Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 150655
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
255 AM EDT Mon Sep 15 2014
.SHORT TERM (Now through Tuesday)...
Issued at 250 AM EDT Mon Sep 15 2014
Will continue a patchy fog mention across the area this morning as
we sit under sfc high pressure with good subsidence, calm winds, and
decent low level moisture. However, invading cirrus from the west
and slightly drier air sinking south from central Indiana do look to
limit fog density and areal coverage. Thus, believe the 0Z NAM
visibility progs to be too pessimistic. Think the most likely
scenario given current conditions and trends early this morning
would be for patchy fog formation between now and dawn over some
areas with the best spots being over east central and south central
KY. Widespread dense fog does not look likely at this point,
however, will watch the south and east closely for any patches of
dense fog forming.
Any fog will quickly burn off after sunrise, with increasing mid and
upper level clouds throughout the day ahead of an approaching cold
front and upper trough. This feature will be in a weakening state
by the time it arrives tonight although it may have enough forcing
left to provide 20-30% coverage of showers as it moves through
tonight. High pressure and cooler air will then settle in for Tues.
Temperatures will rise into the mid 70s today...slightly warmer than
yesterday. Tonight lows will be tricky depending on exact cold
fropa. Will use a gradient of mid 50s over southern IN to upper 50s
to around 60 over central KY. Tuesday will be cooler in the post
frontal airmass with highs ranging from 67-73.
.LONG TERM (Tuesday Night through Sunday)...
Issued at 300 AM EDT Mon Sep 15 2014
A dry northwesterly flow will be well established across the Lower
Ohio Valley late Tuesday in the wake of a disturbance lifting
eastwards over New England. Surface high pressure will dominate the
region, restricting any substantial deep moisture to areas well
south across the northern Gulf States.
This pattern will bring continued dry weather to the area, and
preclude any meaningful chance of rain until Sunday. Under mostly
clear skies and light northeasterly winds, low temperatures early
Wednesday will cool considerably from than those a day earlier. Some
of our cooler locations may reach the upper 40s, while the majority
of spots stay in the lower 50s.
Strong high pressure will slide southeast across New England
Thursday, Its associated push of cooler air will miss us to the
northeast. However, it will reinforce surface ridging, which will
arc from New England through the Missouri Bootheel Wednesday through
late Friday. This somewhat stagnant weather pattern will bring
multiple days of light winds and mostly clear skies. A slow warming
trend will begin Wednesday, as highs rebound into the lower to mid
70s. Friday will become noticeably warmer, with highs in the upper
70s. Overnight lows will slowly warm from the lower 50s early
Thursday to near 60 by Saturday morning.
Saturday will warm even more, and will become our first day that
will feel even slightly humid, as southwesterly flow begins ahead of
a surface trough moving across the upper midwest. Highs will likely
exceed 80. A weak frontal passage Sunday may bring some isolated to
.AVIATION (06Z TAF Update)...
Issued at 125 AM EDT Mon Sep 15 2014
The main TAF challenge will be fog tonight. With sfc high pressure
over the region, light winds, and good subsidence, the potential
exists for fog development if low levels are moist enough. Given
lack of significant rainfall over the last 24 hrs and overall a dry
atmosphere, won`t get too pessimistic with fog in the TAFs.
However, dewpts have been running higher than MOS guidance suggests
and the 0Z NAM, NARRE, and simulated WRF do indicate fog development
over the area. Based on a blend of all guidance will go with IFR
conditions for BWG/LEX toward sunrise and keep SDF at 6sm br. This
is a low confidence fog forecast and may not pan out due to cirrus
arriving from the west and/or drier air sinking south from central
IN. Any fog will quickly burn off after sunrise.
Winds will be mostly calm through the morning hours and then SW
through much of the daylight hours. A cold front will approach the
region tonight bringing the possibility of showers to SDF in this