Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 180724
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
324 AM EDT TUE JUN 18 2013
.SHORT TERM (Now through Wednesday)...
Issued at 324 AM EDT Mon Jun 18 2013
Radar continues to show widespread light rain continuing across the
forecast area this morning. Convectively induced MCV continues to
push through middle Tennessee this morning with the heaviest
activity mainly staying to our south. Some moderate rain showers
will be possible across our southern Kentucky counties over the next
few hours...and a rumble of thunder or two can not be ruled out.
Elsewhere, light rain is beginning to diminish across our northwest
and western sections. Expect to see precipitation come to an end
toward sunrise over our northwest sections. Additional convection
is forecast to develop just to our northeast...between Indianapolis
and Covington later this morning...according to our local WRF model
run. Indeed, convection has developed over the last hour in this
general area. This activity is forecast to slide southeast and may
affect our far NE counties after sunrise. However, the local WRF
shows this activity decaying in the 13-14Z time frame. Temperatures
this morning will continue to be nearly steady state with lower to
middle 60s in the north and upper 60s to around 70 in the south.
Patchy fog will be a possibility in the typical low-lying and fog
prone areas until sunrise.
Somewhat of a complicated and overall low confidence forecast today
regarding cloud cover and additional convection. Widespread
convective debris will initially limit our solar insolation this
morning...keeping morning temperatures in the lower to middle 70s.
However, as the afternoon wears on, we should see cloud cover
decrease...especially across the west and northwestern sections
which will allow temperatures to warm into the lower to middle 80s.
Real question mark is over the east...where cloud cover may keep
temperatures in the upper 70s to around 80. Should clouds break up
faster, temperatures in future forecasts may need to be increased
As we heat up, we will destabilize once again thanks in part to
slightly cooler mid-level temperatures which will allow lapse rates
to approach 7 C/km. The afternoon heating combined with dewpoints
in the 60s should yield a moderately unstable atmosphere resulting
in isolated-scattered convection to develop across the region. With
this in mind...plan on keeping isolated-scattered PoPs in the
forecast for this afternoon.
More interesting convective development is possible late this
afternoon and evening as mid-level wave dives down from the Dakotas
into the Ohio Valley. As this feature pulls into the region, it
will encounter the moderately unstable and weakly sheared
atmosphere. Overall shear is not that great as we will be located
on the southern edge of the westerly flow with values pegged at 35
to maybe 40 kts. Latest high resolution NAM...WRF...and LMK WRF
models all develop convection across central Indiana this afternoon
and then drop it southeast into our southern Indiana counties by
this evening. This activity should continue into areas south of the
Ohio River early this evening, but is expected to weaken with the
loss of heating and increasing PBL stability. Some storms could be
on the strong to severe side this afternoon across our northern
sections. Based on the severe parameters of shear/instability that
damaging winds and near severe hail would be possible. Overall, feel
that the threat is likely to be more to our north where the stronger
shear would be located (up around the I-70 corridor). After the
activity dissipates, clear to partly cloudy skies are expected for
the overnight period with lows in the lower-middle 60s.
More quiet and tranquil weather looks likely on Wednesday with
afternoon highs warming into the lower to middle 80s.
.LONG TERM (Wednesday Night through Monday)...
Issued at 252 AM EDT Tue Jun 18 2013
The long term will be fairly quiet with just occasional slight
chances for thunderstorms. At the surface high pressure will slide
east of the region early in the period and we will then remain in
between the high pressure to the east and low pressure to the west.
Aloft a ridge will build from Texas to the Lower Mississippi River
Valley and then shift slowly eastward.
Mainly dry conditions are expected through the long term. A few
different weak disturbances may bring a slight chance of showers
thunderstorms to south central Kentucky on Friday, to northeastern
portions of the forecast area on Sunday, and to the whole area on
Monday. These storms are not expected to be widespread at this time.
Temperatures will warm into this weekend. Highs Saturday through
Monday are expected to top out in the upper 80s to lower 90s. Lows
will go from the lower 60s on Thursday morning to upper 60s and
lower 70s this weekend.
.AVIATION (06Z TAF Update)...
Issued at 112 AM EDT Tue Jun 18 2013
Rather low-confidence continues for the overnight period especially
with regards to potential for low clouds and fog. Widespread shower
activity across western KY will continue to move eastward while
diminishing in coverage. Some light rain will be possible at the
terminals through at least 18/10Z. Cigs and Vsbys look to start off
as VFR, but the guidance suggests some IFR/MVFR cigs developing late
tonight as low clouds build downward. At this time...feel that MVFR
cigs are attainable and will place those into the upcoming
forecast...mainly after 18/08Z through 18/12-14Z. Patchy fog will
also be possible...mainly at KBWG and KLEX. Conditions should
improve a bit after 18/13Z as drier air works in from the NW.