Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 220715
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
315 AM EDT Wed Oct 22 2014
.SHORT TERM (Now through Thursday)...
Issued at 305 AM EDT Wed Oct 22 2014
...Frost likely across the region late tonight...
Cyclonic flow around a stacked low pressure system along the
mid-Atlantic coast is beginning to lose its grip on the Ohio Valley.
One more lobe of low clouds will pinwheel south across the Bluegrass
region this morning, but should give way to pleasant fall conditions
by midday. That will leave us with a temperature forecast for the
balance of the short term, and that is significant due to the
potential for frost tonight.
High pressure centered over Wisconsin this morning will modify
slightly as it builds southeast today, leaving a weaker ridge axis
over Indiana and central Kentucky tonight. This along with clear
skies will mean ideal radiational cooling conditions, allowing temps
to easily drop into the 30s. Look for mainly upper 30s in the cities
and west of I-65, but most rural locations across the Bluegrass
should dip into the mid 30s easily. Can`t even rule out a freeze in
some of the more sheltered valleys. Will go with areas of frost from
the Bluegrass region south to Lake Cumberland, with just patchy
frost across most of the remainder of the area. Based on
coordination with neighboring WFOs, will leave the issuance of any
frost/freeze headlines to the day crew.
Daytime temps will run below climo, but some uncertainty as to just
how much. Temps have overachieved recently, but the shallow cold air
and N-NE flow favors cooler temps. Will still lean toward the warmer
GFS MOS given Tuesday`s overachieving temps to our NW.
.LONG TERM (Thursday night through Tuesday)...
Issued at 302 AM EDT Wed Oct 22 2014
A weak shortwave trof will move through the region at the beginning
of the long term, and may bring a few instances of sprinkles or
light rain to southern Indiana and north central Kentucky late
Thursday night into early Friday morning. High pressure building to
our south will cut off any substantial moisture supply, though, so
most locations will experience increasing clouds but dry conditions.
Lows Thursday night will mostly be in the 40s, but the eastern
valleys will slip into the upper 30s. Decided to go on the cool side
for high temperatures Friday given expected clouds, but readings
should still peak in the 60s.
Weak surface ridging will give us quiet weather Friday night with
low temperatures in the 40s. On Saturday a cold front will push
through from the northwest, but it will be weakening as it does so
and will be bereft of any deep moisture. So, the forecast will
remain dry, with highs in the 60s.
Saturday night through Monday night high pressure will travel from
the Red River of the North to Cape Hatteras, continuing our placid
weather. Low temperatures during this period will moderate from mid
40s to mid 50s, and highs from the upper 60s to mid 70s.
Tuesday a cold front will approach from the west and bring a chance
of showers, especially by afternoon west through north of
Louisville. Highs will reach the 70s.
.AVIATION (06Z TAF Update)...
Updated at 1245 AM EDT Wed Oct 22 2014
The western edge of a broad area of strato-cu extends across Indiana
and central Kentucky, and has been slowly eroding from the west and
south. LEX is the one sure bet to maintain a ceiling through the
night, but it is initially VFR. However, lower strato-cu with MVFR
ceilings lurks over western Ohio, and models suggest that these
lower clouds could pinwheel southward into LEX shortly before
daybreak. Look for a few hours of MVFR ceiling, but will stay above
fuel-alternate thresholds. SDF will be a last-minute decision
whether we even carry a ceiling.
At BWG the bigger question is fog. Looks like we are well on track
to cross over afternoon dewpoints, but with drier air filtering in
and light north winds that might not stay completely calm, there is
some uncertainty. Believe that there will be fog, but it should be
less dense and less persistent than what we had Tuesday morning.
Will carry a TEMPO for IFR conditions.
Once mixing gets going around mid-morning, look for VFR conditions
and unlimited ceilings for the rest of the TAF period. Light north
winds and diurnal cu will diminish around sunset.