area forecast discussion
National Weather Service Louisville Kentucky
641 am EDT Sat may 25 2013
..updated aviation discussion...
Short term (now - sunday)...
issued at 300 am EDT Sat may 25 2013
Surface high pressure ridging in from the north will shift very
slowly to the east through Sunday. Aloft the region will remain in
northwesterly flow through this period.
Today will start out on the cool side with temperatures in the 40s
in most locations, with a few upper 30s in sheltered areas possible.
Some valley fog is showing up on area webcams this morning. This
should dissipate quickly once the sun rises. Today should be dry
across the area. A few models are trying to develop some
precipitation this afternoon over northern portions of the area.
However, with very dry air aloft, it looks like the moisture
streaming in will mainly enhance cloudiness. Some virga may be
possible as well.
Chances for some measurable precipitation increase tonight and
tomorrow, though it still does not look to be widespread. The
atmosphere will become more saturated by tonight and a couple
of weak waves will move southeast through the flow aloft. However,
am still not really certain as to how much precipitation we will see
through this period. Thunderstorm chances look fairly limited as
soundings indicate a decent cap will remain in place at least Sunday
morning. Will only mention isolated thunderstorms on Sunday.
Temperatures today will range from the upper 60s in the northeastern
portions of the forecast area to the mid 70s near the Tennessee/Kentucky border.
Lows tonight will be a bit warmer in the lower 50s. Tomorrow's highs
will top out in the lower to mid 70s areawide.
Long term (sunday night - friday)...
issued at 317 am EDT Sat may 25 2013
Sunday night through Monday night...
Surface warm frontal boundary will be located somewhere across the
Ohio Valley at the start of the forecast period. With a
northwesterly flow aloft, several mid-level waves will likely move
down along the upper trough axis. These waves will likely lead to
several rounds of mesoscale convective system activity passing close to the region. The
models still have a large spread across the region with the American
GFS and NAM being more on the wetter side of the guidance envelope
and the European trending more drier. For now, plan on keeping
isolated to scattered storm chances in for Sunday night and into
Monday. Still does not look to be a washout by any means, but the
best threats of rainfall would likely be more favored over northern
areas. Surface warm front will slide to the north of the region
Monday night ending the threat of rainfall. Lows Sunday night will
be in the mid-upper 50s in the north with upper 50s in the south.
Highs Monday look to warm into the upper 70s to around 80 in the
north and lower 80s in the south. Lows Monday night will cool into
the upper 50s to around 60.
Tuesday through Friday...
Not much change to the ongoing forecast through this portion of the
forecast period. The latest suite of deterministic and ensemble
guidance continues to show relatively good agreement with the
overall synoptic pattern. All of the guidance agrees that a
strengthening area of high pressure and ridging aloft will develop
over the eastern US. With a strong high pressure system anchored
over the western Atlantic, we should see a good, sustained southerly
fetch coming north off of the Gulf. With the good southerly flow
and plenty of insolation, it will certainly feel like Summer around
the Ohio Valley as temperatures warm into the middle to upper 80s.
Generally went close to multi-model consensus for temperatures here,
but given the strength of the ridging and high sun angles, the
models...in particular the statistical guidance is probably lagging
on temperatures a little bit. So it would not be out of the
question that an increase in Max temperatures may be required with
subsequent forecasts. Overnight lows through the period will be in
the upper 60s to around 70.
&&
Aviation (12z taf issuance)...
issued at 640 am EDT Sat may 25 2013
VFR conditions are expected at all taf sites through the next 24-36
hours. High and mid level clouds will filter in through the day
today, becoming a broken deck by this afternoon or evening. Calm
winds this morning will pick up to 5-6 knots out of the east. Lex
and sdf may see a wind shift for a few hours this afternoon to more
northeasterly. Winds will then become light and variable to calm
again tonight. A few showers may approach sdf tonight, but
confidence is low and they should have no impact on flight
categories, so will keep the forecast dry.
&&
Lmk watches/warnings/advisories...
in...none.
Kentucky...none.
$$
Short term.......eer
long term........mj
aviation.........Eer
