329 
fxus62 krah 131450 
afdrah 


Area forecast discussion 
National Weather Service Raleigh NC 
1050 am EDT Monday Oct 13 2008 


Synopsis... 
high pressure will build south across the middle Atlantic region and 
settle over the southern Appalachians on Wednesday. Temperatures 
will warm to near record values on Tuesday and Wednesday. A cold 
front will swing across the area late Thursday and Friday and 
produce a cool down to near normal temperatures for the weekend. 


&& 


Near term /through Tuesday/... 
as of 1045 am Monday... 


Surface analysis this morning showed high pressure over the Middle-Atlantic 
States...with the highest pressures (1032-1033 mb) in southwest Virginia. 
Aloft...12z radiosonde observation analysis showed an unseasonably strong ridge aloft 
(250-500 mb) centered over the deep south and Ohio Valley. 


Today: 
beautiful day on tap today with strong surface high pressure over 
the middle-Atlantic and Carolinas and an unseasonably strong ridge 
aloft west of the southern Appalachians. A very dry low level 
airmass will continue to filter into the area from the north 
today...allowing sunny or mostly sunny skies across central NC... 
aside from some low stratus/fog this morning that should burn off no 
later than 16-17z...and aside from few/scattered upper level clouds (15-25 
kft) this afternoon dropping south through the middle-Atlantic on the 
eastern periphery of the ridge aloft. High temperatures today are expected 
to be above normal...around 80f plus/minus a degree or so...based 
primarily on thicknesses. This is below or on the low end of MOS 
guidance...which is indicating warmer high temperatures in the 80-85f range. 


Tonight: 
other than a few upper level clouds moving south through the 
middle-Atlantic into the Carolinas on the eastern periphery of the 
ridge aloft to our west...mostly clear skies are expected tonight. 
With mostly clear skies...calm winds...and a dry airmass in place 
courtesy of surface high pressure over/near the area...expect 
excellent radiational cooling. Low temperatures should range from the middle 
40s in the typical cold spots (vuj tta igx tdf) to the upper 40s and 
lower 50s in urban areas and the warmer southeast coastal plain. Patchy fog 
will also be possible in the typical areas. 


Tuesday: 
the upper level ridge axis is expected to shift closer to the 
Carolinas...becoming centered around Alabama/GA/SC and western NC by Tuesday 
afternoon. This will bring stronger subsidence aloft over the 
forecast area...allowing Crystal clear/sunny skies. 1000-850 mb 
thicknesses are prognosticated to start out near 1395 meters 12z Tuesday... 
increasing to around 1405 meters in the afternoon. Based on local 
temperature research...this equates to high temperatures in the middle 80s...around 
85f plus/minus a degree or two. It is likely that we will come very 
close to tying the record highs at rdu/gso (86/85) on Tuesday...and 
breaking one or both records is a possibility as well. -Vincent 


&& 


Short term /Tuesday night through Wednesday night/... 
as of 225 am Monday... 


An impressive deep layer ridge will shift southward from the Ohio 
Valley into southern Appalachians during the period. This will 
result in fair weather with mainly clear skies and moderating 
temperatures. 


High temperatures will approach record values of 88/87 on Wednesday (see 
climate section below for more details.) Low level thickness values 
at 12z on Wednesday range from 1395-1400 meters. Will undercut guidance 
consensus by a degree and keep maxes close to NAM MOS values in the 
86 to 87 range on Wednesday. Low temperatures will be in the lower 50s on Wednesday 
morning...a few degrees warmer than Tuesday morning lows due to the 
moderating airmass. Scattered cloudiness and mixing ahead of an 
approaching front on Thursday will keep temperatures up on Wednesday night/Thursday 
morning. Adjusted mins into the upper 50s to near 60. -Hartfield 


&& 


Long term /Thursday through Sunday/... 
as of 245 am Monday... 


Shortwave trough across the western Ohio Valley on Wednesday shears out as 
it moves east on Thursday and Friday. Heights across the Carolinas 
fall on Thursday an Friday as Southeast Ridge slips further south in the 
eastern Gulf of Mexico. Much of the moisture associated with the 
approaching shortwave lifts northeast into Canada with limited 
return flow out of the Gulf of Mexico reducing the threat of 
significant precipitation across the Carolinas. A weak cold front 
associated with the shortwave moves across central NC late Thursday 
night and Friday bringing enhanced cloudiness and a slight chance of 
precipitation. Instability is marginal so will not include mention of 
thunder. 


Another shortwave associated with a GFS prognosticated 140 knots jet of the 
Dakotas at 2z Friday moves out of the Midwest and into the Ohio 
Valley early Saturday. This jet will carve out a deeper eastern US 
trough and Saturday. With cold front lingering near or south of the 
area and increasing dynamics aloft a fair amount of cloudiness and a 
slight chance of precipitation can be expected during the period. Timing of 
these features is difficult and will try to confine probability of precipitation to slight 
or very low chance range for Friday into Sat when precipitation chances are 
greatest despite the fact that precipitation is possible from Thursday afternoon 
into Sat evening. 


With falling heights...cloudiness...cold advection and possible 
precipitation a cool down can be expected for Friday into the weekend. 
Note that 13/00z GFS brings the 800 mb 0 degree c line to kgso on 00z 
sun...a sign of the changing seasons. Daytime highs will range in 
the upper 60s to lower 70s on Sat and sun. -Blaes 


&& 


Aviation /12z Monday through Friday/... 
as of 700 am Sunday... 


VFR conditions are expected to dominate today through tonight as 
deep and dry high pressure settles over the region... however areas 
of isolated IFR/LIFR ceilings will persist until 13-14z elsewhere across 
central NC... and this could edge into the vicinity of some taf 
sites. An area of IFR/LIFR stratus and fog has expanded over much of 
northeast NC in recent hours... and rwi has seen fleeting banks of 
shallow fog and low stratus overnight. Scattered LIFR clouds have 
also been noted just south of Fay. Tafs at rwi/rdu/Fay will reflect 
possible brief IFR/LIFR conditions until middle morning. Otherwise... 
once these low clouds/fog burn and mix out... high thin clouds will 
sweep over the area the afternoon through tonight... although 
abundant sunshine is still expected. Northeast winds should not 
surpass 9 kts and should go light/variable near sunset. 


Looking beyond tonight... VFR conditions are expected to prevail 
through at least Thursday as the high pressure holds firm over the 
region. MVFR ceilings are possible Friday as a cold front approaches the 
area. -Gih 


&& 


Climate... 
record highs for Tuesday October 14: 
rdu - 86 (1985) 
gso - 85 (1975) 


Record highs for Wednesday October 15: 
rdu - 88 (1985) 
gso - 87 (1985) 


Record highs for Thursday October 16: 
rdu - 85 (1989) 
gso - 85 (1953) 


&& 


Rah watches/warnings/advisories... 
none. 


&& 


$$ 


Synopsis...Vincent 
near term...Vincent 
short term...blaes 
long term...blaes 
aviation...Hartfield 
climate...Hartfield 

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)