Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Wakefield Virginia
754 PM EDT Thu Jun 22 2017
Bermuda high pressure begins to shift back towards the eastern
Seaboard through tonight. The high becomes centered off the
southeast coast Friday and Saturday...as a surface cold front
approaches the region from the northwest. Tropical moisture from
the remnants of dew point Cindy will push across the region ahead of
the front for Friday night through early Saturday...before the
front shifts offshore late in the weekend.
Near term /until 6 am Friday morning/...
latest weather analysis features Tropical Depression Cindy
moving north-NE over the arklatex region of the lower Mississippi
River valley. Out ahead of the system, a broad plume of mid to
upper level clouds has pushed across the mid-south into the
Carolinas. To the north, a quasi-stationary boundary remains in
place along and just north of the Mason-Dixon line, extending
northwest into the western Great Lakes. Meanwhile, the Bermuda high is
settling in off the southeast coast and will remain there
through at least Saturday. 12z soundings indicate south-southwest flow has
allowed for quick moistening out ahead of the system, with precipitable water
values already ~1... just a bit faster than model
Slight to low end chance (20-30%) pop continues for isolated to
widely sct convection over the southern 1/3 of the area (mainly
US-460 south) this aftn. A couple of lobes of shortwave energy
out ahead of dew point Cindy lift east-northeast from the Tennessee Valley/southeast states this
afternoon. Given that shear is still on the low side, expect
activity over the local area to drop off quickly with loss of
heating, with most pcpn remaining to our W-SW through midnight.
Overall, increasing clouds, very warm/muggy for the balance of
this aftn with highs reaching into the lower 90s most areas and
dewpoints around 70f.
More widespread area of showers pushes in late tonight as
Theta-E ridge pushes across the Piedmont toward the Eastern
Shore late tonight into Friday morning. Expect a period of
moderate to locally heavy rainfall during this time frame, and
have therefore continued likely pop mainly northwest of a fvx-ric-sby
line. Farther south, have gone with a low chance pop for some
isolated showers over south central Virginia and NE NC. Warm and muggy
overnight with lows in the 70s.
Short term /6 am Friday morning through Saturday night/...
the core remnants of dew point Cindy will merge with the approaching
cold front on Friday, and lift NE from the mid-south toward the
central and southern Appalachians Friday afternoon and night
before crossing the local area late Friday night through
Saturday morning. Out ahead of the system, rain showers
associated with lead shortwave/Theta-E ridge will push across
the northern tier of counties Friday morning. Expect a brief
period of partial clearing behind this initial wave, which
should allow for strong surface-based instability. Precipitable water values
will creep to and above 2" by Friday morning. Additionally,
expect 0-6km deep layer shear will be on the order of 35-45 kt,
with hi-res models showing a pronounced low level jet streak of
~50 kt just to the north by mid to late afternoon. The caveat to
all this thunderstorm potential is that regional soundings
continue to indicate a fairly substantial capping inversion that
will need to be overcome to realize the strong convective
threat. Given strong amount of lift to the north, expect that
best chance for T-storms tomorrow afternoon will be across our
northern tier of counties, and have oriented a high end pop for
scattered T-storms Friday afternoon. Farther south, removed from
the better dynamics, have tapered back to a 20-30 pop tomorrow
afternoon. Very warm and humid tomorrow with highs again u80s to
low 90s inland. Warm and muggy Friday night with lows in the
After another brief lull tomorrow night, the actual remnants of
Cindy track across the approaching cold front early Saturday
morning. Given favorable dynamics and precipitable water values at or above 2", expect a
period of moderate to locally heavy rainfall across the northern
half of the region. Despite short-lived heavy rain rates in the
tropical airmass Sat morning, progressive nature of system
should preclude too many flooding issues. However, important to
note that flash flood values are lower than they typically would
be for this time of year, especially along the I-64 corridor.
Therefore, we will have to watch this time frame closely. Front
will push to the coast and then offshore by Saturday evening,
with pops gradually diminishing Saturday afternoon and early
evening. Locally heavy rainfall possible along the coast and
southern zones into the early evening hours on Saturday.
Remaining warm and moderately humid Saturday. Highs mainly in
the mid to upper 80s to around 90 southeast zones.
Long term /Sunday through Thursday/...
cold front pushes offshore Saturday night, stalling along the
coast Sunday. Height falls ahead of a deepening upper level
trough over the Great Lakes/Ohio Valley Sunday and remnant
moisture along the boundary will result in isolated to scattered
showers and thunderstorms across northeast North Carolina Sunday
afternoon. Drying inland. Highs Sunday in the low to mid 80's. A
secondary front pushes into the region Sunday night and Monday.
Have only kept slight chance pops inland Monday given limited
moisture. Highs in the low to mid 80's. Potent shortwave digs
into the Ohio Valley and central Appalachians Monday night into
Tuesday with a stronger cold front pushing through the region
Tuesday. Moisture return along the coast will result in isolated
to scattered showers and thunderstorms across eastern Virginia.
Cooler Tuesday with highs in the mid to upper 70's. Dewpoints
mix into the 50's, resulting in pleasant afternoon conditions.
Dry and comfortable conditions forecast again Wednesday as the
trough pushes offshore and heights build over the Ohio Valley.
Surface high pressure settles over the mid-Atlantic. Highs
Wednesday generally in the low 80's. Cool Thursday morning, with
lows in the upper 50's inland to mid 60's near the coast. High
pressure slides offshore Thursday with return flow resulting in
moderating temperatures. Highs in the mid 80's.
Aviation /00z Friday through Tuesday/...
the Bermuda high pressure ridge extended from the east into the
Carolinas. Tropical Depression Cindy was over western
Louisiana. A warm front reached from low pressure over the
northern Great Lakes to Connecticut.
As of 23z...high clouds covered the mid Atlantic states.
Isolated showers were staying away from the taf sites and will
end shortly. A moist flow from the Gulf of Mexico ahead of a
cold front will produce scattered showers and isolated
thunderstorms fri8day. Most of these will be north of the taf
sites and went no more than showers in vicinity in the tafs.
Winds will continue from the southwest through the period.
Outlook...the remnants of Cindy will cross the northern portion of
the mid Atlantic states Saturday morning and will be located along a
cold front. That front will cross the taf sites during the day
Saturday. Showers and thunderstorms will be likely Saturday
afternoon. These will come to an end Saturday evening. Far southeast
portions will have a slight chance for showers and thunderstorms
Sunday. There will be a chance for showers and thunderstorms Monday
through Tuesday across the area. Patchy MVFR or IFR ceilings and
visibilities will be possible each morning within a few hours of
latest surface analysis centers high pressure off the southeast
coast with a weak frontal boundary over the northeast. Southwest
wind of 10-15 knots prevails over the waters this afternoon with
waves 1-2 feet and seas 2 feet. High pressure prevails off the
southeast coast through Saturday as the remnant low of Cindy
tracks along a cold front through the Tennessee Valley Friday
and Friday night and into the mid-Atlantic Saturday morning.
Southwest winds increase over the waters Friday afternoon, with
speeds increasing to 15-20 knots in the northern waters Friday
afternoon. Have raised Small Craft Advisory headlines for the Upper Bay Friday
afternoon for gusts of 20-25 knots. Pressure gradient
strengthens Friday night ahead of the remnant low as winds aloft
increase. Southwest winds increase to 15-25 knots with gusts up
to 30 knots in the Bay and coastal waters Saturday morning. Seas
increase to 4-6 feet out 20 nm north of Parramore Island. 3-4
feet elsewhere. Waves increase to 2-4 feet. Small Craft Advisory headlines have
been raised for the Bay beginning late Friday evening, but have
held off on additional headlines due to the time frame being
late 4th period. The remnant low lifts north of the region
Saturday afternoon as pressure rises return over the waters mid
to late afternoon. Expect improving conditions late Saturday as
winds become west to southwest at 10-20 knots. Seas subside to
2-4 feet Saturday evening. Winds become northwest Saturday night
as the front pushes across the region, but a lack of cold
advection and weak gradient winds expected to keep conditions
sub-sca. Another cold front pushes across the waters Monday
night with high pressure building over the region through the
middle of next week.
Marine...Small Craft Advisory from 10 PM Friday to 6 am EDT Saturday
Small Craft Advisory from 1 PM Friday to 6 am EDT Saturday for