Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 021703
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1203 PM EST Mon Mar 2 2015

...Updated Aviation Discussion...

.SHORT TERM (Now through Tuesday)...
Issued at 315 AM EST Mon Mar 2 2015

Surface cold front continues to push southward into Tennessee this
morning.  Some light precipitation continues to trail behind the
front across south-central KY.  Temperatures remain at or just above
freezing in southern KY which is keeping the precipitation in liquid
form.  As the precipitation moves on out, the colder air will
continue to funnel in and a short period of light freezing rain or
freezing drizzle will be possible down across those regions.  A
light glaze may develop on some road surfaces down that way.  A
Special Weather Statement has been issued to cover those threats.
Elsewhere, mostly cloudy skies were noted across the region.
Temperatures were generally hovering around the 31-32 degree
mark. We expect the cloudy skies to continue, but some partial
clearing will work southward out of Indiana toward dawn. Lows
still look to cool into the upper 20s to the very low 30s.

For today, surface high pressure will build into the region and
continue to funnel drier air into the region.  Skies are expected to
become partly cloudy by mid-late morning and into the afternoon
hours.  Temperatures will likely top out in the mid-upper 30s in the
north with upper 30s to the lower 40s across the south.

For tonight, the high will move off to the east and the cold front
that passed through on Sunday will retreat back northward as a warm
front.  Near surface temperatures will cool into the upper 20s in
the north with lower 30s in the south late tonight. However, a
low-level jet axis will send a surge of warmer air in aloft.
Precipitation is expected to develop within in this warm air
advection type pattern across AR/TN/MO and gradually spread
northeastward overnight.  Current thinking is that southern KY will
stay warm enough for all liquid precipitation tonight.  However,
areas along and north of the BG/WK Parkways will see temps drop
below freezing and initial precipitation will likely be a light
wintry mix of freezing rain and perhaps a little sleet.

The wintry mix will likely be short-lived as the warmer air to the
south will quickly spread northward throughout morning hours.
Temperatures are expected to warm into the 40s by late morning and
then through the 50s in the afternoon.  There looks to be a gradient
of temperature across the region with readings topping out in the
low 50s in the north with lower 60s down along the KY/TN border.
Widespread light to moderate precipitation is expected across the
region on Tuesday.  Some elevated instability is likely to develop
during the afternoon hours which will likely result in some heavier
showers with some thunder embedded.  Given the good model agreement
here, have gone ahead and pushed PoPs for Tuesday up to 100%.

.LONG TERM (Tuesday Night through Sunday)...
Issued at 335 AM EST Sun Mar 2 2015

...Potentially Significant Rain and Snow Expected through Mid Week...

A low pressure system will track across the upper Midwest through
Tuesday and join with a stronger low tracking across Canada Tuesday
night. This will drag a strong cold front through the area late
Tuesday night into Wednesday morning.

Tuesday Night

At the beginning of the night the area will be solidly in the warm
sector with temperatures ranging from around 50 in the north to
around 60 in the south. Temperatures will begin to fall swiftly
overnight after the front moves through. Far northern portions of
southern IN will fall to near freezing by 12Z Wednesday. However,
for the most part, precipitation will stay all rain Tuesday night.
Have kept the mention of thunderstorms in for the overnight period
given soundings continue to indicate some elevated instability. With
precipitable water values an inch to an inch and a quarter, there
will be plenty of moisture to work with. Rainfall amounts will be
one to possibly two inches overnight and some gusty winds will be
possible with thunderstorms.

Wednesday - Thursday

The latest suite of guidance indicates the potential for a
significant winter storm Wednesday through Wednesday night.
Temperatures will be falling quickly through the day on Wednesday
while precipitation will continue in the wake of the front. Thus
precip will change from rain to snow through the day. As is typical
for this type of system, there is some question of temps aloft and
whether there will be a period of sleet before the changeover to all
snow. For now it looks like most of the area could change over to all
snow by mid to late afternoon.

For Wednesday evening and night a shortwave will approach the area.
Most of the models, excluding the GFS, shows this wave will bring
another wave of precipitation across the forecast area. The GFS is
much further suppressed with the precip and moves it out quicker.
Have leaned more towards WPC guidance and ensembles with this
forecast which would bring more significant snow to much of the area
Wednesday night. There will likely be a sharp northern cutoff to
this system which at this time looks to be across southern IN.
However, even given that, it is looking likely at this time that
much of the forecast area will eventually reach Warning criteria for
snowfall Wednesday afternoon through Wednesday night. The caveat
would be if the more progressive GFS pans out. Then lighter amounts
would be expected, particularly across the northern half of the
forecast area. Light snow may linger across east central KY into
Thursday morning, but the most significant snow should be out of the
area by that time.

Thursday Night - Sunday

High pressure will build in behind the front and remain over the
area through Saturday. The next shot for precipitation could be on
Sunday. Temps Friday morning will likely be very cold under the high
pressure. Look for lows in the single digits or possibly lower.
Temperatures generally look to warm thereafter through the weekend.
We could have highs in the mid 40s by the weekend.

&&

.HYDROLOGY...

Issued at 340 AM EST Mon Mar 2 2015

The remaining snow pack across the area contains anywhere from about
a half inch up to two inches of liquid in a few locations.
Temperatures today will rise to the 30s to 40s helping to melt more
of this snow pack.

A new storm system will move into the region Monday night. At this
time, it appears that southern Indiana will see one to two inches of
rain on Tuesday and Wednesday. Kentucky will see two to three inches.
Since soils will be saturated from snow melt, the new rains could
trigger flooding.

It appears that flooding on the major rivers would likely start
around midweek and continue into the weekend. This would affect the
Salt, Green, Licking, and Kentucky river basins. Minor flooding on
the Ohio River could occur as well. Residents in flood prone areas
should closely monitor water levels over the coming days and be
prepared for possible flooding by mid to late week.
&&

.AVIATION (18Z TAF Update)...
Issued at 1145  AM EST Mon Mar 2 2015

Light NE winds and cirrus ceilings expected this afternoon, but a
lowering and thickening of cloud cover will take place through the
night as an incoming storm system takes shape. Can`t rule out some
light rain or drizzle at SDF and LEX toward daybreak, and temps will
be very close for FZRA or FZDZ. Probabilities still low enough that
it will not be included in the TAF at this time.

Will see MVFR ceilings by daybreak, and go fuel-alternate fairly
quickly. Precip shield moves in Tuesday morning, initially as light
stratiform rain. IFR conditions are quite possible at some point,
but not yet confident enough in getting that low, so will go with
borderline IFR/MVFR ceiling and visibility. By the afternoon
planning period at SDF, we`ll get into more of a warm sector regime
with heavier and more showery precip on stronger SW winds.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&

$$

Short Term........MJ
Long Term.........EER
Hydrology.........EER
Aviation..........RAS






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