Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jackson Kentucky
209 PM EDT Wednesday Jun 3 2015
issued at 209 PM EDT Wednesday Jun 3 2015
Updated ndfd to lower maximum temperatures in the north to lower
70s and highs in the far south to near 80. Flow just above the
surface from the southeast has continued to aid in erosion of low
level clouds in the southeast with temperatures rising into the
middle 70s...while temperatures hold in the middle 60s where low
overcast skies have persisted. Partial clearing continues to work
northwest. At the same time convection has developed over Virginia and some
showers have moved into eastern Pike County.
Update issued at 1058 am EDT Wednesday Jun 3 2015
Have added thunder chances to the forecast for this afternoon.
This change is based on several factors. We are expecting some
sunshine in the southeast this afternoon...and in fact much of
Harlan County is already seeing considerable sunshine. While
surface winds continue from the NE...jkl vwp from earlier this
morning showed southeast winds at 3k mean sea level. We are seeing some
downsloping off the higher terrain in the far southeast...and this will
continue to help with breaking up the shallow cloudiness over at
least the southeast part of forecast area. The hrrr supports this idea.
Convective available potential energy are forecast to increase to 1800 to 1900 this afternoon
with fairly steep low level lapse rates. Yesterday thunderstorms
occurred to the south and southeast of the forecast area where
sunshine occurred. So based on current local analysis have added
thunder to forecast. Storm Prediction Center also has entire forecast area outlooked
in the general thunder area for this afternoon. Updated ndfd and
associated products including zone forecast product and severe weather potential statement.
Update issued at 649 am EDT Wednesday Jun 3 2015
A deck of low clouds continues to hang across much of Kentucky...and
will likely hold on through much of the day. Fog is currently
being reported...especially in the far east...where visibilities
have now gone down to below 1/4 mile in sjs and Pikeville. Expect
the fog to slowly mix out through the morning...though expect the far
east to be back to a mile or above within the next hour or so.
Otherwise...with clouds lingering around throughout the
day...still expecting temperatures to stay well below normal. Loaded in
the latest observational data for temperatures...dew points...and
winds...to make sure the near term grids well reflected these
ongoing conditions. Otherwise...forecast seems to be well on track
and no further changes were needed at this time.
Short term...(today through thursday)
issued at 350 am EDT Wednesday Jun 3 2015
The upper level low will continue to shift slowly southeast across
the Appalachians today...and then eastward across the Carolinas and
towards the Atlantic on Thursday. This will likely keep the clouds
around through much of the period. Despite low clouds
overnight...fog has continued to set up across much of the
region...with visibilities as low as 1 mile observed in a few
locations. This fog will likely be hard to burn off in the
morning...given the continued cloud cover and lack of sun/heating.
Clouds will also likely keep temperatures on the cool side once
more today. Forecasted high temperatures well under guidance again...and
would not be surprised to see temperatures similar to the ones we
saw yesterday...perhaps just a few degrees warmer. While a few
showers could pop up this afternoon...there again...lack of
instability could limit aerial coverage of showers to more
isolated. Models have been handling the instability...
temperatures...and cloud cover poorly...so its hard to put Faith
on any precipitation forecast from a model. Previous forecast
seemed to match up well with the latest hrrr and nam12...with best
coverage across the far east...and likely no probability of precipitation for the western
portion of the County Warning Area. Leaned more towards a solution of these
three...with a slight bit of superblend added in.
There is no push for moisture to exit by tonight...so will go for
another cloudy night for Wednesday night with the potential for fog
redevelopment in the valleys once more...much as it is currently at
7z. This would put lows back into the 50s for another night. By
Thursday...the low will have shifted slightly farther away from the
region as it traverses the Carolinas...but its proximity to the
Atlantic will allow for continued moisture flow into the region.
Once again...expect this to promote some degree of afternoon
convection...though the amount of westward progression across the
County Warning Area is still somewhat uncertain. Just based on the latest short
range models...expect it to move in a little farther west than
today thanks in part to slightly higher temperatures and resulting better
instability. Speaking of instability...based on the latest
soundings...a rumble of thunder cannot be ruled out...though
overall dynamic support is lacking. Went ahead and included
mention of isolated thunder in the forecast for during the day
Thursday...which seemed to be a bit more in line with surrounding
Long term...(thursday night through tuesday)
issued at 359 am EDT Wednesday Jun 3 2015
The extended forecast period begins on Thursday night begins with
the upper low that has been hanging around the area for the past few
days finally beginning to weaken and shift to the east. With upper
level ridging developing...another shortwave will travel the ridge
and move into the lower appalachian range and into the southeast.
Following this...a stronger shortwave moves along the northern
stream and into the Ohio Valley by Sunday night and will be the
featured weather system over the area through the last couple days
of the extended.
Closer to the surface...a remnant boundary over eastern Kentucky
couple with upper level disturbances will keep active weather over
the area through Saturday. This will mainly be diurnal in nature
and will expect enough instability each afternoon for some
development. By Sunday a mention strong upper wave will move into
the area dragging a strong cold front into the area. This will
provide a good chance of showers and thunderstorms. Some storms
may actually be strong...especially on Sunday and Monday with
good instability and increase in moisture.
For the period...temperatures look to rebound well and will be in
the lower 80s for highs and in the middle 60s for lows. With warm
southern and moist air moving into the area through the period.
Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 209 PM EDT Wednesday Jun 3 2015
The upper level low which has controlled our weather for the past
several days is drifting south...and is currently over the far
western tip of North Carolina. The low clouds which have covered
eastern Kentucky are eroding from the southeast towards the northwest with
downsloping southeast winds off of the higher terrain. As a result
do expect low clouds to lift and decrease in coverage especially
in the southeast. In all areas expect the MVFR ceilings to lift
to VFR by late afternoon or early evening. Where more sunshine has
occurred over Virginia and Tennessee showers and thunderstorms have developed.
The chance of a thunderstorm affecting a taf site this afternoon
is very low...with the best chances in the east and southeast.
Have included thunderstorms in the vicinity in the sjs and jkl tafs for a couple of hours
this afternoon...but have left this out of the other tafs. With
breaks in the clouds do expect some fog development tonight...so
VFR conditions are expected to decrease to MVFR or IFR later
tonight. Once the fog dissipates Thursday morning VFR conditions
will prevail on Thursday.