Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 291119
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
619 AM CDT Mon Sep 29 2014

.SHORT TERM...(Today through Wednesday night)
Issued at 317 AM CDT MON SEP 29 2014

Main challenges for this short term forecast period will be first
period (today) temperatures and relative humidity and timing of
precipitation into the WFO PAH CWA near or after midnight going
into Thursday morning.

Short term guidance indicating a slightly cooler bias with maximum
temperatures for this afternoon high temperatures. These
temperatures are approximately 3-5 degrees cooler than surrounding
NWS forecasts. The key balance will be the combination of dry/cold air
advection and subsidence of air parcels below 850 mb. At this
time, am not inclined to go a complete 30 degree spread from
morning minimum temperatures, but at least a 27 degree Fahrenheit
temperatures spread. The 13km RAP guidance is the closest to this
solution for maximum temperatures today.

Ridging across the WFO PAH forecast will remain dominant through
at least 15z-18z (10am-1pm CDT) Wednesday, before cyclonic flow,
increased large scale, lift, differential vorticity, and
acceleration of low level moisture develop and move close to the
area. The main trough axis, near the U.S./Canadian border, near
North Dakota, will be in the process of enhancing/deepening along
the western limb of the trough, deepening the low. This will likely
slow the southeastward movement of the low until along or after
midnight going into Thursday morning. The forecast may still be
too aggressive in timing, but will keep chance PoPs going over the
northwest 1/2 of the WFO PAH CWA until at least 4 am Thursday
morning, before ramping up to match the Thursday daytime PoP
forecast in the extended part of this forecast package.

.LONG TERM...(Thursday through Sunday)
Issued at 317 AM CDT MON SEP 29 2014

Above average forecast confidence continues in the long term as
latest model solutions vary slightly with timing and coverage of
the upcoming weather event, but for the most part are still in the
same ball park.

Chances for showers and thunderstorms increase from the west on
Thursday as a storm system approaches from the central plains. As
mentioned above, models are slightly different with timing and
placement of selected parameters of this system, but right now the
best timing and coverage area-wide for showers and thunderstorms
should be Thursday night as the system actually crosses the region.

The cold front should be entering the far western portions of our
CWA around 7 PM Thursday and clearing the far southeast sections
around 7 AM Friday. Precipitation chances Friday morning rapidly
diminish from west to east as the front moves off to the east.

In the wake of the front, strong surface high pressure and northwest
flow aloft will usher in a very cool airmass which will keep things
dry and temperatures below normal through the end of the long term
period.

&&

.AVIATION...
Issued at 619 AM CDT MON SEP 29 2014

With the 12z Monday issuance, kept a mention of MIFG in place for
KCGI and KPAH. Dealing with ground fog or an elevated and shallow
fog layer overnight. Attempted to deal with this feature with a
higher prevailing visibility with embedded patches of dense ground
fog. The remaining groups basically account for variance of wind
from calm to a prevailing wind direction during maximum mixing,
then back again to calm winds with the development of an inversion.

&&

.FIRE WEATHER...
Issued at 317 AM CDT MON SEP 29 2014

Today and Tuesday will probably be the most ideal time period for
fire agency plans for prescribed burns. Should dry air advection
develop as advertised today, widespread minimum relative humidity
values will fall into the 23 to 33 percent range. Ten hour fuel
moisture`s have been staying above at least 9 or 10 percent which
should moderate the speed of fuel drying with tolerance levels.
Mixing heights today and Tuesday will be ideal between 11 am and 9
pm CDT, but diminish from the West as the impact of the upper
ridge dominates over Missouri late Tuesday into Wednesday.
Transport winds and 20 foot winds should remain below 15 mph, but
become more variable in direction on Tuesday and Wednesday. All
factor should remain below critical fire danger levels the next
several days.

&&

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

$$

SHORT TERM...Smith
LONG TERM...JP
AVIATION...Smith
FIRE WEATHER...Smith






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