Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 191101
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
701 AM EDT Tue Aug 19 2014
...Updated Aviation Discussion...
Issued at 533 AM EDT Tue Aug 19 2014
Some showers with potentially some embedded thunder have developed
in the Lake Cumberland area in response to a weak wave moving into
the forecast area from the TN Valley. These showers are not expected
to last long and should dissipate/move out of the area within the
next couple of hours. Rest of the forecast remains on track.
.SHORT TERM (Now through Wednesday)...
Issued at 345 AM EDT Tue Aug 19 2014
Currently through mid-morning:
Fog will remain the primary weather hazard through sunrise before
burning off by mid-morning. Plenty of low-level moisture, thanks to
recent rains and a warm, moist airmass in place, light to calm
winds, and only some mid- to upper-level clouds streaming by has
allowed for areas of fog to take over. Look for temperatures to
remain steady and in the upper 60s to around 70 degrees with
This afternoon through tonight:
Deterministic models are having a difficult time keying in on the
mesoscale evolution of convection throughout much of the short-term.
Have attempted to compromise between the high-res guidance,
suggesting a broken line of storms developing across IL by
mid-afternoon and diving southeastward, dissipating as it crosses
the forecast area this evening, and some of the lower-res models,
holding off on developing convection until later tonight, hinting at
a possible MCS tracking through, affecting the western half of the
area. This compromise leads to a forecast of focusing chance PoPs
across most of the forecast area late this afternoon through late
this evening and slight chance after midnight through Wednesday
morning. This lines up with a vort max rotating through, allowing
for a focus of convection. The caveat for potentially bumping PoPs
up in future updates for the overnight hours is the ramping up of
the low-level jet and the upper trough axis traversing through,
helping to continue convection long after the loss of assistance
from daytime heating.
Highs today will reach the mid to upper 80s and with the moist
airmass locked in, dewpoints will deviate little from the 70 degree
mark, only ranging +/- a few degree points. Lows will mimic those of
this morning, ranging from the upper 60s to lower 70s.
Models have sped up the timing of the upper trough moving through to
earlier in the day Wednesday, as compared to guidance from 18/00Z.
However, shear parameters, steep lapse rates, continued low-level
moisture transport across the region, and excellent instability all
point toward any convection that develops having the potential to
become strong. Uncertainty exists for the possibility of any early
morning convection leaving behind cloud debris, and how much
dynamical support will be in place. Bottom line is that the
short-term period is riddled with multiple waves crossing the
region, prompting the possibility of convection throughout much of
the period, and leaving uncertainty in specifics given the lack of a
decent handle on the mesoscale features.
Better confidence exists in the high temperature forecast for
Wednesday, although cloud cover again throws a wrench into things.
Looks to be a few degrees warmer on Wednesday, ranging from the
upper 80s to lower 90s.
.LONG TERM (Wednesday Night through Monday)...
Issued at 330 AM EDT Tue Aug 19 2014
...Heat is on the Way...
We`ll remain in an active NW flow through Thursday evening with
several rounds of sct-num showers and storms possible. Wednesday
evening we could see a round of strong to possibly severe storms
with gusty winds and hail near a warm front. However storms
will be declining in strength throughout the late evening hours.
Storms Wed night will still pose a heavy rain threat throughout the
overnight hours with PWATs in the 1.8-2 inch range.
Thursday/Thurs evening we`ll continue to see rounds of showers and
storms although strength and exact organization is uncertain due to
several factors including a strengthening ridge building in from the
west, warm front position pushing farther north, and clouds from
previous convective complexes. At this point, some strong storms
look possible with at least heavy rain Thu/Thu night. The potential
is there for strong to severe storms but too many negating factors
stand in the way at this point.
The ridge will continue building in from the south through the
weekend. This will limit convection to mainly southern IN and
northern/eastern KY for Friday. Then look for a transition to more
diurnal type t-storms most numerous near the periphery of the ridge
for the weekend and early next week. Some of these storms could be
strong but no organized severe complexes look apparent attm.
The bigger story for the end of this week through early next week
will be the long awaited arrival of typical summer temperatures.
The strong ridge will bring an airmass with h85 temps in the 22-24
degree C range. Although antecedent wet conditions with lush green
vegetation will limit our max temps some as previous forecaster
noted, think that high temps will solidly reach the low to mid 90s
for Fri-Mon with heat indices topping 100 degrees especially west of
I-65. Will need to watch this period for possible heat index/air
.AVIATION (12Z TAF Update)...
Issued at 651 AM EDT Tue Aug 19 2014
The three terminals and surrounding areas have had rather dynamic
visibility issues, ranging from MVFR to LIFR at various times this
morning. The reduction in visbys is not anticipated to last much
longer, burning off within a couple hours after full sunrise. A
shift in aviation concerns occurs by midday today through the
remainder of the TAF period as a series of upper-level disturbances
rotate through the Ohio Valley. The primary concern for impactful
weather within the terminal areas will be focused around this
evening. However, the unorganized and relatively unpredictable
nature of these storms limits the ability to include definable
mention in this issuance.
Light to calm winds this morning will increase throughout the day
and remain primarily out of the SW through tonight. Winds should be
around 10 knots during the daylight hours and will be stronger in
and around any storms that develop, with the added concern of quick
KY...DENSE FOG ADVISORY until 9 AM EDT /8 AM CDT/ this morning FOR
IN...DENSE FOG ADVISORY until 9 AM EDT /8 AM CDT/ this morning FOR