Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS62 KRAH 281740
Area Forecast Discussion
National Weather Service Raleigh NC
140 PM 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/...
-- Changed Discussion --As of 1058 AM Thursday...
...Have upgraded the Heat Advisory to an Excessive Heat Warning for
areas along and east of I-95...
...Heat Advisory continues for all of the Piedmont counties...
The Subtropical ridge in place over the SE U.S. will continue to
produce very warm and humid conditions across Central NC today.
A mid-level shortwave trough, currently over the TN Valley, will
skirt the NW periphery of the subtropical high in place over the
region and will track newd across the southern and central
Appalachians this evening, shearing along the way before reaching
the Northern Mid-Atlantic States by Friday morning. In response to
the approaching trough, the persistent lee side surface trough in
place east of the Appalachians will sharpen with a weak surface
wave expected to develop invof of Virginia/DC later this evening.
Dangerously high dew points in the mid 70s to upper 70s has and will
continue to pool on the east side of the sharpening surface trough.
As of 10 am, heat indices along and east of the I-95 corridor are
already in the 100 to 105 range. When combined with afternoon
temperatures in the upper 90s to 100 F range, heat indices of 110 to
115 F are expected and thus have upgraded the heat advisory to a
heat warning for areas along and east of the I-95 corridor.
Elsewhere across the western and central piedmont will leave heat
advisory in place with heat indices expected to range between 103 to
As far as rain/convective chances:
Regional mosaic radar shows a band of showers and storms across
eastern KY/TN that has developed along ahead of the approaching
trough. While the bulk of the convection is expected to affect
TN/KY/WVA/VA, associated outflow boundaries may set off new
convection, at least on a scattered basis, over much of the northern
tier into the mid-evening hours. While the stronger mid-level flow
is expected to be just north of the region, 20 to 25 kts of deep
layer shear bordering the northern counties combined with moderate
to strong instability of 2500 to 3000 J/KG of mlcape will yield a
threat for one or two severe clusters to develop, with damaging wind
the main threat.
The threat will diminish rapidly this evening as is typically the
case with strongly diurnally driven storms. We will carry 30 to 40
POP across the N, with only 10 to 15 POP SE.
Lows tonight 70-76.
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.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/...
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
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --As of 140 PM Thursday...
Isolated to widely scattered strong to severe storms are possible,
mainly across northern portions of the forecast area through the
early evening. Otherwise generally VFR conditions are expected with
some patchy early morning ground fog possible Friday morning.
Outlook: Outside of isolated to scattered storms each
afternoon/evening and some patchy early morning fog, expect
predominately VFR conditions through Friday. Rain chances are
expected to increase by the weekend and into early next week.
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Excessive Heat Warning until 8 PM EDT this evening for NCZ011-027-
Heat Advisory until 8 PM EDT this evening for NCZ007>010-021>026-