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Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
759 PM EDT Thu Oct 27 2016

A weak cold front crossing the area this evening will be followed by
warm high pressure on Friday. Another weak frontal passage occurs
late Sunday...before strong and dry high pressure returns early next


As of 755 PM, brief, very isolated showers, really not enough to 
even warrant a 20 pop continue to occasionally develop over the 
area. Nevertheless, a 20 pops has been maintained near the TN 
border, esp for later this evening, when a decent NW flow will 
become established, and across the eastern and southern zones for 
the next couple of hours. However, any mention of thunder has been 
removed from the forecast, as no convective cells developing so far 
today have even come close to being deep enough to produce 

The cold front to our NW moves across the area late tonight or early 
Friday. Winds are expected to diminish later tonight, and forecast 
soundings show a good potential for at least patchy fog development 
near daybreak. Best chance for any dense fog will be in the mountain 
valleys. Despite the front moving through, there is not much of an 
air mass change as thicknesses remain high. Lows tonight and highs 
Friday will be around 10 degrees above normal.


As of 125 pm EDT Thursday: The numerical models and ensembles 
feature strong agreement through the short range period. These 
solutions indicate that broad ridging will build over the southern 
U.S. from Texas to the Carolinas on Saturday. The associated surface 
high will set up over the coastal Carolinas with a weak lee trough 
in place just east of the Blue Ridge. Plenty of lower 80s maximum 
temperatures will result from this setup and excellent insolation.

A weak upper level impulse will cross the Great Lakes on Sunday and 
create modest height falls along the eastern seaboard. Any shortwave 
forcing is expected to pass mainly north of our forecast area. The 
main impact from the passing wave will be to push a back door cold 
front through the region, most likely on Sunday night. With the area 
remaining in the warm sector through Sunday afternoon, maxes could 
approach record high values across the region. See the climate 
section of the discussion for details on the records. Unfortunately, 
the boundary should move through the region dry.


As of 130 pm EDT Thursday: Model agreement remains quite good 
through the medium range. A stronger southeast ridge will build over 
the region Monday through Wednesday. Most operational models hint at 
some very light QPF briefly developing in the easterly upslope flow 
behind the departing back door front Monday night. This will likely 
produce some increased cloudiness, but any appreciable precipitation 
in escarpment areas seems very unlikely. Thus, dry weather should 
continue, with temperatures remaining above climatology. 

The ridge will get suppressed southward on Thursday as heights fall 
strongly over eastern Canada. This will send yet another back door 
cold front toward, or into, our area on Thursday. But, once again it 
will most likely be a dry fropa - if the boundary makes it through 
at all. Drought conditions are very likely to worsen considerably 
over the next week with most areas receiving no rainfall during the 
period and the airmass remaining relatively warm and dry.


At KCLT and Upstate SC terminals: very isolated showers will 
continue to move across the region for the next few hours, but 
coverage will not even be close to being sufficient to warrant a 
VCSH. The main concern will be the potential for development of fog 
and/or low stratus toward daybreak, as surface moisture has really 
increased over the past 24 hours, the mid/upper levels will continue 
to dry out this evening, and surface winds are expected to become 
very light or calm after midnight, as weak surface trough settles 
over the area. Signals in statistical guidance are mixed at best 
regarding the potential. The ground is also extremely dry owing to 
the extended period of dry weather, which typically precludes much 
in the way of fog/low stratus concerns. Nevertheless, with favorable 
observational ingredients, opted to forecast 4-6SM at most of the 
terminals late tonight. Would not at all be surprised if conditions 
are not worse than this, but confidence is in the cellar at this 
point. Otherwise, light/calm winds will become light NW by late 
morning, then NE during the afternoon.   

Elsewhere, the aviation forecast at KAVL will be rather tricky 
tonight, as winds are expected to turn up-valley later and remain 
through the morning. Although they will be light, this often serves 
to keep the atmosphere mixed just enough to prevent fog/low stratus 
development. Excluding the wind concern, conditions will be 
favorable, so opted to advertise prevailing MVFR visby (w/ SCT 
LIFR/IFR clouds) with tempos for IFR visby later tonight. Meanwhile, 
confidence is much higher in fog and low stratus development in the 
valleys west of KAVL later tonight. Expect KHKY to see similar 
conditions to KAVL. Any flt restrictions will improve quickly after 
sunrise Friday, with VFR conditions through the remainder of the 

Outlook: Dry high pressure will build in through the weekend. The 
influence of the high will continue into early next week with VFR 
conditions expected.

Confidence Table...

            00-06Z        06-12Z        12-18Z        18-00Z 
KCLT       High 100%     High 100%     High 100%     High 100%     
KGSP       High 100%     High  92%     High  92%     High 100%     
KAVL       High 100%     High  85%     High  93%     High 100%     
KHKY       High 100%     High 100%     High 100%     High 100%     
KGMU       High 100%     High 100%     High  94%     High 100%     
KAND       High 100%     Med   68%     High  89%     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:



  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      79 1946     32 1910     59 1984     21 1976    
   KCLT      82 1984     48 1925     67 1984     27 2001    
                1927        1910                    1976    
   KGSP      84 1927     47 1925     66 1984     25 1976    


  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      81 1946     36 1925     58 1996     20 1910    
                1922                    1896                
   KCLT      84 1996     42 1925     66 1918     26 1965    
                1961                    1881        1952    
   KGSP      83 1950     42 1925     65 2004     25 1910





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