Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 291107

Area Forecast Discussion
National Weather Service Raleigh NC
705 AM EDT Sat Jul 29 2017

An area of low pressure and associated cold front will move east
through the area this morning. Trailing the cold front, a strong
upper level trough will dive south into the area late this afternoon
and evening. High pressure will build into the area overnight,
bringing cooler and drier air into the area through early next week.


As of 350 AM Saturday...

Compact upper low currently over the central Appalachians will
gradually devolve into a still vigorous positively tilted
upper-level trough as it tracks southeast into the DELMARVA region
and NC late this afternoon and evening. With increasing influence
from the upper low, the emergence and then offshore progression of a
prominent surface low off the DELMARVA coast later this morning,
will finally drag the frontal zone east through the area AOA 15z.
Moisture convergence within the low-level frontal zone will support
a chance of scattered showers and a few storms as the front crosses
the area. Expect the bulk of this convection to be east of the area
by lunch time, with a brief lull during the early afternoon period
before we start to see showers spreading in from the north during
the mid to late afternoon period as the strong vort max/DCVA pivots
SE across the eastern half of the CWA, before fading in both
intensity and coverage with loss of heating.

Expect to see more clouds than sun today with the onset of strong
CAA during what is normally the warmest part of the day resulting in
falling temperatures across the northern half of the area, indeed a
rarity for late July. Highs ranging from mid 70s north to mid 80s
SW. Additionally, with the onset of the strong CAA, northerly wind
gusts of 20 to 25 mph will develop along with lowering ceilings.

In the wake of the exiting vortmax, subsidence and cool dry air
advection will lead to decreasing clouds. Lows in the lower to mid


As of 245 AM Saturday...

High pressure will build into the region from the NW on Sunday as an
unseasonably deep upper level low, attendant sfc low, and associated
cold front progress offshore the Carolina/Mid-Atlantic coast. Expect
unseasonably cool/dry conditions (comparable to mid-September), with
highs in the upper 70s to lower 80s, surface dewpoints in the 50s,
and a NE breeze at 10-15 mph. A light N/NE wind could persist
overnight over portions of central NC. Maximum radiational cooling
is most likely to occur in rural and low-lying areas across the
Northern Piedmont and NE Coastal Plain where lows Mon morning are
expected to bottom out at 57-60F. Expect lows in the lower 60s
elsewhere. -Vincent


As of 245 AM Saturday...

The 00Z ECMWF/GFS are in good agreement in this period. NW flow
aloft over the region early this week will transition to broad
cyclonic flow aloft by the end of the week, followed by unseasonably
deep troughing over the eastern US next weekend. In the lower
levels, a stagnant MSLP pattern will prevail over the Carolinas
through mid/late week. Southerly return flow will develop by the end
of the week and persist through the weekend, in advance of a cold
front approaching the Mid-Atlantic from the NW. With a stagnant MSLP
pattern and little/no advection through Wed-Thu, expect very
slow/gradual airmass modification. As a result, unseasonably dry
conditions /low dewpoints/ should persist through mid-to-late week.
Moisture and diurnal convection will return by the end of the week
(Friday), followed by at/above climo chances for convection next
weekend as troughing amplifies over the eastern US. -Vincent


As of 705 AM Saturday...

An area of low pressure and associated cold front will push SE
through the area through 12 to 15z. Showers and a few storms and
associated sub-VFR ceilings are expected to develop ahead and along
the front as it pushes east through the area. Trailing the cold
front, a strong upper level trough will dive south into the area
late this afternoon and evening, producing scattered showers along
with MVFR ceilings spreading in from the north. Additionally, strong
CAA will result in breezy conditions this afternoon and into the
evening, with northerly gusts to around 20 kts. In the wake of the
departing upper trough, VFR conditions will return between 03 to 09z
Sunday as drier air filters in from the north.

High pressure will dominate Sunday through midweek, resulting in VFR
conditions through the period.





SHORT TERM...Vincent
LONG TERM...Vincent
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