Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 250538
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
138 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 /Overnight/...
As of 915 pm Sunday...

An expansive (albeit small amplitude) ridge aloft spanning ~10
degrees of latitude (30-40 degrees) from coast to coast will
dominate the upper level pattern through mid-week, confining the
primary belt of westerlies above 40 degrees latitude. Light/variable
steering flow and synoptic subsidence overnight will leave central
NC isolated from upstream convection/disturbances in a nocturnally
stable thermodynamic environment otherwise unable to support
convection. As a result, confidence is high in dry conditions
overnight with lows in the mid 70s. -Vincent

&&

.SHORT TERM /Monday through Monday night/...
As of 255 PM Sunday...

...Heat Advisory in effect for much of Central NC from Noon to 8 pm
EDT Monday...

More of the same, with very warm temps aloft (approaching 3 standard
deviations above normal) helping to limit instability and thus
suppress most convection, with very weak deep layer shear. The
stacked deep ridge axis will hold across NC, with a fairly dry
column persisting, although models do indicate some moistening aloft
just to our W and NW over the Appalachians. The HRRRX indicates
scattered storms developing over the NC mountains by late morning
Mon, and the larger-scale models support this, but with the very
weak steering flow, these cells should meander very slowly to the E
or SE during the afternoon, and may not quite reach the western CWA
before daytime heating wanes. Will stick with no pops for now,
although we may ultimately need a couple hours of isolated coverage
very late in the day over the Triad. Statistical guidance and
forecast thicknesses suggest highs once again in the mid-upper 90s,
and while dewpoints should mix out somewhat during the day (although
they did not mix out much today especially in the eastern CWA due in
part to the very light low level winds), the heat index values are
still likely to exceed 100 degrees over the eastern two-thirds of
the forecast area, with some spots reaching or exceeding 105. Even
if values don`t quite reach 105 Mon, the lack of much recovery at
night (temps holding at 75-80 for a good portion of the nighttime
hours) and the multiple successive days of hot/humid weather still
support a heat advisory for tomorrow. Will place the advisory along
and east of a line from Wadesboro to Siler City to Hillsborough to
Roxboro. We should see the stagnant surface air of the last few days
pick up a bit from the SW during the afternoon. Lows Mon night
should once again be in the low-mid 70s. -GIH

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
As of 210 PM Sunday...

A low pressure system over eastern Canada moves offshore on Tuesday
and leaves behind a frontal zone just north of the area. This
boundary is not expected to move much for several days as high
pressure over the southeast and westerly flow aloft maintain a hot
and fairly stagnant pattern over central NC. The Piedmont trough is
the only discernible boundary that remains over the area and could
be the focus of some afternoon convection but not much in the way of
severe weather to speak of. Wednesday and Thursday afternoons
feature the best instability and shear comes up a little bit by late
Thursday afternoon above 20 knots but confidence and timing at this
point are very low.

What is confident is that temperatures will remain hot with highs in
the mid 90s every day through the long term and lows in the mid 70s.
Dewpoints will also continue to be in the 70s. This will result in
heat index values close to heat advisory criteria, especially in the
south and east each day.

&&

.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...Vincent
SHORT TERM...Hartfield
LONG TERM...Ellis
AVIATION...WSS


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