137 
FXUS62 KILM 220006
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
806 PM EDT Fri Jul 21 2017

.SYNOPSIS...
Hot and humid conditions will prevail today through the weekend
with only isolated rain chances. Storms will increase next week
as a series of weak fronts approach the coast, with near normal
temperatures for late July.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 645 PM Friday...Quick update issued to account for 
isolated convection drifting into the NW portions of the ILM CWA
thru sunset. 

Previous......................................................
As of 300 PM Friday...Steep low level lapse rates have combined
with just enough low level moisture to pop some cu throughout 
the forecast area, especially along the sea breeze boundary 
where moisture advecting in off the ocean provides a little more
fuel. However, it is very dry above 850 mb so still looks like 
the remainder of today will be a dry one with only the odd spot 
shower or thunderstorm possible. Best chances for anything look 
to be well inland in closest vicinity to the persistent thermal 
trough. As this is all diurnally-driven, expect overnight to be 
clear and dry with lows in the mid 70s.

Similar story for Saturday, with diurnally-driven slight chance POPs 
at best during the afternoon and early evening. It is possible that 
a heat advisory may be required for heat index values of 105F or 
higher, but confidence is not high enough at this time for issuance. 
A consensus of guidance has actual temperatures for Saturday much 
the same as today, with highs from around 90 near the coast to the 
mid 90s inland.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 330 PM Friday...Overall expect hot and humid weather with
heat advisory conditions over most of area on Saturday. A Broad
trough in the mid to upper levels extends just far enough south
into Carolinas as to prevent strong ridging to build in from 
west or east to push temps high enough for any record heat, but
enough to produce temps a good 3 to 7 degrees above normal. 
Temps should reach into the mid 90s over most of the area. Temps
overnight will remain well into the 70s most places. SW sfc 
winds around Bermuda High will become quite gusty Sun aftn into 
Sun eve as sea breeze and trough inland become more pronounced, 
and should see winds increase further Sun night as trough pushes
east and tightens pressure gradient. 

Both the Atlantic ridge and strong ridge over central CONUS 
seem to exert enough influence with enough dry air and 
subsidence to keep area mostly rain free, but with with 
troughing inland and decent sea breeze on Sunday, can not rule 
out an isolated shower Sat night into Sunday. By Sun night, the
mid to upper trough begins to dig a bit more south and a
shortwave rides by as well as a disturbance moving up the coast
from the south. This will all lead to better chc of shwrs/tstms
late Sun into Mon.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 300 PM Friday...A shortwave trough moving through New England 
on Monday night, and a large upper low developing across southern 
Quebec late in the week will help put a dent in the heat. Falling 
upper level heights associated with these systems will shift the 
core of the upper ridge (and its associated heat) farther west into 
Texas and New Mexico. Don't expect a cleansing frontal passage by 
stretch, (06Z GFS ensemble 850 mb temps don't fall below climatology 
next week) but at least we should lose the 100+ heat indices for a 
few days.

Both the GFS and ECMWF show a cold front moving into northern North 
Carolina on Tuesday. The GFS then sinks the boundary a little 
farther south by Wednesday morning. There are enough GFS ensemble 
members showing the front making it into South Carolina that I'm 
leaning toward the GFS in this case. This front should enhance the 
coverage of t-storms Tuesday night and Wednesday, and I've placed my 
highest forecast PoPs (50-60 percent) of the extended period during 
this period. 

With a progressive upper level pattern to our north, surface high 
pressure will push off New England and out into the western Atlantic 
Thursday and Friday, probably with enough southerly wind developing 
over the Carolinas to lift the front or its remnants back to the 
north.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
As of 00Z...High confidence with VFR conditions across all
terminals during the 24 hr TAF issuance period. The only fly in
the ointment will be the possibility of BR across the inland
terminals during the 08Z to 12Z timeframe. If winds stay
decoupled long enough and the sfc temp/dewpt spread drops below
2, then the possibility increases. For now, will keep the fog
out of the fcst due to latest model mos guidance keeps the sfc 
dewpoint depression at 3 degrees or hier during the Sat early 
morning hrs. Given the isolated convection that developed along
the Piedmont trof today, expect this to likely re-fire again
during Sat aftn and evening. As a result, will include VCTS for
the inland terminals. Winds this evening and overnight inland 
will become SW less than 5 kt and occasionally may go calm
especially across the LBT terminal. Across the coastal
terminals, look for the demise of the sea breeze circulation
with S-SSW 10 to 15 kt winds diminishing and veering to the SW 
around 5 kt by or just after 04Z. Will repeat the sea breeze
circulation process again during Sat with winds backing to S-SSW
around 10 kt by midday and increasing to 10 to 20 kt during the
aftn and evening.

Extended Outlook...VFR through Sunday. Brief MVFR/IFR possible 
in scattered showers and tstorms Mon and Tue due to a slowly 
approaching cold front from the NW.

&&

.MARINE...
NEAR TERM /THROUGH SATURDAY/... 
As of 300 PM Friday...Circulation around high pressure over the
western Atlantic will keep winds from the SW, generally in the 
10 to 15 kt range, through the period. Seas will likewise show 
little variation, running right around 3 ft through Saturday. 


SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... 
As of 330 PM Friday...Precautionary headlines may be needed Sun
into early Mon as winds increase to 15 to 20 KT winds and seas 
reach 4 feet offshore and possibly up to 5 ft. The afternoon sea
breeze circulation will keep winds gusty and seas choppy near 
shore Sun afternoon to early evening. Very little TSTM activity 
is expected until Sun night into early Mon when activity will 
increase across the waters as trough shifts farther east toward
the coast. 

LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 300 PM Friday...Bermuda High Pressure well offshore will lose 
its influence on our weather by the middle of next week as low 
pressure in the Canadian maritime provinces pushes a cold front down 
the U.S. East Coast. This front is shown by the latest GFS and ECMWF 
models to make it down to near Hatteras on Tuesday. Models diverge 
slightly on Wednesday as the ECMWF keeps the front stalled to our 
north and the GFS brings it down to the Myrtle Beach vicinity 
Wednesday morning. Regardless of which solution is correct, the 
frisky southwest winds of the weekend should diminish by Tuesday 
within the weaker pressure gradient near the front. Unfortunately 
thunderstorm potential should also increase as the front approaches.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...Coastal Flood Advisory until 10 PM EDT this evening for NCZ107.
MARINE...None.

&&

$$
SYNOPSIS...RGZ
NEAR TERM...DCH/REK
SHORT TERM...RGZ
LONG TERM...TRA
AVIATION...DCH
MARINE...