Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 170104
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
904 PM EDT Wed Aug 16 2017

.SYNOPSIS...
Summertime heat and humidity will continue across the area
through Friday with widely scattered showers and thunderstorms.
Convection coverage will increase during the weekend into early
next week as a cold front approaches from the northwest late
Friday and stalls just inland from the coast thru the weekend
and continuing into early next week.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 845 PM Wednesday...Majority of the convection across the
ILM CWA is weakening and dissipating given the loss of the days
insolation. Plenty of interacting sfc boundaries that helped
with the forcing portion of enabling convection to occur.
However, with the loss of heating, so goes the fuel or CAPE to
sustain these storms. However, there is a weak mid-level s/w
trof progged to push eastward across north central NC this
evening and overnight that could develop a few storms that may
come close to the ILM CWA. For now, will mention it here in this
discussion but hold off from raising overnight POPs. Have
basically tweaked overnite hrly temps and dewpts upwards to
account for latest trends and what 18Z progs indicated for the
overnight period. Could see winds decouple late this evening
and overnight and could give rise to possible ground fog
especially locations that receive rainfall from today`s
convection.

Previous...................................................
As of 300 PM Wednesday...With dewpoints in the mid 70`s and
temperatures in the upper 80`s to low 90`s, heat indices have
reached at or just above 100 degrees across much of the area
already. The Heat Advisory will remain in effect through this
afternoon for portions of the area.

Latest visible satellite illustrates quite the healthy cu field
across the area, while latest radar imagery only shows a few
showers and thunderstorms which have developed outside of the
forecast area. With latest guidance, do continue to expect
isolated to scattered showers and thunderstorms to develop
this afternoon into the early evening hours with the assistance
of the the afternoon sea breeze and piedmont trough. Any
convection that does develop will dissipate later tonight , with
conditions remaining fairly quiet overnight with overnight low
temperatures in the mid 70`s. Patchy areas of fog are possible
towards the morning hours.

On Thursday, upper level ridging will move into the Carolinas
ahead of the approaching cold front which is progged for later
this week. However, even with ridging in place, some available
moisture, low level convergence and lingering boundaries, have
kept in slight chance/chance pops for isolated to scattered
convection. The heat will be of discussion again as well, as
higher dewpoints combined with temperatures in the each aftn
and evening thru the weekend. low to mid 90`s will likely
allow heat indices to reach 100 degrees, with some locations
reaching advisory criteria.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...High pressure will give way Thursday
night as a Piedmont trough develops over the Carolina`s on
Friday ahead of a cold front that will move into the central
Carolinas by early Saturday morning.

The deep 2+ inch precipitable water will continues its hold
over the area through this period. Convection is expected on
Friday and Friday night with the established trough and the
approaching cold front. With the 850 millibar temperatures
hitting the 19 to 20C range expect another hot day with
possible heat advisories for portions of the forecast area.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...Cold front stalled either just to our
west or even over western counties on Saturday while moderately
strong trough crosses through the Northeast and MidAtlantic.
Thunderstorm coverage should be elevated above the norm.
Thunderstorm coverage may also not show the normal diurnal
decrease due to the presence of the boundary. The higher
concentration of storms will be over northern zones where there
also may be a small severe weather threat. Temperatures will be
running close to normal. The boundary will show little movement
into Sunday but height rises aloft will be underway. Overall
expect a downward trend in storm coverage and a warmer
afternoon.

Attention to Monday`s forecast continues to increase each day
due to the solar eclipse. Unfortunately there isn`t much
different in the way of thinking and even less fortunate the
news isn`t great. True the front will be weakening but
convective signals in the models are still suggesting ample
moisture for considerable coverage of thunderstorms that
afternoon. The silver lining could be the rising heights aloft,
possibly capping thunderstorm formation until after the eclipse
or at least its peak. Even so all it takes is one vigorous
towering cumulus to ruin the view over a given location.

By Tuesday the front no longer appears in the models but a well
defined piedmont trough develops. Thunderstorms forming within
this boundary and moving east paired with seabreeze activity
calls for scattered POPs just about area-wide. By Wednesday some
mid level troughiness starts breaking into the area in
association with a large trough forming north of the Great
Lakes. A continued moist boundary layer paired with energetic NW
flow likely means a continuation of the unsettled weather.

&&

.AVIATION /01Z THURSDAY THROUGH MONDAY/...
As of 00Z...Weakening isolated showers and thunderstorms will
continue thru 02Z and could provide brief MVFR/IFR conditions
with a direct hit. Otherwise, after 02Z, look for convection to
dissipate. Have indicated MVFR fog conditions mainly after 06Z
thru 12Z. Any terminals that experience pcpn, could see fog
conditions drop vsby to IFR thresholds. Winds this evening,
mainly variable, will become calm across the inland terminals
and possibly the coastal terminals as well. The fog and sct
low stratus will dissipate by 13-14z with diurnal cu quick to
develop. Once again, will have a sea breeze and the piedmont
trof provide forcing for convection to develop from. There-
after, outflow boundaries will interact with one another as
well as the sea breeze and piedmont trof...keeping convection
development going from 17Z thru 24Z. Winds generally SE-S
during Thu at 5 to 10 kt speeds except 10 to possibly 15 kt
along the coastal terminals if the sea breeze is able to fully
develop.

Extended Outlook...A brief period of MVFR/IFR conditions can
not be ruled out in isolated to scattered showers and
thunderstorms Thu and Fri aftn and evening. A better chance
for flight restrictions due to showers and thunderstorms will
occur on Sat and Sun. Low stratus and some fog during the
overnight and early morning hours may result in flight
restrictions as well each day.

&&

.MARINE...
NEAR TERM /TONIGHT THROUGH THURSDAY/...
As of 845 PM Wednesday...Outflow from convection over the
mainland will temporarily push across portions of the local
waters and temporarily disrupt the weak synoptic flow. Overall,
wind speeds will run 5 to 10 kt and that may even be too high.
Wind directions will be a challenge until the outflows
dissipate and/or get absorbed in the overall weak synoptic
flow. Significant seas will run around 2 ft and primarily be a
function of a 1 to 2 foot ESE ground swell at 7 to 8 second
periods.

Previous....................................................
As of 300 PM Wednesday...Conditions will remain fairly quiet
across the waters as Hurricane Gert continues to move well
away from the waters, off to the northeast. Southwest winds
up to 10 kts tonight will veer to the north and then northeast
Thursday morning, and back to the southeast by the afternoon
hours. Winds will remain around 5 to 10 kts. Seas will be
around 2 to 3 ft.

SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...Winds will be from the south and will
veer to the southwest of Friday and Friday night ahead of a
cold front that will stall inland. This will increase the winds
from around 10 knots to 15 knots late Friday. Seas will
respond by increasing from around 2 to 3 feet to 3 to 4 feet
late Friday night.

LONG TERM /SATURDAY THROUGH MONDAY/...
As of 300 PM Wednesday...A front will be stalled over land
over the weekend and into Monday in a weakening state. This
boundary will serve a similar function to the piedmont trough
normally seen during the warm season and we should still see a
fairly typical southwesterly flow. Seas will run 2 to 4 ft for
the most part, highest offshore in the coast-parallel flow.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.

&&

$$
SYNOPSIS...DRH
NEAR TERM...DCH/SGL
SHORT TERM...DRH
LONG TERM...MBB
AVIATION...DCH



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