Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 021634
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
1235 PM EDT Sun Aug 2 2020

.SYNOPSIS...
Hot and humid conditions are expected today ahead of Tropical Storm
Isaias. Impacts from Isaias will likely develop by late Monday as
the storm approaches the Carolinas and continue through early
Tuesday. As the storm moves away on Tuesday, typical warm and humid
summer weather will follow with a chance of afternoon thunderstorms
each day next week.

&&

.UPDATE...
Tropical Storm Warnings have been issued for the ILM CWA with
the exception of Darlington and Marlboro Counties. Storm Surge
Watch in effect south of Cape Fear. See HLSILM and
www.weather.gov/ilm for additional details.

&&

.NEAR TERM /THROUGH MONDAY/...
Vertically stacked ridging extending into the area from the ESE will
keep shower and thunderstorm activity limited today. Latest high res
models show a couple of isolated cells developing late this
afternoon and early evening mainly away from the coast, so have kept
in some marginal 15-20 POPs for this. Main threat today will be
potentially life-threatening rip currents and rough surf along our
beaches as mid period SE swell continues to reach the area from TS
Isaias. Otherwise expecting another hot and humid day with temps
mostly in the low to mid 90s except immediate coast. Heat indices
should top out around 100 today so no advisory planned. Should be
quiet most of tonight with lows in the 70s, though have increasing
shower chances in late for early activity within developing SE
flow in advance of Isaias...with best chances over SC coastal
areas into early Monday morning.

Biggest concerns for Monday at this point appear to tornado
potential and gradual increase in heavy rainfall threat as Isaias
begins to near from the S/SSW. The area will slowly enter the
favored northeast quadrant for TC tornadoes, and expect threat to
increase into the evening as low level shear values increase NNE Of
Isaias. Have also raised a Flash Flood Watch with moist SE flow and
convergence N/NE of Isaias allowing heavy rainfall threat to begin
during the day on Monday and continue until the storm passes. High
risk of rip currents continues on Monday, with surf heights
increasing through the day. Does not look like we will hit advisory
level surf heights until Monday evening though so have held off that
headline for now.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
On Monday night, portions of SC will be seeing the direct
effects of Isaias. Main impacts from this system will be heavy
rainfall and the potential tornado threat overnight Monday as
the NE quadrant of the storm will be positioned over
southeastern NC and coastal NE SC. This coupled with near-
surface shear will likely produce a few short-lived spin- ups.
The heavy rainfall threat will continue overnight with the
potential for Flash Flooding. Given the proximity of the storm
to the US coastline and the potential for the interaction with
land to cause fluctuations in the forecast intensity and
position, the exact location of these impacts remain hard to pin
down. Confidence is growing that tropical storm conditions will
effect most of the area on Monday night and early Tuesday
morning. Models are in good agreement however, that the forward
speed of the system will push the system out of the area
quickly. The slowest guidance shows the storm out of the area by
Tuesday afternoon at the latest. A tight pressure gradient will
continue to bring breezy conditions to the area on Tuesday
night with slow clearing expected as the storm races towards the
northeast.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Upper-level trough will develop over the central and eastern
portions of the CONUS upon the exit of Tropical Storm Isaias. Deep
southwesterly flow will flood into the area with weak pockets of
upper-level energy assisting with the development of afternoon
showers and thunderstorms. Coverage will remain scattered through
late next week and into the early portions of the weekend. Over the
weekend, we are likely to see the pattern trend toward a more zonal
configuration which would bring a more typical summer forecast with
isolated coverage of afternoon storms and increasing temperatures.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Models indicate much less convection today, with only isolated
storms expected along the sea breeze resultant. Dewpoints have
dropped ten degrees since this time yesterday. More of a southerly
flow today versus southwest.

Monday, things will deteriorate noticeably as Isaias moves up the
coast. Look for bands of convection by mid morning. Winds will jump
up 10 kts in the bands with MVFR/IFR conditions.

Extended Outlook...Mainly VFR expected outside of mainly afternoon
and evening showers and thunderstorms. Isaias`s forecast track will
bring the system in the vicinity late Monday night with potential
high impacts on airport operations. A mid-level trough creates
afternoon convection and flight restriction headaches towards the
middle of next week.

&&

.MARINE...
Mostly moderate S winds at or below 15kts are expected today. Swell
from TS Isaias has dropped in period some from yesterday and heights
may actually fall slightly today as well given some recent blockage
of the upstream fetch by Bahamas and Turks and Caicos. That will be
short lived though as SSE swell edges up again late tonight and
especially Monday in advance of TS Isaias. 10-15kt SE winds Monday
morning will gradually increase through the day. At this time it
appears tropical storm force winds will hold off during most of the
day on Monday though, but will get close for our southern waters in
gusts late. Note that waterspout potential will also increase Monday
as Isaias nears.

Significant marine impacts will continue on Monday night as the
center of Tropical Storm Isaias approaches the South Carolina coast.
Current forecast shows tropical storm conditions developing
overnight with seas 8-12 feet possible. The storm is likely to exit
the region quickly on Tuesday morning with offshore winds weakening
quickly by mid-day. On Tuesday night, most of the area will return
to typical southerly winds with dominating wind waves at 2-3 feet.
An upper-trough will maintain a good chance of showers and
thunderstorms during the afternoon and evening through late next
week. Bermuda swell (1-2 feet at around 9 seconds) and typical
southerly winds return by the weekend as the Bermuda high re-
establishes itself over the southwest Atlantic and the upper-trough
flattens.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Tropical Storm Warning for SCZ024-032-033-039-054>056-058-059.
     Flash Flood Watch from Monday morning through Tuesday
     afternoon for SCZ017-023-024-032-033-039-054>056-058-059.
     High Rip Current Risk until 8 PM EDT this evening for SCZ054-
     056.
     Storm Surge Watch for SCZ054-056.
NC...Tropical Storm Warning for NCZ087-096-099-105>110.
     Flash Flood Watch from Monday morning through Tuesday
     afternoon for NCZ087-096-099-105>110.
     High Rip Current Risk until 8 PM EDT this evening for NCZ106-
     108-110.
     Storm Surge Watch for NCZ110.
     Coastal Flood Advisory from 8 PM to 11 PM EDT this evening for
     NCZ107.
MARINE...Tropical Storm Warning for AMZ250-252-254-256.
&&

$$
SYNOPSIS...ILM
UPDATE...MCK
NEAR TERM...MCW
SHORT TERM...21
LONG TERM...21
AVIATION...43
MARINE...21/MCW


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