Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
FXUS62 KRAH 311945
Area Forecast Discussion
National Weather Service Raleigh NC
335 PM EDT Tue May 31 2016
.SYNOPSIS...The remnant circulation of Tropical Storm Bonnie
will continue to drift slowly northeast just off the Carolina coast
through Thursday. A cold front will approach the region from the
west late in the work week and then stall in our region.
.NEAR TERM /through Wednesday night/...
As of 335 PM Tuesday...
Latest surface analysis shows the remnant circulation center from
Tropical Storm Bonnie was located just off the coast east of Myrtle
Beach. A compact vorticity maximum in the mid levels was located
with the surface low as the circulation remains vertical and
weakening. The air mass across central NC is very moist with PW
values ranging from 1.4 to 1.7 inches and weakly unstable with
MLCAPE values ranging around 500 to 1000 J/Kg. Regional radar shows
a slowly westward moving band of showers and a few thunderstorms
moving across the southern coastal region. Elsewhere, isolated
showers have developed in a few spots across the Piedmont two
parallel northeast-southwest bands of enhanced cumulus resulting
from differential heating alongside a more persistent area of
Convection allowing models still maintain that convective coverage
and development will be more limited than previous days with
isolated to scattered convection across the Piedmont and scattered
convection pushing west and spreading across the southern/central
Coastal Plain and Sandhills. The convection is largely diurnally
forced so it should gradually wane this evening but its worth
noting a few CAMs push lingering showers into Southern Piedmont
during the prime time hours. Only an isolated shower or two is
expected after midnight. Another period of fog and stratus is
expected to develop tonight, but it will likely develop later and
wont be as widespread as previous nights with the fog likely to be
concentrated across the Sandhills and Coastal Plain.
Lows in the mid 60s to around 70.
A persistence forecast will be used for Wednesday and Wednesday
night with the surface and mid level circulation associated with the
remnants of Bonnie expected to move little and with very little air
mass change across NC. CAMs again highlight an area of scattered
convection across the Coastal Plain that pushes west with coverage
that is not surprisingly a little bit more limited than the previous
day. Convection will be diurnally driven and should tape off after
sunset. While the air mass is again weakly unstable, limited
updraft strength and shear should preclude and severe weather
concerns. Highs should be similar to perhaps a degree warmer than
today and range in the lower to mainly mid 80s with lows Wednesday
night in the mid to upper 60s.
.SHORT TERM /Thursday through Friday night/...
As of 255 PM Tuesday...
Remnants of post-tropical storm Bonnie will linger under short wave
ridging aloft and remain nearly stationary along the central NC
coast on Thursday. The ridging is tamped down Thursday night and
Friday due to eastward progression of a strong short wave across the
Great Lakes. This will modestly increase westerly flow and nudge the
remnant low offshore Thursday night and Friday. We will see a lull
in the threat of convection over most of the area on Thursday as the
remnant low wraps more stable in from the north. Moisture will begin
to edge into the west by late day, however, in increasingly westerly
flow which will be fed moisture off the western gulf by a closed
low over Texas.
Will maintain ongoing small chances for convection in the east
Thursday as precipitable water will remain above 1.5 inches with mid
level lapse rates exceeding 6K/km to enhance instability. Highs will
benefit from periods of sun to reach the mid 80s, with perhaps some
upper 80s in the southeast. Precip chances will diurnally fall off
Thursday night concurrent with the low moving offshore, and mins
will be seasonable, in the upper 60s. More unsettled weather with
increasing convective coverage will return quickly on Friday as a
cold front very slowly sags south out of the Ohio Valley to provide
a convergence zone to enhance lift in the moisture rich environment.
Highs are potentially in the upper 80s across the area, but heavier
cloud coverage in westerly flow would temper that down a bit to mid
80s north and upper 80s across the southern tier. The frontal zone
will be in the vicinity Friday night, perhaps even lying across the
area per latest GFS, keeping chance of ongoing showers overnight
with persistence mins near 70.
.LONG TERM /Saturday through Tuesday/...
As of 255 PM Tuesday...
Upcoming weekend still looks wet but confidence is not high as there
are a number of details that will determine the coverage and
intensity of convection. The cold front sagging south aligns
parallel to the upper flow and stalls in the vicinity of the area
and makes a jog back to the north as a stronger short wave rotates
across the Ohio Valley. Will have a strong warm and moist advection
on Sunday as this wave pushes a much stronger cold front across the
area Sunday night. As such, will modestly nudge the PoPs up both
Saturday but particularly Sunday due to the relative consensus of
model solutions. Highs will be persistence in the unchanged airmass,
with mid to upper 80s, with the potential for some very low 90s
in the south given an extra hour or two of sunshine.
Dryness returns Monday and Tuesday as the upper system pushes
offshore with somewhat cooler and dry ridging building in through
mid week. Highs Monday and Tuesday will be pleasant, in the low
80s after morning lows in the mid 60s.
.AVIATION /18Z Tuesday through Saturday/...
As of 225 PM Tuesday...
VFR conditions are noted across central NC this afternoon with a
deck of SCT-BKN cumulus clouds at several layers between 3-6kft.
A band of showers and thunderstorms across the far southeastern NC
this afternoon will shift slowly northwest into the Sandhills and
southern Coastal Plain this afternoon, likely impacting KFAY and
KRWI with a period of MVFR CIGS an VSBYS from 20-24Z. These showers
will likely diminish in coverage and intensity as they move into the
eastern Piedmont toward KRDU late this afternoon or early evening.
Elsewhere, isolated to scattered showers and thunderstorms are
possible although the overage will preclude a mention in the TAF.
Just about all of the convection will wane during the course
of the evening with little activity after midnight.
Stratus and fog will likely develop again late tonight although
later than previous nights and with reduced coverage and duration
than previous nights. Look for a period of MVFR-IFR CIGS and VSBYS
tonight with the worst conditions likely to occur across the Coastal
Plain and Sandhills impacting the FAY and RWI terminals with a much
reduced chance of reductions in the Triad at the INT/GSO terminals.
The stratus and fog should quickly dissipate Wednesday morning with
VFR conditions expected to dominate by 14Z Wednesday.
Looking beyond 18Z Wednesday: Another round of scattered afternoon
and evening showers and isolated storms is expected on Wednesday
and Wednesday evening with brief MVFR conditions. A repeat of
MVFR/IFR stratus/fog is expected to develop Wednesday night. Chances
of afternoon/evening storms on Thursday decrease a bit compared to
previous days before increasing again on Friday into Saturday as a
cold front approaches from the west. -blaes