Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 201821
Area Forecast Discussion
National Weather Service Raleigh NC
221 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 /THROUGH TONIGHT/...
As of 1030 AM Saturday...
Generally flat flow continues across the Southeast US, though
some ridging is noted across the TN valley and more northwesterly
mid/upper level flow at KGSO this morning. At the surface, a
remnant trough, modulated by outflow last evening, appears to
have settled across the Sandhills and southern coastal plain,
though radar imagery from last night suggests an outflow boundary
may arch back across the central and northern Piedmont. northerly
850mb flow is advecting some drier air across the northern half of
the CWA and the higher, near 2 inch PWs are confined to the south
and east where RAP/HRRR soundings indicate MLCAPE of around 1500
j/kg will develop this afternoon. There aren`t any really obvious
disturbances aloft in water vapor, so coverage may not be as great
as yesterday, but the best coverage should be from Albemarle
toward Fayetteville based the morning analysis and CAM guidance.
A ribbon of 25kt mid- ]level flow should still support at least an
isolated strong storm or two, and those storms a little further
north toward HWY 64 may have a little better DCAPE environment to
Overall changes to the forecast grids are minimal, with highs
still expected to reach the upper 80s and lower 90s as morning
stratus over the coastal plain burns off.
Lows in the lower 70s tonight as mostly diurnally driven
convection dies off by midnight.
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
As of 345 AM Saturday...
Flow aloft will further strengthen Sun/Sun night as the
aforementioned upper low progresses ENE into southern Canada and
additional shortwave energy digging southeast through the central MS
river valley amplifies an upper level trough over the OH valley and
Great Lakes, and an attendant surface cold front approaches from the
NW Sunday afternoon, progressing through central NC sunday evening/
night. Expect the best overall potential for convection this weekend
to occur late Sunday afternoon through Sunday evening as the surface
cold front /low-level trough/ progresses into the region in vicinity
of peak heating in the presence of above normal moisture, marginal
to moderate destabilization, and small amplitude waves embedded
within relatively speedy westerly flow aloft. Deep moisture
/cloud-cover/ and weak mid-level lapse rates may temper instability
such that more favorable deep layer shear attendant stronger flow
aloft may not be fully realized/capitalized upon by updrafts at this
latitude. Weak DCAPE suggests weak cold pools, though ~20 kt
westerly flow in the lower-levels may support upscale growth
/downdraft consolidation/ and eastward propagation, perhaps evolving
into a multicells line along/east of hwy 1 with an isolated potential
for damaging winds via precip loading and downward momentum
transport. Regardless, expect the best potential for convection in
the late afternoon and evening, ending from west-east Sunday
evening/night as the surface front low-level trough progress east
toward the Carolina coast. Expect highs in the upper 80s to lower
90s and lows Sunday night driven by cold advection, ranging from the
lower/mid 60s far NW to lower 70s far SE. -Vincent
.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 245 AM Saturday...
Surface high pressure will build into the area behind the cold front
early next week, resulting in much lower afternoon humidity values
and temps near to below normal along with dry weather. The surface
high will slowly shift off the Mid-Atlantic coast mid to late week,
allowing for moisture and temps to slowly increase. However, dry
weather is generally expected to continue through the end of the
workweek. High temps are expected to be in the 80s early to mid
week, before increasing into the upper 80s to lower 90s by late
week. Low temps will follow a similar trend, with lows generally in
the 60s throughout the week though (with possibly a few 50s in the
usual rural cool spots early to midweek).
.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --As of 210 PM Saturday...
VFR conditions this afternoon, with brief periods of sub-VFR
possible within showers and storms that are developing in an axis
of low-level convergence that extends from KFAY northwest toward
KGSO/KINT and KTDF. Most of the convection should diminish by 06z
and yield predominately VFR conditions through the overnight
period as a light southwest wind develops. Some areas of IFR
ceilings are possible late, though the best chance should be east
of KRWI. On Sunday, a cold front will approach from the west and
cross the area between 21z and 03z Monday, with scattered (south)
to numerous (north) showers and storms.
Looking ahead: Showers and storms will be moving through the area
Sunday evening and east of the area Sunday night, followed by VFR
conditions through at least midweek.
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