Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 292328

Area Forecast Discussion
National Weather Service Wilmington NC
728 PM EDT Sat Apr 29 2017

High pressure will extend across the area from offshore through
early Monday with warm and humid conditions continuing. A cold
front will bring a likelihood of showers and thunderstorms late
Monday into early Tuesday. High pressure will follow for the
mid-week period. A Low pressure system will impact the region
Thursday into Friday amd may bring widespread showers and
thunderstorms and heavy rain.


As of 730 PM Saturday...Very few changes were needed to the
previous forecast. An exceptionally humid and warm airmass for
this early in the season will continue to spread onshore
tonight. Temperatures should run a solid 15 degrees above
normal with low temps around 70 degrees. Dewpoints will remain
in the 60s and lower 70s. Much like we saw last night, low
stratocumulus clouds should develop and persist through daybreak
Sunday. We`re already seeing some cloudiness develop now in the
Cape Fear area, probably an early sign of what will come.
Between 10 PM and 1 AM expect skies to become cloudy to mostly
cloudy area-wide except perhaps right on the beaches as these
clouds will be the result of humid air lifted up over the
shallow nocturnal inversion near the coast.


As of 315 PM Saturday...Strong mid level ridging which has been
responsible for the summer like conditions of the past few days
will give way to a dampening cyclone moving from the Central
U.S. to the Great Lakes region through the period. At the
surface, Bermuda High pressure will be displaced by a cold front
moving across the area late Monday into early Tuesday. The
timing of the front is becoming more consistent within the
guidance suite and there should be a broken to almost solid line
of showers and thunderstorms moving west to east across the
area from about 0 to 6z Tuesday. Severe potential doesn`t look
overly impressive with 850mb winds only 45-50 knots with the
higher values to the north. Still, the timing could make things
a bit interesting over the western zones early in the evening.
Warm temperatures continue with highs in the 80s monday
following another night with lows in the 60s Monday morning.


As of 315 PM Saturday...Broad high pressure behind Monday night`s
cold front will expand across the Southeast Tuesday creating dry and
seasonable weather with highs and lows right around climo.

This high will remain in place Wednesday with slightly warmer
temperatures but continued dry weather before it shifts offshore
Thursday. This occurs in response to a deep mid-level trough digging
into the middle of the country and then evolving across the eastern
CONUS into the weekend.

There exist two distinct camps in the guidance: the GFS has this low
cutting off and dropping southeast through the end of the period.
The CMC/ECM have a similar pattern initially to the GFS, but the
upper low drifts north before cutting off  overhead the Northeast.
The biggest difference between the guidance appears to be the
evolution of the ridge across the middle of the country. The CMC/ECM
keep the ridge axis aligned N/S, while the GFS produces a more
tilted NE/SW ridge which suppresses the upper low. The agreement
between the ECM/CMC tends to favor that solution a bit more, despite
the fact that the GFS has been consistent and we had a similar setup
just last week so there is precedent. The evolution of this upper
pattern is critical because, while all scenarios support showers and
thunderstorms late Thursday and Friday, the CMC/ECM would dry things
out for the weekend, while the GFS would maintain unsettled and
possibly very wet weather for several days. Without a clear solution
at this time range, will hedge with a WPC favored blend of guidance
but with a bit more weight on the drier ECM by the weekend. This
would also bring much cooler temperatures to the region Fri/Sat with
highs and lows falling below climo.


An unseasonably humid airmass will probably produce widespread
stratus overnight with cloud ceilings in the 1000-2000 foot AGL
range. Although IFR ceilings cannot be ruled out, surface
dewpoints are 1-2 degrees lower than at this same time yesterday
both on land and at the offshore buoys where our air is blowing
in from. Confidence is moderate that we will see stratus
develop overnight, however the time given in the TAFs for the
development for the clouds has only low confidence. Model
consensus of low cloud development has actually diverged in the
past couple hours, trending later in the night. Any stratus
lingering after sunrise Sunday should lift above 2000 feet AGL
around 14Z.

Extended outlook...Periods of IFR/MVFR conditions are possible
in showers and thunderstorms late Monday into early Tuesday.


As of 730 PM Saturday...High pressure well offshore will
maintain a southerly wind tonight around 10 knots. Stronger
winds this afternoon along the coast were the result of the
seabreeze, which produced gusts over 20 knots at times. Seas
around 3 feet should continue overnight in a mix of 5-second
wind waves and 8 second SE swell.

As of 315 PM Saturday...A southerly flow will be in place most of the
period with wind speeds increasing Monday as a cold front approaches
from the west. Initial speeds of 10-15 knots will increase to a
respectable 20-25 knots late Monday and persist into the evening
hours. The front will move across with a modest westerly flow
setting up by early Tuesday. Small craft conditions are likely
for Monday. Significant seas will ramp up as well increasing
from 2-4 feet early to 5-8 feet late.

As of 315 PM Saturday...Broad high pressure builds across the waters
behind a cold front Tuesday. Residual gusty W/NW winds of 15 kts and
4-6 ft seas will fall quickly during Tuesday as winds back to the SW
at 10-15 kts late Tuesday before a secondary surge flips winds
around to the NW by Wednesday at less than 10 kts. As the high
shifts offshore into Thursday, southerly winds will ramp up quickly
becoming 15-25 kts, driving seas back to 4-7 ft after being just 2-3
ft much of Wednesday. An SCA will likely be needed beginning late in
the extended.


NC...Coastal Flood Advisory from 11 PM this evening to 3 AM EDT
     Sunday for NCZ107.



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