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FXUS62 KGSP 171006

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
606 AM EDT Thu Oct 17 2019

A dry airmass will remain over the area through Friday. Moisture and 
rain chances return late Saturday into Sunday as a low pressure 
center moves across the area. Brief drying returns for Monday before 
a cold front crosses the area Tuesday.


As of 600 AM: Winds have dropped off below advisory levels for some 
areas in the northern mountains. However, will maintain the current 
wind advisory as a secondary peak in wind often occurs after
sunrise. Changes made to the forecast are focused towards 
aviation interests. 

Otherwise, quiet and dry weather will continue through the near 
term. Broad northwest flow will continue atop the region as we 
remain on the back side of a trough centered near the East Coast. 
Waning cold air advection and upper level support with weaken 
surface pressure gradients will support winds gradually weakening 
through the day. With the cool continental airmass in place, expect 
highs to come in just below normal today with highs generally in the 
60s, although it'll feel a bit brisk across higher elevations with 
the breezy conditions continuing there. A weak 1020 mb high will 
begin building east of the Appalachians tonight supporting light 
winds and clear skies. Fairly dry air in place will allow for good 
radiational cooling conditions with the first frost of the season 
possible across many mountain locations and possible into the North 
Carolina foothills to Piedmont. As a result, a wind advisory has 
been posted for the North Carolina mountains and northern foothills, 
in effect for tonight. Widespread lows in the 30s are expected 
except low 40s for much of the Upstate of South Carolina into 
portions of the I-40 corridor.


As of 325 AM Thursday: Good agreement on the forecast for Friday as 
high pressure slides east across the area. A dry forecast with 
highs a couple of degrees below normal. 

The forecast scenario remains in flux through Sunday as the models 
differ on the details regarding the developing Gulf low that moves 
up the southeast coast through the weekend. Confidence remains low 
as the guidance continues to differ from run to run, but the fact 
that they are trending toward a similar solution is promising. The 
GFS is faster and weaker with the low keeping it along the coast. 
The ECMWF has come in faster than its previous run and closer to the 
coast. However it is stronger and not quite as fast as the GFS. 
Therefore, have trended faster as well. Now have precip spreading in 
from the southwest Saturday afternoon and across the area Saturday 
night. Precip chances slowly taper off Sunday as the low moves east 
of the area. Temperatures will be tricky as the low remains to our 
south putting a wedge like surface pattern over the area with gusty 
northeast winds, clouds, and rain. Have gone below normal with highs 
and above normal with lows. Moderate to possibly heavy rainfall may 
develop Saturday night as well. No surface instability is expected, 
but can't rule out a rumble of thunder along and south of I-85 with 
some elevated instability and strong forcing.


As of 335 AM Thursday: The guidance is trending toward each other 
with some detail differences in this period as well. Dry high 
pressure briefly builds in Sunday night and slides east on Monday as 
a strong frontal system approaches from the west. The GFS is faster 
and weaker with this front bringing it in Monday night and moving it 
east on Tuesday. The ECMWF is stronger and slower bringing it in 
Monday night with a wave of low pressure forming along the front to 
our southwest. This wave travels north along the front as it slowly 
crosses the area Tuesday, then moving east of the area Tuesday 
night. Of course, this would have a significant effect on the 
sensible weather with the GFS indicating mainly light to possibly 
moderate showers. The ECMWF would indicate the potential for showers 
and thunderstorms, some with heavy rainfall and possibly severe. 
Obviously, there is a lot of uncertainty here, but it will need to 
be watched as we get closer in time. Have gone with a model blend 
for timing. Dry high pressure builds in on Wednesday. Temps rise 
well above normal ahead of the front and fall to near normal behind 


At KCLT and elsewhere: VFR expected to prevail thru the period. Lee 
troughing may support SW wind direction east of the mountains at 
times thru 17Z. Low end gusts are possible thru 16Z except thru 00Z 
at KAVL. Weak high pressure building into the region tonight will 
support light northerly or variable winds. Can't rule out patchy fog 
for protected mountain valleys (not KAVL) such as the Little 

Outlook: A Gulf low pressure system will likely another round of 
rain and associated restrictions sometime this weekend.

Confidence Table...

            10-16Z        16-22Z        22-04Z        04-06Z 
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:


NC...Frost Advisory from midnight tonight to 9 AM EDT Friday for 
     Wind Advisory until 10 AM EDT this morning for NCZ033-049-050.



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