Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 261713
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1213 PM EST Thu Feb 26 2015

...Updated Aviation Discussion...

...Forecast Update...
Issued at 1115 AM EST Thu Feb 26 2015

Bumped up highs across the area a few degrees as sky cover has been
a bit less than anticipated and readings are already in the upper
20s to mid 30s. Snow showers moving in are drying up and radar
returns upstream have noticeably diminished. Trimmed back POPs a bit
and refined some timing. Overall, some conversational snow showers
through the afternoon will be possible. Not expecting more than a
dusting, if at all.

Issued at 845 AM EST Thu Feb 26 2015

Updated morning POPs to time snow showers moving in from Indiana and
Illinois. As the upper wave passes, the forcing begins to weaken out
and lift isn`t overly impressive. Nonetheless, still expecting
scattered snow showers to cross the entire area, ending northwest to
southeast by early evening. Adjustments were made to sky cover to
account for clear slot ahead of the approaching system and to refine
temperatures this morning per observations. Highs remain on track
from the upper 20s to mid 30s.

.SHORT TERM (Now through Friday)...
Issued at 300 AM EST Thu Feb 26 2015

Light snow, with total accumulations of mostly less than one inch
will end during the predawn hours southeast of a line from Bowling
Green through Richmond, which is located in Madison County. Will let
the ongoing Winter Weather Advisory currently in effect for the Lake
Cumberland Region expire naturally at 430 am.

Arctic high pressure building southwards into Iowa will push much
colder air into the Commonwealth beginning this afternoon. North
winds will freshen up to 10 to 12 mph later today, with
nearly steady or slowing falling afternoon temperatures. Tonight and
Friday will become quite cold as the center of this sprawling high
pressure moves across Illinois. Even with mostly to partly cloudy
skies tonight, lows will fall to into the low teens to around 10.

Forecast soundings hint at steepening lapse rates this afternoon and
still some moisture between 3 and 7 kfeet at temperatures colder
than -12C. Flurries will become likely late this afternoon and
evening, with a chance of scattered snow showers. Any snow showers
should be light enough for scattered totals of just a few tenths of
an inch. Roads in some locations that experience a heavier snow
shower may become briefly white and slick.

With the proximity of high pressure Friday, north winds will become
light. Highs will stay very cold, only rising into the lower to mid
20s.

.LONG TERM (Friday Night through Wednesday)...
Issued at 322 AM EST Thu Feb 26 2015

Friday Night through Monday...

Arctic high pressure center to the north will slowly move eastward
across the northern Ohio Valley Friday night and Saturday.  This
will result in a generally quiet weather period from Friday night
through Saturday.  While the weather will be quiet, it will be quite
cold across the region.  Lows Friday night remain quite tricky as
the model guidance is wanting to advect in some higher level
moisture into the region.  This may result in more cloudiness than
the previous forecast indicated and perhaps warmer overnight minimum
temperatures.  For now have gone with the RawBlend guidance and cut
it by a few degrees.  This results in near zero readings across our
far north with mainly single digit readings north of the WK/BG
Parkways...with lower teens south.  Temperatures should rebound a
bit on Saturday with highs rising to near 32 in the north with
mid-upper 30s down along the KY/TN border region.

By Saturday night, the first in a series of mid-level waves will
move in from the west.  An increasing southerly flow ahead of this
wave will allow temperatures to bottom out in the middle of the
night, but then start to rise toward morning.  Leading edge of
precipitation should make it into our far western and northwestern
counties late Saturday night.  Initial precipitation type still
looks to be more of a wintry mix at this time.  As the day wears on
Sunday, the increasing southerly flow in the low-levels will allow
temperatures to warm above freezing resulting in precipitation going
over to plain rain.  Rain looks to continue into Sunday night and
Monday.  With colder air pushing back in late Sunday night, the
precipitation may change back over to a wintry mix...especially
across our northern sections.  Precipitation should diminish in
coverage during the day on Monday, with the highest chances down
across the south.  This will be a short precipitation reprieve as
the next wave approaches by Monday night.

Highs Sunday look to warm into the upper 30s to around 40 in the
north with mid-upper 40s across far southern KY.  Lows Sunday night
look to cool into the upper 20s to the lower 30s in the north with
mainly low-mid 30s across the south.  Highs on Monday will range
from the upper 30s in the north to the mid 40s in the far south.

Monday Night through Wednesday...

By late Monday night, the global models are in agreement with
increasing the ridging across the SE US in response to a deepening
trough over the desert southwest.   The 26/00Z operational GFS and
European models are general agreement with this configuration and
show a surface wave moving from the Plains northeastward into the
southern Great Lakes.  The ensemble solutions are generally similar
here as well with this pattern.  As the surface low pushes toward
our region, it is likely that a stronger south to southwesterly flow
will develop and pump both moisture and added warmth into our area.
The moisture and warmth will result in moderate to occasionally
heavy rainfall over our from Tuesday through early Wednesday.  Some
weak instability looks increasingly likely, so some thunderstorm
activity can not be ruled out.

Model QPFs continue to be wide ranging in both amounts and
placement.  The Euro solutions of late generally show 2-3 inch
rainfall amounts across the region during the middle of next week.
The GFS appears to be suffering from some convective feedback issues
as it was painting some 6+ inch amounts across the state.  Even if
the lower amounts from the Euro were to verify, these QPF amounts,
combined with snowmelt and already saturated ground, may result in
hydrologic issues across the region, including localized flooding
and rapid rises on area creeks and streams.  This will be something
to watch over the next several days.

Temperatures will be challenging depending on the extent of snowpack
and the strength of the southerly flow.  The latest model solutions
are a little more aggressive suggesting that lower 60s may penetrate
into southern KY by Tuesday afternoon.  Overall, that seems
reasonable, given the upper level pattern.  However, we plan to go a
bit more conservative with that since there continues to be
fluctuations in the northward extent of warmth in the last several
model runs.  For now, plan on pushing temps solidly into the 40s for
Wednesday with mid-upper 50s across southern KY.  The relative
warmth will be brief as colder air will work back in beginning
Wednesday with highs cooling back into the lower 40s in the north
with upper 40s in the south.  The core of the colder air looks to
arrive by Thursday and continue into the weekend as another Arctic
high drops into the central US.

&&

.AVIATION (18Z TAF Update)...
Issued at 1210 PM EST Thu Feb 26 2015

Broken strato-cu with bases mainly VFR will slowly move over the TAF
sites this afternoon. However, drier air and overall weakening of
the system will limit coverage somewhat. As a result, removed VCSH
from TAF but still could not rule a brief snow shower or flurry
though impacts to aviation should be minimal. Confidence in sub-VFR
clouds increases this evening as better/deeper moisture pivots into
central Kentucky associated with fetch from the Great Lakes. Plan on
winds 5 to 10 kts to remain out of the north through the period.
Overnight, stratus could be stuck across the area beneath the low
level inversion, with the highest probability at LEX. Look for
scattering of the clouds between 12-18z Friday as high pressure
moves in.

&&

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

$$

Update.........ZBT
Short Term.....JSD
Long Term......MJ
Aviation.......ZBT





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