Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 250708
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
308 AM EDT MON JUL 25 2016

.Synopsis...
Strong high pressure aloft will extend across the region through
early Wednesday, bringing a period of hot and humid conditions to
central NC. The chances for afternoon storms will increase by mid
week.

&&

.Near Term /through Tonight/...
As of 305 AM Monday...

...Dangerously hot conditions expected today across much of central
NC...

An area of high pressure centered aloft over the Carolinas will
maintain the hot and dry conditions today. Low level thicknesses
around 1440m Sunday are projected to inch upward to 1443/44m this
afternoon, supportive of max temps in the mid-upper 90s. Surface
dewpoints mixed out quite a bit in the northwest Piedmont Sunday
afternoon with mid-late afternoon dewpoints in the mid 60s. While
expect sfc dewpoints to mix out again, do not think that they will
go as low as Sunday afternoon. Thus, should see heat index values
around 105 degrees over most of central NC, excluding the nw
Piedmont. Thus, little change required to the current heat advisory.

Cannot rule out the potential for an isolated t-storm, mainly across
the far south. However, considering the pocket of warm air aloft(as
per 00Z GSO sounding), convective inhibition will be high.
Thus,will refrain from mentioning an isolated t-storm for now.

Tonight, very warm and muggy conditions will persist with most
places not dropping below 80 degrees until after midnight.
Min temps generally in the mid 70s.

&&

.SHORT TERM /Tuesday and Tuesday night/...
As of 305 AM Monday...

Tuesday, a minor s/w approaching from the west will weaken the upper
high overhead. This lowering of heights, the approach of the
slightly cooler air aloft associated with the s/w, and a sfc tough
over the Piedmont may be enough to allow for the development of
isolated-scattered afternoon convection, mainly north of the I-40/85
corridor late Tuesday afternoon-evening. Elsewhere, presence of the
upper ridge should inhibit convective development south of highway
64.

Low level thicknesses projected to be just as warm Tuesday as today.
Thus, will forecast max temps comparable to today in the mid to
upper 90s.  Another heat advisory may be warranted for most of the
region.

Any convection occurring early Tuesday evening across the north
should quickly dissipate after sunset. Continued warm and muggy with
overnight temps only cooling into the mid-upper 70s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 3 AM Monday...

Wednesday through Wednesday night: The remnants of a weak cold front
will settle southward into northern portions of the area on
Wednesday into Wednesday night eventually merging with a surface
trough over the area. Meanwhile, the strong mid level ridge
currently over the area will be located off the Southwest U.S. Coast
by Wednesday. This will leave central NC on the southern fridges of
the better westerlies for Wednesday. Given the the weak boundary
will reside across northern portions of the area and potential for
weak impulses to move across the area in the westerly mid level
flow, expect we will see scattered to locally numerous showers and
storms Wednesday afternoon/evening.

Locations across the north will stand the best chance of seeing
convection (closer to the actual boundary where better coverage is
expected). With central NC on the southern fringe of the better
westerly mid level flow (maybe around 20-25 kts at 500 mb across the
north) we may see some multi-cell clusters of storms. Given this and
expected mlcape values of around 1500 J/KG or higher during the
afternoon into the evening and expected frontal zone placement we
may see a better chance for severe storms on Wednesday than past
days (especially across the northern half of the area). Though hard
to time disturbances/mcv`s from upstream convection can and will
have and impact on the eventual convective chances and placement.
High temps on Wednesday are again expected to be above normal
despite increasing chances for storms. Expect high temps to range
from the lower to mid 90s north/northwest to the mid to upper 90s
elsewhere, with heat index values from around 100 north to around
103-105 degrees southeast. Lows Wednesday night are expected to
generally be in the mid 70s.

Thursday through Sunday: Isolated to widely scattered showers and
storms are expected each afternoon/evening through Saturday as the
mid level ridge to our south/southeast is expected to bulge
northward a bit late week into the first half of the weekend. This
should result in high temps continuing to run in the mid to upper
90s for highs, with perhaps a few sites touching 100 by late week.
This combined with a continued moist low level air mass (especially
to the east of the lee side trough expected over the area) will
allow for heat index values of around 100+ across the
southern/southeastern half of the area which may result in
additional heat advisories even if we dont reach heat index values
of 105 degrees, thanks to the prolonged stretch of heat and humidity.

The mid/upper level ridge is expected to shift eastward as s/w
energy is expected to track across the Great Lakes into the
Northeastern U.S next weekend. This should result in another weak
frontal zone approaching central NC from the north by Sunday,
yielding and increasing chance of mainly afternoon/evening
convection. High temps by Sunday are expected to generally be in the
lower to mid 90s. Low temps for the period are expected to generally
be in the mid to upper 70s.

&&

.Aviation /06Z Monday through Friday/...
As of 138 AM Monday...

Pockets of MVFR fog will develop across central NC between 09Z and
11Z, dissipating within an hour or two of sunrise. Otherwise, there
is a high probability that VFR conditions will persist across
central NC through Tuesday as an area of high pressure aloft remains
overhead.

There is a good probability that VFR conditions will persist through
much of the remainder of the work week. Chances for afternoon-
evening scattered convection will increase the later half of the
week, along with the possibility of early morning fog and low clouds.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon today to 8 PM EDT this evening for
NCZ007>011-024>028-040>043-074>078-083>086-088-089.

&&

$$

SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...BSD
AVIATION...WSS



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