Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 220819
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
319 AM EST Sun Dec 22 2013
.SHORT TERM (Now through Monday)...
Issued at 300 AM EST Sun Dec 22 2013
The synoptic pattern early this morning features a broad, deep
trough across the central CONUS, with a downstream ridge across the
far eastern seaboard. This trough will build east into the Ohio
Valley through the short term period, bringing one additional shot
of some light precipitation tonight.
The severe QLCS that rolled through earlier has quickly pushed east
across KY and weakened. This system was quite impressive, bringing
a few instances of 70+ MPH measured winds as multiple bowing
segments developed along the line. Some stratiform rain continues
across much of the region this morning, but will quickly move out by
mid to late morning as the surface cold front finally sweeps
through. Will keep the Flood Watch intact due to the ongoing flood
issues, but any additional rainfall amounts will be quite light. As
of 3AM, the cold front could be seen on reflectivity as a fine line
across Ohio County northeast to Washington County, IN. This front
will progress to the east this morning, bringing much cooler
temperatures in it`s wake. Highs today will be in the morning,
dropping into the 40s and 50s through the daylight hours as cold air
advection ramps up.
Another wave will eject out of the longwave trough tonight. The
main forcing for ascent with this wave will be across southern
Indiana, but the better deep moisture will reside across southern
and eastern KY. This may lead to two areas of very light
precipitation, one across southern IN/northern KY under the best
forcing, and another across southern/eastern KY near the deepest
moisture. Forecast soundings show that this precipitation will
likely fall as some light rain, but soundings are marginal enough
that some light snow mixing in cannot be ruled out. Either way, no
accumulations or impacts are expected.
Much drier air will finally move in on Monday, ending precipitation
chances. A secondary surge of cold air will infiltrate the Ohio
Valley, meaning highs on Monday will remain confined to the 30s and
.LONG TERM (Monday Night through Saturday)...
Issued at 316 AM EST Sun Dec 22 2013
Monday Night through Wednesday Night...
Latest suite of deterministic and ensemble guidance remains in
pretty good agreement through this portion of the forecast period.
Upper trough is forecast to swing through the Great Lakes and the
northern Ohio Valley in the early part of the period. This trough
is forecast to lift northeastward into New England by Tuesday
afternoon with the flow aloft going zonal across our region for
Christmas Eve and into Christmas Day. At the surface, high pressure
is forecast to build into the region from the Midwest and then drift
southeastward across the forecast area. Sensible weather will be
dry conditions with cold temperatures expected.
Lows Monday night are expected to drop into the middle to upper
teens across southern Indiana and the northern half of Kentucky.
Southern Kentucky should see temperatures drop to around 20-22
degrees. For Tuesday, the guidance in the last few days has been
trending slightly colder on each run. The multi-model consensus
continues to come down as well and in turn, we have lowered
temperatures a bit. Highs Tuesday only look to warm into the lower
to middle 20s across southern Indiana and northern Kentucky. Middle
to perhaps some upper 20s will be possible across southern
Kentucky. Christmas Eve looks will be cold as well with lows in the
upper teens to the lower 20s. Christmas day looks cooler as well
with highs mainly in the upper 30s in the north with highs in the
lower 40s down across southern KY. Lows Wednesday night look to
cool into the middle 20s.
Thursday through Saturday...
In the longer term, the multi-model consensus suggests that a
progressive flow aloft will continue across the eastern US. Several
trough and ridge axes will swing through the region during this
period. With each trough passage, we`ll likely see a re-reinforcing
shot of colder air. The first of these upper troughs look to swing
through the region later on Thursday. Without a substantial
southerly flow kicking up ahead of this feature, it looks as if it
will be more moisture starved than in previous forecasts. Most of
the guidance has lowered PoPs and we have trended PoPs down as well
due to the fact that much of the forcing will be concentrated well
to our north. Enough moisture may be available for a few snow
flurries Thursday night across our northern areas.
Secondary wave looks to swing through Friday night and Saturday.
However, this wave will have little moisture to work with and
generally bring another dry front with a reinforcing shot of colder
air from the north.
Highs Thursday look to warm into the upper 30s to the lower 40s, but
readings will take a tumble on Friday with highs only warming into
the lower to middle 30s. Highs Saturday look to warm into the
middle to upper 30s. Overnight lows through the period look to cool
into the 20s. These numbers are right down the middle of the
guidance envelope and are very close to the multi-model consensus
which has been verifying well lately.
Just beyond the forecast period, there some signals within the data
that suggest that a more active weather period may emerge by early
next week (around 12/30). The signals point out that some
amplification of the upper pattern will take place with a fast
moving wave scooting through the Ohio Valley. With cold air in
place, this could bring a period of light wintry weather to the
region. This will be something to watch over the coming week.
.AVIATION (06Z TAF Update)...
Updated at 1223 AM EST Sun Dec 22 2013
Behind the departing storms showers will continue for several more
hours. Will cautiously bring in low-end VFR conditions behind the
squall line, but that may be too optimistic.
Low clouds are then expected to come back in this morning,
especially at SDF.
Gusty WSW winds behind the storms will eventually make it to
northwesterly by Sunday evening.
KY...FLOOD WATCH until 1 PM EST /Noon CST/ this afternoon FOR
IN...FLOOD WATCH until 1 PM EST /Noon CST/ this afternoon FOR