Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 290110
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
911 PM EDT Wed Jun 28 2017

.SYNOPSIS...
Canadian high pressure will drift offshore the Mid-Atlantic coast
tonight. High pressure will extend into the region from the east on
Thursday. An increasingly moist southerly return flow will prevail
Friday through the weekend.

&&

.NEAR TERM /Today and Tonight/...
As of 911 PM EDT Wednesday...

A modified ~1023mb cP surface high will move off the DELMARVA coast
this evening with attendant sfc ridge axis extending east into the
area overnight. Mostly clear skies, light winds and antecedent dry
air in place (BL dewpoints in the mid 50s and PWATS between 0.5-
0.6")will result in good radiational cooling conditions overnight.
So expect another night of below normal low temps, ranging from the
mid/upper 50s to lower 60s, coolest in the typical rural/low-lying
areas.

&&

.SHORT TERM /Thursday and Thursday night/...
As of 135 PM EDT Wednesday...

A relatively dry airmass associated with modified Canadian high
pressure extending westward (from the Atlantic) into the Carolinas
will persist on Thu, albeit with a gradual increase in moisture from
the S/SW during the aft/eve as the surface high moves further
offshore, the ridge weakens, and a light return flow commences.
Upper level moisture will also increase on Thu as a deamplifying
upper level low progresses NE from the TX/LA Gulf coast into the
Deep South. With the above in mind, expect dry conditions and
increasing cloud cover on Thu with highs in the mid to upper 80s,
warmest E/SE. The deamplifying upper level low is progged to make
little progress Thu night, progressing NE into northern AL/northwest
GA. Strengthening southerly return flow /moisture advection/ is
expected to result in the development of stratus from S/SW to N/NE
overnight. As a result, expect much warmer lows than observed in
previous days, in the mid to upper 60s, except in the far NE Coastal
Plain where lower 60s cannot be ruled out. Will introduce a slight
chance of showers after midnight in the far S/SW, though the best
potential for showers should remain upstream in upstate SC,
southwest NC and northern GA where richer low-level moisture will be
juxtaposed with DPVA attendant the upper level low. -Vincent

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
As of 205 PM EDT Wednesday...

Increasingly hot and more humid, with scattered diurnal convection,
through the weekend. Continued hot, but less humid and with a
reduced risk of diurnal convection, over the wrn half of the
forecast area by early to mid next week.

The models remain consistent in their depiction of an amplifying
trough aloft from west-central Canada to the upper MS Valley by Fri,
and across the Great Lakes on Sat. Between this trough and a sub-
tropical ridge initially over the swrn N. Atlantic, perturbed swly
flow aloft will result from the lower MS Valley to the middle
Atlantic states; and the most notable (synoptic-scale and
predictable) of these disturbances will be a mid level trough now
over the nwrn GOM that the models indicate will lift newd across the
Carolinas on Fri. The sub-tropical ridge is forecast to expand wwd
into the GOM through the weekend, then bulge nwd across the srn U.S.
through early to mid next week, while a weakness in the ridge, in
the form of a weak shear/trough axis, lingers along the East Coast.

At the surface, expansive high pressure will remain over the central
N. Atlantic and extend wwd to the sern U.S. coast through the end of
the forecast period, while an Appalachian-lee trough sharpens over
VA and the Carolinas.

Return flow around the high will yield gradually increasing
temperatures and humidity levels, marked most abruptly by the
passage of a warm front on Fri. Despite mid level warmth associated
with the sub-tropical ridge, with resultant weak mid level lapse
rates of less than 6 C/km, the aforementioned warming and moistening
low levels should prove sufficient for at least scattered diurnal
convection throughout central NC Fri-Sat, and probably aided by the
aforementioned mid level trough on Fri. Thereafter, the sharpening
of the lee trough and mixing out of surface dewpoints (into the
lower to middle 60s) to the west will probably shift the focus for
convection into the Coastal Plain Sun-Wed. Temperatures will trend
from the middle 80s to around 90 degrees on Fri to lower to middle
90s by early next week. Heat indices may near or minimally exceed
100 degrees over the Sandhills, ern piedmont and srn-central Coastal
Plain Sun onward.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 820 PM EDT Wednesday...

24 Hour TAF Period: VFR conditions are expected to continue tonight
as surface high pressure located near the coast slowly shifts
further eastward. This should result in insufficient moisture
recovery to accommodate any sub-VFR conditions through the 24 hour
TAF period. Light and variable to calm winds tonight will become
south to southwesterly on Thursday as the surface high continue to
shift eastward and away from the area. A scattered to at times
broken cumulus clouds will fill portions of the sky on Thursday
afternoon generally in the 05-07 kft range.

Looking Ahead: Some sub-VFR conditions will be possible on Friday
morning, with any sub-VFR conditions generally improving to VFR by
noon or so. Isolated to scattered showers/storms are expected to
develop late Friday afternoon, potentially affecting all terminals,
with the overall best chance at the FAY/INT terminals. Diurnal
convection and early morning stratus/fog are expected to affect all
terminals over the weekend and possibly through early next week, as
well.

&&

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

&&

$$

SYNOPSIS...Vincent
NEAR TERM...CBL
SHORT TERM...Vincent
LONG TERM...MWS
AVIATION...BSD/Vincent



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