Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 270717
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
317 AM EDT Mon Jul 27 2015
.SHORT TERM (Now through Tuesday)...
Issued at 308 AM EDT Mon Jul 27 2015
Isolated to widely scattered showers associated with a weak MCV will
slide across SE IN and northern KY through the remainder of the
pre-dawn hours. Meanwhile, additional scattered showers and a few
storms associated with weak moisture convergence along a weak
boundary will continue across southern IL/SW IN and western KY
through the morning hours. Main batch of this precipitation should
slide south, staying west of I-65 through the morning.
Today - Tuesday...
A strong upper ridge currently centered over the southern Plains
will gradually shift eastward through the short term, becoming more
established over the Great Lakes and Ohio River Valley. As this
occurs, the stronger belt of NW flow aloft will shift NE of our CWA,
taking us out of the threat of weak disturbances embedded within the
flow. In the meantime, a weak surface boundary will drop to across
our NE CWA today, remaining over or near the region through Tuesday.
This feature may be able to create enough surface convergence for
isolated to widely scattered coverage later this afternoon/evening
(mainly NE), and again on Tuesday. However, given the warmer H7
temps from mid level subsidence and overall weak mid level lapse
rates not expecting coverage to exceed 20-30% (that may be
generous). Slow shower/storm movement combined with a juicy
atmospheric profile will allow for some brief heavy rainfall,
although with coverage so low not too concerned about any hydro
problems at this point.
Left a 20% pop in for Tuesday, but think the main story will be the
warmer and muggy conditions. Looking for highs mostly in the upper
80s NE to low 90s SW combined with dew points in the low and mid
70s. These ingredients will combine to create heat indices in the
100-104 range near Bowling Green on Tuesday. Heat indices elsewhere
will generally be 95-100 for a few hours. Highs today should range
between 87 NE to 92 SW. Tonight will again be mild/muggy with lows
mostly in the 71-76 range.
.LONG TERM (Tuesday Night through Sunday)...
Issued at 310 AM EDT Mon Jul 27 2015
Tuesday Night - Thursday...
Hot upper-level ridge initially over the southern Plains will
retrograde into the Four Corners region, opening the door for a
developing eastern CONUS trof to drive a cold front southeast across
the Ohio Valley Wednesday night. Wednesday could be the hottest day
of the week with most of central Kentucky getting solidly into the
90s, and heat indices pushing 100.
T-storm chances will be on the increase especially late Wednesday
into Wed night as the front approaches. Wind fields are quite weak,
so the main threat will be heavy rainfall from slow-moving storms.
Precipitable water surges over 2 inches just ahead of the front, but
slightly faster storm motion should be a mitigating factor.
Rain chances will linger into Thursday over south central Kentucky
as the front makes a slow exit.
Thursday Night - Sunday...
Eastern CONUS upper trof sets up, and should be sharp enough that
most of the NW flow disturbances should split the Ohio Valley.
Surface high pressure will be fairly weak, but it will bring a drier
air mass with dewpoints as low as the upper 50s/lower 60s for
Friday, and still only recovering to the mid 60s by Sunday, which is
quite reasonable for the end of July/beginning of August. Given
recent model performance, temp forecast slightly undercuts the
extended GFS MOS especially by day, and just does recover to normal
.AVIATION (06Z TAF Update)...
Updated 108 AM EDT Mon Jul 27 2015
Scattered shower activity (and a rumble or two of thunder) will
meander across the TAF sites through the overnight, although
coverage will be pretty hit or miss. Will only include VCSH for a
few hours. Main impacts overnight will be for ongoing haze and the
potential for some fog through the pre-dawn hours. Cloudy skies
don`t help confidence in just how low visibilities will go, but
given the very moist low level atmosphere and some obs sites already
MVFR, felt that some brief periods of IFR will be possible at
BWG/LEX. Will keep SDF in MVFR toward dawn.
A WSW wind will take hold through the daylight hours today, with
variable cloudiness and some haze hanging around. There is also a
chance for some isolated shower/storm coveage through the afternoon
hours as a frontal boundary hangs in the area, however will only
include at LEX for now. Winds will veer to NW and then variable as
the front passes late afternoon evening.