FXUS62 KRAH 280808

Area Forecast Discussion
National Weather Service Raleigh NC
408 AM EDT SUN AUG 28 2016

High pressure will persist over the region through today. An upper
level disturbance over the Atlantic will then drift west along the
Carolina coast Monday and Tuesday.


As of 400 AM Sunday...

An well defined upper low off the Carolina coast will continue to
drift west beneath the 595dm 500mb ridge over the Mid-Atlantic
states today, while a surface ridge extends into the area from the
Northeast coast. We`re starting to see a little stratus spreading
inland across the coastal plain in northeast flow, which will lead
to mostly cloudy skies through mid-morning as the stratus slowly
burns off. Deeper mixing over the Piedmont may result in dewpoints
in the lower 60s, limiting instability and confining the best
precip chances tot he coastal plain, where increasing moisture and
moderate instability will support scattered storms as the
aforementioned upper low approaches the coast and likely enhances
convection along the seabreeze. Shear parameters are generally
weak, so the main impact from convection will likely be from
brief heavy downpours given PW increasing above 2 inches. The CAMs
are in pretty agreement in the favored area being from
Fayetteville to Goldsboro and to the east. 850mb temps fall from
20C to 18C today, which combined with a little more northeasterly
flow and morning cloud cover, should keep highs a few degrees
lower than yesterday, 89-92.

Convection will generally be diurnally driven today, though the
approaching upper low and easterly low-level flow may continue to
support some inland moving showers into the overnight hours.
Stratus is expected again across the coastal plain by Monday
morning, with lows in the upper 60s and lower 70s.


As of 400 AM Sunday...

Monday looks fairly similar to today, with the upper low drifting
inland over SC and briefly stalling. A strong moisture gradient
will set up again with the surface ridge and deeper mixing in
the west, and better moisture/instability over the coastal plain.
A weak offshore surface low drifting toward the NC coast will have
little impact here, and scattered showers and a few storms will
again be confined to the southern coastal plain. Highs in the
upper 80s and lower 90s. Lows monday night in the upper 60s and
lower 70s.

As of 226 PM SATURDAY...

WV imagery this morning depicts an increasingly well-defined mid to
upper level low off the SERN U.S coast. The forecast models continue
to indicate this feature will drift W --around the SRN periphery of
the initially strong sub-tropical ridge centered over the Middle
Atlantic states-- and stall along the SERN U.S.
coast early this week, before shearing out and lifting away from the
region through the middle of the week.

The presence of this mid-upper low, and a NRN stream trough forecast
to migrate across the NERN U.S through early week, will cause the
preceding sub-tropical ridge to succumb over the Middle Atlantic
states and ultimately split, with one center expected to retrogress
into the central U.S. and the other retreat into the central N.
Atlantic Ocean. A broad trough will develop between the two /over
ERN U.S./ through the end of the week.

This pattern aloft will play an important role in what becomes of
the now well-advertised tropical wave along the NRN coast of Cuba
this morning, which the models now generally agree will enter the
ERN Gulf of Mexico early to mid-week. Significant model spread
regarding the track and timing of the associated low develops
thereafter, though it seems reasonable that low will eventually be
influenced by the aforementioned ERN CONUS trough aloft and be drawn
NEWD through or along the SERN U.S coast, with an associated
increased probability of rain, through the end of the forecast

Of greater predictability will likely be a NRN stream cold front
forecast to settle through the SRN Middle Atlantic states and
Carolinas Thu-Fri, with an accompanying chance of convection
maximized in central NC Thu-Thu night. Cooler and drier conditions
in post-frontal high pressure ridging across the Middle Atlantic
region would follow, though the duration of this post-frontal regime
will hinge upon what happens with the tropical low and associated
moisture potentially approaching from the south later Fri and Sat.


As of 200 AM Sunday...

Early showers and storms have pushes west through the southern
Piedmont and conditions are mostly VFR across the area at 06Z. Skies
have mostly cleared across eastern NC, which may lead to some fog
after 08z, though northeasterly flow may favor more low clouds than
fog, possibly as low as LIFR.  Confidence is pretty high that RWI
and FAY will see IFR or LIFR conditions by 09z.  To the west, RDU
may end up right on the end of the low clouds, but sub-VFR vsbys
will still be possible at RDU, GSO, and INT given earlier rainfall.

If stratus does indeed develop over the coastal plain, models
suggest it will be slow to lift through  the morning hours, with a
period of MVFR ceilings as far west as RDU between 12z and 15z.
Scattered storms will likely develop later this afternoon, mainly
from FAY to RWI and to the east.


VFR conditions are expected to prevail across central NC through
most of the upcoming work week. There will be a good chance for
early morning IFR/low end MVFR conditions each day due to low clouds
and/or fog. In addition, there will be scattered showers and storms
each afternoon, with the highest concentration expected in the
vicinity of KFAY.





NWS RAH Office Area Forecast Discussion