Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 020718
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
318 AM EDT Sat Aug 2 2014
.SHORT TERM (Now through Sunday)...
Issued at 250 AM EDT Sat Aug 2 2014
A broad trough will remain in place across the eastern CONUS through
the short term. A vortmax will swing through this trough today and
shift east of the region through tomorrow.
Isolated showers are ongoing early this morning across southern IN
and the Lake Cumberland region of KY. This shower activity is
expected to diminish over the next few hours with dry conditions
through at least mid morning. Isolated to scattered showers and
thunderstorms are then expected to develop lat this morning into the
afternoon hours. The best chance for storms will be across portions
of southern IN and north central Kentucky. These storms should
dissipate this evening as daytime heating wanes and the vortmax
Soundings show a drier airmass settling in Sunday, with PWAT values
dropping under an inch. In addition surface high pressure will build
in from the west and we will likely see some capping by the
afternoon. Thus, it looks like Sunday should be dry.
Temperatures today and tomorrow will top out in the mid to upper
80s, with the lowest temps today across the northeastern portion of
the forecast area. Lows tonight will be in the lower to mid 60s.
.LONG TERM (Sunday night through Friday)...
Issued at 315 AM EDT Sat Aug 2 2014
Long Term Synoptic Overview
500 hPa positive height anomalies located over the western Atlantic
and in the desert southwest will result in the eastern US and Ohio
Valley remaining under the influence of upper level troughing. This
pattern looks to hold through about midweek. An emerging signal
within the model data suggests that a large negative height anomaly
will develop over southern Canada while above normal height
anomalies will continue over the southwestern US. This scenario
would result in a NW-SE oriented baroclinic zone setting up from the
northern high Plains through the Carolinas. Within this set up,
numerous perturbations within the flow would bring numerous chances
of convection from midweek through next weekend.
Model Preference / Confidence
In the front end of the extended and general blend of the 02/00Z
operational GFS and Euro was preferred. While the model spread
remains quite high from the middle to the end of the week, a bit of
forecast convergence appears to be emerging with the overall
evolution of the synoptic pattern. The aforementioned baroclinic
zone setting up looks increasingly likely, but where specifically
the boundary sets up is still uncertain. The 02/00Z operational GFS
is on the northern side of the spectrum with the 02/00Z Operational
Euro encompassing the southern end of the spectrum. For now, have
used a blend of the previous forecast combined with the 01/12Z
global ensembles to trend the forecast slightly wetter as the week
wears on. Forecast confidence in the front end of the extended is
slightly above average in both temperatures and precipitation.
Confidence decreases to slightly below average from midweek onwards.
Sensible Weather Impacts
Generally quiet and dry weather conditions are expected from Sunday
night through Tuesday. As southerly flow increases on the back side
of the western Atlantic ridge, we should see an increase in both
temperature and dewpoints early next week. Highs Monday and Tuesday
look to be near seasonal normals with highs in the middle to upper
80s in the north with upper 80s to the lower 90s in the south.
Overnight lows will generally be in the mid-upper 60s. Precipitation
chances will likely start to ramp up by Wednesday as the baroclinic
boundary drops southward toward the Ohio Valley. Initially low
chance PoPs are expected for Wednesday with greater chances of
precipitation expected as we go into Thursday and Friday. A decent
amount of QPF will be possible along the frontal boundary. As
stated above, where this boundary sets up is still a bit murky, but
total QPF amounts through Friday could easily top 1-2 inches where
repeated rounds of convection train over areas.
With the expected increase in cloud cover and precipitation, high
temperatures will be more tempered Thursday and Friday with highs
mainly middle 80s in the north/northeast with middle to upper 80s
down across the south. Overnight lows will generally be in the
.AVIATION (06Z TAF Update)...
Issued at 1240 AM EDT Sat Aug 2 2014
Some mid to high level clouds will stream across the region
overnight from the dissipating convection. Winds will be light and
variable to calm. This may allow for some light fog/haze formation
towards sunrise at all sites. Any fog or haze should be short lived
and dissipate shortly after sunrise.
Cu will develop once again this afternoon with isolated to scattered
showers and thunderstorms possible. Think that coverage of
convection will be low enough that it is not worth mentioning in the
TAFs at this time. Winds will be generally out of the north and less
than 8 knots.