Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 191905
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
305 PM EDT Sat Apr 19 2014
.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 (18Z TAF Update)...
Issued at 1247 PM EDT Sat Apr 19 2014
VFR conditions will prevail through this TAF period with high
pressure in control at the surface and aloft. A steady NE surface
flow has developed today with the tightening pressure gradient
between high pressure over the Great Lakes and a low over Florida.
These winds will peak early to mid afternoon between 10-15 mph,
becoming light and variable shortly after sunset. Expect skies to be
sunny the remainder of the afternoon, and clear overnight. Could see
a brief period of visibilities around 6 SM at BWG toward dawn.
Otherwise, expect VFR Sunday with winds light out of the SE on
Sunday. Expect a few Cu around 4 k feet and a few upper level