006 
fxus62 kilm 051935 
afdilm 


Area forecast discussion 
National Weather Service Wilmington NC 
335 PM EDT Sat Jul 5 2008 


Synopsis... 
seasonably warm and humid conditions will persist through the 
next seven days as high pressure remains anchored offshore. Showers 
and thunderstorms will develop each afternoon...but should remain 
most numerous through Monday as several weak upper level 
disturbances move across the Carolinas. 


&& 


Near term /through tonight/... 
as of 3 PM Saturday...thunderstorms developing along the Piedmont 
trough and resultant seabreeze this afternoon. These thunderstorms 
should continue to intensify and increase in coverage with the 
approach of a potent shortwave. This shortwave will move by to the 
north...but the southern fringes of the forecast area will impact the 
area this afternoon and evening. Highest probability of precipitation will be across inland 
areas through this evening...with probability of precipitation tapering to slight chance right 
along the coast. 


Weak steering flow will make for some slow moving thunderstorms and 
so risk of ponding water in low lying areas is relatively high. 
Soundings continue to show an inverted-v profile this afternoon and 
evening and so can not rule out a microburst with the capability to 
produce strong to perhaps damaging wind. Hail seems a more remote 
possibility given wet bulb zeros are at or over 12500 feet...but we 
did have one report of large hail on Friday. 


A shortwave is expected to move north-northeast along the coast overnight and so 
will show probability of precipitation increasing along the coast after 06z while 
diminishing inland as airmass slowly stabilizes. 


As low level jet subsides inland...later this evening...winds will 
lighten up to 5 knots or less and broken clouds may thin and become 
scattered...and with that there may be a brief opportunity for some 
fog inland...but it should not be significant or widespread. 


Cloud cover and low level jet will aid in keeping temperatures up overnight 
and so went with the highest of the guidance for overnight 
minimums. 


&& 


Short term /Sunday through Monday night/... 
as of 3 PM Saturday...a middle-level trough extending south from the 
eastern Great Lakes into Georgia will provide the needed lift and 
cooling aloft to ignite several waves of impressive thunderstorms 
over the next couple of days. As precipitable water values reach 
or exceed 2 inches some locations across the eastern Carolinas 
are going to pick up several inches of rain...with widespread 
average amounts 0.50-0.75 inches. Surface-based cape over the next 
few days from virtually any model fluctuates between 1500-3500 
j/kg depending on time of day and location relative to the coast. 


Timing of individual weak disturbances aloft is key to the 
rainfall forecast. The models agree one such disturbance will move 
north along the coast just after sunrise Sunday. This could lead 
to convection early in the day in the Cape Fear region. A second 
disturbance appears to move east through the central Carolinas 
Sunday afternoon. There is less agreement Sunday night into Monday 
with the disturbances aloft...but probability of precipitation remain high (50-70%) again 
on Monday...with the axis of highest chances possibly shifting a 
little closer to the coast. 


Storm motion will increase to around 20 knots Sunday into Monday. 
Nearly unidirectional wind profiles will minimize severe weather 
risk...but heavy rainfall producing localized flooding or an 
isolated wet microburst cannot be ruled out. Diurnal temperature ranges 
will be constricted with all the deep moisture in place. Lows 
should range from 71-75 with afternoon highs 85-89 both days. 


&& 


Long term /Tuesday through Saturday/... 
as of 3 PM Saturday...once again not much change in the extended 
forecast this afternoon as Bermuda high pressure will be the main 
focus through Thursday. A front will push south into the area 
Friday as the midlevel flow veers to northwest via a subtle trough 
and the midlevel ridge retrograding to the west. 


With precipitable waters hovering near two inches throughout...will 
keep a diurnal pattern of showers and thunderstorms...maximized from 
the early afternoon through evening hours for each day. Have timed 
the highest probability of precipitation for Friday as Omega fields have good low and middle 
level coupling with the front and divergence aloft. 


Time heights show dramatic drying through all levels Saturday but 
confidence is low in moving the front much off the coast as the 
attendant trough is weak. Will maintain slight chance probability of precipitation for 
Saturday. 


No change in temperature forecast. 


&& 


Aviation /18z Saturday through Wednesday/... 
strong heating will continue to steepen the lapse rates through middle 
afternoon and expect scattered to numerous showers and thunderstorms 
to develop along and east of the Piedmont trough which lies west of 
Interstate 95 early this afternoon. As the southern fringes of a 
shortwave move across the area late this afternoon and this 
evening...expect showers and thunderstorms to increase in coverage and 
intensity. Kflo and klbt will likely have thunderstorms in the 
vicinity and any one of these storms could move over the terminal. 
Best chance for thunderstorms across klbt and kflo will be 20-24z. 
Atmosphere will slowly stabilize middle to late evening and with that 
expect coverage of showers and thunderstorms to diminish. East of 
seabreeze...to include kilm/kcre/kmyr showers and thunderstorms will 
be isolated through early this evening and confidence is too low to 
include in taf. However...after 08z...a shortwave is expected to 
move north-northeast along the coast and so will include mention of thunderstorms in the vicinity at kcre 
and kmyr 04-13z and at kilm after 08z. Later forecasts should be 
able to be a little more specific as to timing of this round of 
convection. Thunderstorms that do affect the terminals will likely 
drop conditions to MVFR and there is a possibility that IFR 
conditions could develop as thunderstorms are expected to be slow 
movers. As low level jet subsides inland...later this evening...winds 
will lighten up to 5 knots or less and broken clouds may thin and become 
scattered...and with that there may be a period of MVFR br at klbt 
and kflo 09z-13z. 


Outlook Sunday through Tuesday...showers and thunderstorms will 
increase in coverage Sunday through Tuesday. MVFR to IFR conditions 
possible in thunderstorms Sunday through Tuesday. 


&& 


Marine... 
near term /through tonight/... 
as of 3 PM Saturday...near shore waters will be influenced by 
seabreeze circulation into this evening. Low level jet will kick in this 
evening and with that...expect winds to increase and persist well into 
the night. Sustained winds from the S at 15 knots will gust to around 
20 knots. The approach of a shortwave from the S overnight...will allow 
convection to Blossom across the waters and this should serve to 
keep seas agitated as well. Given this scenario...will forecast 
seas to build to 4 to 5 feet across the northern two legs and so will 
headline an exercise caution from Little River Inlet to Surf City. 
Further S...expect conditions will remain just below exercise 
caution criteria. 


Short term /Sunday through Monday night/... 
as of 3 PM Saturday...Bermuda high pressure will continue to feed 
a southerly flow across the area Sunday through Monday night. A 
series of upper level disturbances will increase the potential for 
showers and thunderstorms...mainly occurring over the waters during 
the early and middle morning hours...than perhaps again during the 
afternoon if the inland storms are able to push across the 
seabreeze boundary intact. Seas could build to 4-5 feet...highest 
Sunday afternoon and evening...in a combination of local short- 
period wind waves and a continuing southeast swell with 8-9 
seconds period. 


Long term /Tuesday through Wednesday/... 
as of 3 PM Saturday...reflecting the synoptic pattern of the public 
forecast...little change if any for the extended coastal waters 
forecast. Bermuda high pressure will be the primary focus. Any 
weak shortwaves embedded in the flow which would enhance the low 
level jet and surface winds are all but impossible to time and 
place this far out in time. A persistent south to southwest wind 
of 10-15 knots should suffice. 


The latest wavewatch guidance has come in a bit on the high 
side...especially for late Wednesday into Thursday when it develops 
six footers based primarily on wind waves. The reefcast 
ensembles...which display remarkable agreement through 
midweek...look more reasonable with a four to five foot range. 


It appears any swell from Bertha has been delayed further at least 
from the GFS/wavewatch. However...manual graphics from HPC are more 
progressive with the system. Another complication is the eventual 
strength of the system and just how much swell will be emanating 
across the western Atlantic. Will hold off making adjustments for 
now...but subsequent forecasts will have to monitor wave forecast 
closely for the end of the week. 


&& 


Ilm watches/warnings/advisories... 
SC...none. 
NC...none. 
Marine...none. 


&& 


$$ 


Near term...rjd 
short term...tra 
long term...shk 
aviation...rjd 

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