Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Wilmington NC
615 am EST Friday Jan 30 2015

Synopsis...
a cold front will move further offshore this morning. Dry and
cold Canadian high pressure will follow in the wake of this cold
front through Saturday. A storm system will approach on
Sunday...bringing warmer temperatures and increasing rain chances.
The cold front associated with this system will cross on
Monday...followed by high pressure and a return to cold
temperatures early next week. Low pressure moving up from the Gulf
Coast middle week may spread significant rain northward into the
Carolinas Wednesday into Thursday.

&&

Near term /through tonight/...
as of 330 am Friday...a progressive weather pattern to continue through
this period. Surface high has slid southeast-S of the area to start this
morning. An amplifying and nearly a full latitude upper trough to
affect the area today...with its north to south axis sliding off the
Carolina coasts this afternoon. Models hint that the upper trough will
becoming negatively tilted and possibly close off. By the time this
occurs...the weather and surface low will have moved away from the ilm County Warning Area.
However...we are not out of the Woods yet...the intensifying surface low
and the Canadian surface high will combine to produce a tightened surface pg
across the forecast area by late morning and continuing well into tonight. The
cold front passage is slated to occur between 4 to 6 am this morning. In its
wake...cold Canadian high pressure will ridge across the forecast area...
settling across the forecast area later tonight. Drying will occur at all
levels as depicted by various model time height displays across the
forecast area. The northwest downslope trajectory off the Appalachians will further
scour or wring out any leftover moisture from midday today through
tonight. It now becomes basically a temperature forecast after this
mornings cold front passage. As for temperatures...excellent cold air advection after frontal passage which
continues well into the night. 800 mb temperatures drop from +5 to +9 degrees
celsius early this morning...to -3 to -8 degrees celsius at the peak
of the cold air advection. Overall...the NAM MOS guidance continues to be the
colder one when compared to GFS MOS, however...given temperature
verification the past several days...the GFS MOS is outperforming
the NAM MOS. Thus will lean toward the GFS...with roughly todays maximum
between 50 and 55...and tonights lows in the 20s thruout.

&&

Short term /Saturday through Sunday night/...
as of 330 am Friday...deep northwest flow will lighten up through
Saturday as high pressure shifts closer overhead. At the upper
levels winds will back and heights will rise slightly through the
day with a zonal flow or weak ridge developing. Air mass will
remain dry for the most part with plenty of sunshine on Saturday
but may see some cirrus streaming in by end of day associated to
next approaching system over the Mississippi Valley. Downslope
flow... height rises and sunshine should help temperatures rebound after
a cool start to close to 50. Pcp water values down less than a
quarter of inch Sat morning will rebound up to around a half inch
by Sat night. Sat evening should see a quick temperature drop off as high
clouds will not be too thick yet to prevent decent radiational
cooling with calm winds as high pressure remains overhead. Expect
overnight lows down near freezing most places.

The high will slip off shore through Sat night with a weak return
flow setting up into Sunday morning. Expect a deep increasing SW
to west return flow through Sunday. Will tap into some Gulf moisture
by Sun night into Monday. Initially will just see thickening middle
to upper level clouds through Sun night. As moisture increases
through the column in low level jet up to 45 to 50 kts Sun night expect pcp
chances to increase. Warm air advection through the day will kick temperatures up to
near or above normal...55 to around 60. Temperatures will not drop much
Sun night with warm air advection and increasing clouds and pcp.

&&

Long term /Monday through Thursday/...
as of 330 am Friday...local area in warm sector in decent SW
return flow Monday morning ahead of an approaching cold front.
After a warm start temperatures will increase several more degrees most
places before cooler and drier air makes its way in behind cold
front. Latest model runs show front making it off the coast around
noon time on Monday. Pcp will taper off latest at the coast with
lingering clouds through much of the afternoon until middle to upper
trough finally shifts off the coast by Monday evening. May see a fair
amount of quantitative precipitation forecast in some heavier showers through the morning. High
temperatures will come early in the day most places before clearing and
cold air advection through late Monday into Tuesday as high pressure builds in.
Temperatures inland will have less time to warm before cold front blows
through and therefore temperatures closer to the coast will be the
warmest with cooler northwest flow developing from west to east through
the day.

High pressure will build in Monday night moving swiftly east reaching
over the middle Atlantic coast by Tuesday evening. Expect a cool and mostly
sunny day on Tuesday. Developing low pressure along the Gulf Coast
Tuesday night may spread enough moisture north with increasing
isentropic lift over the Carolinas to produce some pcp by Wednesday
morning. As the high slips off shore and farther east through
Wednesday...it will continue to extend back over the Carolinas in a more
typical wedge like fashion. At the same time the low pressure will
move up from the Gulf Coast riding up along the southeast coast.
Initially the warm air overrunning the shallow cold air in place
may produce a narrow window of possible freezing rain inland very early
Wednesday morning...but it looks like the pcp will not spread far
enough north into the below freezing temperatures. Enough warm air will
move in through Wednesday into Wednesday night to not cause any mixed pcp
concerns over the coastal Carolinas. Temperatures should rise into the
50s most places on Wednesday and increasing clouds and pcp will keep
temperatures up in the middle 30s to around 40 Wednesday night. The low will track up
through the Carolinas approaching the Hatteras coast by Thursday
morning. As the low lifts off to the northeast a deep middle to upper
trough will push a cold front through with plenty of cold and dry
air moving in for late Thursday into Friday.

&&

Aviation /12z Friday through Tuesday/...
as of 12z...front pushing to the coast as we speak. Light to
occasional moderate precipitation will occur along the coast for the next
hour or two. Post frontal...look for clearing skies with northwest
winds increasing with the cold air advection. Gusts to 25 kts are
possible by middle morning. Expect cold air advection to continue
through the afternoon hours...with a continued tight gradient. Winds
will become less gusty this evening...however they should stay above
6-7 kts most of the night with no fog expected.

Extended outlook...VFR through Saturday. Showers/MVFR likely late
sun through Monday morning...then becoming VFR again through Tuesday.

&&

Marine...
near term /through tonight/...
as of 330 am Friday...cold front passage early this morning will result in winds
veering from the SW-west early this morning...and from west to northwest later
this morning. Strong Canadian high pressure and intensifying low
centered offshore from the NE states...will combine to produce a
tightened surface pg across the local waters. In addition...cold air advection surge
will be ongoing. All of this spells a strong Small Craft Advisory thruout this
period...with gusts approaching 35 knots for the ilm NC waters.
Significant seas will range from 3 to 6 feet today and 2 to 5 feet
tonight. With an offshore wind trajectory...a limited fetch will
keep significant seas in check. Short period wind driven waves will
dominate the sig. Seas.

Short term /Saturday through Sunday night/...
as of 330 am Friday...high pressure will move toward the waters
reaching overhead by Sat evening. This will allow pressure gradient
to relax considerably through the day. West to northwest flow will become
light and variable and eventually shift around ot the southeast to S by
Sunday morning as high shifts farther off shore. As winds weaken
to less than 10 kts through late Sat seas will drop to less than 3
feet . Expect an increasing south to southwesterly return flow
during the day Sunday as gradient begins to tighten with the
approach of next system. Winds will increase up to 10 to 20 kts
through Sunday night. This will push seas up to 4 to 6 feet reaching
into Small Craft Advisory thresholds after midnight on Sunday night.

Long term /Monday through Tuesday/...
as of 330 am Friday...tightened gradient flow ahead of cold front
Monday morning will producing SW winds up to 20 kts will keep Small Craft Advisory
conditions over the waters with seas up to 5 to 8 feet Monday morning.
Should see Small Craft Advisory conditions lasting into Monday as winds shift
around to the west-northwest as cold front moves through. By Monday
afternoon a quick shift to northwest winds will occur as a cold
front moves across. With some cold air advection...winds will remain in the 15-20
knot range. For Tuesday high pressure will move quickly from the
Ohio Valley to offshore with the wind direction making the typical
progression from north to northeast to east/southeast...remaining
10 kts or less. Seas will subside through the day.

&&

Ilm watches/warnings/advisories...
SC...none.
NC...none.
Marine...Small Craft Advisory until 6 am EST Saturday for amz250-252-
254-256.

&&

$$
Synopsis...rgz
near term...dch
short term...rgz
long term...rgz
aviation...43

National Weather Service Glossary of Abbreviations