Area Forecast Discussion
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FXUS62 KILM 221920
Area Forecast Discussion
National Weather Service Wilmington NC
320 PM EDT Wed Mar 22 2017
Freezing temperatures possible over a portion of the area
tonight as cold Canadian high pressure builds into the
Carolinas. As this high moves more offshore Friday into the
weekend, a warm-up will ensue. Minor rain chances are expected
Sunday as a weak upper disturbance passes well to our north.
.NEAR TERM /THROUGH THURSDAY/...
As of 300 PM Wednesday...A broken layer of post-frontal strato-
cu blanketing the Cape Fear region this afternoon will continue
to break up and scatter out as we head into the evening hours.
Model soundings show very dry air at all levels moving in from
this evening into Thursday as a deep-layer NW flow takes hold.
At the surface a cold and dry high will drop SE across the
eastern Carolinas through the near term as ridging builds aloft.
Breezy and gusty winds will continue into the evening hours as
the cold surge barrels down from the north.
Considering how poorly guidance has performed recently, see the main
forecast challenge for this period will be overnight temperatures.
Considering past performance, have stayed on the low side of
guidance and thus have raised a Freeze Warning for all our NC
counties excluding the beach forecast zones. Our SC counties will be
mainly in the mid 30s, with upper 30s at the beaches.
Thursday will be dry and unseasonably cool as the Arctic airmass
moves overhead. Expect highs only in the mid to upper 50s.
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...Cold Canadian high pressure will move
eastward shifting from the Mid Atlantic coast farther off shore
through Fri. This will allow a return flow to set up with
increasing moisture and warmth. Initially, though, the dense
shallow cold air mass in place will set the stage for very cold
temps once again Thurs night. Models are showing a coastal
trough becoming more defined overnight Fri as high pressure
wedges in over inland areas with lighter NE winds while just off
shore a more easterly wind develops pushing moisture on shore.
Most places should be a few degrees warmer than previous
night..mid 30s for the low, but would expect some traditionally
cooler spots to drop toward freezing. The moisture return will
bring RH values above 80% overnight Thurs and this will allow
some frost to develop under decent radiational cooling
conditions as skies remain mainly clear and winds drop off Thurs
eve. Upon the expiration of the Freeze Warning for tonight,
there will be an evaluation as to which counties would need an
frost advisory or possibly another Freeze Warning. The most
likely candidates would be Pender and Bladen counties, but
other spots mainly across NC could surely see frost if forecast
remains on track.
As high pressure shifts farther off the Mid Atlantic coast on
Friday, a southeasterly return flow will bring warmer and
moister air into the area while a deeper SW to W flow will
develop aloft. Mid to upper ridge will build up the southeast
coast with heights rising and 850 temps return up near 7C Fri
aftn. This will push temps back up toward normal...closer to 70
most places. The on shore flow will keep places closer to the
cooler waters in the 60s. There may be some clouds around, but
pcp will remain at bay through the period and overall there will
be a good deal of March sunshine. Temps on Fri night will remain
at or above normal.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 300 AM Wednesday... Return flow underway on Saturday expected
to bring unseasonable warmth. Upper ridge axis should stay close
enough to the coast to keep mid levels fairly dry. This changes
fairly quickly Saturday night into Sunday and moisture depth may
increase. Two large shortwaves try to impinge upon our upper ridge
but appear to largely be shunted over it to the north. It appears
that late period moisture depth may actually decrease. So while some
minor late weekend rain chances may materialized they should dwindle
heading into next week. Daytime highs will remain above climo,
generally in the mid to upper 70s but trending towards 80 inland
late in the period. Nighttime lows will similarly be mild, and the
deviations from climo will tend to mirror the degree of cloud cover.
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
As of 18Z...High confidence VFR through the TAF valid period.
Main concern would be gusts from N to NNE winds this afternoon
and evening, which could approach 25 kts at times. ILM and CRE
will see broken CIGS at around 3.5 to 4.0 kft through the
NEAR TERM /THROUGH THURSDAY/...
As of 300 PM Wednesday...Small Craft Advisory will remain in
effect from this afternoon and into Thursday as a cold and dry
High Pressure system drops in from the NW. Conditions will begin
to moderate Thursday afternoon and the ridge axis moves
overhead. Expect NE winds of 20 to 25 kts tonight diminishing to
15 to 20 kts on Thursday as seas drop from 4 to 6 ft tonight to
3 to 5 ft on Thursday.
SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...High pressure will shift farther off
the Mid Atlantic coast through the period. This will allow a
return flow to set up with winds shifting around from NE Thurs
evening to E-SE through Fri and southerly by Sat morning. The
models are hinting at a coastal trough overnight Thurs which
may act to produce enhance a more NE flow near the coast with a
greater easterly flow off shore. Either way, an on shore flow
will be the rule through much of the period diminishing to 10
kts or less. This will allow seas to subside from near 3 to 4 ft
Thurs eve down to 3 ft or less Fri morning.
LONG TERM /SATURDAY THROUGH SUNDAY/...
As of 300 AM Wednesday...The above normal temperatures will give a
clue as to expected marine conditions. That is, the area will be in
a return flow regime around sprawling Atlantic high pressure. Wind
will thus be southerly and for the most part be capped at 10 kt
though a few higher gusts certainly hard to rule out. A minor
increase in the long shore swell energy could make for an increased
presence of 4 ft seas along the outer portions later Sunday in an
otherwise 2 to 3 ft wave environment.
NC...Freeze Warning from 4 AM to 9 AM EDT Thursday for NCZ087-096-
MARINE...Small Craft Advisory until 5 PM EDT Thursday for AMZ250-252-