Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jackson Kentucky
1030 PM EDT Friday Jul 31 2015
issued at 1030 PM EDT Friday Jul 31 2015
Overall the forecast is still on track for tonight. Clear skies
and calm winds have set the stage for a Ridge Valley temperature
split overnight and fog formation in our valleys and near bodies
of water. The only tweaks that have been made to the grids were
the ingest of observation data to establish trends. Aside from that...the
forecast is being left as is.
Update issued at 735 PM EDT Friday Jul 31 2015
The forecast so far this evening is right on track. Clear
skies...calm winds and late night fog are still on tap...along
with a modest Ridge Valley temperature split across the area.
Short term...(this evening through Saturday night)
issued at 310 PM EDT Friday Jul 31 2015
Today has turned into a beautiful Summer day with highs topping
out in the middle 80s and dew points in the middle 50s. Dew points
today are an impressive 10 degrees lower than just a few days ago.
Skies will remain clear overnight allowing temperatures to once
again dip into the upper 50s in the valleys and lower 60s on the
ridges. With clear skies and calm winds some patchy valley fog is
anticipated towards dawn.
High pressure will remain in control of the sensible weather
through Sunday morning so can expect similar high and low
temperatures through the short term. There will be a brief
increase in some cloud cover tomorrow evening as a weak cold front
falls apart and passes through our area.
Long term...(sunday through friday)
issued at 344 PM EDT Friday Jul 31 2015
The period is expected to begin with a ridge extending from the
Southern Plains into the central rockies and a trough trough over
much of the eastern Continental U.S. Extending south from a closed low over
the southern Hudson Bay region. At that point...a few shortwaves
will be moving into the trough across the Great Lakes region. A
few shortwaves will also be working around the ridge across the
western Continental U.S. To start the period...with another further north
moving into southwestern Canada. At the surface...high pressure is
expected to be centered over the central Appalachians at that
point...with surface low pressure also centered over the southern
Hudson Bay region and a cold front extending south into the
northern Great Lakes and northern plains...before becoming
stationary and extending northwest into the northern rockies.
The closed low initially near southern Hudson Bay should meander
south and southeast into Ontario and Quebec and open up a bit
through the early to middle part of next week. A shortwave or two
rotating around this low should work into the northern Great Lakes
to end the weekend and rotate through the Great Lakes and into
the northeastern states through Tuesday. Then a shortwave working
around the ridge should approach the MS River Valley. The models
are not in agreement with the evolution and timing of the
shortwave entering southwest Canada early in the period working
into southwest Canada the corresponding surface area of low pressure
should track into Quebec with the trailing cold front gradually
dropping south of the Great Lakes during the Monday into Tuesday
period...before stalling out and becoming nearly stationary near
the Ohio River. The shortwave moving into the MS valley around
midweek should lead to a surface wave or waves developing along this
boundary and moving through the Ohio Valley region. The frontal
zone itself could also pass through the area late in the period.
Overall...the expected surface and upper air pattern will leave the
region susceptible to at least diurnally driven convection and
possible mesoscale convective system or nocturnal activity. The northern and eastern parts
of the area may be impacted early in the week...possibly as early
as the start of the work week.
As for probability of precipitation...Sunday is expected to bring a dry end to the weekend.
Isolated to scattered convection cannot be ruled out at any point
from Monday to possibly as late as Friday. The track and timing of
the shortwave that enters SW Canada early in the period will play
a key role in the duration of the threat for convection. With the
models relatively in good agreement through about Thursday with
the surface and upper air pattern and the shortwave expected to near
at midweek...chances for convection appear greatest from Wednesday into
Temperatures should moderate to a few degrees above normal during
the Monday into Wednesday period...before the cold front gradually
Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 735 PM EDT Friday Jul 31 2015
High pressure will continue to bring cooler and drier weather and
mostly clear skies to the taf sites through the weekend. VFR
conditions will prevail at the tafs sites for most of the period.
The exceptions late tonight into early tomorrow may be sym and
sjs...both of which could experience some MVFR fog between 6 and
12z on Saturday.