Area Forecast Discussion
Issued by NWS Paducah, KY
FXUS63 KPAH 180942
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
342 AM CST Thu Dec 18 2014
.SHORT TERM...(Today through Saturday night)
Issued at 342 AM CST THU DEC 18 2014
Main forecast issues revolve around the ongoing light mixed wintry
precipitation event followed by our next minor winter weather event
A mix of wintry precipitation continues to spread across the
forecast area early this morning. The precipitation has been a
mix of rain, sleet, and a little snow up to this point. Sleet was
the predominant precip type at the onset owing to evaporative
cooling processes. Thereafter, the precipitation has tended to be
mainly rain across the southern half of the area where 850 mb
temperatures are just above freezing. Mixed light rain and snow
was more prevalent across the northern half supported by a cooler
sub-freezing temperature profile.
The mid level energy responsible for the ongoing precipitation
will be slow to depart today. As a result, we lingered a mention
of light precipitation through much of the day. Shortly after
daybreak, we lose the best moisture in the favored -10 to -15 C
ice nucleation layer, so water droplets will be predominant. Light
rain and drizzle will therefore be predominant, though some light
freezing precipitation cannot be ruled out where temperatures are
just below freezing. This would be mainly across southwest
Indiana, southern Illinois, and western Kentucky except for most
of the Purchase area. Not expecting much impact at this time, but
some patchy slick spots on elevated surfaces, secondary roads,
sidewalks, and parking are certainly possible through mid morning.
Temperatures warming above freezing should negate any impacts by
Dry weather will return tonight and Friday before the next weather
system arrives Friday night. This one has been quite a challenge
to pin down--starting with the abysmal model agreement over the
weekend and early in the week to the continued southward shift in
the storm track in all the models. The southward trend has gone
far enough that it now looks as though the northern half of the
area may squeeze by with little to no precipitation at all.
Meanwhile, southern areas stand the best chance at receiving light
snow Friday night and perhaps early Saturday morning. But even
there, we`ll be lucky to see an inch of snow. And yes, with the
southward shift and a colder temperature profile as a result,
anything that falls should be snow--but just not much of it.
.LONG TERM...(Sunday through Wednesday)
Issued at 342 AM CST THU DEC 18 2014
The 00Z ECMWF and GFS show pretty good agreement in the larger-scale
features through the extended portion of the forecast. There are a
few issues with the sensible weather, but overall this is a fairly
high confidence forecast.
We will begin with high pressure at the surface and aloft Sunday,
but by 00Z Tuesday, both models generate a closed upper low over the
upper Midwest/northern Plains. They then intensify the low as it
wobbles slowly eastward reaching Quebec Canada Wednesday. At the
surface, a cold front with an associated band of rain will sweep
eastward sometime late Monday into Monday night.
The southern end of what is by then a deep upper trough will rotate
through the region Tuesday into Tuesday night, and then behind it we
will stay in cyclonic flow aloft with rather low heights over the
region. Will have mainly chance PoPs from Monday through Wednesday.
Really don`t have tremendous confidence in measurable precipitation
beyond the frontal rain band Monday/Monday night. Wednesday we may
be cool enough in the low-levels for flurries or some light snow, as
the freezing level will be just off the deck. Kept a mention of rain
and snow Tuesday night and Wednesday, but would be surprised to see
any tangible snow accumulation.
We may see some sunshine Sunday, but otherwise, we will revert right
back to the dreary stuff through Wednesday of next week. Thankfully,
there is no sign of any Canadian or Arctic air through the period.
Clouds and a deep trough aloft impacting the region, will keep
temperatures just a bit below normal behind the front Tuesday and
Wednesday. Sunday will start off the period a bit below normal, but
Monday could see a few locations reach the 50 degree mark just ahead
of the front.
Issued at 1144 AM CST WED DEC 17 2014
AT KCGI/KPAH, VFR cigs will drop to MVFR and IFR with the onset
of RAPL changing to SNPL, with brief dips to IFR possible. Vsbys
will be VFR and MVFR. For KEVV/KOWB, cigs will be VFR dropping to
MVFR, with KOWB having a better chance of seeing SNPL after 10z,
with both sites seeing -SN after daybreak. Precip will end by 18z,
with an increase back to VFR conditions.