Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 261735
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1235 PM CDT Mon Jun 26 2017

.UPDATE...
Issued at 1235 PM CDT Mon Jun 26 2017

Updated Aviation discussion for 18Z TAFs.

&&

.SHORT TERM...(Today through Wednesday night)
Issued at 308 AM CDT Mon Jun 26 2017

Remote sensing from area NWS radars and GOES satellite IR data
suggest more moisture and lift than suggested by some of the
numerical model guidance early this morning. The ESRL HRRR and RAP
appear to be latching on the patchy overnight shower activity.
Surprisingly, the deterministic GFS/GFS 1hr guidance is also
picking up on this convection as well, while the Canadian/ECMWF
are showing some mixed results.

Instability for any thunderstorm development with this
Monday/Monday night system remains quite limited in duration and
scope. Recent trends suggest that any isolated thunderstorm
convection will remain near the I-64 corridor in Southeast
Illinois and Southwest Indiana.

PoPs and weather for Monday and Monday Night first showed up with
model runs this past Saturday. The signal for the precipitation
chances has remained consistent for the aforementioned time
period, but the reliability on the coverage and timing remains
elusive still. With this forecast issuance, backed off on the
overall coverage of precipitation to reflect the focus on the
elevated nature of the convection. There has been a slight delay
in the sharpening of the upper trough through the WFO PAH forecast
area, placing the majority of the convection in the 03z-12z time
frame on Tuesday versus the 00z-06z time frame on Tuesday (i.e.
overnight Monday versus Monday evening).

Enhanced cloud cover a little more today and tonight. This will
impact maximum/minimum temperatures somewhat in combination with
low level weak cold air advection around the surface high pressure
moving across the area today.

Dry and gradually warming conditions will dominate the remainder
of the short term from Tuesday through Wednesday. Kept close to
regionally blended model guidance during this time period.

.LONG TERM...(Thursday through Sunday)
Issued at 308 AM CDT Mon Jun 26 2017

Much lower confidence in the extended due to an apparent flaw in the
latest forecast builder run. We had to serp/blend pops with
surrounding offices to even remotely blend.

starting Thursday the surface high will have drifted off into the
atlantic...allowing the gulf to be wide open for abundant moisture
supply. Forecast sounding indicate the column becomes more and more
saturated as we head into the weekend. Thursday is not looking as
good for storms as previous model runs restricting pops to along and
north of interstate64 corridor. Even Friday the when pops spread
across the region the moisture is still not optimum through the
column although adequate in the lower levels for storms. By this
weekend it becomes saturated through the entire column. At the same
time the near zonal flow starts to trough over the area which will
greatly enhance storm chances. On Saturday the LI`s will approach
negative double digits with CAPE`s around 2-3k during the daylight
hours. The instability decreases dramatically overnight but we still
have elevated instability. So storms will be possible both day and
night. In addition PW`s approach 2" so the storms will be efficient
rain producers. Winds are fairly unidirectional and not that strong
but the instability will be capable of producing strong or even a
severe storm. I think the main threat will be heavy rain and
lightning but we could get damaging wind out of the strongest
storms. Tornadoes are not anticipated with the forecast shear but
not impossible with the strongest storms. Some of the models try to
bring a front through while others keep it north of the region as
previous runs. Instability decreases Sunday but still enough for
another round of storms. Temperatures and dew points will return to
near normal for the extended with temps approaching 90 and dew
points near 70.

&&

.AVIATION...
Issued at 1234 PM CDT Mon Jun 26 2017

Main issue will be with shower activity, with some potential for a
few rumbles of thunder, entering our northwest counties around
21z and progressing eastward through the evening and overnight
hours. Guidance tends to show the most concentrated activity
affecting southeast Missouri into far west Kentucky and adjacent
portions of southern Illinois. Only included VCSH mention at
terminals at this point and will amend as necessary as timing and
best coverage area becomes better defined. May be some brief
reductions in cigs/vsbys associated with the heavier activity.
Otherwise, VFR conditions throughout with mainly just a mid level
cloud deck moving in with this system. Light and mainly variable
winds through tonight will become more easterly tomorrow and
remain light.

&&

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

$$

UPDATE...SP
SHORT TERM...Smith
LONG TERM...KH
AVIATION...SP


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