Area forecast discussion...updated
National Weather Service Jackson Kentucky
353 am EDT Thursday Jun 20 2013
Short term...(today through friday)
issued at 353 am EDT Thursday Jun 20 2013
The latest surface map reveals a nice bubble of surface high pressure
centered across New England...while a deep Lee-side low pressure
system is crossing The Rockies. Aloft...an upper level ridge is
centered across northern Mexico...with a deep upper level low
spinning over the Pacific northwest.
Eastern Kentucky remains under the influence of the New England high
pressure...with a more pleasant air mass in place...as lows have
dipped down into the 50s in places...with areas of dense fog showing
up nicely on the fog channel in the east.
The models are in good agreement through the short term...very
gradually expanding the sub-tropical ridge northeast...allowing for
some weak trouginess across the Ohio and Tennessee valleys to
conclude the work week. At the surface...high pressure will be
shifting to the northern Atlantic...allowing for a bit more moisture
return each day.
The inherited forecast was in excellent shape...and will not stray
too far. Once the fog Burns off by around 9 am this
morning...temperatures will soar up into the middle 80s...with perhaps a
few storms able to break the cap along the Tennessee/Virginia borders during the
afternoon and into the early evening. Lows tonight will bottom out in
the low to middle 60s...with perhaps a few valleys north of the
mountain Parkway slipping into the upper 50s.
On Friday...the cap will be weaker...so can not rule out isolated
convection for most locations as highs return to the middle 80s with
more moisture in the air.
Long term...(friday night through wednesday)
issued at 353 PM EDT Wednesday Jun 19 2013
A large ridging pattern will be at play during the beginning of the
extended period...encompassing much of the southeast...and remaining
in place through much of next week. Though models have a pretty fair
agreement on the overall 500mb ridge/trough set up...subtle features
are still highly disagreed upon. Regardless...with little upper air
influence...and warm moist southerly flow off of the Gulf...main
concerns during the extended forecast are the warm and humid
temperatures...and the possibility for convection during the
afternoon hours as a result. Models seem to be pinpointing best
chances for convection over the more mountainous south and
southeastern sections of the County Warning Area...where moist air will be forced to
lift upon encountering the mountains.
Despite model disagreement on subtle features in the overall
ridge/trough set up...there is at least enough agreement that with
ridge extending well to the north of the County Warning Area...most shortwaves will
not directly impact Kentucky. However...some of the instability associated
with these shortwaves can only help to engage some of these
above-mentioned afternoon thunderstorms. The best chance for area
wide convection will then be Wednesday into Thursday as a strong
500mb low over the eastern coast of Canada continues to wrap up and
gain strength...dropping a potentially potent cold front from the
Great Lakes to the Ohio Valley and southward. Obviously this far
out...exact timing and severity are quite uncertain. But if this
holds together...looks to be a good chance of a line of potentially
strong thunderstorms moving from north to south in concordance with
the movement of the front. European model (ecmwf) lapse rates peak out between 7.5
and 8.0c by Wednesday afternoon and GFS soundings showing cape above
3000 j/kg as the front nears. Regardless of whether these values
hold true this early in the game...this will obviously be a system to
watch as it continues to near.
&&
Aviation...(for the 06z tafs through 06z Thursday night)
issued at 159 am EDT Thursday Jun 20 2013
High pressure will provide mainly VFR conditions and light winds
through the period. There will be some MVFR fog to contend with at
loz and sme between 09 and 13z...with IFR or worse expected in the
deeper river valleys. Some cumulus will develop during the day around the
4k foot above ground level level. An isolated shower or storm can not be completely
ruled out during peak heating along the higher terrain bordering
Tennessee/Virginia as well.
&&
Jkl watches/warnings/advisories...
none.
&&
$$
Short term...geogerian
long term...sbh
aviation...geogerian
