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FXUS62 KGSP 261809

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
209 PM EDT Sun Mar 26 2017

Low pressure lifting from the Midwest to the Great Lakes will push a 
band of moisture into the southern Appalachians today. Deeper 
moisture and persistent southwesterly flow will then linger over the 
southeast through Tuesday, with several rounds of showers and 
thunderstorms possible. Drier air should briefly return by the 
middle of the week as a cold front settles south of the region. 
Another plains low pressure system will bring moisture back to the 
southeast Thursday through Friday as weak cold air damming develops 
east of the mountains.


1025 AM EDT Update...the main line of showers has been steadily 
moving eastward across the CWFA over the past few hours with no sign 
of thunder. This round of precip will likely move out of the fcst 
area by the mid afternoon with only pockets of sct showers lingering 
for the remainder of the day. Latest profiles remain pessimistic wrt 
instability across the area, so unless cloud cover diminishes 
significantly over the next several hours, it's going to be 
difficult to get much thunderstorm activity. Max temps could also 
struggle to reach their fcst values today if cloud cover remains ovc 
to bkn. Good moisture overnight should hold min temps 10 to 15 
degrees above normal.


As of 245 AM EDT Sunday: A briefly closed 500 mb low pressure system 
crossing the southern plains Sunday evening will open up over 
Missouri on Monday and ride up the Ohio Valley through Monday night. 
Deep layer southwest flow will keep fairly abundant moisture in 
place on Monday ahead of this feature, but triggers for convection 
will be hard to find. Still, SBCAPE values in excess of 1000 J/kg 
will support scattered convection in the southwesterly flow. The 
best upper support ahead of the system will cross the southern 
Appalachians Monday night, but with weakening convective trends 
given the loss of daytime instability.

The best omega with the passing upper support will move east of the 
area by midday Tuesday. Meanwhile, a surface cold front will 
approach the Appalachians from the northwest on Tuesday and settle 
southeast across the region through Tuesday night. Anticipate the 
best combination of lingering Tuesday PM instability and forcing to 
occur across eastern sections, generally east of I-77. Some piedmont 
locations could push 80 degrees for maxes Tuesday just ahead of the 


As of 255 AM EDT Sunday: Strong upper level ridging will cover the 
eastern CONUS through Wednesday as yet another closed low pressure 
system moves from the four corners region to the southern plains. 
Meanwhile, surface high pressure will build southward from the Great 
Lakes as a passing, weak cold front settles south of the forecast 
area. Temperatures will remain warm on Wednesday, with plenty of 
lower 80s in southern sections, as the thermal contrast across the 
boundary is weak and insolation will be good.

The upper ridge will migrate across the forecast area on Thursday 
and off the southeast coast Thursday night. At low levels, an 
Atlantic moisture return will develop on Thursday and cold air 
damming may onset as the returning moist upglide encounters high 
pressure extending southward from a 1030 mb high center east of the 
Appalachian mountain chain. Deeper upglide and moisture will then 
arrive Thursday night through Friday as the upstream surface low 
moves out across the mid/deep South early Friday and then crosses 
the region around the retreating wedge, in Miller B fashion, through 
late Friday. Instability should be uncovered from the south and 
southeast on Friday as the wedge boundary retreats northward. This 
could lead to a severe thunderstorm threat in southern sections if 
the instability and shear appropriately line up. Will lean toward 
the cooler side of the guidance envelope for Thursday and Friday 
maximum temperatures.

Model differences increase Friday night into Saturday, but with a 
consensus blend bringing a trailing surface cold front through the 
area from the northwest after 12Z Saturday - ushering in drying. 
Temperatures should rebound about a category Saturday as downsloping 
flow develops east of the mountains.


At KCLT: VFR conditions prevail thru the first part of the TAF 
period with MVFR cigs from roughly 10z onward. I included a TEMPO 
group for the first couple of hours for reduced visby and cigs 
associated the rain showers currently moving over the area. I also 
included a TEMPO group from 10 to 12z for early morning IFR visby 
and cigs with MVFR cigs otherwise prevailing. Winds should remain 
SLY thru the period before becoming more SWLY by the end of the 

Elsewhere: I kept cigs at MVFR for most of the period with periods 
of IFR cigs during the early to mid morning hours. I also included 
PROB30 groups for IFR and MVFR visby from roughly 08z onward but 
these will likely be very hit and miss during that time. Otherwise, 
I don't expect conditions to improve to VFR again until after 18z. 

Outlook: moist pattern with sly low-lvl flow will persist into mid-
week with another frontal system impacting the area late Monday into 
Tuesday. This system will likely creating additional flight 
restrictions across the region.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z 
KCLT       High 100%     High 100%     High  82%     High  81%     
KGSP       High  98%     High  98%     Med   67%     Med   68%     
KAVL       High  90%     Med   61%     Med   69%     High  80%     
KHKY       Med   79%     High  89%     Med   76%     Med   79%     
KGMU       High  98%     High  98%     Med   69%     Med   76%     
KAND       High 100%     High 100%     Med   68%     High  87%     

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:





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