Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Greenville-Spartanburg SC
640 am EDT sun Mar 9 2014
a weak cold front will cross the region from the northwest early
today. Dry and warm high pressure will redevelop over the area
through Tuesday. A low pressure system will approach the western
Carolinas and northeast Georgia from the west by Wednesday...with
temperatures turning colder late week following an associated cold
Near term /through tonight/...
as of 635 am...high clouds continue across the area this morning as
lower clouds have begun moving into the mountains regional radar shows
no precipitation associated with the cold front moving into the area. 06z
guidance...except for the continued wet GFS...have all trended even
drier with the front. Hourly near term models are also basically dry
this morning. Therefore...have removed pop and gone with a dry
forecast...but cannot rule out a brief sprinkle across the Tennessee border
counties early this morning. Still expect the low clouds to increase
across the mountains through the morning then scatter out for the afternoon.
Also still expect the low clouds to spill out of the mountains this
afternoon...with brief periods of broken ceilings possible. Winds have
increased across the mountains with gusty and breezy conditions likely
through the day. However...still expect winds to remain below advection
level. Highs still look on track.
As of 300 am...a shearing short wave moves across the area today
pushing a weak cold front across the County warning forecast area. Moisture is quite limited
with this system. Sat pictures Show Low clouds upstream of the County warning forecast area...
but regional radar shows little in the way of showers. Latest
guidance...especially hourly near term models...have greatly reduced
precipitation chances as the front moves in this morning. Given the clouds
and westerly upslope flow...do not want to remove pop completely.
Therefore...have lowered pop to slight chance and limited them to
mainly the Tennessee border counties...maximized around 12z. Any precipitation
that does develop...will be very light. Temperatures remain relatively
warm...so with the very light precipitation...still expect only liquid
precipitation. Expect the clouds to move into the mountains during the morning
then scatter out for the afternoon. As low level moisture moves out
of the mountains...scattered to possibly broken stratocu will develop for the
afternoon. These clouds should not significantly reduce heating
outside of the mountains given the increasing thicknesses and downslope
winds. Gusty winds develop over the mountains behind the front...but
should remain below advection level. Highs will be around 10 degrees above
normal...even across the mountains as no significant cold air advection develops behind
Skies clear and winds diminish tonight as northwesterly upper flow develops
and the front slides south of the area. Lows will range from near
normal to 5 degrees above.
Short term /Monday through Tuesday night/...
at 125 am EST Sunday...on Monday...surface low pressure will continue to
organize off the Texas coast as a weak cold front runs across the
middle west. Conditions across the forecast will be sunny...with mild
low level thicknesses...and west 850 mb winds around 20 kts. High
temperatures are forecast to range 10 to 15 degrees above
normal...or upper 60s within the mountain valleys to low to middle 70s
across the foothills and Piedmont. Monday night...0z GFS indicates
that 850 mb temperatures will warm to 10 to 12c across the western Carolinas.
Surface winds are forecast to remain from west-northwest across the mountains...with SW
winds east of the mountains...speeds between 5 to 10 kts. Lingering mild
thicknesses and mixing winds should result in min temperatures
around 5 degrees above normal.
Tuesday...a positively tilted middle level trough sliding across the
plains will begin to phase with a closed low near the Mississippi
Delta. At the surface...a broad area of low pressure will develop across
the middle and lower Mississippi Valley. As the low approaches...return
flow will strengthen across the deep south and southeast U.S. On
Tuesday. High clouds will steady increase across the forecast area
through the day. However...warming low level thicknesses and west-southwest winds
should warm high temperatures a degree or two warmer than Monday.
Tuesday night...deep moisture will increase across NE Georgia and the
western Carolinas as low pressure approaches from the SW and west. Weak
isentropic lift should spread from S to north across the region. The
combination of the low level lift and moisture should support scattered light
rain across the region by sunrise Wednesday. The arrival of the thick
clouds and steady surface winds should keep temperatures around 15
degrees above normal...or 40s across the mountains to low to middle 50s east.
Long term /Wednesday through Saturday/...
as of 300 am Sunday...a complex pattern to start out the medium
range...with a southern stream shortwave crossing eastward from the
Gulf states while a northern stream trough approaches from the upper
plains. At 12z Wednesday...the surface low is forecast to be over southern Kentucky
and moving NE. The previous run of the GFS had cape values between
300 and 400. The current run of the GFS has much more stable
conditions at 18z Wednesday with convective available potential energy around 100. If this trend
continues...we would have only showers and no thunder. The GFS and
European model (ecmwf) both have the low moving out of the area with a few hours of
northwest flow against the NC mountains the Canadian has no wrap around and
dries all out by midnight Wednesday. The pressure gradient indicates 40 to
50kts 850mb flow Wednesday PM and 925mb flow 20 to 35kts.
The center of the high pressure moving in from behind the departing
low will be over our region from 00z to perhaps as late as 18z
Friday. The above normal temperatures on Wednesday will drop with the cold air
advection Wednesday night and Thursday...lowering temperatures to well below normal.
Highs Thursday in the 40s and 50 to 55 across the Piedmont. With
southerly flow late Friday into early Sat...highs Sat will be 60 to 65
across much of the area except higher elevations. The next system
will be organizing over the Texas Panhandle Sat night and will not
affect our region until after the current day 7.
Aviation /12z Sunday through Thursday/...
at kclt and elsewhere...light west to northwest wind continues through the
morning...northerly at kavl with low end gusts developing with mixing. Broken
high clouds outside of the mountains with increasing low VFR clouds
across the mountains this morning. The low VFR clouds scatter out across
the mountains during the afternoon and spill out of the mountains and become
scattered elsewhere. Winds turn more west-southwest for the afternoon...but
remain west-northwest at kclt and northerly at kavl. Winds turn more northwesterly and
diminish in speed during the evening as the low clouds dissipate
leaving only cirrus.
Outlook...dry high pressure will return through the early week. Rain and
associated restrictions may spread back into the area by Wednesday...with
dry high pressure returning Thursday.
10-16z 16-22z 22-04z 04-10z
kclt high 100% high 100% high 100% high 100%
kgsp high 100% high 100% high 100% high 100%
kavl high 100% high 100% high 100% high 100%
khky high 100% high 100% high 100% high 100%
kgmu high 100% high 100% high 100% high 100%
kand high 100% 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)