Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
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FXUS62 KRAH 271828
Area Forecast Discussion
National Weather Service Raleigh NC
228 PM EDT SAT AUG 27 2016
An upper level ridge will persist over the region through the
weekend. An upper level disturbance over the Atlantic will then
drift west and linger over the Southeast states early next week.
.NEAR TERM /THROUGH TONIGHT/...
As of 1042 AM Saturday...
12Z upper air analysis along with the 14Z meso analysis suggest that
best chance for scattered convection this afternoon across roughly
the south half of our forecast area. A mid/upper level anti-cyclone
positioned to our north will maintain a deep ely flow over our
region with the best moisture confluence across the sandhills and
the southern piedmont. While the atmosphere will be slight-
moderately unstable across the northeast piedmont/northern coastal
plain, difficult to discern any mechanism to initiate lift, aside
from strong heating. Even across the southern counties, little if
any support discernible aloft to initiate/sustain convection. Thus,
appears we will need to rely on orographic lift and residual outflow
boundaries from previous days convection along with strong heating
to initiate lift. With the meso analysis depicting the best moisture
axis residing across our southern and western counties, should see
the greatest concentration of convection in this part of the
forecast area (though no worse than scattered (30-40 percent)).
A few strong storms possible with the main hazard being strong gusty
winds ~40-45kts and frequent lightning. This has been addresses in
the latest HWO product.
Afternoon temps in track to reach the low-mid 90s. Counting on some
cloud build up/scattered convection to moderate temps a little this
afternoon. If this does not occur, places such as Fayetteville and
Laurinburg may reach the upper 90s. Afternoon heat index values
expected to vary from 98-102 degrees across the north and 102-105
degrees across the south. Do not plan an advisory at this time but
will continue to monitor.
What convection is occurring at 6 PM will quickly diminish/dissipate
around sunset. Under clear-partly cloudy skies, overnight temps will
lower into the low-mid 70s.
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
As of 350 AM Saturday...
The upper level ridge will continue a northward drift on Sunday,
while an upper disturbance over the Atlantic slowly drifts west
and undercuts the ridge, essentially settling over the Southeast
US through early next week. This disturbance along with increasing
moisture flux off of the Atlantic - PW increasing to around 2
inches - and weak to moderate instability will likely result in
enhanced convective coverage along the coast, drifting inland
through the day. Coverage will be best over the coastal plain,
diminishing with westward extent into the Piedmont where deeper
mixing and drier air will limit coverage. Some of the showers may
continue into the evening and overnight hours, mainly across the
southern coastal plain. Highs 89-92, warmest west. Lows 69-74.
.LONG TERM /MONDAY THROUGH SATURDAY/...
-- Changed Discussion --As of 226 PM SATURDAY...
Monday through Wednesday: The models still indicate a mid- to upper-
level low over the western Atlantic will move westward along the
southern periphery of the high from Bermuda to the east coast of the
U.S. through early next week. The high will weaken as the low
approaches and stalls along the Carolina coast through Wednesday. At
the surface, some weak ridging lingers over western NC as the low
sits just off the coast. Surface winds will be primarily
northeasterly. Chances for showers and storms should remain limited
to the southern and southeastern portions of Central NC. Highs will
be in the mid 80s to around 90 degrees and lows in the upper 60s to
low 70s expected.
Thursday through Saturday: An upper level trough will amplify over
the eastern U.S. Wednesday night and Thursday, when it`s expected to
absorb the stalled coastal low. The trough axis should then shift
offshore late in the week. At the surface, a cold front is forecast
to slide southward into Central NC Thursday night or Friday,
although the extent of southward progression is still fairly
uncertain. Highest confidence of frontal passage in the northeast
and lowest in the southwest. As a result, best chances for
convection will be with the front as it moves into and stalls over
the Carolinas, though that will also depend on the diurnal timing.
The temperature forecast gets a bit more difficult with the
aforementioned front, but for now expect a decrease in highs from
near 90 degrees on Thursday into the mid 80s Friday and Saturday
with lows generally in the mid 60s to low 70s.
-- End Changed Discussion --
.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
As of 1255 PM Saturday...
There is high confidence that VFR conditions will prevail across
central NC through Sunday night. The exception will be isolated-
scattered showers and storms through 00Z and associated MVFR
ceilings and visibility. The stronger storms will also be
accompanied by gusty sfc winds up to 40kts. The scattered convection
will be most probable near KFAY between 18Z-22Z...and near and south
of the Triad terminals between 20Z and 00Z. The bulk of convection
will dissipate with loss of heating, though a shower threat will
linger until midnight south of the Triad. After 04Z, should see
pockets of low clouds develop and eventually overspread most of
central NC with IFR/LIFR ceilings highly probable at most TAF sites
between 09Z-14Z Sunday. VFR conditions expected to prevail by 16Z
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.