Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 200446
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1246 AM EDT Sun Apr 20 2014
...Updated Aviation Discussion...
Issued at 815 PM EDT Sat Apr 19 2014
As a deep closed low slowly moves east of coastal Georgia, mostly
clear skies will continue overnight and Sunday for the Commonwealth.
A very thin shield of cirrus will move just far enough west to
affect the Bluegrass and areas east of Interstate 75 early tonight.
With such a dry airmass, temperatures will drop pretty
readily late this evening. Lows near 40 are likely in some of the
sheltered valleys across eastern Kentucky and the Bluegrass.
Winds will stay quite light Sunday, especially by late afternoon and
during the evening hours.
.SHORT TERM (Now through Sunday Night)...
Issued at 305 PM EDT Sat Apr 19 2014
Pretty impressive dry air mix down event going on across the region
at this hour as dewpoints have dropped into the lower 30s in spots
over the past hour or two. Don`t have any recent ACARS soundings to
go off of, but forecast soundings do show the mixing extending well
up into a dry layer just above H85 mb and this has caused as much as
10 degree dew point drops in an hour or less. Most spots are
generally in the 25-35% range for relative humidity values, although
a few are in the 20-25% range at this hour. Additionally, NE surface
winds are sustained around 10-15 mph with a few gusts up around 20
mph at times. Finally, small fuels are quite dry and ranging from
5-8%. Although we are hitting critical thresholds for fire danger in
some spots for short periods of time, overall conditions are
marginal. Have issued an SPS to highlight a slightly elevated
wildfire danger, but will not issue any headlines at this time.
Otherwise, the weather is quiet across the region as the Ohio Valley
sits in between surface high pressure over the Great Lakes and low
pressure centered over NE Florida. Temperatures have risen into the
low 70s across the area under full sun and should find their way up
toward the low and mid 70s by late afternoon.
Winds will slacken around and just after sunset as both features
mentioned above slide off to the east. Meanwhile, an amplified upper
ridge axis will build in. Winds will go light and variable or calm
overnight, with good radiational cooling conditions. Expect lows to
dip into the low and mid 40s in most spots, although several cool
eastern valleys could drop around 40, especially as dry as it got
Another beautiful day is in store for Sunday as the ridge axis holds
and mostly sunny skies prevail. Expect temperatures to be 3 to 4
degrees warmer than today as inhibiting NE flow will be gone and
thicknesses suggest the trend upward. Have gone with upper 70s to
right around 80 degrees for highs, very much in line with the
Sunday night will be slightly milder as we start to see a few upper
level clouds streaming in with the upper level ridge axis moving
east. Additionally, a light southerly wind will take hold toward
dawn and could mix the low levels just enough to keep the low levels
mixed. Look for lows mostly in the upper 40s and around 50.
.LONG TERM (Monday through Saturday)...
Issued at 300 PM EDT Sat Apr 19 2014
A couple of systems will affect the region this period. Models
continue to have good agreement, within a half day, for the timing
of these systems, the first bringing rain chances Monday
night/Tuesday and the second Thursday night/Friday. Our best chance
for storms looks to be with that first system Monday night. Not
worried about severe threat with though, as instability is limited
and the associated wind field is not overly strong.
Temperatures will roller coaster around these systems, with highs
starting above normal Monday, then go near or just below normal for
mid week, before returning above Thursday. Friday`s temps will
depend on the timing of that second front, then Saturday we return
to below normal. At this point the coldest morning looks to be
Wednesday. The center of a high pressure behind the first front will
pass north of the region. For now will assume winds stay up some and
keep readings in the low/mid 40s. Should the high get closer than
forecast, we could see some upper 30s in our cold spots.
.AVIATION (06Z TAF Update)...
Issued at 1245 AM EDT Sun Apr 20 2014
VFR conditions will prevail through the period. High pressure will
remain in control over the Ohio Valley through the next 24-36
hours. This means winds will be rather light and variable today,
with only a few passing cirrus or diurnal cu. This cirrus shield
may increase a bit toward this evening and overnight, but it will be
of no impact to aviation operations.