Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS62 KRAH 241735
Area Forecast Discussion
National Weather Service Raleigh NC
135 PM EDT SUN JUL 24 2016
-- Changed Discussion --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
-- End Changed Discussion --
.Near Term /through tonight/...
As of 1015 AM Sunday...
Little change needed to the forecast. Continued hot and humid today
with minimal convection chances. Temperatures through the column are
anomalously warm, more so than yesterday, with very low deep layer
shear resulting from the presence of the mid and upper level ridge
directly overhead. The deeply dry air is noted well on water vapor
imagery, and this should change little today. This factor combined
with the warmth aloft (2-3 standard deviations above normal) and the
deflection of any moisture or disturbances by the ridge will greatly
limit any convection. And any cells that can get going over the
higher terrain appear unlikely to drift into the CWA given the weak
and unfavorable steering flow. However, the chance for isolated
lower-rooted sea breeze convection is still high enough to retain
low chance pops over the southeast CWA. No changes are planned for
the existing heat advisory over the eastern half of the CWA,
although based on high-res dewpoint forecasts and observations of
air just aloft (925 mb) that is slightly drier than yesterday (based
on upper air data), with mixing we may fall just short of 105+
degree heat index values over portions of the advisory area.
Nevertheless, we`re looking at consecutive days of above normal
temps and high humidity, with many folks likely to be outdoors
today, so as far as impacts are considered, an advisory is still
Previous discussion from 325 am: An expansive area of high pressure
across the southern half of the U.S. will build east across the
Carolinas today. The rising heights and associated arming aloft will
inhibit convective development across much of central NC. An
isolated storm cannot be ruled out in vicinity of Sampson and Wayne
counties associated with an inland moving seabreeze, or over our far
western-nw periphery from any convection that drifts off the higher
Low level thicknesses today projected to be 7-8m warmer than
Saturday, supportive of high temps 2-3 degrees warmer.This suggest
high temps solidly in the mid-upper 90s. Heat index values this
afternoon will flirt with the 105 degree mark. Plan to maintain
current advisory as is, and not expand westward.
Tonight, warm and muggy conditions will persist with overnight temps
only cooling into the upper 70s after 2 AM.
.SHORT TERM /Monday through Tuesday night/...
As of 325 AM Sunday...
Little change anticipated for Monday as upper high expected to
remain overhead. The continued warming of the atmosphere will
maintain decent cap, inhibiting convective development. Max temps
comparable to today, in the mid-upper 90s.
May need another heat advisory, primarily for locations in the
sandhills and coastal plain, dependent upon sfc dewpoints mix out
in the afternoon.
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, isolated convection
expected. While there will be more clouds over the north, enough
sun will occur to warm temperatures into the mid 90s with heat index
values in the 98-103 range.
Continued very warm and muggy both Monday night and Tuesday night.
Temperatures will likely not cool below 80 degrees until 2 AM or
later, with early morning temps starting out in the mid-upper 70s.
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 250 AM Sunday...
Medium range models continue to be in general agreement depicting a
mid/upper level ridge located just to our southeast, extending into
our region some to start the period, with a general trough to our
north. At the surface a weak remnant cold front/surface trough is
forecast to sink a bit further southward on Wednesday and help to
focus scattered to numerous showers and storms across central NC,
with locations across the north standing the best chance of seeing
convection (closer to the actual boundary where better coverage is
expected). Given this and 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 90s north to the mid to even upper 90s south,
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.
A general broad trough is expected to develop across our area and
points northward as the mid level ridge is forecast to be suppressed
a bit further south late week into the weekend. This should lead to
scattered showers and storms each afternoon/evening, with more in
the way of isolated showers and storms generally expected during the
overnight/morning hours. However, with a lack of any airmass change
we should still remain hot an humid through the period, with the
possibility of heat advisories needed thanks to the number of days
with heat index values of 100+ across the eastern/southeastern
portions of the area. Highs are generally expected to be in the
lower to mid 90s with lows in the mid 70s.
.Aviation /18Z Sunday through Friday/...
-- Changed Discussion --As of 135 PM Sunday...
VFR conditions are likely to dominate through Monday afternoon.
Strong, dry, and deep high pressure in the middle and upper levels
of the atmosphere will hold overhead for the 24 hours and beyond,
leading to minimal cloudiness (scattered daytime cumulus based above
4 kft) and little to no chance of storms. Light fog (MVFR) is
possible mainly at RWI/FAY late tonight into Mon morning, and
isolated banks of shallow, more dense fog may occur, mainly near
RWI. Surface winds will stay light and variable through tonight
before becoming southwesterly at 6-10 kts.
Looking beyond 18z Mon: An extended period of mostly VFR conditions
is anticipated. One exception will be in the late night and early
morning hours each day this week, when pockets of sub-VFR fog are
possible. Storm chances will remain fairly low through Tue, then
increase Wed through the end of the work week. -GIH
-- End Changed Discussion --
Heat Advisory from noon today to 8 PM EDT this evening for NCZ010-011-