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Area forecast discussion 
National Weather Service Paducah Kentucky
1141 am CST Tuesday Mar 3 2015

issued at 1141 am CST Tuesday Mar 3 2015

Updated aviation section for 18z taf issuance.


Short term...(today through Wednesday night)
issued at 322 am CST Tuesday Mar 3 2015

First short term concern is the potential for heavy rain and
thunderstorms this afternoon and tonight. The next concern is the
potential for a significant winter weather event Wednesday into
Wednesday night.

The chance of light precipitation will be on the increase this
morning as warm advection develops in association with a passing
warm front. In fact...high temperatures this afternoon are
forecast to range from the upper 40s along Interstate 64 to the
lower 60s near the Tennessee border.

By this afternoon and especially tonight...copious subtropical
moisture will stream into the region as a strong cold front
approaches from the plains. This will result in the development
of more widespread and steadier rains through the period. The
presence of marginal elevated instability will result in a slight
chance for thunderstorms this afternoon and evening. However...
severe weather is not anticipated.

With precipitable water values approaching 1.5 inches and on the
high end of climatological expectations for early March...heavy
rain will become likely tonight and persist into Wednesday
morning. The focus for the heaviest rain will likely be in a
southwest to northeast oriented band across western Kentucky and
far southeast Missouri. Rainfall totals of 1 to 2 inches will be
possible by daybreak Wednesday in Kentucky...with a sharp gradient
to much lighter amounts northwest of the Ohio River. Would not
normally issue a Flood Watch for this amount of rain...but the
recent snowmelt and saturated ground is a concern. As a result...
we plan to issue a Flood Watch for most of western Kentucky and
far southeast Missouri valid tonight through noon Wednesday.

Our next blast of Arctic air will follow the passage of a strong
cold front tonight. As temperatures fall late tonight and
Wednesday...lingering precipitation will transition to sleet and
snow. The big question at this point is how long does the sleet
continue before transitioning to snow. The GFS...ECMWF...and
Canadian are all on a similar Page in depicting more snow and less
sleet. Meanwhile...the NAM is the warmest in the 850-700mb layer
and would suggest hours and hours of sleet...especially over the
southern half of the area. At this point...I believe the NAM may
be onto something...but it is difficult to argue against the model
consensus. Therefore...we plan to strike a balance between the NAM
and GFS/ECMWF/Canadian to allow some wiggle room in the forecast
as developing conditions warrant.

We continue to base our quantitative precipitation forecast and snow amounts on a blend of model
guidance and wpc. At this point...our snow accumulation grids
range from 2 to 4 inches along the northwestern periphery of
counties in southern Illinois to as much as 6 to 8 inches in the
pennyrile region of western Kentucky. Before the snow falls...we
estimate that as much as one half to one inch of sleet may
accumulate before the precipitation changes over to snow. There is
some potential for a light ice accumulation early Wednesday...but
any freezing rain should be short-lived.

Lingering snow will taper off from northwest to southeast
Wednesday night as high pressure begins to build in. Lows by
Thursday morning will likely range from 10 to 15 degrees.

Long term...(thursday through monday)
issued at 322 am CST Tuesday Mar 3 2015

The big winter storm will be all but wound down by the time we
pick up the forecast at 12z Thursday. The European model (ecmwf) is a little more
regressive with the upper trough passage than the GFS...but the
collab consensus was to lean toward the GFS here and so we've
eliminated all probability of precipitation by 12z Thursday...even in the farthest
southeastern counties.

After the upper trough passage...the Arctic cold airmass reinforces
the cold over our region...on the strength of about a 1040 mb
surface high pressure system that settles overtop the
Ohio/Tennessee valleys. Highs Thursday will range through the 20s
while lows Thursday night bottom out in the lower single
digits. The only caveat may be going a little lower given the
anticipated snow cover that occurs...we tweaked a degree or two
down from the blend in account but may want to go more
was prudent last/recent system.

High pressure more or less holds at the surface as the
predominant weather influence through the remainder of the long
term...while precipitating weather systems tend to move just beyond our
borders. We'll keep the forecast dry accordingly...and seasonally
cool temperatures in a broadly northwest-westerly predominant upper flow
pattern through the end of the package.


issued at 1141 am CST Tuesday Mar 3 2015

IFR/LIFR ceilings expected through taf period. Scattered rain showers today will
become widespread rain after 00z. Rain will switch to sleet/possibly
freezing rain around 12z, then precipitation will become snow around
15z at kevv/kowb, and kcgi/kpah around 18z. SW winds around 10kts
will become northwest/north around 03z with the passage of a strong cold
front, becoming gusty after 12z. Visibilities with fog, dense at times,
will become mainly MVFR by 00z. MVFR/IFR visibilities expected with precipitation.


Pah watches/warnings/advisories...
Illinois...Winter Storm Watch from Wednesday morning through late Wednesday
night for ilz075>078-080>094.

MO...Winter Storm Watch from Wednesday morning through late Wednesday
night for moz076-086-087-100-107>112-114.

Flood Watch from 6 PM CST this evening through Wednesday morning
for moz112-114.

In...Winter Storm Watch from Wednesday morning through late Wednesday
night for inz081-082-085>088.

Kentucky...Winter Storm Watch from Wednesday morning through late Wednesday
night for kyz001>022.

Flood Watch from 6 PM CST this evening through Wednesday morning
for kyz001>013-015>017-019>022.



Short term...rjp
long term...dh

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