Area forecast discussion
National Weather Service Jackson Kentucky
136 am EDT sun may 26 2013
Update...
issued at 136 am EDT sun may 26 2013
Have further refined probability of precipitation/precipitation for the overnight into Sunday. Radar
trends and model data suggest that if measurable precipitation occurs...it
would most likely be in the SW part of the forecast area. Will
continue a 20 percent pop there...with sub 20 and a mention of
sprinkles elsewhere. Looks like it will be dry by 12z and stay that
way through the day. Have also raised min temperatures a bit for the
overnight. Observation were warmer than forecast...with clouds restricting
cooling.
Update issued at 1105 PM EDT Sat may 25 2013
Relatively stronger echos are now moving south of the Ohio River.
Measurable precipitation appears to be limited to a narrow band
roughly along a line between Danville Illinois and Louisville Kentucky. Elsewhere
am hard pressed to find much more than possibly a sprinkle reaching
the ground per surface observation. A quick look at the 0z NAM does show some
potential for rain between 06z and 09z...but at the same time looks
less than impressive overall. Have decided to let the slight pop ride
for the remainder of the overnight. Only update was to tweak grids to
hourly trends.
Update issued at 910 PM EDT Sat may 25 2013
A quick update this evening to introduce probability of precipitation across the entire
forecast area. Radar mosaic is showing an uptick in the strength and
coverage of echos...with some lightning even being produced by one
shower. We still have a relatively dry boundary layer and returns are
moving fairly rapidly...which should make it somewhat difficult to
see measurable rainfall. But echos are climbing to around 40dbz...
strong enough that at least a few locations could measure. Went with
isolated coverage...20 pop for now. But if coverage becomes more solid
may have to update to increase probability of precipitation once again. While the threat of a
few isolated showers will remain at dawn in the south...went ahead and
removed any mention of sprinkles during the day Sunday behind exiting
shortwave disturbance. Otherwise only minor tweaks to bring hourly
grids in line with most recent surface observation.
Update issued at 735 PM EDT Sat may 25 2013
Northwest flow aloft with an embedded disturbance is kicking off some
very light rain showers...and sprinkles upstream. Boundary layer is
quite dry at this time...so feel sprinkles is the correct way to go for now.
But if upstream echos enhance much more will be tempted in increase
probability of precipitation just a bit through the overnight with some isolated to scattered
showers. With exception of sky cover hourly grids were on track. Made
some minor adjustments accordingly. Brought in the chance for
sprinkles a bit sooner as well. Otherwise no other changes to the
forecast package.
&&
Short term...(this evening through Sunday night)
issued at 252 PM EDT Sat may 25 2013
The area remains underneath the influence of middle level ridging this
afternoon. A shortwave trough is pushing across the Central
Plains...generating some showers and thunderstorms. The remnants of an
overnight mesoscale convective system that tracked across Iowa and Missouri is starting to
weaken as it drops southeast across central Illinois this afternoon.
A few scattered showers associated with this activity is pushing
towards the Louisville area presently. Dry air remains trapped in the
low levels in eastern Kentucky...which will likely prevent any of
this initial rain shower activity from reaching the surface.
However...a baroclinic zone is expected to tighten up tonight into
Sunday in the form of a warm front slowly lifting northeastward. This
will result in increasing cloud cover as isentropic ascent increases
along this boundary. This will help to moisten the middle and upper
levels this evening into tonight...producing a good deal of cloud
cover through Sunday and Sunday night. As the middle levels moisten
up...cloud bases could fall to 8-9kft. Given the presence of a weak
impulse early tomorrow morning...going to at least bring in a few
isolated rain showers into our southwest counties. Sprinkles will be
possible elsewhere through the day as middle level cloud cover remains
fairly robust through the day tomorrow. A stronger impulse will push
across the Ohio Valley late Sunday night and lift the warm front
northward. This will bring a chance of rain into northeast Kentucky.
If an mesoscale convective system gets going upstream....could not rule out a stray lightning
strike...although instability is fairly meager. Regardless...looks
like any rain chances will be minimal through Sunday night. Any rain
which does occur should be fairly light given the drier low levels.
As for temperatures...going to trend a bit milder tonight and Sunday
night with lows as clouds will help to keep temperatures a bit
higher. Highs on Sunday may be tempered by the cloud cover as well
with readings only slightly milder than today.
Long term...(monday through saturday)
issued at 345 PM EDT Sat may 25 2013
Height rises are expected on average through the period across the
southeastern states and eastern Seaboard with ridging expected to
be the dominant weather feature locally for most of the period. A
warm front will lift north and east of the area early in the
period...leaving the region in the warm sector for most of the week.
The isc consensus and model consensus/MOS guidance and 15z sref all
support at least slight chance probability of precipitation for Monday. As the warm front
lifts north and east of the area by Monday night...precipitation chances will
decrease. In general...the data grid Load was followed with slight
terrain adjustments to temperatures...mainly at night where a bit of
a Ridge/Valley temperature difference was introduced under the
influence of the high. The grid Load had some low probability of precipitation on Wednesday and
Thursday PM in the high terrain...but opted to continue with a dry
forecast as the 12z European model (ecmwf) came in dry for these periods.
As the ridge builds...from midweek and through the end of the
period...enough capping should be in place for just a diurnal
increase in cumulus and we have continued with a dry forecast for Wednesday
through Sat. Some of the model guidance and sref has probability of precipitation in on Tuesday
or even later in the week...but the models generally hint at a
weaker cap on Tuesday. The model consensus is that locations closer to
the WV border and in the higher terrain would appear to be the most
likely locations for any convection on Tuesday.
As the ridge builds moderate temperatures are expected with highs
warming to the middle and upper 80s on average by the second half of the
week and lows in the upper 50s to middle 60s.
&&
Aviation...(for the 06z tafs through 06z Sunday night)
issued at 136 am EDT sun may 26 2013
VFR and light winds are expected through the period. There will be
some showers trying to move into the area from the northwest at taf
issuance. They are falling out of a middle layer cloud deck around
8-10k feet above ground level. The precipitation is falling into a dry layer near the
ground...with a large amount of virga. Measurable precipitation at the
ground level is expected to be rather isolated...with little
restriction to visibility.
&&
Jkl watches/warnings/advisories...
none.
&&
$$
Update...hal
short term...kas
long term...jp
aviation...hal
