Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 282323
Area Forecast Discussion
National Weather Service Louisville KY
623 PM EST SAT NOV 28 2015
...Updated Aviation Discussion...
.SHORT TERM (Now through Sunday Night)...
Issued at 300 PM EST Sat Nov 28 2015
Afternoon surface analysis reveals a cold front located just south
of the Ohio River. In the frontal wake, winds were out of the north
across southern IN and far northern KY. Temperatures north of the
front were in the upper 40s. On the southern side of the front,
large shield of rainfall continued to work eastward across the
Commonwealth. Temperatures were generally in the upper 50s to the
lower 60s. In the near term, we expect the rain showers to continue
to stream eastward across the region. The highest chances of rain
will be generally south of the Ohio River across KY with more
scattered rain showers across southern Indiana. Temperatures will
max out in the next hour and then slowly fall this evening.
For tonight, model soundings continue to show a rather deep
saturated atmosphere across the region. As the front sinks
southward, near surface cool layer will ooze southward and will
likely result in an near surface inversion developing. This would
likely result in a continued cloud ceiling build down and perhaps
development of patchy/areas of fog. The fog potential looks to be
most likely contained to southern Indiana and much of north central
KY (generally areas north of the stalled out front). Therefore,
will continue to mention patchy fog in the forecast for the
overnight period. Periods of showers will continue to move through
the region overnight. The highest PoPs will be confined to central
and southern KY with lesser chances up across our southern IN
counties. Low temperatures tonight will cool into the lower-mid 40s
across southern Indiana and parts of north-central KY. Upper 40s to
the lower 50s look likely for low across southern KY.
For Sunday/Sunday night, clouds and periods of showers are likely
once again as the frontal boundary remains stalled out across
southern KY. Have continued to trend the forecast a little drier
across southern Indiana and far northern KY as the main lift/forcing
will remain across southern KY. Plan on keeping likely-categorical
PoPs across southern KY for Sunday and Sunday night. Highs during
the day on Sunday will likely top out in the upper 40s to around 50
across southern IN and northern KY. Lower-mid 50s look likely
across southern KY. Lows Sunday night will cool into the lower-mid
40s in the north with mid-upper 40s across the south.
.LONG TERM (Monday through Saturday)...
Issued at 310 PM EST Sat Nov 28 2015
Early in the period, the upper level low over the Intermountain West
will start to kick out and head eastward. This feature will cross
the Midwest on Tuesday and then head into the Great Lakes states by
Wednesday. This upper level low`s surface cyclone will move
slightly ahead of the main feature. The stalled out front to our
south will lift back northward as a warm front across our region on
Monday/Monday night followed by the cold front pushing through the
region on Tuesday. Sensible weather will be more of the same of
what we`ve seen since the weekend...clouds and periods of rain
showers for Monday and into Tuesday. A brisk west-southwest flow
will overspread the region on Tuesday, so surface winds may pick up
a bit on Tuesday with the cold frontal passage. Instability still
looks rather meager ahead of the front, so thunderstorm chances
remain quite limited. Perhaps, a rumble of thunder would be
possible down across the far south along the KY/TN border/Lake
Upper trough axis will swing through the region on Wednesday with a
rather large area of surface high pressure building eastward out of
the Plains. The high will translate eastward and will keep our
region dry from Wednesday through next Saturday. Given that this
high is of Pacific origin and that we`re likely to continue to see a
flood of modified Pacific air pushing through the CONUS, temperatures
will remain seasonal if not a bit above normal for the forecast
period. Highs Monday/Tuesday will be the warmest with readings in
mainly in the 50s and overnight lows in the in the 30s. A cool shot
will come into the region on Wednesday with highs in the 40s and
overnight lows dropping into the lower 30s. A slow moderation in
temperatures is expected for Thursday through Saturday. Highs
Thu/Fri will top out in the upper 40s to around 50 and warming into
the lower 50s by Saturday. Overnight lows will be lower 30s in most
spots, though a few of our colder locations may drop into the mid-
upper 20s as the high passes overhead Thursday night/Friday.
For the end of the period and beyond, current forecast
teleconnection indices look to be in a +EPO/+AO/+PNA/+NAO pattern.
With a large positive height anomaly developing over central Canada
due to large negative height anomalies being centered over Bering
Strait and over southern Greenland. This will lead to a split jet
pattern once again with disturbances rolling through the southern
stream resulting in an upper level cut off low developing over the
western CONUS and then lifting out across the Plains and into the
Great Lakes. This would likely bring another swath of wintry
weather to the Rockies northeastward through the northern Plains,
while bringing the Ohio Valley another round of disturbed
weather (rain showers) centered in the 12/7 to 12/8 time frame.
.AVIATION (00Z TAF Update)...
Updated at 610 PM EST Sat Nov 28 2015
Cold front situated just south and east of SDF is expected to make
very slow progress tonight, which really limits confidence in BWG
and LEX wind forecasts. Fortunately wind speeds are weak enough to
minimize the impact, and we could have a period of light/variable
Bigger challenge is ceiling and vis, and just when BWG and LEX will
drop into IFR to stay as the strong frontal inversion makes its way
south and east. This forecast will have the ceilings going down
shortly after the valid time of the TAFs, but initialization will be
a last-minute decision. May even be able to start above fuel-
alternate, but that will not last long.
By mid-evening we should be IFR across the board, and as the
inversion strengthens the stratus will build down into LIFR.
Visibilities will drop to just a mile or two as well, especially if
the stratus builds down into a fog. Rain may taper off to drizzle
after midnight, especially at SDF, but cig/vis will remain just
above minimums (if at all) through the night).
As the front continues a slow push to the south, SDF has the best
chance of breaking into MVFR on Sunday afternoon, but ceilings will
remain below fuel-alternate. BWG and LEX will be closer to the
front, and the strong inversion will keep ceilings solidly in IFR
through the valid TAF period.