Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

000 
FXUS62 KGSP 231543
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1043 AM EST Tue Jan 23 2018

.SYNOPSIS...
Dry high pressure will overspread the region and persist into the 
weekend. Another moist cold front will affect the region over the 
weekend, crossing from the west on Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1030 AM EST...The cold front has completed its passage thru 
the CWFA, with clear skies and gusty SW winds in its wake. Hourly 
T/Td grids were adjusted to line up with the METAR trends. Winds 
were also adjusted with the latest LAMP/CONSSHORT, which bumps up 
gusts a bit thru midday, but otherwise, little change. No changes 
needed to the Wind Adivsory with this update.

High pressure will build in from the west rather quickly this 
morning behind the front. This will create a tight p/grad and along 
with momentum transfer from stronger winds aloft...moderately gusty 
conds will develop and persist thru most of the afternoon over the 
entire FA. Across the nrn NC mtns...gusts will reach adv levels as a 
llvl jet is tapped into...so will issue a wind adv for these zones 
thru the overnight. Expect a good feed of llvl moisture associated 
with an upper low reaching the wrn NC mtns and NW flow lift to 
produce -snsh developing aft 00z continuing thru daybreak Wed. The 
overall depth of moisture will be relatively shallow...so not 
expecting great amounts of snow accum during this time...prob arnd a 
half inch to an inch or so.  

Max temps will be be tricky today as morning temps arnd 11z could 
wind up being the max due to an airmass mix/change this morning. 
However...will count on good insol and some w/ly h925 downslope 
warming to reach a diurnal max by 20z a few degrees abv normal most 
locales. Mins shud be right arnd normal...or at freezing non/mtns 
and upper 20s across the mtn valleys.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 230 AM EST Tuesday: Additional shortwave energy rounding the 
eastern trough will sharpen up over the lower Ohio Valley on 
Wednesday. This feature will cross the area quickly Wednesday 
evening. Limited mid-level moisture will accompany the wave passage 
across the northern tier of the forecast area, but shallow low-level 
upslope moisture may continue in the W to NW flow along the TN line 
in the northern NC mountains for the first half of the short term 
period. Otherwise, sprawling surface high pressure will build across 
the southern tier of the U.S. on Wednesday, dominating the east by 
Thursday, with deep layer northwesterly flow and dry profiles 
setting up across the region. Temperatures will be fairly close to 
climatology both days, except a touch cooler in the NC mountains on 
Wed.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 215 AM Tuesday...the extended fcst begins at 12z on Friday 
under a upper ridge with axis from the Great Lakes to Florida Friday 
morning. Also on Friday morning, dry high pressure will be moving 
off the East Coast. As the ridge axis moves to the East Coast late 
Friday night, the surface high pressure moves more east over the 
Atlantic. Surface wind flow will become from south to north bringing 
Gulf moisture first early Saturday over the western Gulf states. The 
GFS has a fading band of moisture coming at our area from the west. 
On the GFS this moisture max reaches us early Sunday then drying us 
out late Sunday. The EC still has a broad band of moisture enhanced 
by low pressure coming out of the northern Gulf early Sunday with 
the low reaching us early Sunday afternoon. This would give us a 
saturating rain for Sunday and Sunday night while GFS has very 
sparse rainfall.  Even with the slower EC, we completely clear of 
any rain by late Monday with dry high pressure centered over us at 
12Z Tuesday. Max Temps will be maintained a few degrees above normal 
and Min Temps will be several degrees above normal due to cloud 
cover.

&&

.AVIATION /16Z TUESDAY THROUGH SATURDAY/...
At CLT...Expect MVFR CIGS thru daybreak and then improving to VFR 
conds arnd 14z as a FROPA with a weak linear precip line crosses 
east. Winds will pick up out of the SW and become gusty...veering 
w/ly and becoming less gusty by late afternoon.    

Elsewhere: Continued MVFR conds at KHKY this morning due to CIGS 
ahead of a crossing frontal zone. Dry air mixing in will improve 
conds to VFR arnd daybreak. A wind shift behind the front wont be 
too drastic...but expect moderate gusts to develop all sites as 
strong hipres builds in from the west. Gust will diminish all sites 
except KAVL aft 00z.         

Outlook: Dry high pressure will dominate the area through the
remainder of the week. Another system will move in over the weekend, 
bringing another round of -SHRA and restrictions.

Confidence Table...

            15-21Z        21-03Z        03-09Z        09-12Z 
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  98%     
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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Wind Advisory until 10 AM EST Wednesday for NCZ033-049-050.
SC...None.

&&

$$

National Weather Service Glossary of Abbreviations