Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS62 KRAH 231447
Area Forecast Discussion
National Weather Service Raleigh NC
1045 AM EDT SAT JUL 23 2016
-- Changed Discussion --A ridge of warm high pressure aloft will extend across the region
through early next week, bringing a period of hot and humid
conditions to our area.
-- End Changed Discussion --
.Near Term /through tonight/...
-- Changed Discussion --As of 1045 AM Saturday...
See no reason to depart significantly from the earlier forecast. The
current surface analysis shows a diffuse MSL pressure pattern with
weak lee troughing holding in place and a soggy air mass with
dewpoints in the 70s areawide. We should see some dip in dewpoints
with mixing this afternoon, down into the upper 60s to lower 70s,
however given that observed thicknesses this morning are nearly 10 m
higher than yesterday, heat index values are still expected to reach
the upper 90s to around 100. The weak shear/moisture axis aloft
along which last night`s convection developed is slowly pushing
through southern NC, and the latest CAM runs suggest this feature
serving as a focus for deeper moisture resulting in organized
convection formation this afternoon. Will retain the greater rain
chances across the southern CWA, in line with the RAP/HRRR/SSEO
output, although we`ll need to monitor development trends as a bump-
up to scattered coverage may be warranted. We should see highs in
the mid 90s, factoring in high-res temp guidance, current trends,
and expectations of more diurnal cloudiness in the south this
Previous discussion as of 315 AM: An expansive area of high pressure
aloft centered over the central/southern plains will shunt the main
band of westerlies near or north of the Canadian border. This
pattern will result in a weak flow aloft over central NC. Thus, any
convection that develops later today will be focused on outflow
boundaries from Friday`s convection, or move into our region from
the higher terrain to our west-nw. Expect the highest chance for
isolated convection south of highway 64 where better low level
moisture expected to reside. if later meso analysis depicts
sufficient low level convergence, a bump up in PoPs to chance may be
warranted. Strong low level lapse rates suggest strong gusty winds
probable in vicinity of any convection.
Afternoon low level thicknesses projected to be 7-10m warmer than
Friday. This is supportive of max temps solidly in the mid 90s. Heat
indices will be in the upper 90s northwest to 100-104 degrees
Tonight, any isolated convection will quickly dissipate with loss of
heating. Overnight temps will lower into the mid 70s. -WSS
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.SHORT TERM /Sunday THROUGH MONDAY NIGHT/...
As of 310 AM Saturday...
Sprawling area of high pressure will build more so into the
Carolinas, bringing hot and dry conditions to our region. The
warming aloft will cap the atmosphere, limiting convective
development to just a stray thunderstorm or two.
Thicknesses Sunday afternoon approach 1450m in the Piedmont,
supportive of temps well into the 90s, and heat indices in the heat
advisory criteria. Comparable conditions expected Monday, though
bulk of short term models drag a westward moving s/w across northern
FL/coastal GA, the tail end of which may brush our southern
counties. This feature interacting with available moisture and
instability may trigger a concentrated area of convection.
Overnight conditions will remain muggy. Most places will likely see
temperatures remain above 80 until well after midnight. Any
convection that develops Monday afternoon should dissipate within an
hour or two after sunset.
.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 245 AM Saturday...
Additional s/w energy is expected to track across
Southern/Southeastern Canada and the Great Lakes and Northeast U.S.
next week, which will allow a weak cold front to approach the region
(likely stalling to the north of the area though). This will allow
the mid level ridge to dampen across our region early next week and
relocated to the south and southeast of central NC. This should
place central NC on the southern fridge off potential disturbances
tracking atop/around the ridge, which should lead to a better chance
of mostly diurnal scattered showers and storms each
afternoon/evening. Given the predictability of such hard to time
features this far out in the forecast, will go with around 30-35
percent chance for showers and storms each day (generally climo).
This additional associated cloud cover is expected to lead to temps
a bit cooler, though highs are still expected to at least be in the
lower to mid 90s.
.Aviation /12Z Saturday through Wednesday/...
As of 750 AM Saturday...
VFR conditions expected to prevail across central NC through Monday
as an area of high pressure aloft builds over the region. While
isolated thunderstorms will be possible each late afternoon-early
evening through Monday, probability of convection affecting a
specific TAF site is too low to mention in the terminal forecast at
this time. Patchy MVFR fog will be possible early each morning,
primarily between the hours of 10Z-12Z.
While VFR conditions will likely dominate through Wednesday, there
will be periods of MVFR conditions associated with either early
morning fog, or late afternoon/early evening convection.