Area Forecast Discussion
Issued by NWS Paducah, KY

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763
FXUS63 KPAH 131741
AFDPAH

AREA FORECAST DISCUSSION
National Weather Service Paducah KY
1141 AM CST SAT FEB 13 2016

.UPDATE...
Issued at 1141 AM CST SAT FEB 13 2016

Updated the aviation discussion for the 18Z TAF issuance.


&&

.SHORT TERM...(Today through Monday night)
Issued at 351 AM CST SAT FEB 13 2016

Our next potential winter storm system will begin to impact the
region late tonight as low-level warm advection cranks up in
response to a storm system moving eastward through the upper
Midwest. Precipitation with this system will be the result of warm
advection generally at or below 600mb. Would not be surprised to
northwest portions of the region get very little with this system,
while the southeast corner could see over 3/4" of liquid
equivalent precipitation.

A look at NAM and GFS soundings throughout the region indicates
that saturation may not reach -10C, which really calls into
question whether we will activate ice nuclei. If not we could see
rain or freezing rain for most of the event, rather than the snow
that has been advertised. Also, the models tend to struggle to
be warm enough with the precipitation type in these warm advection
situations.

Decided to go with the consensus of raw 00Z model output for
temperature trends Sunday through Monday. This is more in line
with the cooler MET guidance, but still gets southeast portions of
the area at or above freezing Sunday evening, and the entire area
above freezing by midday Monday. We won`t be surprised if this
warming trend is not fast enough, and we will definitely be
rooting it on.

The 00Z GFS and ECMWF bring a warm nose near 850mb northeast into
portions SEMO and the Purchase Area Sunday afternoon, so will
begin the transition to sleet and possibly freezing rain in the
far southwest after 18Z Sunday. Prior to then we are expecting
pure snow.

Once the initial surge of warm advection moves through the area
Sunday, the forcing is a bit suspect for Sunday night, and most
of the QPF will be over west Kentucky, especially the far
southeast portions of the area, where temperatures will be
flirting with the freezing mark. The suspect forcing Sunday night
will make it hard to get saturation deep enough for snow to
develop, so will have freezing rain and snow mentioned throughout
the area, with a chance of just rain mixed in over the far
southeast.

We will dry out the far northwest Monday, and elsewhere we will
maintain a mention of rain, snow and freezing rain, with just rain
in the far southeast corner of the area in the morning. The entire
area should be warm enough for rain by Monday afternoon. The
accumulating ice and snow should come to an end early Monday. The
rain may linger into Monday evening in the far east, and we may
begin to see some light precipitation spread southeast into the
region overnight Monday night, as our next compact storm system
approaches from the northwest. This could be rain, freezing rain
or snow, but we should not see enough of anything to be a problem.

The official forecast is well aligned with our surrounding offices
with a total of 1-3 inches of snowfall, mainly falling during the
day Sunday. We also have just a hundredth or two of icing from
freezing rain over much of the area Sunday evening. This snowfall
forecast is likely overdone for all of the reasons mentioned
above, so would not be surprised to see future forecasts trend
lower with snow and upward a bit with icing and warm rain. Any
issues should be short-lived with temperatures warming well above
freezing throughout the region by midday Monday.

Given all of the uncertainties we will not be issuing a Winter
Weather Advisory with this forecast package, but we will address
the many concerns in a Special Weather Statement and the HWO.

.LONG TERM...(Tuesday through Friday)
Issued at 351 AM CST SAT FEB 13 2016

Two systems to monitor in the long term, one more certain, the other
- not so much. The first system is a compact system barreling
southeast out of the northwest flow pattern, arriving on Tuesday.
The operational GFS/ECMWF are in good agreement on timing but not as
great on the placement of highest QPF. General consensus of greatest
moisture appears to be our northeast, so highest POPS will be
highlighted there. This matches up well with the latest GFS ensemble
precipitation mean.

Looking at latest soundings, thicknesses etc...it looks like this
will be an all rain event. The only issue might be first thing in
the morning (12Z-15Z) and mainly up in the EVV tri state region,
if precipitation is even reaching there by then. Sfc temperatures
are below freezing during that time. Will not get fancy with wx
grids attm since this is day 4 and models are still not in
agreement just how warm it will be. The GFS indicates the entire
area will be above freezing; the ECMWF is colder and ensemble data
is not too helpful but the mean sfc temp does most of the area
above freezing on 12Z Tuesday.

However, later on, there will be plenty of moisture aloft to
produce snow but a fairly warm low level layer near the surface
should prevent that from reaching the ground as snow. This system is
a quick mover and whatever falls should be done by evening, so will
leave the Tuesday night period dry.

One more minor upper level perturbation is seen in some of the
model data that will yield some clouds on Wednesday but little QPF
should be associated with it. Temperatures on Wednesday will be a
few degrees cooler than Tuesday. However, after that passes, we
will finally see a pattern shift to much warmer weather, at least
for a few days. An upper level ridge steadily builds over the area
Wednesday night through Thursday night. At the sfc, high pressure
shifts east and we will see winds shift to southerly and increase.
Temperatures will respond by surging well into the 50s to possibly
low 60s as early as Thursday. These warmer temperatures will
remain in the region at least through the end of our extended
period.

The next weather system that could yield some precipitation arrives
Friday or Friday night. Right now, QPF looks rather limited so will
only advertise low end POPS.

&&

.AVIATION...
Issued at 1141 AM CST SAT FEB 13 2016

VFR conditions will prevail until Sunday morning as mid clouds
enter the area ahead of an approaching winter storm system. Could
see brief light snow near KEVV, KOWB, and KCGI for a few hours
before dawn. All sites will likely see cigs drop to MVFR, and even
IFR cigs/vsbys at times, once snow starts mid morning. Winds will
veer from north/northeast today to east/southeast by Sunday
morning.

&&

.PAH Watches/Warnings/Advisories...
IL...NONE.
MO...NONE.
IN...NONE.
KY...NONE.
&&

$$

AVIATION UPDATE...BP2
SHORT TERM...DRS
LONG TERM...CW



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