Area Forecast Discussion
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FXUS62 KRAH 270543
Area Forecast Discussion
National Weather Service Raleigh NC
143 AM EDT Mon Mar 27 2017
A surface high pressure area will extend from Bermuda westward into
the Carolina`s through Monday. A cold front will drift southward
across central NC late Tuesday and Tuesday night.
.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 /TUESDAY NIGHT THROUGH SUNDAY/...
As of 230 PM Sunday...
Wed-Wed Night: With a shortwave ridge aloft, expect mostly sunny to
partly cloudy skies with above normal highs in the mid/upper 70s.
Thu: High pressure is expected to extend southward into the
Carolinas Thu morning (in the form of a backdoor cold frontal
passage) in association with height/pressure rises in the wake of an
upper level low moving offshore New England into the Canadian
maritimes. With low-level NE flow emanating from the cool Labrador
current in NE portions of the state and an increased likelihood for
cloud cover in SW portions of the state, temps Thu afternoon could
be as much as 15-20F cooler than Wed afternoon. With the above in
mind, have decreased highs to the mid/upper 50s west to lower 60s
Thu night: Expect an increasing potential for rain from west-east
between midnight and sunrise Fri as an upper level low progresses
from the central MS river valley to the Ohio valley and low level
flow backs/strengthens downstream over the Carolinas and Mid-
Atlantic. Lows in the mid 40s to lower 50s, depending on rain
Fri-Fri Night: Confidence in the evolution of the aforementioned
upper level low, attendant sfc cyclone and associated warm/cold
fronts at this range is low to begin with, let alone when a CAD
wedge may be in place at the beginning of the period. All guidance
continues to indicate precipitation, thus have increased precip
chances to high likely (60-70%). From a pattern recognition
standpoint, a potential for severe weather cannot be ruled out,
however, little more can be said at this range in the forecast. The
temperature forecast on Fri/Fri night is challenging to say the
least. At this time will show the coolest temps in the Triad (highs
in the low 60s) and warmest temps in the Sandhills and SE Coastal
Plain (lower 70s). Expect clearing skies in the wake of a cold
frontal passage Fri night, with lows in the upper 40s to mid 50s.
Sat-Sun night: Expect a warming trend with dry conditions Sat in the
wake of the aforementioned upper level low progressing offshore the
Mid-Atlantic coast. A continued warming trend with dry conditions is
expected on Sun as a shortwave ridge aloft tracks into the region
from the west. -Vincent
.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.