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fxus62 kgsp 201018 
afdgsp 


Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
618 am EDT Sat Mar 20 2010 


Synopsis... 
weak but warm high pressure moves off the Carolina coast today. A 
cold front will move across the western Carolinas and northeast 
Georgia from the west Sunday night...with an upper level low passing 
over on Monday. High pressure will again be the main influence on 
Tuesday and Wednesday. A weak cold front moves in from the north 
Thursday...with another storm system moving in on Friday. 


&& 


Near term /through tonight/... 
onset of increasing warm air advection/return flow today...but sensible weather limited 
to few-scattered cumulus development and later day cirrus encroachment. Advection of 
higher low level thickness values should allow maximum temperatures a few degree f 
warmer than Friday...about 12 degree f above climatology. Strengthening and 
moistening south-southeasterly low level flow on tap for tonight...but late night 
shower possibilities driven by nominal low level forcing remain small... 
and 00 UTC op models keep response west of the County warning forecast area through 12 UTC 
Sunday. 


&& 


Short term /Sunday through Tuesday/... 
as of 320 am Saturday...models remain in general agreement on the 
upper low affecting the area through the short term. However...some 
timing differences remain. The GFS is still the fastest and the NAM 
the slowest. That said...the GFS has slowed...especially with the 
lead short waves and low level jet. The moisture and lift with the 
lead wave remain to our south. This means only minimal precipitation at 
most during the morning...and mainly west of I-26. The lead wave 
moves east during the afternoon as the occluded front moves into the 
western County warning forecast area. Any thunder should be limited to I-26 and west during the 
afternoon nearer the front. 


The front sweeps across the County warning forecast area Sun night. Models show weak 
instability with the front. Shear will be quite high as the low 
level jet strengthens and moves coincident with the front. Will 
keep isolated thunder wording...but chances of severe storms are very 
low...but not zero. The southwestern NC mountains and the SC/Georgia Blue Ridge will 
see some decent precipitation amounts given the upslope enhancement with 
the southerly low level jet. However...the quick movement of the system 
will limit widespread flooding. But again...the chance is higher 
than zero. With the general slower movement of the system...the 
colder air aloft does not move into the southwestern NC mountains until very late 
overnight. Have kept any snow wording limited to the very high 
elevations toward morning. 


The cold pool associated with the upper low is still forecast to 
move right across the County warning forecast area Monday and Monday night. This should lead 
to some steep lapse rates Monday. There could be a storm or Tow with 
the scattered to isolated showers during the day. However...the best 
precipitation chances will be over the mountains where the best moisture and 
lift remain. Scattered to isolated showers will continue Monday night as 
the low move moves slowly over the area. Best precipitation chances will 
remain over the mountains once again. With the cold pool moving 
over...snow will fall at the highest elevations...and could mix in 
at lower elevations. However...any accums should be limited to the 
high elevations...but how much is still in question. Upper lows have 
a tendency to produce surprises regarding snowfall amounts. 


The upper low pulls east of the region Tuesday leaving low level 
moisture and northwest flow across the mountains expect decreasing coverage of 
showers during the day. However...850 mb temperatures warm during the day 
bringing an end to the snow. 


&& 


Long term /Tuesday night through Friday/... 
as of 400 am Saturday...brief ridging surface and aloft moves into the 
area Wednesday. A short wave passes north of the area Wednesday night. This 
pushes a back door cold front into the area which dissipates or 
returns north as a warm front Thursday. Models agree on increasing 
clouds...but disagree on precipitation chance. Will leave Wednesday night dry and 
slight chance Thursday afternoon. Models agree in general that another wave 
moves across the area during the Friday time frame. However...they 
disagree on the details. Therefore...will leave current forecast as is 
with slight chance pop Thursday night and chance Friday. Models still show some 
instability...so thunder wording will be maintained. Lows near 
normal Tuesday night...rise above normal through the period. Highs above 
normal Wed/Thu...drop to near normal Friday with the precipitation. 


&& 


Aviation /10z Saturday through Wednesday/... 
at kclt...going forecast remains on track with clear skies with very 
light winds through middle-morning and giving way to a few cumulus about 6k feet 
and SW winds about 10 kts this afternoon. South winds less than 6 kts 
expected for tonight as scattered VFR level stratocu lingers. 


Elsewhere...VFR through the period with few-scattered cumulus this afternoon with 
scattered stratocu tonight along with thickening cirrus. 


Outlook...ahead of an approaching cold front...showers and perhaps 
thunderstorms will be likely Sunday afternoon and evening. Scattered showers 
and gusty westerly winds will linger into Monday...but diminish 
through Tuesday...with a mainly dry Wednesday expected. 


&& 


Gsp watches/warnings/advisories... 
Georgia...none. 
NC...none. 
SC...none. 


&& 


$$ 
Synopsis...rwh 
near term...csh 
short term...rwh 
long term...rwh 
aviation...csh