Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 011717
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
117 PM EDT Fri May 1 2015
...Updated Aviation Discussion...
.SHORT TERM (Now through Saturday)...
Issued at 249 AM EDT Fri May 1 2015
The cold upper low that brought us showers and thunderstorms
yesterday has advanced to North Carolina this morning, and will move
off the coast this evening. Without the assistance of the upper
low, the cu field today should remain scattered and flat enough to
preclude shower activity. The best chance of a rogue pop-up would be
east of I-75. Highs today will be in the mid 60s to around 70 with a
cool northerly breeze.
The diurnal clouds will clear out tonight. Patchy fog will be
possible towards morning in southern Kentucky as winds go calm under
mostly clear skies with tight dew point depressions. Low
temperatures will be in the mid 40s to around 50.
On Saturday high pressure will come in from the west and will be
centered right over Kentucky by evening. Moisture will once again
be available for cumulus clouds to develop. Some model data suggest
a small chance of showers in the afternoon associated with this
moisture and an upper shortwave trof dropping down from the north.
However, the wave will be weakening as it approaches, and
precipitable water values will actually be below normal for this
time of year. Soundings become unstable in the low levels, but
mid-level lapse rates are much weaker. Also, the layer of moisture
is quite shallow, and we`ll have that surface high moving in. So,
after conferring with IND, ILN, and JKL, will continue with the dry
Provided there are no showers, Saturday will be a picture perfect
May day with fluffy white clouds against a blue sky, only a slight
breeze, and temperatures climbing into the 70s.
.LONG TERM (Saturday Night through Thursday)...
Issued at 251 AM EDT Fri May 1 2015
The main story in the long term forecast is the extended period of
dry and above normal temperatures for the lower Ohio Valley.
The synoptic pattern Saturday evening is expected to feature weak
northwest flow aloft as a surface high pressure asserts itself
across the eastern CONUS. Plan on a mostly clear night as
temperatures fall into the upper 40s to lower 50s.
Plan on dry weather Sunday through at least Wednesday night as
ridging aloft and at the surface settles over the southeast US into
the lower Ohio Valley. Main energy and upper level forcing will be
focused across the central Plains into the lower Great Lakes region.
01.00z guidance does show that dewpoints creep up each day, reaching
the low/mid 60s by mid-week. So, it`ll begin to feel a little more
muggy/humid and with daytime instability, couldn`t rule out a stray
shower or t-storm. But the lack of any appreciable triggers and
mid-level subsidence is enough to keep the dry forecast going.
850 mb temperatures remain between 10-12C for the period as well, so
daily highs will be in the upper 70s to low 80s. Nudged temperatures
slightly above model consensus, as bias-corrected guidance suggests
some locations could approach the mid 80s toward mid/late week.
Overnight lows will be in the upper 50s to low 60s, though typical
warm spots and urban areas may hold in the mid 60s.
By Thursday, a central Plains trough looks to advance far enough
east to provide forcing for ascent across the region. A stalled
frontal boundary will begin to also approach from the northwest, so
shower/storm chances look reasonable Thursday into next weekend.
.AVIATION (18Z TAF Update)...
Updated at 115 PM EDT Fri May 1 2015
High pressure will continue to build into the region this afternoon
resulting in VFR conditions. Some low end VFR cigs will be possible
at KLEX this afternoon with cigs running around FL030-035. However,
expect these to break up later this afternoon and evening. Skies
are expected to be clear tonight with mainly VFR conditions. There
remains a slight chance of some low-level fog at KLEX/KBWG in the