Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 061641
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1141 AM EST Fri Mar 6 2015
...Updated Aviation Discussion...
.SHORT TERM (Now through Saturday)...
Issued at 300 AM EST Fri Mar 6 2015
Despite a practically non-existent pressure gradient across the
region, several sites 3-5 knots of wind through 2 AM. This wind has
kept us just mixed enough, at least so far, to prevent quick drops
in temperatures. The more sheltered locations, such as the
Cynthiana, Brandenburg, and Richmond mesonet sites, have gone calm
and consequently there temperatures have dropped to several degrees
below 0. We still have a window for temperatures to drop quickly,
and at 3 AM more of the sites are coming in calm, so still have
forecast lows down at or below zero for most sites.
Surface high pressure over us now will sink southeast of the area
tonight and Saturday. Winds will start to pick up out of the south
later this afternoon, bringing a little more moisture into the
region as well as warmer temperatures. Have lows tonight down into
the teens and possibly some single digits. Higher dewpoint air
moving into the region may cause some fog to form over the snowpack,
but not confident enough in this scenario to put more than patchy
fog into the forecast. For Saturday southwesterly winds will
continue to bring in warmer air, with highs likely in the 40s for
.LONG TERM (Saturday Night through Thursday)...
Issued at 400 AM EST Fri Mar 6 2015...
The good news in the long term is warming temperatures. The bad news
is that will cause lots of melting, which will keep creeks and
rivers running high, and may cause water problems for low-water
crossings on rural roads.
Another fly in the ointment for the long term is yet another precip
maker coming into the southeast U.S. on the southern branch of the
jet Monday night and Tuesday. The northern extent of this one is
still being battled by the models, with the GEM bringing it north
farther than either the ECMWF or GFS, which has the southern-most
track. For now will split the difference and go with the
middle-ground Euro, which brings a chance of showers to our southern
through eastern counties. Unlike the past two rain events, through,
this one appears to be relatively light for us, with expected
rainfall less than 0.10" - at least for now.
With a 500 mb pattern that thinks it`s in the Groundhog Day movie,
another disturbance ejects out of the semi-permanent SW U.S. trof,
into the southeast U.S. by Friday, complete with abundant tropical
moisture. While still far too early to place any faith on exactly
where this one will track, at least there does not appear to be any
cold air close enough to make us think we`re in Boston, as this one
should remain all rain.
Temperature-wise through the extended, we`ll warm from the 40s on
Sunday to the 50s by Tuesday, and even into the 60s for at least
southern Kentucky by Wednesday and Thursday. Overnight lows will be
in the 20s Sunday morning, then moderate 5 degrees upward each night
through the period. With warm air and dewpoints above 32 riding
north over the snowpack, this will likely result in some areas of
nighttime fog each night through the extended.
.AVIATION (18Z TAF Update)...
Issued at 1141 AM EST Fri Mar 6 2015
High pressure will keep our weather quiet during this TAF period. A
weak storm system will cross the Great Lakes but precipitation
associated with it should remain to our north.
There will be some low level moisture in the area tonight, but at
this time it appears that clouds, if any, should remain scattered.
Variable winds today under the high will concentrate from the SSW
tonight into tomorrow as the high moves away.