continue to lift newd through the PAH forecast
area over the next 24 hours. With the exception of MVFR fog at
KCGI/KPAH early this morning, VFR conditions should prevail through
the period. Some showers are possible mainly along the I-64
corridor (including KEVV/KOWB) near the aforementioned frontal
boundary. Light and variable to calm winds will pick up out of the
south southwest at 5-7 knots today.

&&

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

$$






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