Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Newport/Morehead City NC
638 am EST Sat Dec 20 2014
weak low pressure will develop off the southeast coast today
then drift slowly east through Sunday. Another low will develop
near the coast Sunday night into Monday then lift to the northeast
Monday night. A strong cold front will approach from the west
Tuesday night and cross the region Wednesday. High pressure builds
to the south of the area through the end of the week.
Near term /through today/...
as of 635 am Sat...dampening southern stream short wave will cross
region today. This feature will lead to weak surface low forming to
the southeast with some light rain developing over the region. Models continue
to show bulk of rain over southern tier with little to the north will continue
previous forecast of slight chance to low chance probability of precipitation north to high chance/likely southern
tier. Even across southern tier rainfall amounts will remain light
with less than 1/4 inch expected. Clouds and NE flow will keep
temperatures cool with highs mainly 45 to 50.
Short term /tonight/...
as of 235 am Sat...bulk of moisture will be offshore by early
evening with just small pop southern CST early then dry. Will continue to
have good deal of clouds over the region overnight...espcly CST.
Shld see enough breaks for lows mainly 30 to 35 inland with upper
30s to around 40 beaches.
Long term /Sunday through Friday/...
as of 410 am Saturday...northeast flow will persist Sunday with
increasing clouds throughout the day due to southwest flow aloft
transporting moisture rich airmass into the region. A weak low
pressure will develop off the Florida/GA/SC coast Sunday night that
will move northeast along the Carolina coast through Monday.
Guidance continues to indicate the low is ill-defined and weak
with consensus of around 1015 mb low off Cape Hatteras by Monday
evening. Minor tweaks to ongoing forecast probability of precipitation/temperatures Sunday into
Monday...keeping Sunday dry and cooler then increasing probability of precipitation Sunday
night to likelies late with mild temperatures Monday. Medium range temperature
guidance has had a cool bias as of late so hedged closer to GFS
MOS which matches well with low level thicknesses increasing near
1370 meters for southeastern zones...though there will likely be a
sharp temperature gradient from the coast to the coastal plains.
A deep longwave trough will amplify across the central Continental U.S. On
Tuesday with deep southerly flow increasing across the eastern
Continental U.S.. could see some showers on Tuesday as moisture and dynamics
increase ahead of the system...though best chances for widespread
organized rain come in Tuesday night into early Wednesday. The
main low becomes vertically stacked over the upper Midwest/Great
Lakes region Tuesday night/Wednesday...and models developing a
secondary low along the cold front and ahead of the upper
trough...moving through the Carolinas and mid-Atlantic. Area will
be in vicinity of approaching digging jet streak...and large scale
Omega/frontogensis will sweep through Tuesday night into early
Wednesday. Will continue mention of thunderstorms Tuesday night into
Wednesday morning...mainly along and east of Highway 17 as expecting to
see a high shear/Low Cape setup as trough becomes negatively
tilted...with models showing 0-6km shear 40-50kt and increased low
level helicity values due to backed south-southeast surface flow. Temperatures will be
mild Tuesday night with values holding in the 50s and even
increasing overnight to the 60s.
Precipitation chances decrease significantly Wednesday afternoon as the
front wings through and deep layer west-southwesterly flow begins
to dry the column. Gusty winds expected ahead of and behind the
front Wednesday with strong upper jet over the area. Wednesday
looks to be the warmest day as low level thicknesses build into
the 1380-1390 meter range...translating to highs in the upper 60s.
For Wednesday night through Friday...expect high pressure to build
across the region from the southwest yielding dry and cooler
conditions. Temperatures will be near climatology behind the front for Christmas
day as upper trough moves off the East Coast. Upper ridging builds
over the region Thursday. Low level thickness values support highs
in the low/middle 50s Thursday...moderating into the upper 50s Friday.
Aviation /12z Saturday through Wednesday/...
short term /through tonight/...
as of 635 am Sat...mainly VFR expected through period. Overcast skies today
as weakening southern stream short wave crosses. Best chance of light rain
will be middle/late morning through afternoon over southern sites however shld not be
heavy enough to reduce visibilities much. Ceilings shld mainly hold above 3000
feet this afternoon however did and tempo MVFR for a period later today at
oaj. Overnight good deal of clouds will linger as precipitation ends southern
tier...however most guidance and forecast soundings show VFR ceilings. There
is plenty of low level moisture around so some lower ceilings
poss...espcly closer to CST but will keep in VFR range for now.
Long term /Sunday through Wednesday/...
as of 330 am Sat...VFR conditions expected Sunday. Sub-VFR conditions
will be possible late Sunday night into Monday as a weak low/coastal
trough moves along the Carolina coast. Sub-VFR ceilings could linger
Monday night into early Tuesday as the boundary layer remains very
moist with weak surface flow. A strong low pressure system
develops in the deep south and moves northeast along the
Appalachian Mountains...dragging a strong cold front through the
region Wednesday into Wednesday night...with the potential for rain
and reduced ceilings/visibilities through Wednesday afternoon.
short term /through tonight/...
as of 635 am Sat...weak surface low will develop to the southeast today then
drift slowly east tonight. As the low develops gradient will tighten a
bit along the CST with high pressure to the north...this will lead to north/NE
winds increasing to 10 to 15 kts. With the low only slowly
drifting east tonight winds will continue at 10 to 15 kts...highest south.
Seas will continue mainly in the 2 to 3 foot range...however a few 4
footer poss over the outer waters.
Long term /Sunday through Wed/...
as of 415 am Saturday...a weak low pressure system is expected to
move along the southeastern U.S. Coast Sunday night into Monday.
NE winds will back east then south along the coast on Monday. Could
see brief period of Small Craft Advisory ahead of the weak coastal low as NE/east
gradient is pinched as the low rides up the coast. Weak low will
continue to lift North/East of the area Monday night and Tuesday...and
expect light/variable winds with seas 2-4 feet. Strong cold front
approaches Tuesday night and crosses the waters Wednesday. Winds
will become south and increase rapidly late Tuesday night and
Wednesday before becoming westerly Wednesday evening. Seas respond
by building and peaking at 6-10 feet Wednesday...then slowly
subsiding Wednesday night into Thursday. 00z European model (ecmwf) suggests winds
could gust near gale force range for portions of the central
waters Wednesday into Thursday though the European model (ecmwf) remains 5-10 knots
stronger than other guidance...thus will use a blend for winds middle
week. Gusty west winds will diminish late week.