Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 121726
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1226 PM CDT Tue Sep 12 2017

.UPDATE...
Updated aviation section for 18z taf issuance

&&

.SHORT TERM...(Today through Thursday night)
Issued at 313 AM CDT Tue Sep 12 2017

What has now been downgraded to Tropical Depression Irma will
continue to weaken and move northwest out of Ga/Al today. Will
continue ongoing Lake Wind Advisory this morning for some 15-20
mph winds, but the pressure gradients should weaken this
afternoon as the depression continue to fill and high pressure
weakens to our north. What`s left of the remnants will be
centered over the forecast area by Wednesday.

Bands of rain will rotated northwest out ahead of this system
today, but much of the deep moisture is being cut off to the
system with time. Thus, rain amounts should not be as nearly as
high as with Harvey over wrn KY. Still, some locations in the
southern Pennyrile region could pick up an inch or so of rain
before the system finally dissipates on Thursday.

With northeast winds, extensive cloud cover and on/off rains,
diurnal temp swings will be minimal. In fact, some locations will
not change by more than 4 to 7 degrees through Wednesday. A
warming trend should get underway on Thursday tho as the system
dissipates, winds shift more southerly and some sunshine returns.
Most places will pop back in to the mid 70s to lower 80s on
Thursday afternoon.

.LONG TERM...(Friday through Monday)
Issued at 315 AM CDT Tue Sep 12 2017

Maintain high forecast confidence on a drier/warmer weather scenario
for the latter part of this week and into the middle of next week.

Dry forecast dominates the extended forecast period. Following the
departure of the low circulation off the east coast near the
beginning of the forecast period, a longitudinal high pressure ridge
extending from northeast Mexico to the Great Lakes will dominate the
WFO PAH forecast area.

While most of the numerical guidance suite was somewhat off with
respect to initialization with remote sensing, the Canadian (CMC)
and European (ECMWF) seem to fare better in the long range.  The big
key to any precipitation potential at all for the WFO PAH forecast
area is tied to the evolution of a series of mid/upper level lows
rotating over the Pacific northwest into the weekend. At this point,
the Canadian and ECMWF appear to be modeling the trans-
position/transformation of the Pacific Northwest the next several
days. For the WFO PAH forecast area, this will mean a prolonged
period of ridging over the local area into early next week.

Most of the energy that has been recently translate across the upper
Midwest will likely be shunted into south central Canada,
maintaining ridging across the Quad State region. It will be worth
watching the trough/lows in the northwest by the middle of next
week, as this system may become quite unstable (thermodynamically
speaking) once it moves east of the intermountain region. There is
some hint that this will be a deep cold core system.

With respect to temperatures, made a slight adjustment from the
regionally blended model initialization to weight temperature slight
closer to the ECMWF and Canadian numerical model solutions. This
maintains middle and upper 80s for the local area through early next
week.

&&

.AVIATION...
Issued at 1226 PM CDT Tue Sep 12 2017

Widespread mvfr cigs overspread the area this morning in association
with rain from the remnants of Irma. There were even some patches of
ifr conditions. Winds were gusting to near 20 kt from the ne at some
sites.

Periods of rain will continue through this taf period as the
low pressure center slowly lifts northward from Alabama to western
Kentucky. There should be a gradual decrease in cigs and vsbys
tonight as winds become light. The combination of light winds and
very moist air will result in widespread ifr conditions by morning,
with local lifr conditions. Conditions will be slow to improve on
Wed morning, and many places could remain ifr through the morning.

&&

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

&&

$$

SHORT TERM...GM
LONG TERM...Smith
AVIATION...MY



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