Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 240250
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
950 PM EST Sun Nov 23 2014

...Forecast Update...
Issued at 950 PM EST Sun Nov 23 2014

The forecast is in good shape -- just some tweaks made based on
current radar trends and short term model projections.

Area of showers currently over the LMK CWA will continue to pull
quickly off to the northeast.  We will then get a break before the
next wave of showers, over Missouri at 0245Z, slides to the ENE
across southern Indiana during the early morning hours on Monday.
There could be a few rumbles of thunder with this activity as well.

Headline still looks good, as do temperatures.

.SHORT TERM (Now through Monday Night)...
Issued at 225 PM EST Sat Nov 22 2014

...Strong winds expected early Monday through late Monday
afternoon...

The synoptic pattern this afternoon features two significant PV
anomalies of note, one across the Southeast with another further
west across MO/AR.  These anomalies will phase through the short
term period, leading to a rapidly deepening surface low across the
Midwest and Great Lakes region tonight into early Monday.

The forecast is playing out largely as expected with this system
thus far.  Isentropic ascent on the nose of a 50-60 knot low-level
jet has led to widespread shower development this afternoon.  This
activity will continue to develop and expand northeastward from the
southwest late this afternoon into this evening, leading to a
widespread swath of precipitation.  Not overly sold on the thunder
potential given mostly moist adiabatic lapse rates, but forecast
soundings do show just enough elevated instability for an embedded
rumble or two of thunder.  QPF amounts tonight look to range from a
half inch across the eastern CWA to around an inch across southern
Indiana.

The upper-level and associated surface pattern becomes a bit more
complex tonight.  One surface low seen swirling across portions of
AL/LA this afternoon will push north into KY this evening.  The
pressure gradient will increase as this low approaches this evening
into the overnight hours.  However, it appears that low-level lapse
rates will remain quite poor and a near-surface stable layer should
limit our gusts below Wind Advisory criteria (gusts upwards of 40
mph) for this evening into the early overnight hours as this low
swings through.  However, sustained winds of 20-25 mph with gusts up
to 35 mph do appear possible.

The main wind threat will come early Monday morning into Monday
afternoon.  The aforementioned PV anomalies will phase and a coupled
jet structure will allow for a rapid deepening of the surface low
across IL/IN/MI.  The pressure gradient will really increase across
the Ohio Valley early Monday morning as a strong cold front sharpens
out to the west.  This front will push into the western CWA around
12Z Monday, clearing the eastern CWA by around 18Z.  Low-level lapse
rates will improve ahead and behind this front, meaning strong winds
(around 50 knots just 3000 feet AGL) should mix down.  Will also
have to watch for some convective showers/isolated thunderstorm
right along the front as guidance continues to hint at some SBCAPE,
which would aid in getting showers to a depth around 15k feet.  This
convective potential coupled with the strong low-level wind fields
could make for a few isolated wind gusts perhaps approaching 50 mph
Monday morning.  However, think the synoptic wind gusts will be
around 40-45 mph Monday morning into early Monday afternoon.  Given
these forecast wind speeds, will be hoisting a Wind Advisory for
tomorrow.

The pressure gradient will relax by Monday evening, which will allow
the winds to die down a bit.  Behind the front, much cooler air will
spill into the region with overnight lows on Monday dropping into
the low to mid 30s.

.LONG TERM (Tuesday through Sunday)...
Issued at 300 PM EST Sun Nov 23 2014

The first part of this forecast period has higher confidence,
whereas the mid and latter part actually are coming up a little now
that the 12Z Euro has moved closer to the other model solutions.
Tuesday, we`ll see high pressure moving across the Ohio Valley, with
temperatures back below normal (a condition likely to persist
through this forecast period). Tuesday night will be chilly as well,
with light winds and mostly clear skies. A hindrance to that may be
thickening high clouds over the southeast forecast area, as a low
pressure system deepens off the GA coast.

The 12Z European has changed its tune from the last several model
runs about the low pressure system dropping into the Midwest
Wednesday. The previous several runs called for a much deeper low,
well outside of the spread of MSLP in the ensembles from the
GFS/GEM/NOGAPS. This run now is in line with the GFS, and is finally
helping to increase the confidence in what the models are seeing.
Thus the forecast will contain a little higher confidence in precip
during the day Wednesday, which would be in the form of rain, as we
see highs in the low to mid 40s.

Wednesday night and even Thanksgiving morning, we will continue to
see some chance for light snow across the area, as the flow aloft
brings a fetch of moisture from the Great Lakes and works with some
lift across our eastern forecast thanks to topography. We dry out
for Friday and then get some warm air advection back in here Friday
night, which may lead to some light precip, ahead of another cold
front forecast to move across the region some time during the next
weekend. Model forecasts are a little spread here, so will not get
too specific on timing at this point.

&&

.AVIATION (00Z TAF Update)...
Updated at 642 PM EST Sun Nov 23 2014

Wind will make for uncomfortable flying conditions, and ceilings
(and to a lesser extent visibilities) will add to planning
challenges during this TAF period.

Low pressure over Missouri this evening will strengthen as it
charges northeast into Michigan tonight and southeast Canada
tomorrow, dragging a cold front through central Kentucky Monday
morning.

South to southeast winds will be strong and gusty this evening out
ahead of the low. Though winds of 45 to 50 knots will be possible
this evening between 1500 and 2000 feet off the surface, surface
winds are expected to be strong enough and directional shear minor
enough such that we should fall just shy of LLWS criteria.

The main shield of rain will sweep northeastward out of central
Kentucky about the time the TAF period starts.  Scattered showers
are then expected for the rest of the night with MVFR ceilings
prevailing.

Winds will be quite strong Monday, especially in the morning as the
cold front moves through and takes winds to the southwest and then
WSW.  MVFR ceilings will continue through the day.  The best chance
for showers will be in the morning coincident with FROPA.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...WIND ADVISORY from 4 AM EST /3 AM CST/ to 7 PM EST /6 PM CST/
     Monday FOR KYZ023>043-045>049-053>057-061>067-070>078-081-
     082.

IN...WIND ADVISORY from 4 AM EST /3 AM CST/ to 7 PM EST /6 PM CST/
     Monday FOR INZ076>079-083-084-089>092.

&&

$$

Update.........13
Short Term.....KJD
Long Term......RJS
Aviation.......13




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