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Area forecast discussion 
National Weather Service Jackson Kentucky
742 PM EDT Sat Aug 1 2015

Update...
issued at 742 PM EDT Sat Aug 1 2015

No major changes to the forecast were needed at this time. The
forecast in general is still on track. A Ridge Valley temperature
split and valley fog...confined mostly the valley floors and near
bodies of water...are both still on track for tonight.

&&

Short term...(this evening through Sunday night)
issued at 345 PM EDT Sat Aug 1 2015

As of middle afternoon...a middle level ridge was centered near The
Four Corners region and extended across much of the western Continental U.S.
And south into parts of northern Mexico. Meanwhile...a closed low
was over the Hudson Bay region with a trough extending south into
the eastern Continental U.S.. the region is currently in northwest flow aloft
between these two...with some middle and high level debris clouds
passing through from time to time. At the surface...a weak moisture
starved cold front continues to drop southeast across the region
this afternoon. Behind this front...a ridge of surface high pressure
building into the Ohio Valley is already ushering in some
reinforcing drier air. Further north and northwest...a shortwave
rotating around this closed low and associated surface low pressure
and cold front are heading toward the northern plains and Great
Lakes region.

The ridge of surface high pressure is expected to slide east and
settle across the WV coalfields by dawn on Sunday...before
gradually departing. At the same time...the closed low now over
Hudson Bay will drop south into Ontario later tonight or on
Sunday...with a shortwave trough moving around this closed low and
into the Great Lakes late in the period. The corresponding surface
low should track from the northern plains and into the Great Lakes
by Sunday evening...before reaching eastern Ontario and southern
Quebec at the end of the period. The trailing cold front should
approach the lower Ohio Valley at that point. Moisture will increase
a bit ahead of the front...but will be limited. Convection
associated with this could drop south of the Ohio River and near
the far north toward dawn on Monday. However...confidence in this
is low and the region may in fact just remain dry.

Tonight...with just a few middle and high clouds and drier air
moving into the area and slackening winds expected...conditions
will be good for radiational cooling. In fact...lows in some
places could be another degree or two lower than the previous
mornings as dewpoints in the middle to upper 50s have become more
widespread across southeast Kentucky this afternoon. River Valley
fog...possibly dense is also favored to develop.

Ahead of the cold front...surface high pressure should dominate for
most of...if not all of the period. Any fog that develops tonight
will lift and and dissipate on Sunday...with temperatures
moderating ahead of an approaching front with the relatively dry
airmass for early August should heat to a few degrees above
normal. Valley fog could again develop late in the period...with
overnight lows Sunday night a couple of degrees below normal...
particularly in the valleys.

Long term...(monday through saturday)
issued at 310 PM EDT Sat Aug 1 2015

Fairly active pattern setting up especially toward the end of the
long term period. The start of the period will feature a surface
cold front approaching from the northwest. Overall upper level
pattern will feature a eastern Continental U.S. Trough...while a upper level
high will eventually shift west and meander around The Four
Corners to western Texas. Several waves are forecast to ride
through the northwest flow and near and along the stalled surface
boundary.

In terms of the sensible weather this will ultimately lead to
unsettled pattern across the Ohio Valley and eastern Kentucky regions.
Monday Monday the approaching cold front will bring a chance of
storms across the region. Right now look like better chances will
reside across the north along and near the i64 corridor then
translating southeast into portions of the far east. The latest 12z GFS
and NAM are a bit more robust with precipitation along the front Monday
into Monday night. They also have trended south with overall front
location...given this plan to make adjustments up on the overall
probability of precipitation. Right now will lean toward isolated to scattered activity.
After this the quasi stationary front is expected to hang up
across the Ohio and Tennessee Valley areas through the rest of the
long term periods. This front coupled with upper level waves will
be the Focal Point for shower and thunderstorm activity through
the period. Right now will lean toward the superblend given the
overall variability in the timing and strength of waves through
the long term. This will lead to higher chances Wednesday into
Thursday where there is a bit more overlap in models. Also should
be mentioned...this pattern will likely give way to mesoscale convective system activity
and this could lead to more nocturnal activity. Overall
temperatures through the period will be near to above normal
range.

&&

Aviation...(for the 00z tafs through 00z Sunday evening)
issued at 742 PM EDT Sat Aug 1 2015

A ridge of high pressure will keep mostly clear skies and light
winds place across the area through the of the taf period. Any fog
that forms overnight should be confined to valley floors and near
bodies of water. As such...the taf sites should all remain free of
fog tonight and early tomorrow morning. That all being said...VFR
conditions area expected at all the airports...with scattered
low and high clouds occasionally drifting across the area through
the end of the taf period.

&&

Jkl watches/warnings/advisories...
none.
&&

$$

Update...Arkansas
short term...jp
long term...dj
aviation...Arkansas

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