Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 221400
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1000 AM EDT Wed Oct 22 2014
Issued at 955 AM EDT Wed Oct 22 2014
Updated the forecast to tweak sky cover grids to current satellite
trends. The Bluegrass should see low clouds through the morning
hours before becoming only partly cloudy. Also increased high temps
for today since we overachieved on high temps yesterday and mostly
sunny to partly cloudy skies are expected over the region today.
High temps should range from the upper 50s to lower 60s.
.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 (12Z TAF Update)...
Updated at 630 AM EDT Wed Oct 22 2014
Prevailing VFR conditions and light N-NE winds are expected through
the valid TAF period, with just a couple of caveats. First issue in
the near term is one last lobe of strato-cu pinwheeling south into
central Kentucky. Expect LEX and possibly SDF to get a barely-VFR
ceiling by issuance time. Can`t rule out high-end MVFR in LEX based
on upstream obs, but will keep it VFR unless it shows its hand
before issuance. Look for clearing by mid-morning at SDF and late
morning at LEX as upper ridging starts to win out.
Other issue is the potential for fog just before daybreak Thursday.
MOS guidance shows dense fog at all three terminals, and given that
crossover temps are likely to be reached, can`t discount this
solution. Won`t jump on board with dense fog without seeing what
afternoon mixing does for dewpoints, but will carry a TEMPO for
borderline MVFR/IFR visibilities as a heads-up.