Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 032304
Area Forecast Discussion
National Weather Service Louisville KY
704 PM EDT SAT OCT 3 2015
...Updated Aviation Discussion...
.SHORT TERM (Now through Sunday Night)...
Issued at 300 PM EDT Sat Oct 3 2015
The synoptic pattern this afternoon features an upper-level low
across the Southeast which will be the main weather maker through
the short term period. It will bring continued cloudy and cool
conditions to the region through tonight, before some improvements
commence on Sunday.
A PV anomaly rounding the base of the upper-level low has helped the
low to become more negatively tilted today. In response, strong
isentropic ascent has enveloped much of SC northwestward through
eastern TN into eastern KY. Guidance suggests this ascent is rather
deep, from 850mb upwards of 500mb. However, northeasterly surface
flow is attempting to advect in drier near-surface conditions over
the Ohio Valley which has helped limit coverage/amounts to some
extent. For this evening, expect the slug of moisture to continue to
advect northwest through the region. The shower coverage remains
broken, but the deep ascent should help to squeeze out at least a
hundredth in mant spots so 80 pops are warranted mainly east of I-
65. Areas west of I-65 could still see measurable rainfall, but
confidence isn`t quite as high given weaker isentropic lift with
westward extent and further displacement from the western Atlantic
moisture stream. Therefore, will keep pops there in the 50-70%
range, but expect many areas will see some drizzle this evening at
the very least.
The nose of isentropic lift will shift to the south overnight as the
upper-level low meanders to the southeast and becomes elongated west-
east. Therefore, expect conditions to dry out through the overnight
hours. Guidance even suggests a weak back-door warm front pushing
though overnight which may cause temps to rise a degree or two
towards sunrise. Overnight lows will be in the low to mid 50s.
While a stray shower or two cannot be ruled out across southern KY
on Sunday, have gone with a dry forecast. Sunday temperatures will
be very tricky, with 03/12Z MAV/MET guidance showing a difference of
10+ degrees tomorrow at SDF. Think the cloud cover will be pretty
stubborn tomorrow given persistent northeasterly flow, so will go
with temps towards the cooler MET guidance. This puts highs in the
upper 60s to lower 70s, with a decent gradient likely to set up from
northwest (warmer) to southeast (cooler with more clouds).
Admittedly, the bust potential is quite high for temps tomorrow
afternoon as trends in cloud cover will be crucial.
At least some cloud cover will persist into Sunday night, but
mid/upper-level heights will begin to rise as the upper low pushes
offshore. Therefore, expect low temperatures to be slightly warmer
than the past few nights, with lows in the mid to upper 50s.
.LONG TERM (Monday through Saturday)...
Issued at 307 PM EDT Sat Oct 3 2015
A quiet long term is in store for the Ohio Valley as we sit under an
upper ridge squeezed between upper lows to our east and west through
Thursday. Surface high pressure moving through the middle part of
the country and the Great Lakes will assist in providing pleasant,
dry weather. High temperatures each day will be in the middle and
upper 70s with morning lows in the 50s.
By Friday-Saturday shortwave trofs will begin to carve into the
eastern ridge while the western Gulf opens up a bit. As a
result,will continue with the possibility of scattered showers to
finish the long term.
.AVIATION (00Z TAF Update)...
Issued at 659 PM EDT Sat Oct 03 2015
Plan on low-end MVFR to IFR ceilings to impact the TAF sites through
the evening hours along with isolated to scattered rain showers and
steady NE winds around 10 kts. After 06z, rain showers will diminish
but low ceilings will persist. Beyond 12z Sunday, forecast
confidence lowers in regard to when cloud deck will begin to lift or
scatter out. Trend in latest guidance is for MVFR ceilings to hang
on a bit longer. Have pushed this idea into the TAF. Eventually, a
push of drier air will lift ceilings to VFR.
Ceilings -- Medium
Visibility -- High
Winds -- High
Precip -- High