Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
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FXUS62 KRAH 210207
Area Forecast Discussion
National Weather Service Raleigh NC
1007 PM EDT SAT AUG 20 2016
An upper level trough and attendant cold front will approach the
region from the west tonight, then progress east across the Mid-
Atlantic and Carolinas Sunday into Sunday night.
.NEAR TERM /TONIGHT/...
-- Changed Discussion --As of 1000 PM Saturday...
Mid to upper level ridging will continue to expand E across the
Carolinas tonight, between a shortwave trough that exited the
Middle Atlantic coast Sat morning and a much larger positive tilt
trough now extending from central Canada to SRN CA.
In the lower levels, a NW to SE-oriented trough axis/weak remnant
frontal zone remains evident in surface and 925-850 mb RAOB data from
WRN VA to east-central NC; and the models indicate this
low level focus for lift will gradually retreat NEWD into ERN VA
and ERN NC by Sun morning. Ongoing scattered convection across
central NC appears to be a result of convergence into, and weak
WAA atop, this low level frontal zone. As such, this focus for
(scattered) showers and storms should likewise move through the
ERN half of the RAH CWFA tonight. While several bands of
disorganized showers and storms are lined up generally along and
W of the Appalachians, this activity will likely diminish as it
moves E through an increasingly nocturnally-cooled environment
over the WRN Carolinas.
Satellite imagery indicates deep-layered cloud cover should be
less than previous nights owing to the aforementioned mid to upper
level ridging building overhead, with associated partly cloudy
conditions supportive of some glimpses of the lingering Perseid
Persistence lows in the lower to middle 70s.
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.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 250 PM Saturday...
The upper trough moving through the OH Valley on Sunday will
propel a long-awaited cold front across the area Sunday evening.
Moderate instability (highest east) should unfold ahead of the front giveN
another day of ~90/72, and a bit stronger mid-level flow (30-35kt)
downstream of the trough should also favor better organization to
convection. However, the core of the associated vort max will pass
well top our north, and the front and trough axis will cross the
area during an increasingly less favorable time frame between 21z
and 03z. thus, the prospects of an organized convective event appear
low, with a low-end severe threat more likely in a more favorable
environment toward the VA border. Highs 88-92 Sunday afternoon, with
lows dipping into the mid 60s in the northwest Piedmont behind the
front Sunday night and near 70s to the east.
.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 310 PM Saturday...
Surface high pressure will build in to the area on Monday and move
off the coast on Wednesday, bringing a drier and slightly cooler
airmass. Highs will be a few degrees below normal through
Wednesday... in the mid 80s.
The high will shift offshore on Wednesday, as upper level heights
increase, and temps will begin to rebound to normal. Shortwave
moving in to the Ohio Valley on Wednesday moves northwestward and
dampens as it encounters the ridge along the east coast. Attendant
front will likely remain north/west of the area before weakening,
keeping conditions dry in to the weekend.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 745 PM Saturday...
Convection has waned across the area, with only isolated showers for
the remainder of the evening. Aside from some localized fog/stratus
at KRWI, expect predominately VFR conditions overnight with broken
cirrus overspreading the area in advance of the approaching trough.
On Sunday, a cold front will approach from the west and cross the
area between 21z and 03z Monday. Westerly flow preceding the front
will limit pops/coverage, especially across eastern and southern
Looking ahead: High pressure in the wake of the frontal passage will
advect much drier air into the area Monday through midweek,
promoting VFR conditions through the period.