Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 030531
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
131 AM EDT Wed Sep 3 2014
...Updated Aviation Discussion...
Issued at 932 PM EDT Tue Sep 2 2014
Last of afternoon convection continues to move eastward through the
Lake Cumberland region of central Kentucky. Expect this activity to
move east of our region by 1100 PM EDT. Otherwise, mid-high level
cloudiness will continue across much of central Kentucky this
evening with clearing taking place overnight. Mostly clear skies
will be found across our southern Indiana counties. The combination
of clearing skies, light winds and adequate low-level moisture will
set the stage for patchy dense fog developing across the region.
Thus, will continue to mention patchy dense fog in the forecast.
There is some concern that we may end up seeing a little bit more of
low-level stratus build down and a little less fog development.
Will continue to monitor data this evening and if fog become more
widespread, a dense fog advisory may be required in subsequent
Update issued at 709 PM EDT Tue Sep 2 2014
Still watching two areas of convection this evening. The first is
over the Bluegrass region of central Kentucky. This activity is
moving through the Lexington metro now and will exit our eastern
counties by 800-830 PM EDT. Some additional development upstream
down along the BG Parkway will be possible as remnant outflow
boundary continues to sag southward. This area of Kentucky has been
worked over from previous convection...thus am not expecting robust
convection to redevelop. However, any storm will be capable of
producing heavy rains and gusty winds.
Other area of convection will be along the KY/TN border region.
Cluster of convection will slowly work eastward. It appears that
most of the heavier convection will stay just south of the KY border
down in Tennessee. We expect this convection to die off after
Skies look to clear later this evening. However, the combination of
clearing skies, light winds, and ample wet ground from this
afternoon`s rainfall will likely lead to good fog production
tonight. Will be inserting some patchy dense fog into the forecast
in the next update. Will continue to monitor data this evening to
see if fog will remain patchy in nature, or go more widespread.
.SHORT TERM (Now through Sunday)...
Issued at 305 PM EDT Tue Sep 2 2014
Scattered showers and thunderstorms will increase in coverage by
late afternoon, with possibly two areas of concentration. The first
area may develop along and south of the Cumberland Parkway, along an
old outflow boundary left over from this morning decaying mesoscale
convective complex. A surface analysis shows our best instability
across our southern counties. Should any robust storms develop
across our south, some may produce gusty winds.
Scattered storms will also scoot across southern Indiana and areas
north of Interstate 64 late this afternoon as well. A weak wave will
cross southern Indiana late this afternoon and scattered storms have
already developed across southern Indiana.
Scattered showers and isolated thunder will diminish by late evening
as surface heating is lost. Drier mid-level air will seep south into
the Commonwealth later this evening as mid-level flow become
westerly. This will finally rid us of our persistent mid and high
level cloudiness associated with our recent tropical air. Some
afternoon cumulus will develop Wednesday, keeping skies partly
Winds will become light Wednesday as surface high pressure moves
over the Lower Ohio Valley. Weak subsidence and drier mid-levels
will keep Wednesday dry, although it will stay warm and humid.
Low temperatures will fall into the upper 60s to the lower 70s
tonight, rising into the upper 80s to around 90 Wednesday.
Skies will clear Wednesday evening. Expect mostly clear skies and
slightly cooler temps for Wednesday night.
.LONG TERM (Sunday night through Friday)...
Issued at 230 PM EDT Tue Sep 2 2014
At the beginning of the long term, surface high pressure will be
centered over the mid-Atlantic with low pressure over the Red River
of the North that will have a cold front dropping southward through
the Plains. This will situate us right in the heart of warm, moist
southerly surface flow. Aloft, strong ridging will be in place from
Thursday into Friday. Some afternoon pop-up storms will be possible
on Thursday, but activity should be rather sparse due to the lack of
a strong trigger. Storm chances will increase Friday as the cold
front approaches from the northwest, though there will still be some
slight capping present through the day. Widespread severe weather
is not expected, but a few storms could put down some gusty winds.
The front will be weakening as it enters the Ohio Valley and will
still be drifting southward from Kentucky into the Tennessee Valley
on Saturday. Thus, we will need to keep storm chances in the
forecast for Saturday. Severe weather looks even less likely on
Saturday than on Friday.
Sunday through Tuesday we`ll sit between surface high pressure
traveling from the Great Lakes to the Northeast and flat upper
ridging to our south. We could be in a position to see some
afternoon pop-up convection, but GFS QPF is probably overdone and
chances and confidence are low enough at this point to keep daily
PoPs out of the forecast.
High temperatures Thursday and Friday will be around 90 in that warm
southerly flow. Saturday through Tuesday will mostly see 80s,
though southern Indiana and northern Kentucky may not make it out of
the 70s on Sunday. With partly cloudy skies, temperatures mostly in
the 70s, and dew points from the mid 50s to mid 60s, Sunday looks to
be the nicest day of the long term, especially over the northern
half of the area.
.AVIATION (00Z TAF Update)...
Issued at 125 AM EDT Wed Sep 3 2014
Weakening surface cold front will slowly drop SE into the Ohio
Valley through the overnight and early morning hrs. Main impact will
be to further wash out the wind field, allowing for fog to develop
anywhere that skies clear sufficiently.
Will continue to carry TEMPO groups for IFR fog around daybreak in
BWG and LEX, but have narrowed the time focus as any development has
been delayed by the lingering cirrus. Confidence is highest in LEX,
given the better chance for clear skies and the quick shot of heavy
rain that fell late Tuesday afternoon. BWG still has a shot at IFR,
but will not hit them as hard. Confidence is limited as cirrus will
hold on a bit longer there. SDF has just come in with a
fuel-alternate MVFR stratus deck, which could well build down to
IFR. However, do not expect substantial vis restrictions as in the
Any fog/stratus will gradually dissipate by mid/late morning, with
VFR conditions for the rest of the day. Weak easterly gradient will
be in play at BWG, with light/variable winds closer to the bubble
high over Indiana/Ohio.