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FXUS62 KILM 231936

Area Forecast Discussion
National Weather Service Wilmington NC
336 PM EDT Mon Oct 23 2017

A strong cold front will approach from the west today and slow,
finally moving completely offshore Tuesday afternoon. Showers
and thunderstorms are expected along and ahead of the front with
the possibility for a line of strong to severe thunderstorms 
this evening and tonight. In the wake of the front, dry and 
cool air is expected through Thursday as Canadian high pressure
takes hold. A warming trend begins Friday. Shower chances
increase Saturday as a weak area of low pressure develops ahead
of a second cold front.


As of 300 PM Monday...Moisture advecting into the area from the
southwest as evident by the roughly 10F difference in dewpoint 
between ILM and GGE. As surface wind veers slightly this evening
this richer moisture should manage to cover more of the area. 
Light rain moving in from the southwest as well indicative of 
fairly weak ascent within the warm sector so far. Later this 
evening into tonight this will change however as weak PVA 
impinges upon the area while low level jet ramps up to 45kt at 
925mb. Mid level height falls largely pass us by to the north 
but the low level lift may get slightly bolstered aloft by the 
left exit region of a 200mb jet developing tonight over Florida.
The back edge of the precipitation shield moving into western 
zones this evening will be associated with a fairly sharp pre- 
frontal wind shift that should offer strong convergence. This 
surface based ascent then to interact with the low level jet to 
yield fairly shallow and thus rather lightning-deprived line of 
convection. The strength of the low level wind fields will offer
a damaging wind threat with the line. Isolated tornados will 
also be hard to rule out due to SRH being maximized in the lower
levels even as lapse rates and thus instability remain meager. 
Cool advection lags considerably behind the wind-shift though 
dewpoints may start dropping Tuesday afternoon temperatures will
still warm up into the upper 70s, a solid category above 


As of 300 PM Monday...Very quiet conditions will settle into 
the area as a deep full latitude mid level trough moves from the
Tennessee Valley to just offshore through the period. 
Precipitable waters dip to near one quarter of an inch by late 
in the period. At the surface a somewhat blustery pressure 
gradient will reside across the area and this is reflected n the
guidance. There may be some decoupling early Thursday morning 
allowing temperatures to possibly drop to the coolest readings 
of the season in some areas with lower to mid 40s area wide. 


As of 300 PM Monday...Very cool temperatures start the extended as 
Canadian high pressure settles across the area before pushing 
offshore Friday. Temps Thursday will likely be about 5 degrees below 
climo before recovering to more seasonable temps Friday as the 
surface high shifts offshore. Moisture will begin to increase 
Saturday on increasing southerly winds as a pre-frontal airmass 
returns ahead of a deep mid-level trough pushing through the MS VLY. 
This will drive a cold front across the area Saturday night into 
Sunday. Ahead of this feature, a weak area of low pressure may
develop and move just off the coast, and while total column 
moisture remains confined below 700mb, showers are possible late
Saturday through Sunday morning associated with this feature. 
This front will bring the potential for the coldest air of the 
season behind it, as 850mb progs drop below 0C and extended MOS 
numbers feature values as much as 10 degrees below climo early 
next week.


As of 18Z...Quite a bit of uncertainty with respect to the timing of 
the precip and ceilings. Safe to say the ceilings and visibilities 
will be highly variable, especially this evening and through the 
overnight hours. Some good dynamics heading our way, with good 
frontal lift and decent helicity this evening. Thunder is a good 
possibility,but mainly inland as the models tend to weaken the 
convection as it reaches the coast. The convection will likely end 
at the inland terminals by 03-04Z, however precip could linger along 
the coast until around 12Z

Extended Outlook... VFR Wednesday through Friday. Slight chance for 
showers Saturday.


As of 300 PM Monday...Prefrontal warm sector to only increase 
in strength through most of the period as surface boundary 
approaches from the west and low level jet develops. The fairly 
sharp wind shift is slated for around daybreak Tuesday or soon 
thereafter. Wind speeds may decrease somewhat quickly with the 
wind shift it throws out wind alignment in the vertical. The 
current Small Craft Advisory is currently posted through Tuesday
afternoon and am not planning any changes at this time. 

As of 300 PM Monday...Northwest winds of 10-15 knots and on 
occasion 15-20 knots will prevail across the area through the 
period. The persistence will be provided by a very deep and slow
mid level trough at 500mb that trudges across the conus from 
the Mississippi Valley. Significant seas will be mostly 2-4 feet
with the higher values across the outer waters with the 
offshore flow.

As of 300 PM Monday...High pressure moving overhead the waters 
Thursday into Friday will create gusty north winds early 
Thursday before weakening to less than 10 kts and shifting 
slowly to NE Friday, and then E on Saturday. A secondary front 
approaching very late Saturday may cause winds to uptick again 
at the end of the period. The gusty north winds early will keep 
seas elevated at 3-4 ft the first half of Thursday, before 
falling back to 1-3 ft Fri and Sat. The increased winds late 
Saturday may cause seas to begin to rise again at that time.


MARINE...Small Craft Advisory until 2 PM EDT Tuesday for AMZ250-252-254-



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