Area Forecast Discussion
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FXUS62 KRAH 261831
Area Forecast Discussion
National Weather Service Raleigh NC
231 PM EDT Thu May 26 2016
.SYNOPSIS...Bermuda high pressure will extend over the area through
Friday. Meanwhile, a storm system will develop over the sub-tropical
Atlantic and drift toward the Southeast U.S. coast through the
.NEAR TERM /through tonight/...
As of 1025 AM Thursday...
A slightly unstable low level air mass this afternoon with sbcape
values of 1000-1500 j/kg will interact with a weakening disturbance
aloft to possibly trigger a few showers and t-storms late this
afternoon and this evening. This potential appears best west of
highway 1, with the greatest threat along the western periphery of
our forecast area. Have adjusted/expanded slight chance pops to
encompass most of the southern Piedmont and the western sandhills.
At this time, atmosphere does not appear that it will support any
severe storms as the shear is very weak/non-existent and instability
Thicknesses this afternoon projected to be near or slightly warmer
than those observed Wednesday. Thus, max temps this afternoon should
be comparable to yesterday, ranging from the mid 80s in the nw
Piedmont, to the upper 80s/near 90 elsewhere. -WSS
The surface ridge axis, accompanied by lower theta e air, will
begin to slowly shift back west over eastern NC tonight, allowing
for good radiational cooling conditions and a range of lows from 61-65
(coolest in the east). -BLS
.SHORT TERM /Friday through Friday Night/...
As of 340 AM Thursday...
Strengthening of the upper ridge and shifting of the surface ridge
overhead will lessen the prospects of convection on Friday, compared
even to the little chance there is today. If there is a chance it
will again be int he northwest Piedmont, but even then the steering
flow should keep any convection confined to the higher terrain.
H10-H85 thicknesses will be around 1415m, yielding highs of 85-
90. Lows mostly in the lower 60s.
.LONG TERM /Saturday through Thursday/...
As of 230 PM Thursday...
The main forecast concern for this period continues to be the
potential tropical/sub-tropical development of an area of low
pressure between the Bahamas and Bermuda this weekend.
The upper level ridge responsible for the recent quiet weather will
break down as the coastal low develops. To the west, an upper level
trough will linger for the weekend. A shortwave will progress from
the southern Rockies northeastward along the trough axis toward the
As the upper level short wave moves through the Great Lakes, the
northeastward moving coastal (tropical) low will progress toward the
SC coast. As of the most recent runs, the models indicate these two
features interacting Sunday night/Monday. The upper level shortwave
could absorb the coastal low (possible tropical system) on Monday.
There is still a fair amount of uncertainty on whether the low will
move up the Mid-Atlantic coast or hand out along the Carolina coast
before slowly moving inland. Regardless of this, the majority of
this period appears to be fairly unsettled, with chances for
convection, highest in the aft/eve, everyday. Much of the coverage,
duration, and timing of convection will depend on how the system evolves
and thus confidence is still somewhat low. With the strong advection
of Atlantic moisture into the region on the northern edge of the
low, expect increasing clouds from the east on Saturday, though much
of the day will remain dry. Cloudy skies could persist through much
of the period.
Temperatures through the period: with the increasing clouds and
chances for rainfall, expect highs to decrease from the mid 80s on
Saturday, to upper 70s to low 80s Sunday. Highs should slowly
moderate back into the mid 80s by the middle of the week. Overnight
lows will remain fairly steady in the mid to upper 60s.
.AVIATION /18Z Thursday through Tuesday/...
As of 115 PM Thursday...
It`s highly likely that VFR conditions will persist across central
NC through Friday. The exception will be a small risk for early
morning fog, limiting the visibility to MVFR criteria for a brief
period. In addition, isolated convection late this afternoon through
this evening, and again Friday afternoon through the evening, will
produce instances of MVFR ceiling and visibility.
Aviation conditions on Saturday will vary between VFR and MVFR
criteria as increasing moisture results in lowering cloud bases and
an enhanced threat for afternoon and evening scattered convection.
Sub VFR conditions appear more likely Sunday and Memorial Day due to
an area of low pressure projected to be positioned off the GA/SC
coast. Circulation around this feature could send abundant moisture
into central NC, resulting in widespread cloud cover and scattered
to numerous showers and thunderstorms. Aviation conditions may
slowly improve by Tuesday, though periods of MVFR conditions are