Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 270847

Area Forecast Discussion
National Weather Service Wilmington NC
447 AM EDT Thu Jul 27 2017

Isolated showers and thunderstorms Thursday will become
more numerous Friday into Saturday ahead of an unseasonably
strong cold front. Some of these storms could reach strong to
severe levels Fri aftn thru early Sat. Drier and cooler air,
relatively speaking, is expected to push across the area in the
wake of the cold frontal passage late Sat and continue thru
early next week.


As of 300 AM Thursday...The local area will remain in
subsidence and dry air through today although the NE to
E flow will come back around to the SE to S by this afternoon.
Temperatures were down near 70 early this morning in a drier and
relatively cooler air mass, but there will be a gradual
moisture return bringing dewpoint temps up a few degrees
tonight. Shallow moisture provided some patchy fog and low
stratus in places, but this will dissipate allowing for plenty
of sunshine through the day today. The developing southerly
winds may bring some of the moisture from convection associated
with lingering front/low over Fl/GA this afternoon. Have
included a slight chc of shwrs/tstms over the Georgetown area to
account for this slight moisture return. Overall expect temps
to return into the mid to upper 80s after a below normal start
to the day.

Mid to upper ridge extending in from the west will get
squeezed out as trough digs down from the north late today
through tonight and weakening low to the south moves off to the
north to northeast. This lingering low pressure to the south
will weaken and move north to northeast through early Fri. This
should produce some shwrs/tstms over the waters by Fri morning
and some of these showers will affect the coast. Convection
associated with shortwaves rotating around mid to upper trough
should remain northwest of area through today but will include
increasing chc of convection reaching into the area by Fri
morning. Pcp water values as low as 1.2 inches today will
increase up near 1.6 inches by Fri morning but just to the south
and north values will be up to near 2 inches. The moisture
return will bring temps back up into the mid 70s for low temps


As of 400 AM Thursday...An active wx period will highlight
this time period. Already under the influence of an upper trof
at the start of this period, it`s amplification is progged to
increase as a vigorous mid-level s/w trof dropping southeast
from the Great Lakes, reaches the Mid-atlantic states early Sat.
Models amazingly even agree in taking this open s/w and closing
it off over the Mid-Atlantic states thru Sun morning. All of
this activity aloft is quite unusual for this time of the year
when the area is usually under the influence of Bermuda High
pressure sfc and aloft with subtle flow aloft.

At the sfc, Friday will see convection fire up along a
pre-frontal trof across the central Carolinas and push to the
ILM CWA during the aftn and evening. By Friday night, will see
sfc low really start to take shape and in association of the
vigorous mid-level s/w trof dropping toward the Mid-atlantic
states. This 1010mb low initially will strengthen to at or
below 1000mb by Sat morning over the DELMARVA area. It`s
associated cold front will be pushing southeast across the FA
Sat aftn and clearing the ILM CWA Coast during Sat evening.
Convection ahead and along the cold front Fri evening thru Sat
will have plenty of dynamics to work with that will result in
strong to severe thunderstorms likely. SPC already has a Slight
Risk across the FA.

As for temps, maintained a blend of model guidance thru the
period. Looking at a decreasing trend to both highs and lows
from Friday thru Sunday morning.


As of 300 PM Wednesday...Primary weather features this period
include an unseasonably amplified upper trough, followed by
Canadian high pressure which may bring a brief feel of very
early Fall, as dewpoints dip below normal for the season. A
surface trough inland Saturday will move offshore Saturday
night, as relatively strong high pressure from Canada barges
in from the NW in earnest early Sunday. The high will drop
dewpoints deep into the 60s Sunday, removing the muggy edge
well into the next week, as the high remains anchored over
the mid- ATLC region. The best rain chances are Saturday,
before mid-level drying and lowering dewpoints inhibit
convection. NE flow in the low-levels may bring in bouts of
oceanic cu and, in conjunction with the Canadian high, will
keep maximum temperatures below normal from Sunday onward.
This accompanied by small rain chances, mainly by the coast.
It`s possible a few storms early Saturday could be capable of
strong gusts.


As of 06Z...Quiet night overall across the terminals but MVFR
ceilings will continue for MYR as some patchy stratus affects
them through early morning. Also included MVFR vsbys for FLO
and LBT for a few hours around day break in patchy fog.
Otherwise no other restrictions expected through TAF period.

East to northeast winds will veer around becoming southerly
through the afternoon, but remaining light. This will allow
moisture to begin to return up from the south, but not
expecting this to affect any terminals until after TAF period.

Extended Outlook...MVFR or lower flight restrictions are likely
in association with numerous thunderstorms later Fri and Fri
night. Some of the thunderstorms may be strong to severe. Flight
restrictions may persist into portions of Sat as well. VFR
Sunday and Monday.


As of 300 AM Thursday...Winds will remain 10 kts or less
through today as they shift from NE-E around to the SE to S as
high pressure extending across the waters from the north shifts
further off shore. The sea breeze will give a little spike to
the winds this afternoon. Seas will remain fairly benign with
heights less than 3 ft. A small SE swell around 9 seconds will
mix in. Winds will veer slightly more by Fri morning as Bermuda
High begins to dominate.

As of 400 AM Thursday...Deteriorating wind and sea conditions
expected thru this period. Ahead of the pre-frontal trof, SW
winds will increase to 15 to 20 kt during Friday and maintain
these speeds into Friday night with gusts to 25 kt being added
to the mix. For Sat, the sfc pg will tighten even more as low
pressure deepens over the Delmarva and Mid-atlantic states. The
sfc cold front dropping southeastward, will be on the doorsteps
by Sat morning. Models take the cold front across the local
waters late in the day Sat or Sat evening. Expect active SW to
WSW winds ahead of the cold front that will likely breach SCA
thresholds until the CFP, Sat evening. After FROPA, winds will
veer to the N-NE around 15 kt.

Significant seas will undoubtedly be dominated by wind driven
waves at 5 second periods on Fri, and around 6 second periods
during Sat. Seas will build to 3 to 5 ft during fri and reach 4
to 7 ft by and during Saturday. The 7 footers primarily the
waters from off Cape Fear to Little River Inlet. This a result
of a longer fetch due to the strong WSW-W wind directions during

As of 300 PM Wednesday...A significant wind-shift will occur
Saturday from WSW to NNE, as a strong cold front for late July
crosses the coast Saturday afternoon or evening. It is possible
a Caution headline or even an Advisory may be needed for gusty
winds ahead of and just behind the front. In addition...TSTMS
and showers will be more numerous Saturday and a few storms may
be strong to severe. NE winds 15 KT Sunday will begin to veer
Monday to E-SE, with seas of 2-4 feet, highest offshore. Sunday
seas a bit messy, as residual SSW waves every 6 seconds mix with
a NE chop and weak SE swell waves. Isolated showers will dot
the waters Sunday and Monday but of light intensity.





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