Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 272150
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
450 PM EST Thu Nov 27 2014
Issued at 440 PM EST Thu Nov 27 2014
Updated the forecast to add scattered flurries through the evening
hours. Regional radar showed a batch of flurries over southwest
Indiana headed ESE into our region. Also, there was another batch
of flurries near Cincinnati and into the northern Bluegrass. Thus,
added the flurry mention through 2z.
.SHORT TERM (Now through Friday Night)...
Issued at 255 PM EST Thu Nov 27 2014
Deep and cyclonically curved NW flow has set up over the Ohio Valley
as the departing Clipper gives way to a 1036mb Arctic high building
from the Upper Midwest. This setup has kept our weather cloudy and
somewhat raw, with unseasonably cool temps and modest NW breezes.
Surface obs over central Illinois and Indiana have shown light snow
off and on, but the precip on radar has diminished substantially
over the last couple hours.
Some hint of a weak disturbance in the NW flow aloft making its way
across Illinois, and this could be responsible for the snow in that
area. This feature is becoming more sheared out, so at this point
expecting even any flurries to remain to our north and east as it
scoots past this evening. Should be a window of clearing for much
the overnight period, allowing temps to get quite cold before a
mid-level deck works in around daybreak. Normally would lean toward
the warmer end of guidance, but since we are already starting off so
cold, will split the difference with lower/mid 20s in most
locations. Traditional cold spots will likely dip into the teens.
By midday Friday the ridge axis will already be retreating into
eastern Kentucky, but return flow looks quite weak. Mid-level
moisture and associated clouds will hold temps back as well,
especially across the Bluegrass region. Should see the most
substantial moderating trend over south-central Kentucky. Will open
a range from upper 30s in the Bluegrass to mid/upper 40s near
Bowling Green. Moderating trend continues Fri night as SSW return
flow keeps temps up. Will even see a slight non-diurnal trend with a
quick evening drop, then flatline or even rising temps after
.LONG TERM (Saturday through Thursday)...
Issued at 305 PM EST Thu Nov 27 2014
Saturday - Monday Night...
The Ohio Valley will be sandwiched between a surface high along the
Atlantic coast and low moving from the upper Midwest into eastern
Canada through the weekend. Meanwhile, flow will transition to
southwesterly aloft. The steady southerly flow will allow for milder
temperatures, and an initial shallow layer of moisture to pool into
the area Saturday, gradually increasing in depth through the
weekend. Meanwhile, a cold front trailing from the northern surface
low will slowly work into the area. This will set the stage for
isolated to scattered chances of measurable rain Saturday through
Sunday, with better chances Sunday night into Monday. Will see
milder temperatures on Saturday in the low and mid 50s, with Sunday
into the 60s despite heavy cloud cover. Temperatures will be tricky
on Monday due to the timing of the slow frontal passage. Will
mention likely chances for measurable rain on Monday, where a tenth
to a quarter of an inch seems reasonable.
A strong surface high begins to push into the area Monday night,
shunting the front and associated deeper moisture south. Expecting
pretty cool overnight lows by dawn on Tuesday along and north of
I-64, however will continue to leave frozen precipitation off the
table as deep moisture is expected to be gone by the time colder air
Tuesday - Thursday...
Low confidence for this portion of the forecast as models continue
to diverge greatly on the upper air pattern through mid week. Do
want to keep the forecast trended toward a drier solution until more
confidence can be gained. That being said, still need to keep some
mention Tuesday and Tuesday night mainly across our east where
lingering low level moisture will be most prevalent and may
interact with a developing central CONUS trough.
Temperatures for Wednesday/Thursday are also low confidence as we
will either be dealing with a warm sector and steady southerly flow
beneath an upper ridge, or under the influence of troughing and a
polar high. Its going to be one or the other, with one solution mild
and the other quite cold. Prefer to lean toward the warmer solution
at this time as it has support from its ensemble mean, its parallel
run, and the NAEFS.
.AVIATION (18Z TAF Update)...
Updated at 1220 PM EST Thu Nov 27 2014
Deep and cyclonically curved NW flow has developed over the Ohio
Valley in the wake of the overnight Clipper. Low cloud deck has hung
in all morning, with persistent MVFR ceilings that have just barely
managed to lift above fuel-alternate thresholds. Expect status quo
through most of the afternoon with high-end MVFR and NW winds around
After sunset look for winds to diminish and ceilings to scatter out.
Another impulse will swing through overnight, but impact will be
minimal as it will only bring in a mid-level ceiling. Light south
winds and VFR conditions expected on Fri.