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899
FXUS62 KRAH 221613
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
1159 AM EDT Sat Jul 22 2017

.SYNOPSIS...
Hot and mainly dry sub-tropical high pressure will expand across the
mid-South and southern Appalachians through the weekend, then
gradually weaken by early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1159 AM Saturday...

...Dangerously hot conditions will expand across central NC
today...

Excessive Heat Warning now in effect for the cities of Raleigh
and Fayetteville (counties of Wake and Cumberland) from 11 AM
until 7 PM today...

Heat advisory in effect for the rest of our region, including
all of the Piedmont, Sandhills, and Coastal Plain from 11 AM
Saturday through 7 PM today.

Excessive Heat Watch remains in effect for the cities of
Raleigh and Fayetteville (counties of Wake and Cumberland) from
7 PM this evening through 7 PM Sunday.

The late morning surface temperatures were already in the upper 80s
to lower 90s. The dew points were in the mid to upper 70s, even in
the climatological drier NW Piedmont and Foothills. The surface
trough was located near the Blue Ridge today, with much higher dew
points and PW`s today than 24 hours ago. These readings yielded heat
indices of 107 at FAY and 103 at Raleigh at 11 am. Even at
Greensboro the heat index was 99 at 11 am.

No changes to the current Warnings/Watches and Advisories on the
heat needed as highs are still expected to reach the mid to upper
90s throughout our region, with 100 at Fayetteville. The well
advertised heat indices will reach 110-115 in Raleigh and
Fayetteville, and 105+ elsewhere.

Satellite data indicated scattered cumulus developing over the
Mountains, along the surface trough in NW NC, and along the sea
breeze convergence along the SE NC beaches. A 20 POP of
thunderstorms seems reasonable at any one spot this afternoon.
MLCapes of 2000+ J/KG along with PW`s in excess of 2+ inches in the
east suggest any storm will be capable of very heavy rain and
strong, gusty wind to 45-50 mph.

In addition, some CAMS models suggest that outflows from upstream
convection may generate thunderstorms over northern NC this evening.
This will be assessed this afternoon. Otherwise, it will be warm and
sticky tonight with lows 75-80.

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
As of 415 AM Saturday...

Excessive Heat Watch remains in effect for the cities of
Raleigh and Fayetteville (counties of Wake and Cumberland) from
through 7 PM Sunday.

Generally persistence, though with a higher probability of
afternoon convection, as heights aloft fall over the srn Middle
Atlantic states and NC consequently becomes increasingly
susceptible to passing perturbations, some resulting from
upstream convection, in wly to nwly flow. Another Heat Advisory
will likely be needed for all of central NC, with a good chance
of another Excessive Heat Warning over at least Wake and
Cumberland counties once again. The coverage and initiation time
of convection, and preceding high level "blowoff" cloudiness
from upstream convection, may result in slightly lower high
temperatures and associated heat index values, however, but the
overall cumulative affects of the heat will persist regardless.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 335 AM Saturday...

A weak but fairly progressive upper level trough will move over the
area on Monday and then continue eastward, taking a surface low off
of the Long Island coast and out to sea. Behind the exiting low, a
high pressure system will move over the northeastern CONUS that will
eventually drop a cold front through the area and bring some relief
to the heat. A general cooling trend will begin on Monday with
temperatures easing back into the lower 90s, but dropping further
into the mid to upper 80s by Wednesday afternoon, after the passage
of the front. Upper 80s to low 90s will prevail through the
remainder of the forecast period.

The Piedmont trough and a lingering frontal boundary
across the southern part of the area will be the focus for
convection for much of the work week as a series of disturbances
tracks along this boundary. The strongest of these disturbances
could come on Tuesday night into early Wednesday morning but will be
short lived before either weakening or moving out to sea. Otherwise
expect diurnal showers and thunderstorms. The best chance for severe
weather may be across the north on Monday as the upper dynamics are
more favorable for supporting severe thunderstorms. As such the SPC
has included northern portions of the CWA in a marginal to slight
risk of severe thunderstorms.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
As of 745 AM Saturday...

Aside from a small chance of showers and storms, and associated
gusty winds and brief sub-VFR conditions, VFR conditions with a
mainly light, 7-13 kt surface wind, are expected through the TAF
period. The relative highest probability of convection will be at
INT and GSO, where upstream convection and associated outflow, from
a couple of MCS`s over the OH Valley and/or from the Appalachians,
may propagate late this afternoon and this evening. Otherwise and
elsewhere, an isolated "pop-up" storm will be possible, but
predictability and timing of any such occurrence is too low to
include for any other TAF site at this time.

Outlook: Mainly VFR conditions will continue through the middle of
next week, with the primary sub-VFR risk coming courtesy of showers
and storms that will grow in coverage each successive day through
Tue.

&&

.CLIMATE...
RDU Records:
Date     | High   Year  |  High Min  Year
------------------------------------------
22 July  |  103   2011  |     78     2011
23 July  |  105   1952  |     78     2011
24 July  |  101   2011  |     79     2011

GSO Records:
Date     | High   Year  |  High Min  Year
------------------------------------------
22 July  |  101   1926  |     77     2011
23 July  |   99   1952  |     78     2010
24 July  |   99   1914  |     78     2010

FAY Records:
Date     |  High  Year  |  High Min  Year
-------------------------------------------
22 July  |  107   1932  |     79     2011
23 July  |  103   2011  |     79     1998
24 July  |  105   1952  |     79     1945

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM this morning to 7 PM EDT this evening
for NCZ007>011-021>028-038>040-042-043-073>078-083>086-089.
Excessive Heat Warning from 11 AM this morning to 7 PM EDT
this evening for NCZ041-088.
Excessive Heat Watch from this evening through Sunday evening
for NCZ041-088.

&&

$$
SYNOPSIS...MWS
NEAR TERM...Badgett/MWS
SHORT TERM...MWS
LONG TERM...RE
AVIATION...MWS
CLIMATE...RAH