Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 271252
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
752 AM EST Sat Dec 27 2014
Issued at 750 AM EST Sat Dec 27 2014
The area of light rain moving across the region this morning
continues to spread eastward into the Bluegrass. In addition some
light showers will shortly be moving into the Lake Cumberland
region. The forecast was updated to introduce pops to these areas
earlier than previously forecast. It still looks like there should
be a small break in precip before the next wave moves in this
Issued at 600 AM EST Sat Dec 27 2014
First in series of precip chances is overachieving this hour, with
several sites in western KY reporting a few hundredths of an inch of
rain already. Have bumped up pop grids in the west this morning to
account for this trend. Overall zone forecast does not change
because the higher rain chances will be this afternoon.
.SHORT TERM (Now through Sunday)...
Issued at 300 AM EST Sat Dec 27 2014
Rainy short-term period set up by a slow-moving cold front now
stretching from a surface low over eastern Iowa southwest through
central Missouri. Flow aloft will remain southwesterly even as the
front passes us tonight. Disturbances within this flow should bring
periods of rain, given ample moisture streaming in here along with
forcing in the vicinity of the front. The best chances today will be
west of the I-65 corridor through early afternoon, then they pick up
quickly as the day wears on. Rainfall totals of a half inch to an
inch should be common by the end of the day Sunday. Rains should
taper off from west to east as the day goes on Sunday.
Temperatures will be above normal both today and tonight, then with
the front clearing the region around daybreak Sunday, we should see
a near normal day for highs.
.LONG TERM (Sunday night through Friday)...
Issued at 310 AM EST Sat Dec 27 2014
By Sunday evening, the cold front will be nearly parallel to the
flow aloft and therefore would take its time exiting to the south
and east. Will carry chance POPs south and east of a BWG-LEX line
Sunday night to account for this. Temps are warm enough to keep it
all rain. Bubble of high pressure will build in on Monday, with dry
conditions and temps near or just above climo. Cloud cover will
limit diurnal temp recovery, so max temp forecast is a couple
degrees below most of the guidance.
A moisture-starved upper shortwave trof will move into the Great
Lakes Monday night, opening the door for a sprawling Canadian high.
Will close out 2014 and begin 2015 with temps solidly below normal,
but by no means bitterly cold as the upper flow is still fairly
zonal. Coldest part of the week will be New Years Eve into New Years
Day, with afternoon highs Wednesday struggling to crack the freezing
mark, and lows Thursday morning in the teens and lower 20s.
The next chance for precipitation will come Thursday night into
Friday as a system moves in from the southwest. ECMWF is currently
12-18 hrs faster than GFS with onset of precip, so confidence is
limited and the models will likely waffle over the coming days with
most of the details. This will impact p-type as the low crosses the
Ohio Valley. If precip begins Thursday night, it could start off as
a wintry mix before transitioning to rain on Friday. This system
will therefore need to be watched closely in the coming days.
.AVIATION (12Z TAF Update)...
Issued at 610 AM EST Sat Dec 27 2014
A cold front currently moving slowly eastward across Missouri will
bring increasing moisture into the region through the morning hours.
We have seen some light rain showers form just west of SDF this
early morning, but upstream obs are not showing much in the way of
vsby or cig issues with this batch. We should see further rains form
by early afternoon, with cigs lowering through the afternoon hours.
The front likely will not clear the terminals until very late in the
period, but the rains will stick around, with IFR conditions likely
through most of the night and sticking around early Sunday. To
simplify the end of the TAF period just put in one line with
variable winds, but the evening hours should continue with southwest
winds then switching to northwesterly in the 05-08Z time frame at
KBWG/KSDF and 08-11Z at KLEX.