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Area forecast discussion 
National Weather Service Paducah Kentucky
550 am CST Thu Nov 27 2014

issued at 549 am CST Thursday Nov 27 2014

The snow is down to patches of flurries at this point as expected.
Temperatures have fallen to or below freezing along and north of
the Shawnee Hills in southern Illinois, as well as, across
southwest Indiana and northwest Kentucky. Decided to issue a
Special Weather Statement for black ice potential in these areas
through 9 am. Figure that the sun angle will be high enough by
then, regardless of whether the clouds have broken, to take care
of a thin layer of ice.

The aviation section has been updated for the 12z taf issuance.


Short term...(today through saturday)
issued at 257 am CST Thursday Nov 27 2014

The light snows are in the process of diminishing and it should be
done by sunrise. Not sure just how much has fallen, but from
pictures and reports on social media, it appears that an inch or a
bit more has fallen over portions of southwest Indiana and
northwest Kentucky overnight. Most of it appears to be on elevated
surfaces, as temperatures have fallen to or just below freezing
only along and north of I-64. Will keep an eye out for reports
after sunrise, and may issue a Special Weather Statement for slick
spots mainly on bridges this morning for Holiday travelers.

Although, it appears that our Thanksgiving day will be dry, it
will not be a very nice day overall. Went very conservative in
clearing the low clouds from west to east mainly this afternoon.
With the clouds, gusty northwest winds, and temperatures
struggling to warm through the 30s, it will feel quite cold today.
The surface high will be settling over the area late today, so the
winds will be gradually diminishing this afternoon. Less wind and
more sunshine will make it feel a little better this afternoon.

Good radiational cooling is expected throughout the area tonight,
with the surface high overhead and a dry northwest flow aloft. The
cooler mav looks better than the milder met for lows, but it may
not be cold enough. As the flow aloft becomes more zonal, gusty
south winds will develop quickly Friday. The consensus of guidance
looks good for highs.

A tight pressure gradient will persist Friday night through
Saturday. The 00z models continue to saturate the surface to 850mb
layer quickly late Friday night and keep it saturated through the
day Saturday. Had to fabricate some hefty sky cover grids to do it
Justice. With the wind, clouds, and possibly some drizzle, Saturday
is not looking like the most pleasant of days. Trended down just a
bit for highs, but the forecast is still closer to the warmer mav
guidance. The slightly milder met guidance looks good for lows
Friday night.

Long term...(saturday night through wednesday)
issued at 257 am CST Thursday Nov 27 2014

Despite a quasi-zonal upper level flow pattern during the long term
period, a couple of surface frontal systems will bring changeable

The first cold front will sweep southeast across our region on
Sunday night. This front will be preceded by a strong southwest low
level jet, around 50 knots at 850 mb. Though very dry air will
persist through most of the lower trop, a shallow layer of very high
rh levels is forecast below 850 mb. The 00z GFS and its ensemble
mean generate some very light qpf Saturday night and Sunday, which
is most likely depicting drizzle or sprinkles. Since the moisture
depth is very shallow, pops will be only in the slight chance
category for most of the region through Sunday. The extensive
cloudiness, low sun angle, and weak lapse rates should inhibit
mixing down of the strong winds just above the surface.

The 00z GFS/gefs mean are in agreement that rain will develop along
and behind the front as it moves through the lower Ohio Valley and
southeast Missouri Sunday night. The Post-frontal rain will persist
through Monday. Some sleet cannot be ruled out at the tail end of
the event, depending on how quickly the colder air arrives. There
will be A Reservoir of Arctic air to our north as a 1040 mb high
passes over the upper Mississippi Valley on Monday. Will introduce a
mention of sleet in parts of southern Illinois and southeast MO late
Sunday night into Monday. It appears the sub-freezing layer will be
below 850 mb, too shallow for snow. The new 00z ECMWF is slower with
the front, delaying the onset and departure of precip about 12 hours
longer than the GFS.

As for Tuesday and Wednesday, there should be a brief period of dry
weather before a weak shortwave approaches. There will be only a
short window of opportunity for moisture return ahead of this
system, so pops will be mainly in the slight chance category. Temps
will moderate ahead of the system and its associated cold front.


issued at 549 am CST Thursday Nov 27 2014

The main issue for the tafs this morning is how quickly the MVFR
ceilings will clear across the region. An area of clearing will
move southeast across the evv and owb areas in the next couple of
hours. This should be temporary. Went on the pessimistic side and
have the sites clearing from west to east in the 19z-01z
timeframe. There is some guidance that holds onto it much longer
into tonight, so this forecast may not be pessimistic enough.

Looks like some mid-level ceilings will move into the area mainly
overnight tonight, assuming the low clouds have cleared by then.
Northwest winds will continue to gust into the teens at times this
morning, but should subside gradually through the afternoon, as
the surface high approaches.


Pah watches/warnings/advisories...


short term...drs

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