Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 201730
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1230 PM CDT Tue Jun 20 2017

.SHORT TERM...(Today through Thursday night)
Issued at 237 AM CDT Tue Jun 20 2017

The short term forecast period begins with CONUS ridged in the
west and trof`ed in the east, and a tropical disturbance in the
central Gulf, drifting slowly west-northwestward. Some weak
energy rounding the base of the mean trof aloft was producing
widely scattered showers early this pre dawn morning, but should
be squeezed out of the flow by sunrise. High pressure at the
surface anchoring across the mid Mississippi and Tennessee river
valleys will be the rule thru mid week, keeping mild wx conditions
in play with surface dew points from the upper 50s to lower 60s
offering pleasant humidity levels for this time of year.

While some additional weak energy aloft could touch off a shower
or two, mainly along the periphery of the FA, our next best bet
for pcpn comes with tropical moisture surging northward from the
disturbance late in the short term forecast period. With most
modeling taking the cyclone`s center into/nr LA/TX, the eastward
flank of moisture surging southerlies will spread abundant
tropical moisture northward, increasing clouds here Wed night with
incoming pcpn chances ramping up for Thur-Thur night. High
pressure throughout the column to our east at that time will
somewhat retard that transport, and looks like it may drift the
cyclone`s center westward with time/after landfall. Still, enough
moisture slings northward up the juicy moist tongue to allow for a
spike into the high chance category Pops by late in the period.
This will mute the slowly warming/humidifying temps off diurnal
peaks about a cat while likewise blanketing lows a little warmer
by the same.

.LONG TERM...(Friday through Monday)
Issued at 237 AM CDT Tue Jun 20 2017

At the beginning of the longer term period, we will be dealing with
the merger of the tropical storm remnants with the belt of
westerlies north of the area. Friday morning, the upper level system
will be in the vicinity of the Arklatex region. This upper low opens
up as it moves northeasterly toward our region. As this occurs, our
chances for precipitation increase throughout the day. Where exactly
the best POPs should be during the day is challenging this far out
but given the consistency in the model data, going up into the
likely category seems reasonable but assume revisions will be made
in the days to come.

A frontal boundary that has been advertised for days to be north of
the area, does eventually sink south Friday night but merges with
the remnants of the Gulf system. The whole conglomeration gets
caught up in the westerlies aloft and gets shunted eastward with
time. This leaves Saturday basically dry especially by afternoon
which is a change from past forecasts. We always knew the weekend
would be in a question depending on the interaction of this Gulf
system with the westerlies aloft. Again, the forecast for the
weekend will likely be fine tuned in the coming days. Heavy rainfall
will be a possibility of course but specific amounts and where, will
have to wait until a better handle on this system arrives.

Big discrepancies between models unfolds Saturday night through the
end of the period. The GFS and the GFS ensemble precip mean suggest
keeping dry upper level zonal flow over the area through at least
Monday. The Euro brings in another system as early as late Saturday
night into Sunday. Will maintain some low end POPs but confidence in
the forecast for that time period is very low. But beyond
that...there are no major signals for additional precipitation.

Warm and muggy conditions will prevail at the beginning of the
period but it does look like unseasonably cooler and drier weather
arrives by early next week.

&&

.AVIATION...
Issued at 1229 PM CDT Tue Jun 20 2017

VFR conditions to remain in place for the 18z WFO PAH routine TAF
issuance. A weak surface trough axis is currently moving through
the forecast area at this time, with west-southwesterly winds in
place. The flow will move back southerly with time. Some influence
of upper level moisture from the southeast U.S. is apparent with
some mid-deck clouds moving over the TAF locations at this time.

&&

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

$$

AVIATION...Smith


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