709
FXUS62 KRAH 021340
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
940 AM EDT Tue Jul 2 2024

.SYNOPSIS...
Canadian high pressure will move across and offshore the Middle
Atlantic through Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 940 AM Tuesday...

No major updates this morning as forecast is track. High pressure to
the NE will continue to influence dry weather today with NE flow at
the surface. Highs will range from 84-87 degrees across the region
this afternoon.

As of 330 AM Tuesday...A subtropical ridge will expand across the
Southeast as a mid/upr-level anticyclone drifts from the lwr MS
Valley ewd and over the TN Valley. Continued rising heights aloft
and subsidence will result across the Carolinas.

At the surface, Canadian high pressure now centered over NY/PA will
drift sewd and reach the Middle Atlantic coast by 12Z Wed, while its
associated ridge will continue to extend swwd across the Carolinas.

The presence and influence of the deep layer ridging will favor
continued deep dryness and stability over cntl NC, highlighted by a
daily record minimum PW of just 0.48" observed at GSO last evening.
Remarkably, that daily record minimum was preceded by a daily record
maximum of 2.14" just 24 hours prior. Unseasonably low surface
dewpoints mostly in the 50s this morning will likely decrease
another several degrees with diurnal heating/mixing and result in
another day of unseasonably low humidity values mostly in the 30th
percentile, as temperatures warm into the mid-upr 80s beneath a
mainly sunny sky. Mainly clear and calm tonight will then favor
strong radiational cooling and below average temperatures in the upr
50s to mid 60s tonight.

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 350 AM Tuesday..

A subtropical ridge over the Southeast may weaken a couple of
decameters and retreat slightly, as convectively-generated
disturbances, in quasi-zonal flow poleward of the ridge, develop and
move from the cntl Plains and mid MS Valley ewd and across the OH
Valley and cntl Appalachians. While associated height falls will be
maximized across the OH Valley and nrn Middle Atlantic, 10-20
meter/12 hr falls will support some gradual weakening of the
preceding strong subsidence inversion in place over cntl NC,
especially Wed night. Some mid/high-level moistening and cloudiness
may result Wed night, after high-based, diurnally-driven
stratocumulus become scattered to broken Wed afternoon and dissipate
through the evening. Otherwise, temperatures will moderate to
slightly above average --highs in the upr 80s to lwr 90s and lows in
the mid 60s to lwr 70s-- as increasingly-modified, Canadian surface
high pressure drifts off the Middle Atlantic coast and directs sely
to sly flow across cntl NC from late afternoon through overnight.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 225 AM Tuesday...

Aloft, the mid-level anticyclone will sit over the Deep South
through Thu night. A potent northern stream s/w will move through
the northern Plains/upper MS Valley Thu/Thu night, picking up a
weaker s/w moving through the central Plains into the mid-MS Valley.
The mid/upper trough will amplify west of the Appalachians Fri/Fri
night, as the s/w disturbances continue eastward through the Great
Lakes and OH Valley. The high over the Deep South will be gradually
pushed eastward through the Southeast on Fri and off the Southeast
US coast Fri night/Sat the trough amplifies west of the
Appalachians. As the initial s/w lifts newd into Canada on Sat,
another northern stream s/w will drop into the northern Plains,
tracking eastward along the US/Canada border into the Great Lakes
Sat night/Sun. As this second s/w moves through the Great Lakes, the
longwave trough will further amplify, extending from the s/w to the
ARKLATEX by Sun night. All the while, central NC will remain
situated between the trough to the west and the high to the east,
with deep southwesterly flow prevailing. At the surface, a lee
trough will set up and remain in place through Sat night, when a
cold front will approach from the west. As of the latest model
solutions, the front will largely wash out along the Appalachians
Sat night, possibly laying W-E through WV/VA Sun as high pressure
lifts newd through the OH Valley and Northeast, but the front
appears to stay north of central NC. Expect swly flow and the
advection of warm, moist air into the area to take over once the
ridge moves out Thu morning and prevail through at least Sat.

Temperatures will be above to well above normal Thu through Mon.
Latest forecast heat index values do creep back to around 105 again
in a few spots on Thu, however the more widespread heat index values
of 105 to 109 (across much of central NC) are expected Fri and Sat.
Some lingering heat index values of 100-105 are possible across the
south and east on Sun and Mon.

As for rainfall, with central NC on the northern periphery of the
ridge, some convection riding the ridge may move across the northern
half of the area Thu aft/eve. Then as the mid-level ridge gradually
gets suppressed south and the lee trough strengthens, expect more
diurnally driven convection Fri, Sat, and Sun aft/eve, possibly
continuing for Mon aft/eve as well.

&&

.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
As of 700 AM Tuesday...

The presence and influence of Canadian high pressure over the Middle
Atlantic will favor VFR conditions in cntl NC through at least the
next couple of days. Nely surface winds around the high may result
in a few gusts into the teens to near 20 kts with diurnal heating
this morning mainly at FAY, with light nely to ely winds
expected otherwise and elsewhere.

Outlook: A chance of showers/storms will exist over the wrn NC
Piedmont (INT/GSO) Thu afternoon-evening and throughout cntl NC Fri
through the weekend.

&&

.CLIMATE...
Record High Temperatures:

July 4:
KGSO: 98/1970
KRDU: 101/2012
KFAY: 98/2019

July 5:
KGSO: 98/2012
KRDU: 102/1999
KFAY: 101/2002

July 6:
KRDU: 102/2022
KFAY: 99/1990


Record High Minimum Temperatures:

July 4:
KGSO: 73/2018

July 5:
KGSO: 74/1999
KRDU: 78/1902
KFAY: 77/2005

July 6:
KGSO: 76/1999
KRDU: 79/1900
KFAY: 76/2017

July 7:
KGSO: 73/2019
KRDU: 77/1900
KFAY: 78/2017

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...MWS
NEAR TERM...CA/MWS
SHORT TERM...MWS
LONG TERM...KC
AVIATION...MWS
CLIMATE...RAH