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Area forecast discussion 
National Weather Service Jackson Kentucky
1058 PM EDT Monday Aug 3 2015

issued at 1058 PM EDT Monday Aug 3 2015

Wow. The past 2 hours or so have been insane busy here at jkl.
Several strong to severe thunderstorms have been moving across the
northern part of the forecast area since around 830...Downing
trees and dumping heavy rain that has lead to major flooding
issues in Rowan and Montgomery counties. A hastily prepared zone
forecast update has just been sent out...focusing on getting the
ongoing showers and storms through our forecast area overnight.

Update issued at 729 PM EDT Monday Aug 3 2015

No major changes were made to the forecast at this time. Will
continue to monitor shower and storm activity that is ongoing
across southern Ohio and north central Kentucky to see how much of
this makes it into eastern Kentucky this evening. Will also
continue to look for newly formed showers and storms as outflow
from existing storms propagate south into our area. At the very
least will eventually need to remove some outdated wording from
the zone forecast text product.


Short term...(this evening through Tuesday night)
issued at 319 PM EDT Monday Aug 3 2015

The outflow boundary from the early morning mesoscale convective system to our north moved
across and out of the forecast area helping to stabilize much of
eastern Kentucky. Destabilization has been occurring slowly...but to
this point the instability axis has remained well to the northwest
of the area. The 18z mesoanalysis shows MLCAPE from 2500 to 3000
j/kg from western Kentucky into central Indiana. At this time convection
is beginning to develop over central Indiana out ahead of a cold
front that is over Northwest Indiana. This convection should develop
further over the next couple of hours and it is possible that at
least the northern part of the forecast area could see a few
thunderstorms this evening. However latest short range guidance
trends make this a low confidence precipitation forecast...and
thus will keep probabilities for any showers and thunderstorms low
for the overnight period. The best chance...but still only a 30
percent probability will be placed in the northeast two thirds of
the forecast area.

The weak cold front which extends from Lake Huron to Northwest
Indiana will make slow southeast progress tonight...and the
front will move into Kentucky on Tuesday. However any forcing will
remain marginal...and will once again carry only 20 to 30 percent
probabilities of showers and thunderstorms on Tuesday...but with
the slightly higher chance across the southern part of the
forecast area.

Long term...(wednesday through monday)
issued at 319 PM EDT Monday Aug 3 2015

Models are showing some significant differences now in the strength
and timing of systems through the region. In general we can expect
west southwest flow through roughly the first half of the period...
before upper level pattern become more northwesterly for the remainder
of the extended. Models suggest two main disturbances through the
Ohio Valley...the first Wednesday night...or more likely Thursday and the
second at the very end of the week...or possibly into the weekend.
While timing is similar the 12z GFS is much less amplified and more
disorganized with the middle week storm system when compared with the
0z European model (ecmwf) to start out the extended. A quick peak at the 12z European model (ecmwf)
shows that it has trended towards the GFS a bit but remains
amplified enough to maintain a more organized surface system Wednesday
night into Thursday.

The GFS is considerably faster than the 0z European model (ecmwf) with the second
main disturbance targeting our area within the extended
12 hours or more at the end of the week...beginning of the weekend.
The 12z European model (ecmwf) has trended weaker with this second disturbance. A low
confidence forecast suggests the best approach is to rely heavily on
model consensus and guidance blends until models come into better

At the surface...until the first disturbance has pushed off to our
east late in the week a lingering quasi/stationary surface boundary
draped across the Ohio Valley region will tend to keep our weather
more active than the past several days. Main challenge is where this
boundary actually sets up as models continue to disagree with
southern extent of this surface frontal zone. Overall confidence is low
in the details of sensible weather though temperatures will most
likely be near to slightly below normal in general...with a slightly
elevated risk of probability of precipitation when compared with norms.


Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 729 PM EDT Monday Aug 3 2015

Featured VFR conditions in the tafs throughout the period for all
sites except sme...which experienced IFR fog late last night into
early this morning. With so much uncertainty regarding the
coverage of showers and showers and storms tonight and
tomorrow...felt it unnecessary to include ts in the tafs at this
time. This situation will need to be monitored of course...but
based on all the latest model appears that shower and
storm coverage tonight and tomorrow will be sparse.


Jkl watches/warnings/advisories...


short term...sbh
long term...ray

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