Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS62 KRAH 280725
Area Forecast Discussion
National Weather Service Raleigh NC
325 AM EDT THU JUL 28 2016
An upper level disturbance will track just to the north of the
region today and tonight around the hot high pressure over the
Carolinas. A weak cold front is expected to move into central NC
late Friday, stalling over the region for the weekend.
.NEAR TERM /THROUGH TONIGHT/...
As of 220 AM Thursday...
...Heat Advisory for all counties today (noon through 800 PM)...
First things first, the dangerously high dew points in the 70s to
lower 80s will combine with the higher temperatures today (96-101)
to produce heat indices of 105-109 degrees, except 100-104 in the NW
Piedmont. All zones will have a heat advisory from noon through 800
PM. It can not be stated enough for everyone to drink plenty of
water, limit time outdoors, take breaks in the shade or in air
conditioning, or relax by a fan to cool off. This is a dangerous
heat wave - not necessarily because of the high temperatures (we are
not breaking daily highs) - it is the dew points in the mid 70s to
lower 80s setting records. Heat indices nearing 110 degrees will be
felt in the southern and eastern part of the Advisory area.
The chance of cooling convection today appears less than yesterday
in all but the NW zones. A weakening mid/upper level short wave
trough over the mid-Mississippi Valley, already aiding in strong to
severe thunderstorms over northern TN, KY, southwest VA, and even
the NW Mountains of NC early this morning, will lift NE over WVA/VA
later today. At the surface, weak low pressure will develop over
northwest NC and southwest VA this afternoon and track NE into
northern VA this evening.
...A few severe storms are likely across northern NC this afternoon
and early evening...
While the bulk of the convection is expected to affect TN/KY/WVA/VA,
some of the storms will affect/develop over the mountains of NC.
Outflow boundaries may set off new convection, at least on a
scattered basis, over much of NW and north-central NC mid afternoon
into the mid-evening hours. This is where there will be a chance of
isolated severe thunderstorms, with damaging wind the main threat.
While the stronger mid-level flow is expected to be just north of
the region, northern NC will be on the southern fringe of the
increased mid=level flow, and it may actually be in the area where
heating will be the strongest (given convection already ongoing to
the northwest. MLCapes of 2500 J/KG are possible as dew points will
be in the 70-72 range as temperatures reach 96-98. Given this
instability, any storm that occurs will become capable of damaging
wind. The threat will diminish rapidly this evening as is typically
the case with strongly diurnally driven storms. We will carry 40-50
POP NW and N, with only 10 to 15 POP SE. Highs 96-101. Lows tonight
.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 250 AM THURSDAY...
The aforementioned short wave trough will be moving off the mid-
Atlantic coast Friday, leaving subsidence and the potential for more
of a westerly low level flow over NC Friday afternoon. Even through
the temperatures will be just as hot as today, the dew points may
mix out a bit more, especially in the western Piedmont. While a heat
advisory will likely be needed again, it may be confined to areas
east of the NW Piedmont (if the dew points are still expected to mix
out into the mid to upper 60s there. Elsewhere, another hot humid
day with heat indices likely at or very near 105. Highs may be just
a bit lower than today, but 93-100 is still hot. POP will be much
lower with mostly 10 percent or less any any given spot.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --As of 325 AM Thursday...
Ridging aloft extending from coast to coast in the mid-latitudes (30-
40 degrees N) will transition to a pattern of broad troughing aloft
over the eastern US this weekend through early next week, followed
by NW flow aloft by the middle of next week as an upper level ridge
re-strengthens over the lower MS river valley and Deep South. With
the above in mind, expect a cooling trend over the weekend with
slightly above normal temperatures becoming near normal by early
next week. With broad troughing aloft, expect above-normal chances
for convection this weekend through early next week. With central NC
situated on the southern periphery of the westerlies, an above
normal potential for severe weather will exist if small amplitude
waves and/or upstream convection /MCVs/ progress into/across the
region, particularly in vicinity of peak heating. -Vincent
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.AVIATION /06Z THURSDAY THROUGH MONDAY/...
As of 200 AM Thursday...
There is a chance of strong to isolated severe storms this afternoon
and early evening across the northern part of NC from KINT to KRWI,
otherwise generally VFR conditions are expected with some patchy
early morning ground fog.
Outlook: Outside of isolated to scattered storms each
afternoon/evening and some patchy early morning fog, expect
predominately VFR conditions through Friday.
Heat Advisory from NOON to 800 PM EDT TODAY for NCZ007>011-021>028-