Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Greenville-Spartanburg SC
946 PM EDT Monday Apr 20 2015
a cold front will cross the area today bringing another round of
showers and thunderstorms. Dry high pressure builds in for Tuesday
and Wednesday. Another cold front will push in from the northwest on
Thursday...possibly bringing showers back to the area. A stronger
storm system will move in for the weekend.
Near term /through Tuesday/...
of 930 PM...communication links were restored to our office and
radar around 9 PM. At this time...one severe cluster of storms
existed across southern Greenwood County. This activity will slide
east over the next 45 mins. Otherwise...the primary forecast concern
will be the timing and placement of the surface cold front tonight.
Latest observation and radar data indicate that the front was located across
the southern Appalachians. The front will sweep west through the
overnight hours...resulting in veering flow and generally thin cloud
scattered severe thunderstorms will continue to form within low level moist
convergence axis in the immediate Lee with a steady expansion along
and eventually southeast of I-85 during late afternoon hours. Observed/forecast
area soundings depict steep lapse rates and moderate amounts of cape
within the hail growth region. Vwp/S and soundings also showing
strong and mostly unidirectional wind shear...but localized backing
of the near surface flow could result in a some spin-ups. The consensus
among the convection allowing models is for discrete deep convection
to diminish 22z to 00z...and have tempered probability of precipitation downward accordingly
during the period.
Progressive Post frontal drying is still on tap for tonight and
noticeably cooler air will be seen overnight...with Tuesday morning
minimum temperatures closer to the middle April climatology. Continental
airmass will linger atop the southeast Continental U.S. Under the large broad very low
amplitude upper trough. Lots of sunshine will push maximum temperatures
to around normal.
Short term /Tuesday night through Wednesday night/...
as of 200 PM Monday...large upper low north of the Great Lakes will
contribute to west-northwest flow in the upper levels across the southeast states.
Dry high pressure moving across the deep south will dominate the
weather in the western Carolinas and NE Georgia Tuesday night into Wednesday.
As the upper low moves slowly southeast and a short wave moves southeast through
its base...a surface cold front will push southeast across the area Wednesday night.
Moisture will be limited with the front due to the deep layer
western flow. However...a few showers and thunderstorms may reach
the NC mountains by late Wednesday afternoon...but weaken and/or dissipate
as they move east into the Piedmont Wednesday night. High pressure will
then build southeast into the western carolians and NE Georgia on Thursday. Maximum temperatures
will be near climatology on Wednesday and then cool a little below average on
Long term /Thursday through Monday/...
of 200 PM Monday...high pressure will dominate briefly Thursday night
and Friday. An upper low over the desert SW is forecast to move
eastward and weaken into a short wave over the Southern Plains and
then minor out across the southeast states late this weekend as a large
upper low remains over the NE U.S. Both the GFS and ecm develop a
surface low near the 4-corners and move it eastward into the Southern
Plains and then weaken it as it moves into the deep south by early
Sunday. The models develop precipitation across the area Sat as isentropic
upglide develops over an in situ wedge. A backdoor cold front then
is forecast to move through the area Sat night in the wake of the
low. Dry high pressure is forecast to build south over the region
during Sunday and continue into Monday. Another southern stream low
may bring showers to the region again late Monday. Temperatures are
expected to be below climatology through the period.
Aviation /02z Tuesday through Saturday/...
kclt and elsewhere...cold front making its way through mountains and
may jump across to central part of forecast area shortly after 00z and
then east of area by 03z or 04z. Deeper moisture and associated
thunderstorm activity has already cleared east of kclt but until
front moves completely to the east of the area cannot completely
rule out isolated shower or event thunder...but not Worth mention in
any tafs. Best chances for a stray shower or storms appears to be at
khky through 02z. Therefore expect VFR conditions to prevail at all
airports...with south to southwest winds shifting west to west
northwest late this evening behind the front and generally less than
10 kts...with the exception of kavl which will shift more northwest
overnight and gust to over 20 kts.
Winds stay SW to northwest during the day Tuesday but generally 10-15kt
range...and continued VFR with high pressure in control.
Outlook...dry high pressure will continue to build in across the
region for the middle of the week...leading to low
00-06z 06-12z 12-18z
kclt high 100% high 100% high 100%
kgsp high 100% high 100% high 100%
kavl high 100% high 100% high 100%
khky high 100% high 100% high 100%
kgmu high 100% high 100% high 100%
kand high 100% high 100% high 100%
The percentage reflects the number of guidance members agreeing
with the scheduled taf issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link: (must be lower case)