Area Forecast Discussion
Issued by NWS Jackson, KY
FXUS63 KJKL 200313
Area Forecast Discussion
National Weather Service Jackson KY
1113 PM EDT TUE JUL 19 2016
Issued at 1113 PM EDT TUE JUL 19 2016
Cirrus continues to stream in from complex of storms to the
northwest, but this will remain west of the Interstate 75
corridor. Despite the cirrus and eventual drier air advection,
patchy valley fog should still develop overnight as temperatures
fall toward dewpoint readings.
UPDATE Issued at 808 PM EDT TUE JUL 19 2016
Storms continue to remain well south of the Commonwealth in wake
of a frontal boundary pushing across the Mid-Atlantic coast
through the Tennessee Valley and southeast U.S. Still seeing a
lingering uncomfortable airmass remain in place, but more
comfortable conditions will be in the offing later tonight into
midweek. Patchy valley fog still a good bet given juicy crossover
temperatures and mostly clear skies other than a few cirrus, but
dry air advection should keep dense fog at bay.
.SHORT TERM...(This evening through Wednesday night)
Issued at 303 PM EDT TUE JUL 19 2016
Drier air continues to seep into the region as a diffuse cold
front sags southward. An isolated shower or storm will remain
possible close to the Tennessee and Virginia borders for a few
more hours before the drier air wins out.
The front will wash out just to our south and west over the next
36 hours with dewpoints dropping back into the slightly more
tolerable mid to upper 60s. MCS activity rounding the top of the
building upper level ridge to our northwest will bring some mid
and high level clouds from time to time but expect any associated
shower/thunderstorm activity to either die out before it can make
it into our area, or drop by to our west. Otherwise, just the
normal valley fog can be expected the next couple of nights.
Very little change is expected with temperatures during this
period despite the passing front. The lower dewpoints will help
overnight lows tonight and Wednesday night fall into the 60s for
most locations, but daytime highs on Wednesday should again reach
the upper 80s to near 90.
.LONG TERM...(Thursday through Tuesday)
Issued at 342 PM EDT TUE JUL 19 2016
A strong upper level ridge will be in control across much of the
southern half of the conus through the extended period, including
the Ohio River Valley and eastern KY. The center of this upper level
ridge will be over the southwest conus states Friday, spreading
eastward across KY and TN through the weekend, then shifting off the
Atlantic Coast Sunday night into Monday. This will allow heights to
lower slightly across the region Monday into Tuesday, though still
strongly influenced by the upper level ridge.
Expect warming temps throughout the rest of the week with the
eastward progression of the upper level ridging. Temperatures
hovering around 90 on Thursday will warm to the low 90s Friday,
Saturday, and Sunday with winds generally out of the SW to W in the
low levels. This, combined with increasing humidity values as well,
will push apparent temperatures to the mid 90s on Thursday, tipping
just over 100 degrees for Friday, Saturday, and Sunday...with
Saturday expected to be the warmest day.
While no shortwaves or surface systems are expected to impact us
through the weekend, afternoon heat and instability could be enough
to spawn some isolated convection. As was noted in the previous
forecast, although this instability does begin to increase each day
as we head into the weekend, the lack of deep layer moisture, warm
air aloft, and the lack of substantial upper level support will
likely preclude best thunderstorm development. Consequently, PoPs
were kept at slight chances, generally on the lower end of the
blended guidance. A shortwave is expected to impact the upper Great
Lakes by Sunday, with a center of low pressure moving across Indiana
and Ohio during this time. This may bring a bit better instability
and moisture to the region for Sunday, so did keep chance pops in
for this day, mainly during peak heating in the afternoon.
The cold front protruding westward from this low will near the Ohio
River on Monday, then push slightly southward into a portion of the
state Tuesday, correlating with the exiting upper level high
shifting off the Atlantic Coast. This will allow for slightly better
instability and lift, so kept chance pops during this time as well.
Clouds and slightly lower heights aloft will also allow a slight
cool off across the region.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 808 PM EDT TUE JUL 19 2016
Fog will be the primary concern overnight into Wednesday morning.
The drier airmass seeping in and exact extent of cirrus complicate things
and confidence on exactly how the visibility forecast will play
out is rather low. Given lower mixing of afternoon dewpoints at
SME/LOZ, raised forecast visibilities to MVFR from previous IFR
mention tonight, while maintaining MVFR conditions at JKL and
keeping VFR criteria in play at SJS/SYM for now. Could very well
see sub-VFR visibilities at these latter sites, so will continue
to monitor this evening/early tonight. Ridging in place will keep
north/northeast winds light through Wednesday.