683
FXUS62 KMHX 200729
AFDMHX

Area Forecast Discussion
National Weather Service Newport/Morehead City NC
329 AM EDT Sat Jul 20 2024

.SYNOPSIS...
A stalled frontal boundary will continue to meander across the
Carolinas for the next several days and be the catalyst for a
prolonged period of unsettled weather that will continue into
next week. Scattered to numerous showers and thunderstorms are
expected each day.

&&

.NEAR TERM /TODAY/...
As of 200 AM Saturday...

- Scattered thunderstorms with gusty winds and heavy rainfall
  again today

Early this morning, a front remains stalled across the
Carolinas, roughly from Columbia, SC northeast through New Bern.
In the vicinity of this front, radar and satellite reveal a
couple of MCVs, one over southern Alabama and the other
currently moving along the Crystal Coast of NC.

Through the day today, short-term guidance is in fairly good
agreement lifting the front north as a warm front in response to
the southern Alabama wave lifting NE through the Southeast US.
This will put much of ENC in the "warm sector", if you will,
with the greatest lift briefly shifting north into northern NC
or southern VA. Through the day, then, that is where I expect
the greatest coverage of convection to be. In light of this, I
lowered the chance of showers and storms during the day.
Locally, it appears sea/bay/river breezes, and possibly areas of
differential heating, will be the main focus for isolated to
scattered diurnally-driven showers and thunderstorms. Where
showers/storms develop, modest instability and a continued high
PWAT airmass should be supportive of heavy rainfall rates.
Because of the scattered nature, I don`t anticipate significant
flooding concerns during the day. However, because of the
recent rounds of rain across northern sections of ENC, flash
flood guidance is notably low (only about 1-3"/hr). Therefore,
even with a scattered coverage of thunderstorms, there could
still be a few instances of flash flooding. A Flood Watch was
considered in this area, but in light of the scattered coverage
and lower confidence on where the greatest lift will be, it was
decided to hold off for now.

With the front lifting to the north, I expect more breaks in
the clouds today. This in concert with a slight bump up in low-
level thicknesses should support a bump up in temps compared to
yesterday.

&&

.SHORT TERM /TONIGHT/...
As of 200 AM Saturday...

 - Watching for a few stronger thunderstorms this evening

A mid-level wave (a remnant MCV from yesterday`s Gulf Coast
convection) is forecast to glance NC and VA this evening,
interacting with a moist and unstable airmass, potentially
supporting an increased risk of thunderstorms. Short-term
guidance is in generally good agreement on the convective risk
this evening and tonight, but it`s not the most solid signal.
Synoptically, the pattern looks very similar to the past few
nights, with an evening/overnight convective risk. The one
difference tonight is the above-mentioned mid-level wave is
forecast to lead to a bump up in the low-mid level flow,
supporting an increase in deep layer shear (on the order of
20-30kt). This will be more supportive of organized convection.
This plus added lift from the glancing wave and the frontal
boundary in the area may support an uptick in the risk of a few
strong to marginally severe thunderstorms. I suspect most storms
will be sub-severe, but the strongest cores could produce
gusty/damaging winds and marginally severe hail (penny to
quarter size). With more flow, storms should have a tendency to
be more progressive. However, it appears the greatest overlap of
lift and instability will be across our northern counties.
Consequently, this is also where flash flood guidance is the
lowest, and we`ll have to keep an eye on this area for the
possibility of some hydro concerns. Please see the "hydro"
section below for additional information.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 220 AM Sat...Key message: Unsettled weather with periods
of showers and thunderstorms with torrential downpours will
persist into much of the upcoming week as moist southerly flow
continues and a wavy, weak front persists over/near eastern NC
through the period.

Sunday through Friday...No end in sight for the unsettled, wet
period that started mid week. A very moist airmass combined with
the proximity to a weak front/boundary will lead to an above
climo chance for rain each day in the form of scattered to
numerous showers and thunderstorms. The showers and storms will
have torrential downpours with PW values remaining 2" or higher.
This will likely result in several inches of rainfall by mid
next week. Frequent downpours will produce localized Flash Flood
issues in urban and poor drainage areas. PoPs were lowered from
the too high NBM which has categorical PoPs through much of the
period. We prefer to keep PoPs in the chance to low end likely
which is still above climo (40%). High temps will run at or
just slightly below normal, while lows will be slightly above
normal through the period.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
SHORT TERM /Through 06z Sunday/...
As of 145 AM Saturday...

 - TSRA to continue to impact the area overnight

 - TSRA risk redevelops Saturday into Saturday night

 - Periods of sub-VFR conditions expected in TSRA

An area of SHRA and TSRA will continue to lift NE through
portions of ENC over the next several hours, clearing the coast
by 12z/8am Saturday. There may be a period of SCT/BKN low clouds
in the wake of the TSRA activity, but based on upstream obs and
satellite imagery, I decided to pull back some on the MVFR CIG
potential. During the day Saturday, a weak frontal boundary is
forecast to lift north into northern NC or southern VA. This
suggests the best lift may be removed from the area for a brief
time on Saturday. Should this be the case, the risk of TSRA
would tend to be lower for several hours during the daylight
hours. If the front gets hung up further south, the risk of TSRA
would be higher. Eventually, a modest upper level wave glancing
the area should support a renewed round of SHRA and TSRA from
central into northern NC during the afternoon and evening hours.
This puts the greatest risk of TSRA focused from KISO to KPGV.
Elsewhere, sea/bay/river breezes may support isolated to
scattered SHRA and TSRA, but confidence is too low for a mention
in the TAFs for now. Where TSRA occur, sub-VFR conditions are
likely (60-80% chance).

LONG TERM /Sunday through Wednesday/...
As of 220 AM Sat...Scattered to numerous mainly diurnal showers
and storms will continue into mid next week with occasional sub
VFR conditions. In addition, overnight fog/low stratus clouds
will be possible early each morning especially in areas that
received heavy rainfall. Expect southwesterly winds at 5-15 kts
through much of the period.

&&

.MARINE...
SHORT TERM /through tonight/...
As of 745 PM Saturday...

 - Building winds and seas this afternoon and evening

 - Thunderstorm risk continues

An area of thunderstorms will continue to impact all ENC waters
early this morning, with occasional wind gusts of 20-40kt where
the strongest thunderstorms occur. In the wake of this
activity, a lull in thunderstorm activity is expected for a few
hours as a warm front lifts north into the tidewater region of
Virginia. Later today into tonight, an upper level wave will
glance the area, with an associated surface low moving northeast
from central NC into southeast VA. The increased gradient
associated with this low may support a few hours of 25kt winds
across portions of the ENC waters. Probabilistic guidance shows
a mixed signal, suggesting about a 40- 60% chance of SCA winds.
With this forecast, I bumped winds up some compared to the
previous forecast to account for this potential, but given the
short nature and only modest probabilities, I opted to keep the
waters headline free for now. We`ll continue to re-evaluate this
potential in later forecast updates. With the increase in
winds, seas are forecast to build to 3-5 ft, especially from
Oregon Inlet south.

Another round of thunderstorms appears plausible later this
evening through tonight as the above-mentioned upper level wave
glances the area. Where thunderstorms occur, there will be a
risk of frequent, dangerous lightning, as well as 30kt+ wind
gusts.

LONG TERM /Sunday through Wednesday/...
As of 220 AM Sat...The flow is expected to remain S/SW all
waters through the period outside of convection. On Sun and Tue
wind speeds will be 10-15 kt while on Mon and Wed winds will be
a little higher in the 15-20 kt range. Seas will be 2-4 ft
through the period. Shower and storm chances are forecast to be
high through mid next week.

&&

.HYDROLOGY...
As of 220 AM Sat...The forecast is for unsettled, wet
conditions to continue well into next week with scattered to
numerous showers and thunderstorms each day, especially during
the afternoon and evenings. While there is considerable
uncertainty in exact details on storm coverage each day, soil
moisture levels continue to increase due to heavy rains from the
previous couple of days such that any additional heavy rains
would runoff more easily and result in local flooding. In
addition with PW values expected to continue seasonally high
(>=2"), locally heavy rain amounts will continue to be a threat
over the next several days. There is the potential for storms to
produce 2-3" in an hour with locally higher amounts which would
be enough generate urban/poor drainage flooding.

&&

.MHX WATCHES/WARNINGS/ADVISORIES...
NC...Beach Hazards Statement from 8 AM EDT this morning through
     this evening for NCZ195-196-199-204-205.
MARINE...None.

&&

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