Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 171900
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
300 PM EDT Mon Mar 17 2014
.SHORT TERM (Now through Tuesday Night)...
Issued at 300 PM EDT Mon Mar 17 2014
Short Term Synoptic Overview
Closed off upper level low over the northern Gulf is forecast to
move eastward tonight pushing a large mid-latitude storm off the
eastern US coast. Across the Ohio Valley, low-level moisture
trapped beneath a developing temperature inversion will result in
continued low-level cloudiness that will be slow to mix out.
Low-level moisture combined with light winds will likely lead to the
development of fog across the region tonight. Fog will probably be
most abundant across central and southern KY where better moisture
resides. Southerly return flow will start during the day on
Tuesday. However, quality of moisture and warmth will be limited as
fast moving mid-level wave approaches the region toward the end of
the forecast period.
Model Preference & Confidence
Generally stuck close the short term multi-model consensus which
bears close resemblance to the 09Z SREF. Forecast confidence on
precipitation though the forecast period is above average. Average
confidence exists on temperatures. Sensible weather impacts such as
fog are slightly below confidence due low stratus which could hinder
fog development in some places overnight.
Sensible Weather Impacts
In the very near term, visible satellite imagery continues to show
extensive area of low stratus across the NW and SE sections of the
forecast area. In the area between Bowling Green and Lexington,
sufficient mixing has occurred and skies are clearing out nicely.
This clearing is slowly expanding northwestward and will work in to
the Louisville metro area over the next few hours. Clearing will
also develop around the Lexington metro area as well. Where the sun
has come out, temperatures have spiked upward. Ky Mesonet
temperatures in the clearing area are in the lower to middle 40s
while areas in the clouds remain in the lower 30s. Overall thinking
is that clearing will eventually work its way into southern Indiana
this evening. Less certain is the clearing across our far east and
southeastern sections (Lake Cumberland region). Current thinking is
that low clouds will likely remain in areas along and SE of a line
from Glasgow to Richmond. Temperatures in the near term will
continue to rise in the clearing areas with middle-upper 40s being
easily attainable. In the cloudy areas (like SW IN and SE KY),
middle 30s is probably the best that we`ll be able to do.
For tonight, expect clear to partly cloudy skies across the region.
Best clearing will be across our northwestern sections while most
cloudy conditions will be across the SE. Latest model data suggests
that low-level moisture will remain quite high below the developing
inversion aloft. This is suggestive of fog developing across the
region. The most tricky part will be across our SE where thicker
stratus will remain. It is certainly possible that the low stratus
may build down in depth toward the surface in this region. For now,
have gone with patchy/areas of fog across the region. Feel that the
most dense will be across central KY. Will need to monitor the
development overnight as area could be large enough to warrant a
dense fog advisory in later forecasts. Overnight lows look to cool
to near freezing across the northwestern half with middle 30s across
the SE sections.
For Tuesday, morning low clouds and fog will likely hang on into the
mid-morning hours. This will limit insolation a bit. In addition,
southerly flow will likely not kick in til later in the afternoon.
As such, the guidance has cooled slightly in the last 24 hours
suggesting highs will likely top out in the middle-upper 50s in the
north with upper 50s to near 60 across the south.
Cloud will be on the increase Tuesday night ahead of the next
mid-level wave approaching from the northwest. Majority of model
guidance suggests that any precipitation will likely hold off until
after midnight. Therefore, slight chance PoPs for late tomorrow
night still look good. Pressure gradient will increase a bit, so
expect surface winds to increase Tuesday night and it may be gusty
at times. The breezy conditions will keep temperatures from falling
off too much. Lows in the 40s look likely based on the latest data.
.LONG TERM (Wednesday through Monday)...
Issued at 245 PM EDT Mon Mar 17 2014
The long-term period will feature an overall progressive and fairly
quiet pattern across the Ohio Valley. There will be two frontal
passages that will bring a chance of precipitation. The first front
will move through Wednesday morning. The pressure gradient will
strengthen with this system, leading to wind gusts between 25 and 35
mph. Moisture return for this system does not look too favorable for
widespread precip at this time. So, expect scattered rain showers to
accompany this front, which will quickly move east during the day
High pressure will slide across the area Wednesday night through
Friday. The next front will approach Friday night and move through
the area Saturday morning. This system will have more moisture to
work with, leading to better areal coverage and higher precip
amounts. It still appears to have a little elevated instability, so
a few rumbles of thunder are certainly possible. High pressure will
then slide across the area Saturday night through Monday, for a dry
As for temperatures, highs will generally be in the 50s to lower 60s
for much of the long-term period. Lows in the 30s and 40s will be
common through the weekend, then trend a little cooler heading into
next week. The warmest day will be Friday, ahead of Saturday`s cold
front. On breezy southwest winds, temperatures should range from the
middle 60s to lower 70s Friday afternoon.
.AVIATION (18Z TAF Update)...
Updated at 120 PM EDT Mon Mar 17 2014
Recent visible satellite imagery shows an expansive area of low
stratus across southern Indiana and central Kentucky. The clouds
are mixing out along a corridor between KBWG and KFFT. Expect this
mixing to continue and expand in size through the afternoon hours.
The clearing will likely affect the KSDF and KBWG terminals starting
around 17/20Z. Should also see some improvement in ceilings over at
KLEX...though it may be a little later as satellite data show
stratus trying to build back northwestward a bit. Surface winds
will remain out of the northeast this afternoon with speeds of
Main forecast challenge tonight will be the development of low
clouds and potential fog. Latest statistical guidance suggests at
least to some MVFR visibilities at all the terminals with higher
risks of IFR visibilities at KLEX and KBWG. For now, have trended
the forecast a bit more pessimistic at KBWG and KLEX with high end
IFR visibilities between 18/08-14Z.