Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 202317
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
717 PM EDT Wed May 20 2015
...Updated Aviation Discussion...
Updated 540 PM EDT Wed May 20 2015
Seeing some heavier returns in eastern PAH`s area as well as more
reports of measurable precip, so as indicated before will continue
the trend up in precip amounts. Visibility still not dropping at
HNB, so it is taking the heavier returns moving over an area to get
measurable, at least at this point. Also removed thunder wording for
all but right along the TN border, closer to where the surface low
will pass later this evening.
Only other thing added in this package is some patchy fog across our
southeast overnight. Guidance calling for some low cigs and possible
fog, just ahead of the surface low. Given lighter winds and all of
the moisture around this thinking is plausible and worth mentioning
in the forecast.
Updated 440 PM EDT Wed May 20 2015
Tweaked pops up some for the shield of rain coming in. Not seeing
visibility reductions at KHNB just yet, despite at least an hour of
higher reflectivity returns on radar. The question for not going
with higher pops at this point is whether the rain will measure more
than a trace or not. Likely will keep adjusting pops over the next
few hours as we see obs come in upstream.
.SHORT TERM (Now through Thursday Night)...
Issued at 230 PM EDT Wed May 20 2015
An upper level shortwave and sfc low pressure will pass through the
region tonight bringing mainly rain showers to the area. The first
batch of rainfall will enter southern Indiana late this afternoon
with light rain overspreading west central KY before sunset. Light
rain will continue to move through the area this evening and exit
the area around or just after midnight. A few rumbles of thunder
will be possible over south central KY as the sfc low moves close to
the KY/TN border providing a bit more forcing. Some light sprinkles
or isld showers may be possible after midnight in low clouds.
Overall though the main rainfall will occur before midnight with
rainfall totals less than a quarter of an inch. Expect low temps in
upper 40s to lower 50s tonight.
For Thursday, low clouds will stick around for much of the day with
skies becoming partly cloudy late in the day over southern IN/west
central KY. As a result, high temperatures will be limited to the
Thursday night sfc high pressure will overtake the region and skies
will clear. With light winds and subsidence over the region,
temperatures should drop into the 40s for lows. Patchy fog will
also be possible under these conditions as well.
.LONG TERM (Friday through Wednesday)...
Issued at 246 PM EDT Wed May 20 2015
High pressure will slowly work its way across the region Friday
through Saturday with northwesterly flow in place aloft. Saturday
night into Sunday will see a transition in patterns as ridging aloft
builds across the southeastern CONUS. The Lower Ohio Valley will be
on the northwestern side of this ridge. At the surface winds will
transition to southerly as the high pressure shifts off to the east.
Dry weather will be in store for the region Friday through Saturday
under the influence of the high pressure. Friday`s highs look to
stay a bit below normal for this time of year, topping out in the
lower to mid 70s. We will continue to see a warming trend into early
next week with highs into the lower to mid 80s by Monday.
The southwesterly winds aloft and southerly surface winds from
Sunday on will bring in more moisture with dewpoints rising back
into the mid 60s. Multiple waves moving through the flow aloft will
bring chances for thunderstorms through Tuesday. In addition, a weak
front will move through towards the end of the forecast period.
Multiple rounds of storms will move through Sunday through Tuesday
with these impulses and daytime heating. Organized severe weather is
not expected, but some strong pulse storms are not out of the
question as instability develops in the afternoons.
.AVIATION (00Z TAF Update)...
Updated at 710 PM EDT Wed May 20 2015
Weak surface low travelling across TN this hour. Given how far south
it is, winds likely will maintain a mostly northerly component this
period. Have some light rain chowers across the terminals this
hour...very light, with only BWG going down to MVFR at last ob. That
should improve to VFR by 00Z, but additional showers will remain in
the area for a few more hours. Low-levels will saturate overnight,
bringing MVFR/IFR cigs at all sites from roughly midnight on. Model
time-height sections indicate the clouds should linger well into
Thursday, with cigs improving by late afternoon.