Area Forecast Discussion
Issued by NWS Jackson, KY-- Highlight Changed Discussion --
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FXUS63 KJKL 220334 AAB
Area Forecast Discussion...UPDATED
National Weather Service Jackson KY
1134 PM EDT THU JUL 21 2016
Issued at 1125 PM EDT THU JUL 21 2016
Hourly grids have been updated based on recent short term model
runs and observations. We are not confident that any activity
overnight will occur in the north as has been in a few recent
HRRR runs, but this scenario will be monitored.
UPDATE Issued at 835 PM EDT THU JUL 21 2016
Debris clouds continue to move into Eastern and South Central KY
from weakening convection over OH and IN. A southward moving
outflow is in the vicinity of the I 71 corridor from near CVG to
near ILN but it also extends further west near or just north of
the OH River and then north near the I 65 corridor to near IND.
Even the more substantial convection that was over parts of
southern IN has waned over the past hour. This convection should
continue to wane as it moves into an area of drier air and with
the loss of daytime heating and a resurgence is not anticipated.
However, the outflow boundary should reach the northern CWA likely
settling somewhere near the I 64 corridor. Some debris clouds
perhaps a bit of mid clouds in this across the far north should
continue to move across the area over the next few hours, but
surface high pressure to the east of the area should bring mostly
clear skies overall with light winds. Sky cover was adjusted
accordingly. The previously forecast lows are on target so no
substantial changes were needed at this time. The outflow boundary
could serve as a focus for convection on Friday afternoon.
.SHORT TERM...(This evening through Friday night)
Issued at 308 PM EDT THU JUL 21 2016
Dewpoints over all but the far southwest part of the area have
fallen into the upper 50s to lower 60s as drier air has mixed down
from the mid levels. Low level moisture will begin to increase
again tonight, with dewpoints getting back to 70 or above on
Friday. Overnight lows should not be quite as low as last night
with the rising dewpoints, but should still see numerous spots get
into the mid 60s. The combination of highs in the lower 90s and
dewpoints around 70 on Friday will push heat index values to
around 100 in some areas, but still below advisory criteria.
After a couple days of dry weather prevailing across the entire
forecast area, we will see a return of thunderstorm chances Friday
afternoon as instability increases and a weak wave moves southeast
around the upper ridge. The chance for thunderstorms will continue
into Friday night.
.LONG TERM...(Saturday through Thursday)
Issued at 308 PM EDT THU JUL 21 2016
Dominant upper level ridge will flatten out through time with the
core shifting to the west as disturbances drop southeast into the
Ohio Valley. This will result in almost daily chances for
thunderstorms throughout the period in an entrenched very warm and
muggy airmass. In fact, the weekend forecast is trending more
unsettled as a weak front is progged to drop into the area on
Saturday then waffle around overhead or nearby into next week.
This stormier forecast means that ambient temperatures may not get
as warm as previously advertised, but dewpoints still climb well
into the 70s and the heat index remains progged to reach near 100
each day Saturday through at least Monday.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 838 PM EDT THU JUL 21 2016
VFR conditions should prevail at the TAFs sites for most of, if
not the entire period. Low level moisture will begin to increase
tonight from current levels, but the current thinking remains that
fog will be limited to river valley locations and near the larger
lakes and creeks. At this time, we have continued to not include
any fog in the TAFs tonight which is a notch less than persistence.
An outflow boundary should settle near the Interstate 64 corridor
overnight and models have some convection either developing or
moving into the area and/or move in additional outflows to focus
some convection during the 16Z to 00Z period in the north.
Chances appear best at SYM and possibly SJS and JKL as well, and
isolated convection cannot be completely ruled out SME and LOZ
either. VCTS was used from 16Z through the end of the period at
SYM and VCSH at JKL, SJS, SME, and LOZ. Winds will remain light
and variable through the period outside of any convection.