Scientific Forecaster Discussion
fxus62 kilm 220140
Area forecast discussion
National Weather Service Wilmington NC
940 PM EDT Mon Oct 21 2019
showers and isolated thunderstorms ahead of a cold front will
affect the area late tonight through Tuesday. The cold front is
expected to move offshore Tuesday night. High pressure and dry
weather will follow Wednesday through Friday morning. However,
rain chances are expected to increase again late Fri into next
weekend as another cold front approaches from the west.
previous forecast remains on track. No big changes necessary.
Near term /through Tuesday night/...
mostly clear skies the rest of today, with lingering stratus
offshore, due to weak surface ridge from the north. Tonight,
warm air advection ahead of approaching cold front will lead to
warming temperatures through the night, with the low occurring
around midnight, and broken stratus deck. A southerly 850mb flow
around 30kts develops tomorrow morning, advecting dewpoints of
70 degrees and cape values between 1000 and 2000 j/kg. Increased
moisture combined with effective shear values of 40-50 kts, has
led to Storm Prediction Center issuing a slight risk of severe weather for our
forecast area tomorrow, with main threat damaging wind gusts and
severe hail and tornados secondary. Despite favorable
ingredients, lifting mechanisms aren't that impressive. Warm air advection
during the day, along with diurnal heating with any breaks in
the stratus, will most likely be main forcing for storms. Cold
front moves through late tomorrow evening, and with it Last
Chance for rain. Temps tonight and tomorrow will run 5-10
degrees above normal, with lows Tuesday night returning to near
Short term /Wednesday/...
time height cross sections indicate a very dry column in place
during Wednesday as the mid/upper trough lifts across New
England and eastern Canada leaving zonal flow in place across
the Carolinas. Surface high pressure will begin to migrate from
the deep south across the Carolinas during this time brining
near seasonable temperatures. A blend of mex/ecx highs and lows
looks reasonable for this time frame.
Long term /Wednesday night through Monday/...
dry weather will persist Thursday into Friday morning then a
transition will occur as the next front comes into play late
Friday into Saturday. Not as much confidence during this part of
the forecast given the differences in the GFS and the 0000 UTC
European model (ecmwf). Specifically the new GFS is more aggressive with a weak
perturbation developing along the front near the coast. Plan to
split the difference with pops and blend toward the warmer European model (ecmwf)
until a better trend is depicted. However, for Sunday with high
pressure either ridging in from the north or northeast favor
the cooler GFS guidance.
Aviation /02z Tuesday through Saturday/...
low clouds will begin to develop across the area as a warm
front pushes northward overnight. Warm ocean temperatures should
keep coastal terminals in MVFR while VFR at our inland sites
crash to IFR after 06z. A couple areas of fog are possible, but
with easterly winds maintaining around 5 knots overnight,
stratus should be the main concern. Around 09z, the first round
of precipitation should being to affect the area with mainly
showers moving from south to north behind the warm front. A
secondary pulse of ts activity is possible tomorrow afternoon
when the main cold front pushes through the area. Dry air
entrainment could lead to a few strong thunderstorms with
damaging winds or tornadoes. Oscillating sub-VFR and VFR
conditions throughout the day on Tuesday will become VFR once
the front passes near the end of the period.
Extended outlook...mostly VFR with possible MVFR/IFR from fog and/or
low stratus Fri morning.
for the rest of today and tonight, relatively calm conditions
over the waters, with east/southeast winds around 10kts and seas 2 ft,
with S waves 2 ft at 5 sec and east swell 1 ft at 10 sec. Rain
chances begin to increase early tomorrow morning as southerly
flow becomes enhanced ahead of approaching cold front. Sustained
winds 15-20 kts late tomorrow morning through Wed morning, with
southerly winds ahead of front becoming westerly behind front
around 3z Wed. Clear skies and dry weather behind the front late
Tuesday night. Will also see an increase in seas tomorrow to
4-5 ft, with S waves 4 ft at 6 sec and southeast swell 1 ft at 9 sec.
Expect conditions to remain below Small Craft Advisory criteria tomorrow through
Wednesday, but may be close.
For Wednesday through saturday: high pressure over the deep
south along with a cold front far offshore will maintain gusty
northerly winds Wednesday morning. Speeds will diminish during
the day as the area of high pressure builds across the
Carolinas. The area of high pressure is expected to shift off
the mid-Atlantic coast during Thursday afternoon allowing for
light northeasterly winds to prevail. A coastal trough may form
allowing northeasterly winds to hang on into Friday, then low
pressure may develop just off the coast Saturday allowing winds
to increase to near Small Craft Advisory thresholds. The
offshore flow will allow for a greater range in seas (especially
for the adjacent Brunswick County waters) initially during
Wednesday. Seas will subside to 2-3 ft for the remainder of the
week, then increase to 4-6 ft during Saturday with the low in
the proximity. Chance for showers developing late Friday, and
becoming numerous Saturday with isolated tstms.
SC...beach hazards statement from 6 am EDT Tuesday through Tuesday
evening for scz054-056.
NC...beach hazards statement from 6 am EDT Tuesday through Tuesday
evening for ncz106-108.