167
FXUS62 KMHX 121732
AFDMHX

Area Forecast Discussion
National Weather Service Newport/Morehead City NC
132 PM EDT Mon Aug 12 2024

.SYNOPSIS...
Cold front will slowly sag south across the Carolinas today
bringing yet another day of heavy rainfall and the threat for
flash flooding as the soils are already saturated. Cold front
pushes offshore tonight while high pressure builds in from the
north. High pressure will then remain over the Eastern Seaboard
into this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1245 PM Monday...

 - Heavy rain/flooding risk continues through early this
   evening

 - Flood Watch in effect until 10pm tonight

 - Overnight fog potential

Early this afternoon, an area of low pressure was analyzed near
Columbia, SC. A stationary frontal boundary extends from
central SC east out into the SW Atlantic. North of the SFC
boundary, there appears to be an elevated (925-850mb) front from
Charlotte east through around Morehead City. It`s this
boundary, plus a modest upper level shortwave aloft, that will
be the focus for showers and thunderstorms through this evening.
Based on radar and satellite trends, it appears the greatest
risk of deeper convection will be focused along and south of HWY
264. The previous shift nicely outlined this area with the
Flood Watch, and this continues to look solid.

Regarding the heavy rain threat, the 12z MHX sounding had a
PWAT over 2", and this should be representative of much of ENC.
The high PWAT airmass plus moderate instability (MUCAPE > 2000
j/kg) should be more than supportive of higher rainfall rates.
1-hr flash flood guidance is around 2-3", and like yesterday, I
expect the deepest convection to be capable of 2-3"/hr rainfall
rates, which will support a flash flood risk. Additional
rainfall will only add to the ongoing river flooding as well.

Regarding the severe weather potential, the combination of
MLCAPE of 1000-2000 j/kg and 25-40kt of deep layer shear appears
supportive of at least some risk. I expect the main hazard
today to be heavy rain and flooding, but if any stronger cores
can develop, there would be an accompanying risk of severe
weather (mainly a wind and hail threat).

In the wake of this afternoon`s shortwave, subsidence and
drying aloft should lead to a decreasing chance of thunderstorms
from north to south. If sufficient clearing occurs overnight,
there will be an increased risk of fog development. A period of
dense fog cannot be ruled out, especially across the coastal
plain.

&&

.SHORT TERM /TUESDAY/...
As of 1245 PM Monday...

 - Scattered afternoon thunderstorms possible

Any areas of fog should mix out by mid-morning, with several
hours of dry conditions expected through early afternoon. By mid
to late- afternoon, another shortwave aloft combined with lee
troughing at the SFC should support isolated to scattered
thunderstorms. I expect the primary focus to be upstream across
central NC, but storms may have a tendency to move east into the
coastal plain of ENC thanks to increasing flow aloft.
Instability is forecast to be weaker on Tuesday compared to
today, but deep layer shear will be stronger, so there`s at
least some support for a stronger storm, or two.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
As of 5 AM Monday...A drying trend will commence mid-week as a
cold front offshore slowly sags southward and high pressure
builds into the area from the NW. However, upper trough remains
centered over the eastern CONUS with a series of shortwave
trough pushing across the area that will aid in initiating
isolated to scattered showers and thunderstorms at times.
Greatest chances will be during the afternoon/evening hours when
instability is maximized. PWATs lower to below 1.25" on
Wednesday so storms will not be the prolific rain makes that we
have been experiencing over the past week. Temps will actually
be a couple of degrees below normal with highs in the mid 80s
and it won`t be quite as oppressive humidity with dew point
temps in the mid to upper 60s.

The upper trough pushes off the East Coast Thursday and Friday
with upper ridging building in from the west. We will be closely
watching the current PTC #5, likely to become Ernesto later
today, as it pushes across the Caribbean Island through the
week. Current NHC forecast is for it to lift north of the
Greater Antilles as it interacts with the departing upper trough
and track well east of the area late in the week. While we are
not expecting direct impacts from this system at this time,
large swells are expected to impact the beaches bringing an
increased rip current risk and large surf beginning Friday and
continuing through the weekend. Locally, high pressure will
continue to dominate across the area and we will finally get a
couple of days to dry out. Temps will continue slightly below
normal with highs in the mid 80s and dew point temps in the mid
60s.

An upper low moves into the Great Lakes Friday into the weekend
with an upper trough digging back into the East Coast and a cold
front slowly advancing toward the area bringing increasing
chances for showers and thunderstorms across the region Saturday
and Sunday. Seasonable temps continue with highs generally in
the mid 80s.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
SHORT TERM /Through 18z Tuesday/...
As of 1245 PM Monday...

 - TSRA likely (60-80% chance) through early this evening

 - BR/FG/sub-IFR potential overnight

SCT to numerous TSRA will impact much of ENC through early this
evening, with periods of IFR, or lower, conditions, especially
in VIS. Lower CIGs will accompany the TSRA as well. The
strongest TSRA will be capable of gusty/erratic winds and hail.
The TSRA risk should decrease from north to south tonight as
slightly drier air works in aloft, and as lift decreases. If
sufficient breaks in the clouds occur, there will be a risk of
BR/FG and sub-IFR conditions. A period of LIFR VIS is possible
(20-40% chance) if FG develops. BR/FG should mix out by mid-
morning Tuesday, with a lower TSRA risk through early Tuesday
afternoon.

LONG TERM /Tuesday night through Saturday/...
As of 530 AM Monday...Chances for sub-VFR conditions will
gradually diminish through the week as high pressure builds in
and we finally begin to dry out. Isolated to scattered showers
and thunderstorms chances continue into Wednesday that could
bring brief sub-VFR conditions with dry weather expected
Thursday and Friday. Light winds and good radiational cooling
conditions will continue to bring the chance for late
night/early morning fog and stratus most morning, especially
giving the saturated ground.

&&

.MARINE...
SHORT TERM /through tonight/...
As of 345 AM Mon...Dense fog has developed along our northern
OBX waters overnight so currently have a marine dense fog
advisory out which is forecast to end at 8AM this morning if
not sooner. Otherwise, not much change in the forecast as
outside of convection, which could be widespread at times today,
favorable marine conditions will exist through Tuesday as a
weak cold front moves across the area. The front is currently
located along the NOBX and will slowly sag southward today and
eventually push off the coast and away from our coastal waters
tonight. To the north of the front winds will turn to the NE/N
at 5-10 kts, while to the south of the front winds will remain
SW at 5-15 kts. Winds wil eventually become N-NE`rly at 5-10 kts
across all waters tonight. Seas are expected to be 2-3 ft
through tonight.

LONG TERM /Tuesday through Friday/...
As of 6 AM Monday...Good boating conditions through much of the
week with high pressure building into the area bringing NE winds
around 5-15 kt through Friday. Wind finally begin to veer to E
and SE late Friday into Saturday as the high moves offshore.
Seas will generally be around 2 to 3 ft through early Friday but
then we will begin to see long period swells from soon to be
Ernesto begin to move into the waters late Friday which will
build through the weekend.

&&

.HYDROLOGY...
As of 345 AM Monday...Scattered to numerous showers and storms
expected again this afternoon. With already saturated soils from
4-10" of rain this week and efficient rainfall rates, flash
flooding will continue to be a concern and have issued a flood
watch from 10 AM to 10 PM for all but, Martin, Washington,
Tyrell, Dare, Hatteras Island, and Ocracoke as most storms are
expected to be to the south of this area as the front has
already moved through these counties this morning.

River flooding will continue across many river basins including
the NE Cape Fear, Trent, Neuse, New and Tar Rivers as well as
several tributaries to the rivers through the weekend and into
next week with abundant rain falling will upstream of the FA.

&&

.MHX WATCHES/WARNINGS/ADVISORIES...
NC...Flood Watch until 10 PM EDT this evening for NCZ044-079>081-
     090>092-094-193>196-198-199.
MARINE...None.

&&

$$
SYNOPSIS...MHX
NEAR TERM...RM
SHORT TERM...RM
LONG TERM...SK
AVIATION...RM/SK
MARINE...SK/RCF
HYDROLOGY...MHX