Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
553 PM EST Tuesday Mar 3 2015
a warm front will lift rapidly northward across the Carolinas
overnight...allowing southwest winds to completely scour out the
cold air...with temperatures rising into the 70s Wednesday away
from the immediate coast. Rain can be expected Thursday afternoon
and night as a cold front moves through...with sharply colder air
invading the region into Friday...lingering through Saturday.
Temperatures will gradually warm Sunday through early next week.
Near term /through tonight/...
as of 3 PM Tuesday...complex situation continues to evolve this
afternoon as a wedge of high pressure holds firm...even as a warm
front begins to lift from the north. The challenge for tonight will
be timing the warm frontal dissipation of the surface wedge...and
then determining how hourlies will develop in a very atypical
Isentropic lift has been spotty and weak through this
afternoon...producing infrequent periods of drizzle and some very light
rainfall. Maximum quantitative precipitation forecast has been no more than a few hundredths of an
inch...and most areas have received only a trace. Some very light
rain due to continued isentropic lift will persist into
tonight...but as The Wedge erodes lift will weaken and shower
activity will be shunted north of the County Warning Area. The warm front is slowly
lifting N/NW...and is aligned from just west of Frying Pan
Shoals...to north of Savannah, Georgia...to about Montgomery, Alabama. This
front will continue to lift north...eventually crossing the entire
ilm County Warning Area overnight. Guidance is really struggling with the strength
of The Wedge today...and the coolest NAM has been the best of a poor
model suite. Therefore...have kept temperatures cooler than guidance into
tonight...and have a slower warm frontal passage than suggested by the models.
Still...expect a very slow warming trend through this evening...with
a much more rapid rise in temperatures overnight. Today's highs will occur
this evening...and will coincide with tonight's lows. So...even
though the min temperature forecast has lows in the low 50s near the coast
and middle 40s inland...these will be eclipsed quickly behind the warm
front and temperatures by Wednesday morning will be around 60 at the
coast...and low 50s inland.
Drying occurs behind the warm front which will further inhibit
shower activity late...but very moist low levels will allow for some
fog early in the night. Winds increase steadily overnight
though...and expect fog to lift into a stratus deck...so fog is
expected to dissipate overnight. The exception to this will be along
the immediate coast (within 2-3 miles) where sea fog is expected to
become significant and advect onshore. The most likely places for
land-affecting sea fog will be the northern Horry County coast up
through the southern New Hanover County coast. Locations within this
area could have a prolonged period of severely reduced
visibility...but again...it will be only within 2-3 miles of the
Short term /Wednesday through Thursday night/...
as of 3 PM Tuesday...main weather headline is exceptionally mild
air Wednesday amid what has been a frigid winter...with February
ranking as the 5th coldest February in 141 years of record keeping
which crunches out to about a 1 in 34 year occurrence of cold. The
other notable highlight is rain Thursday afternoon and night then
followed by a biting intrusion of glacial air and lingering precipitation.
Storm total quantitative precipitation forecast from this system the bulk of it Thursday...looks
to be nearly a half inch across southeast NC and localities west of I-95
and closer to a quarter inch across NE SC and coastal SC. Popped
in a slight chance thunder Thursday given jet support and Storm Prediction Center day
Substantial temperature drops...where maximums Thursday minus
minimums Friday on the order of 30-40 degrees fahrenheit...and
just a fresh reminder old man winter still has breathings into
early March. An overlap of near to sub-freezing temperatures and
lingering precipitation warrants a slight chance of brief light snow 8z-10z
or 3am- 5am early Friday. No accumulations expected at this time.
Long term /Friday through Monday/...
as of 3 PM Tuesday...the middle level pattern will continue to
dominated by a broad trough trough most of the period with some
signs of relaxing by the middle part of next week. Initially the
trough Ushers in yet another Arctic airmass that will be in place
Friday and Saturday. Temperatures will be well below normal with
highs in the 40s Friday and lows in the middle 20s Saturday.
Another shortwave emerging from the Gulf of Mexico rides along the
old front offshore Saturday warranting low chance probability of precipitation for Saturday
through Sunday morning with the highest chances along the coast.
March sunshine wont have much of a chance to warm things up with
highs only the 50s but the moisture will limit lows to the middle
30s. Lethargic warmup continues Sunday through Tuesday under partly
sunny skies as weak high pressure resides at the surface. Medium
range guidance is showing another system for the middle part of next
week with the European model (ecmwf) the faster solution. Will keep the forecast dry
Aviation /00z Wednesday through Monday/...
as of 00z...stubborn wedge hangin in with southwest flow just above
the surface deck. Look for variable mainly northeast winds for the
next few hours before a light southwest flow begins to take over
after 04z. Temperatures will likely rise to the upper fifties
overnight. IFR conditions will dominate for at least the next 12-18
hours. Wednesday...increasing southwest flow ahead of a strong but
slow moving cold front well west of the region. Ceilings will slowly
rise through the morning hours...becoming MVFR in the afternoon with
gusty southwest winds. Do not think we will see sea fog along the
coast...but could not rule out stratus.
Extended outlook...showers Wednesday night...becoming IFR with light
rain and falling temperatures on Thursday. IFR conditions may linger
along the coast on Friday. VFR Saturday through Monday.
near term /through tonight/...
as of 3 PM Tuesday...coastal front/warm front is draped along the
coastal waters this afternoon. Winds at the immediate coast are from
the NE...while the local buoys are featuring east or southeast winds. This
front will lift slowly north/northwest this evening before racing well north of
the area overnight. Winds will become S/southeast early tonight with speeds
around 10 kts...before veering further to the S/SW and increasing to
15-20 kts towards Wednesday morning. Wave heights will rise to 3-5
feet...but conditions are expected to remain just below any scec or
Small Craft Advisory criteria.
Sea fog will become a significant hazard however. As winds become
S/SW they will advect warm moisture laden air over still very cold
shelf waters (ssts in the upper 40s). The setup seems almost classic
for sea fog development. Using a combination of the local marine fog
decision tree...and lots of manual grid editing...have painted a
large area of patchy fog...with areas of fog along the
Horry...Brunswick...and New Hanover County coastal waters. This may
become dense...and it is not out of the question that a marine dfa
will be needed. One caveat to the fog will be the wind speeds.
Previous sea fog events have not materialized due to the strength of
winds reducing air-parcel residence times over the cold shelf
waters...thus reducing saturation potential. Current forecast wind
speeds below 20 kts should be light enough to limit this
affect...but it will need to be monitored. Otherwise...it looks to
be "all systems go" for sea fog overnight and into Wednesday
Short term /Wednesday through Thursday night/...
as of 3 PM Tuesday...marine conditions will become increasingly
unfriendly Wednesday into Thursday associated with an approaching
cold front...but an advisory may not be needed until Thursday...as
the warm air may struggle reaching the cold dense air above the
chilly SSTs in place. If not advisory conditions prior to the
frontal passage then certainly behind it...as very cold air
spills over the waters...with at a minimum 30 knots gusts expected
late into Thursday night. The other hazard prior to frontal
passage is the likelihood of sea fog as balmy air tracks over the
frigid waters...reducing visibilities at times. Rain Thursday afternoon
and night may also restrict line of sight.
Long term /Friday through Sunday/...
as of 3 PM Tuesday...brisk northerly winds on the order of 20-25
knots will prevail across the waters initially and most of Friday as
Arctic high pressure builds in. As we have seen many times this
season the winds gradually diminish as the high moves in with speeds
dropping to around ten knots by midday Saturday. For the remainder
of the period winds will be weakly forced as a weak pressure pattern
develops. If anything winds maintain a northerly component as a weak
shortwave passes aloft with negligible surface features. Significant
seas yield no surprises with some higher values Friday...mostly
confined to the outer waters. By later Saturday values drop to 1-3