Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jackson Kentucky
345 PM EST Wednesday Nov 25 2015
Short term...(this evening through Thursday night)
issued at 256 PM EST Wednesday Nov 25 2015
Middle and upper level ridging over the southeast United States and
surface ridging extending from the northeast U.S. SW across the
Appalachians will continue to control our local weather through
the short term. The main forecast issue for the next 36 hours is
overnight minimums. In the east dewpoints this afternoon range
from the teens through the 20s. With the low dewpoints expect
another significant cool down in the valleys tonight...with
overnight lows ranging from the upper 20s in some of the cooler
valley locations to the lower 40s on the ridges. Dewpoints will be
higher Thursday night...so minimums will not be as low as tonight.
Still expect a significant difference from ridges to valleys in
the east Thursday night with lows from the upper 30s valleys to
upper 40s ridges.
Long term...(friday through wednesday)
issued at 345 PM EST Wednesday Nov 25 2015
Surface and upper level ridging which will dominate during the short
term period will loose its dominance and give way to a prolonged
period of southwest to west southwest flow aloft. The ridging will
initally in place from the western Gulf of Mexico north into the
southeastern Continental U.S. To the middle Atlantic coast. Initially a trough
is expected to be working into eastern Canada and southwest into
the intermountain west. The northern portion of the trough will
leave the southwestern portion of the trough behind with an upper
level flow meandering over the western Continental U.S. To start the period.
At the surface...a cold front will approach the lower Ohio Valley at the
start of the period. This cold front should slowly sag southeast
into the region to start the weekend as the front becomes
increasingly sheared from west to east. As the weekend
progresses...several disturbances will rotate out of the Desert
Southwest and into the plains and MS valley.
Model differences remain with the handling timing of of the
closed low over western US moving into the plains and eventually
into the eastern Continental U.S. Through the end of the period...or perhaps
beyond. Initial downslope flow and the model trend of slowing
down the precipitation a few hours have led to trimming back probability of precipitation
across the southeastern part of the area for Friday night into
early on Saturday. Overall...the best combination of moisture and
lift is during the Saturday to Sunday period. Two distinct rounds
of more widespread showers are expected...Sat into Sat evening as
the front moves into the area and the shortwave trough passes by
to the north and another with a shortwave moving into the Ohio
Valley region from the plains on Sunday and a surface waves moves up
along the boundary. Behind that shortwave...deeper moisture should
depart with the shortwave with the area in the warm sector until a
surface low tracks from the plains and into the Great Lakes during the
Monday to Wednesday period and sends a cold front across the area.
At present model agreement in this is for the front to move
through on Tuesday to Tuesday night...although model differences
remain. Tuesday looks to be another period where precipitation chances
will be higher...although showers cannot be ruled out at any time
starting Friday evening in the west and continuing into late Tuesday
night or next Wednesday.
Temperatures will generally be 10 degrees or so above normal on
Friday...and then near to slightly above normal through Tuesday.
Anticipated cloud cover should limit diurnal ranges through at
least Monday night...with min temperatures several degrees above
normal. Temperatures should cool to below normal behind the front
late in the period.
Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1233 PM EST Wednesday Nov 25 2015
High pressure across the eastern United States will keep VFR
conditions and light winds across eastern Kentucky through Thursday.