Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
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FXUS62 KRAH 270607
Area Forecast Discussion
National Weather Service Raleigh NC
205 AM EDT Mon Mar 27 2017
-- Changed Discussion --A warm moist southerly flow will hold over the area through
Wednesday. An upper level trough will cross the region tonight
through Tuesday, bringing unsettled weather. A backdoor cold front
will drop southward through the area late Wednesday through
Wednesday night, followed by cooler high pressure pushing in from
the north on Thursday. Another storm system will cross the area
Thursday night through Friday night.
-- End Changed Discussion --
.NEAR TERM /THROUGH TONIGHT/...
As of 1025 PM Sunday...
Only a few very light showers and patches of sprinkles are left with
the initial spoke of upper level energy tracking ENE across northern
and northeastern NC late evening. There were reports of a few
hundredths this evening at KGSO and KINT, but generally trace
reports to the east. This activity is on the wane as it moves toward
the Coastal Plain. There is a bit more in the way of more significant
showers around Asheville to Hickory. This activity is expected to
move NE and potentially dampen the NW portions of the Triad later
on. We will keep the POP and QPF essentially unchanged with highest
POP NW and essentially just "slight chances" elsewhere of 0.01 of an
inch. The QPF in W-Salem area by reach 0.10 to 0.25 in the showers
later. Otherwise, low stratus later in the west, with a low chance
of low stratus east.
The increase in low level moisture with dew points into the 50s
suggests that lower stratus are possible if not likely in the
western Piedmont later tonight. Lows generally in the 50s to near
60, with the warmer readings in the west where the low level
moisture and clouds will be most prevalent.
.SHORT TERM /MONDAY THROUGH TUESDAY/...
As of 330 PM Sunday...
Monday, mid/upper level low over the southern Plains, opens up and
lifts into the mid MS Valley. A lead s/w ahead of this feature will
approach central NC late Monday. This feature will aid to back the
mid level flow, leading to moistening of the mid layers of the
atmosphere. This lead s/w will cross our region late Monday,
triggering scattered showers and t-storms. Convective parameters not
too shabby for end of March with MLCAPE off the GFS 750-1000 J/kg.
Effective bulk shear 20-25kts on the cusp of supporting organized
convective bands. While cannot rule out an isolated severe due to
hail, bulk of convection should remain below severe criteria.
Extensive cloud cover early Monday should give way to periods of
sun. The peeks of sun with near sfc flow out of the sw will boost
temperatures into the 75-80 degree range.
The lead s/w will exit our region late Monday night but will be
followed by the main mid-upper level trough by early Tuesday. This
will maintain a threat for scattered showers and a few thunderstorms
Monday night into Tuesday morning. By Tuesday afternoon, greatest
threat for scattered showers and a few storms will be along and east
of highway 1. Convective parameters by Tuesday afternoon may support
a locally strong or severe storm over the coastal plain and
sandhills as MLCAPE recovers to 1000 J/kg, with effective bulk shear
in the 30-35kt range.
A warm air mass will maintain above normal temperatures Monday night
and Tuesday. Overnight temps Monday night should be in the upper 50s
to near 60. Max temps Tuesday upper 70s to lower 80s. If cloud cover
remains extensive or shower coverage is greater than anticipated,
max temps Tuesday could end up being 4-5 degrees cooler.
.LONG TERM /Wednesday through Sunday/...
-- Changed Discussion --As of 205 AM Monday...
Wed-Thu: Behind the departing shortwave through, the mid level ridge
axis will shift eastward over the Southeast through Thu, although by
Thu it will be deamplifying as the next mid level low tracks through
the central CONUS. NC will remain in the warm sector for much of
Wed, as the backdoor front holds to our north until late in the day,
when energy dropping into the polar low SE of the Canadian Maritimes
helps drive the cool dense surface high pressure area southward into
NC, with the front dropping through NC NNE to SSW Wed evening/night
and settling south of the forecast area by Thu morning. Expect
partly to mostly sunny skies Wed with flat cumulus beneath the warm
layer focused around 700 mb. The low levels will cool/stabilize Wed
night with increased moisture pooling around 900-800 mb, so expect
cloudy skies, thickest in the west where moist isentropic upglide
will be deepest. While a uniform northeasterly low level flow into
the area will set up behind the front, the 850 mb anticyclone will
shift off the Carolina coast, resulting in increasing 850 mb winds
and strengthening moist overrunning atop the cool stable pool Thu,
most evident over the NW CWA. Will keep skies mostly cloudy to
cloudy with a chance of light rain or drizzle in the W from late Wed
night through Thu. Highs Wed from lower 70s NE to around 80 SW. Lows
45-55 NE-SW Wed night as cooler air pushes into the NE. Highs Thu
from mid 50s NW to the mid 60s SE within a wedge regime.
Thu night through Fri night: A volatile period as another strong mid
level shortwave moves from the central Plains through the Miss
Valley and Ohio Valley before crossing the Mid Atlantic region. At
the surface, models depict the primary surface low tracking NE over
or just south of SE MI through Fri, while the front to our south
shifts back northward as a warm front, and a triple-point low forms
over SW VA. While we would normally be skeptical about the complete
passage of a warm front through NC immediately following a wedge
regime, the parent high is rather weak and progressive and may be
unlikely to put up much of a fight, so will depict a northward surge
of higher dewpoints through much of the forecast area (excluding the
far NW) on Fri. The primary low will then track up the St. Lawrence
Valley Fri night while filling, as the triple-point low crosses WV
and N VA and becomes the primary low near or just off the Delmarva
peninsula, with W-to-E cold frontal passage through central NC. In
terms of sensible weather, given the improving mechanisms to force
ascent including mid level DPVA, strengthening upper divergence, and
increasing 850 mb moisture transport, expect numerous showers and
thunderstorms starting Thu night, peaking in coverage and intensity
Fri, then exiting to our east Fri night as the mid level trough
moves off the coast. A few strong storms are possible Fri, although
the DPVA will have weakened a bit by the time the trough gets here,
and we`re lacking the instability and strong kinematics that might
prompt greater concern. Lows Thu night mid 40s to low 50s, highs Fri
62-72, and lows Fri night 49-55.
Sat-Sun: Weak modified surface high pressure builds in behind the
front with another rough of shortwave ridging in the wake of
Friday`s trough and ahead of the next system moving from the Four
Corners into the S Plains. Expect dry weather and partly cloudy to
mostly clear skies. Thicknesses are projected to stay a bit above
normal through the weekend, so expect highs from around 70 to the
mid 70s. -GIH
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.AVIATION /06Z MONDAY THROUGH FRIDAY/...
As of 140 AM Monday...
24 Hour TAF Period: A few bands of light to moderate showers moving
through the Triad at this time and this will continue for the next
few hours. Further east, many of the showers will move north of the
area, avoiding the TAF sites. MOS guidance products were hinting at
some fog or low stratus in the south and east near daybreak, but
higher resolution models are not as bullish and therefore have
removed any mention of fog in these areas. For the Triad sites plus
KRDU have left in some MVFR stratus closer to and just after
daybreak. Have left out any mention of rain for Monday afternoon but
there is a nonzero chance of a few lingering showers or maybe even a
thunderstorm that will re-evaluate with the 12z package. Confidence
was low enough at this time to leave out of the forecast. Winds will
be mainly out of the south at 5-10 kts with some gusting to 15-20
kts possible during the Monday afternoon hours.
Long term: A low pressure system will move through the mid-Atlantic
states on Tuesday brining a chance for rain Tuesday evening. A more
potent system will cross the area on Friday through Friday night
with the potential for showers and Thunderstorms. Otherwise, Some
potential for some fog/low stratus in the Triad on Tuesday morning.