Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
1220 PM EST sun Dec 28 2014
high pressure will slip farther offshore...allowing mild air and
increasing moisture to overspread the area today. Rain chances
will peak tonight and Monday as a cold front moves south across
the Carolinas. Clearing and cooler Wednesday and New Years Day as
high pressure builds into the area. Mild and wet weather may
return late week into next weekend ahead of a low pressure system.
Near term /through tonight/...
as of 1220 PM Sunday...forecast adjusted to address the fact that
coastal locations seemingly want to remain quite sunny. A few
places have popped up into the lower 70s and 73/74 in particular
seems to be a 'magical' value that leads to mixing and gusty winds
as seen at kflo and kilm past hour or two.
Short term /Monday through Tuesday night/...
as of 315 am Sunday...the main focus of the short term will be the
front that impacts the region really through the entire period.
The GFS has been hinting at decent probability of precipitation and quantitative precipitation forecast on and off for a few
cycles now and with a small contribution from a 700mb jet moving
across the boundary midday Monday...probability of precipitation and quantitative precipitation forecast amounts have
increased once again. The NAM has this feature but quite a bit
earlier while the European model (ecmwf) has it later. The GFS appears to be a good
compromise. I have increased probability of precipitation somewhat to likely for all areas
but the coastal zones should see the most quantitative precipitation forecast. Enough moisture
lingers to warrant lower chance probability of precipitation for Monday night into Tuesday
where drizzle is the more likely weather type. I have adjusted
temperatures slightly downward for Monday and Tuesday with a slight
adjustment upward for lows all via more moisture and a slightly
slower progression of the system overall.
Long term /Wednesday through Saturday/...
as of 315 am Sunday...the main focus of the extended period begins
to shift to the closed low moving out of the southwest and its
affect on the sensible weather late in the period...Friday and
Saturday. Until this time...massive high pressure will slowly move
across the east and weaken while keeping temperatures slightly
below climatology with dry conditions.
Medium range guidance has trended with a weaker solution as the
ridge...off the southeast coast is a little stronger as the low gets
kicked out. The system eventually opens up and weakens...racing up
into the Ohio Valley with a weakly forced front moving across the
southeast. We saw a similar situation a couple of weeks ago. We have
low chance probability of precipitation from Friday Onward and have made only minor
adjustments to these values. There are signals that a cold air wedge
may develop Friday and extend into Saturday before the front moves
across later in the weekend.
Aviation /18z Sunday through Friday/...
as of 18z...unseasonably warm temperatures this afternoon may usher in a
southerly resultant with a slight chance of sea
fog/stratus...although it seems remote at this time. The front will
wave slightly northward this afternoon but will begin to drift
southward this evening. As the front drops south overnight...look
for deteriorating conditions with IFR developing at all sites after
06z. Likewise overrunning precipitation will begin between 07-09z over the
western portion of the County Warning Area...and around daybreak for the coast
terminals. Models indicate precipitation will be quite light...perhaps only
drizzle. Monday...a pretty rotten aviation day with IFR/LIFR
conditions expected all day in the overrunning conditions.
Extended outlook...rain with MVFR/IFR ceilings/visibilities on Monday. MVFR/IFR
ceilings will persist into Tuesday. VFR on Wednesday. MVFR ceilings possible mainly at
the coastal sites on Thursday. Rain possible late Friday.
near term /through tonight/...
as of 930 am Sunday...no changes to the forecast...spectral density
plots continue to show a Lone Peak at 15sec...even the 'dominant'
period 7 second wind wave hard to make out. Early visible Sat shows no
sea fog but as dewpoints rise later in the period it may develop.
As of 6 am Sunday...pronounced long period waves are arriving
onto the coast from a previous Atlantic distant storm...with wave
periods around 15 seconds propagating ashore. Light wind this
morning will become increasingly SW and rise to 10-15 knots in the
afternoon. Winds will turn slightly onshore near the coast as a
sea breeze develops between 200 PM and 600 PM...but not too much
higher than 15 knots expected. Higher speeds expected offshore today
from SW...due to milder waters there. Long period east-southeast swell will
interact with increasing south-southwest chop to produce moderate bumpy seas
but no advisories are expected through tonight. No thunderstorms but
patchy sea fog could plague some inshore marine locations as winds
turn a bit more onshore later today.
Short term /Monday through Tuesday night/...
as of 315 am Sunday...a few hours of modest southwesterly flow will
continue early Monday but a cold front will drop south during the
day and winds will be northeast by the end of the day. Speeds
increase in the wake of the front to 10-15 knots. Speeds increase
even further Tuesday with slightly more cold air advection and the
increased gradient with the front offshore. An uptick to 15-20 knots
can be expected. Seas increase from 1-3 feet Monday to 3-6 feet late
Tuesday with a marginal Small Craft Advisory possible.
Long term /Wednesday through Thursday/...
as of 315 am Sunday...the coastal waters will see a northerly
component to the winds for most part through the period until very
late. High pressure...centered well west of the area will slowly
shift eastward by Friday when a coastal trough/return flow veers
winds to the east/southeast. Overall wind speeds will be highest
early...10-15 knots diminishing to ten knots or less by later
Thursday continuing into Friday morning. Significant seas will be
1-3 feet with the higher values across the outer waters.