Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 240743
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
243 AM CDT WED AUG 24 2016

.SHORT TERM...(Today through Friday)
Issued at 222 AM CDT Wed Aug 24 2016

Satellite and Radar Mosaic shows some spotty convection extending
from Iowa down into far northern/northwest MO. The GFS is not
handling this well. It thinks this area of pcpn extends as far
south as our FA/doorstep. The NAM has a much better handle on it,
pinpointing its areal coverage/reach.

Both models show the pcpn in association with a weak perturbation
rounding a broad area of high pressure aloft that is anchored over
the heart of the South. Both models lift this weak wave to the
northeast/across the Great Lakes over the course of the day. And
more or less, continue this pattern of periodic ripples of weak
energy riding the peripheral of the broad High pressure aloft,
that builds ever stronger into/across the Tennessee valley.

Honing in on today, there are numerous negating factors that leads
us to minimize, if not altogether eliminate or make silent, the
going small pop. Namely is that H5 heights rise 20 DM as the
sinking air aloft ridges into/across the Tennessee valley, and various
models show 10-11C air working across the FA at H7, as this
occurs. While we cannot altogether rule out an isolated updraft
breaking thru, particularly on the periphery of the High aloft,
where it might overcome the Bernoullian sink, we believe it`s
enough to warrant a minimization of most pop mention.

An exception occurs late tonight, as most modeling shows a piece
of energy making enough southward progress on a dive toward the
middle Ohio valley such that a slight chance mentionable Pop is
warranted for the extreme north/northeast part of the FA. We
inherited that Pop and the 00Z models do not dictate or
necessitate a valid enough argument for us to change it.

Thursday-Thursday night, we see similar reasons to today, to
negate the Pop mention. H7 temps are even more broadly capping,
with the High now strongly centered over the Volunteer state and
extending its center near or even into the Commonwealth.

The wobbling High aloft shifts a little bit eastward by Friday.
While still a strong influence, it looks to be shifted just far
enough eastward to allow its buildup of warmth/humidity to result
in diurnally aided parcel lift, enough to mollify our sinking air
concerns to allow a chance category pop to prevail over the
course of the day.

Summer like synoptics mean summer like temps and humidity through
the course of the short term, or migrating toward/slightly above
seasonal norms.

.LONG TERM...(Thursday night through Tuesday)
Issued at 311 PM CDT Tue Aug 23 2016

Medium confidence toward the end of the week. Low confidence as we
head into next week with vast differences in model solutions.

Starting Thursday night an upper level high pressure system is
firmly entrenched over Kentucky and into the gulf states. This high
is vertically stacked from the surface up through the mid to upper
levels. This will result in a strong gulf flow around the western
edge of the high. Most of this moisture will remain west of the
Mississippi River but we will alsoWith the 06z Wednesday TAF issuance, the middle and upper
level ridge is more advect east of the river with time. Now east
of the aformentioned river could see some diurnal convection but
believe the loss of heating will make for mostly dry nocturnal
conditions. Both the GFS and ECMWF are very similar although the
GFS is advertising a much more dirty high than the ECMWF. We do
have a very weak cold front expected to reach the area Friday into
Saturday which will result in higher pops if it actually makes
into the region before stalling and lifting back north. This will
be a collaboration...extended init...and wait and see scenario.
Now as we start to head into next week both models start to drift
the high off the southeastern seaboard. This very much could guide
be the deciding factor for the low invest (AL99) track which the
latest ensembles have it headed straight for Miami. This would
match up nicely with the ECMWF. The GFS is more stubborn with the
high which hold off AL99 from reaching the coast. Either way it
would have little impact on our area outside of some additional
cloud cover. Temperatures will return to well above normal with
highs around 90 and dew points in the 70s. This will result in
heat index values in the upper 90s to near a 100 through most of
the extended.

&&

.AVIATION...
Issued at 222 AM CDT Wed Aug 24 2016

Evening models show a more pronounced ridge aloft than earlier
numerical model runs through the forecast period. The capping
effect of the ridge will essentially eliminate rain chances for
the flight terminals and reduce the impact of lower VFR ceilings
with time. Therefore, this package is mainly a VFR forecast for
all TAF locations as the ridge dominates the area, mostly likely
through Thursday as well.

&&

.PAH Watches/Warnings/Advisories...
IL...None.
MO...None.
IN...None.
KY...None.

&&

$$



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