Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 231031
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
631 AM EDT Sat May 23 2015
...Updated Aviation Discussion...
.SHORT TERM (Now through Sunday)...
Issued at 255 AM EDT Sat May 23 2015
High pressure ridging from the upper Mississippi Valley to the
Atlantic coast will keep our weather quiet today and tonight. Under
variably cloudy skies high temperatures this afternoon will be
around 80, with lows tonight around 60.
Sunday the surface high will edge a bit further off to the east as a
deep negatively tilted low crosses the Front Range. Widespread
shower and thunderstorm activity will stream northward through the
Plains, with the Ohio Valley on the eastern edge. As the upper trof
digs through the west, ridging will pump up over the southeast
United States. The upper ridge will help to keep most locations dry
on Sunday. In the far west portions of the local forecast area the
cap will weaken some by afternoon and surface-based lifted index
values will go slightly negative. Mid-level lapse rates will remain
weak, though, and precipitable water amounts will only be slightly
above normal. Not much of a trigger present, other than a very weak
surface trof combined with afternoon heating. Will go ahead and
hold on to the 20% PoP in the far west Sunday afternoon. High
temperatures will be in the lower and middle 80s on south winds
gusting to near 20 mph in the afternoon.
.LONG TERM (Sunday night through Friday)...
Issued at 245 AM EDT Sat May 23 2015
Long Term is characterized by above normal temperatures and an
active period of weather. Forecast challenge is timing the various
shortwaves, so right now the forecast sounds like it will rain all
week, but in reality we will have specific shorter duration periods
of stormy weather.
Sunday Night through Monday Mid Morning...
Well...the potent upper ridge axis over SC/GA/FL will move east of
the CWA by Monday morning in response to an ejecting shortwave over
OK/TX. This will shift the deep southerly flow more over the
Ohio River Valley, bringing an increase in temperatures, moisture,
and rounds of scattered storm chances. Will continue to keep Sunday
night basically dry except for an isolated TSRA/SHRA 00-03z. Look
for lows in the mid to upper 60s.
Monday PM - Friday...
An active period of weather takes shape through the remainder of the
week as atmosphere changes to a deep SW flow with disturbances every
18 hours or so over the CWA. Like the idea of mainly keeping
scattered coverage of showers/storms going until details of
individual perturbations work themselves out.
Right now it appears the greatest likelihood of storms will be
Monday afternoon. Next wave is Tuesday afternoon, and another
Wednesday afternoon into evening. Monday PM POPS are likely to
Overall pattern certainly calls for at or above normal highs
(dependent on daily convection and cloud debris) and above normal
lows given the steady southerly flow/higher dew points. High
confidence of mostly cloudy for much of the work week with series of
upper lows coming out of the western USA and into the Rockies. This
portends more severe weather for OK/TX off and on next week too.
Have kept the theme going of milder nights with upper 60s to around
70 each night through at least mid week. Highs will mostly be in the
lower 80s, with mid to even upper 80s possible under less
convection, and upper 70s possible on the better coverage days.
The severe weather threat looks marginal with the deep moist
soundings. PWATS go from 0.75 Sunday morning to 1.7 inches Monday
afternoon. However, it does appear that 25-35 knots of 0-6 km shear
(marginal) may couple with some instability at times to allow for a
few stronger storms. Looks like locally heavy rain, lightning, and
isolated wet microbursts would be worst case scenario.
.AVIATION (12Z TAF Update)...
Updated at 631 AM EDT Sat May 23 2015
High pressure crossing the northeast United States will keep our
weather quiet through this TAF period. The high to our east will
give us light southeast breezes during the daylight hours, and
elevated moisture will produce clouds above 10k ft.