Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 231514
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1114 AM EDT Wed Apr 23 2014
Issued at 1105 AM EDT Wed Apr 23 2014
Updated the forecast to increase afternoon high temps a few
degrees. Plenty of sunshine is expected today, but cooler drier air
sinking south with sfc high pressure should hold high temps in the
60s for the most part although 70 degrees will be possible over
south central KY. Went a few degrees over MOS guidance with this
.SHORT TERM (Now through Thursday)...
Issued at 300 AM EDT Wed Apr 23 2014
Chilly high pressure centered over northeast Wisconsin continues to
build south into the Ohio Valley, but there remains just enough
gradient to maintain a light north breeze. Temps that overachieved
on Tuesday had a long way to drop, and even the coldest of the
mesonet stations in Kentucky are still around 40F. While it is still
possible for a brief sunrise dip to produce some patchy light frost
in the coldest spots, will not continue to play it up as anyone that
would likely take action has already done so.
Main challenge today is the max temp forecast and potential dry air
mix-down. Given what happened on Tuesday and the continued lack of
rainfall, expect temps to once again overachieve and dewpoints to
crash. Went just above the warmest temp guidance and just below the
lowest dewpoint guidance, which yields highs in the mid/upper 60s
and RH values down to 25-30%. However, fire danger issues will be
mitigated by light winds, as we will be hard pressed to see even 10
mph during peak afternoon heating.
Surface ridge slips to our east this evening, and clouds will start
to increase in the return flow. Cloud cover will be most extensive
north of I-64 as an elevated warm front tries to develop over
Indiana, but that feature will remain far enough north (not to
mention sufficiently moisture starved) that precip will not be a
concern. Will then cloud up from the west on Thursday as an upper
trof and associated cold front move into the Mississippi Valley, but
precip chances will hold off until Thursday night. Warm advection
pattern will push temps well above normal, and will again lean on
the warmest guidance.
.LONG TERM (Thursday night through Tuesday)...
Issued at 245 AM EDT Wed Apr 23 2014
A PV anomaly and associated surface cold front will sweep across the
forecast area Thursday night, with all signs pointing to it being
east of the area by daybreak Friday. Showers with scattered rumbles
of thunder will accompany the frontal passage. Total QPF looks to be
a couple tenths of an inch.
Friday through Saturday night still appears to remain dry. Models
differ on the approach of a weakening front from the north early
Saturday. It may make it into our forecast area, but moisture
convergence and forcing remain north of our area and move east with
the upper-level dynamics before the weakening front reaches our
northern counties. So, will continue with a dry forecast. The front
will hang across our area Saturday and Saturday night, but with no
disturbances traversing the region, we should stay dry. It will
begin to retreat northward Sunday as winds become more southerly
ahead of our next system. High temperatures should top out generally
in the middle 70s Friday and Saturday with overnight lows in the 50s.
A large upper low will gradually migrate eastward from the central
CONUS to the Ohio Valley late Sunday through Tuesday. Clouds will be
on the increase Sunday. We may see some showers and a few storms
late in the day Sunday, particularly across our west if we
destabilize enough in the afternoon. The best precip chances appear
to be from Monday into Tuesday as a front, associated with this
large stacked low, moves through the area. However, with the low
projected to spin across the Ohio Valley for a few days, believe
on-and-off showers with a few rumbles of thunder could linger
through much of the work week.
Temperatures will also begin a cooling trend next week, given the
colder air aloft combined with clouds and precip. High temperatures
will decrease a few degrees each day Sunday through Tuesday, with
middle 60s to low 70s expected by Tuesday. That cooling trend will
continue into the latter half of the work week if the upper low
moves directly over the forecast area.
.AVIATION (12Z TAF Update)...
Issued at 650 AM EDT Wed Apr 23 2014
Light N-NE winds and clear skies through the day as high pressure
over Wisconsin continues to build south into the Ohio Valley.
Surface ridge axis will work its way into eastern Kentucky this
evening, initially shifting surface winds to easterly but opening
the door for return flow aloft. Could see mid-level ceilings in SDF
and LEX tonight as a warm front sets up to our north, but no
significant operational impacts are expected.