Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 020742
Area Forecast Discussion
National Weather Service Raleigh NC
240 AM EST Fri Dec 2 2016
High pressure will build over the Eastern U.S. from the west through
the upcoming weekend. An approaching upper level disturbance and
moist flow from the Atlantic and Gulf will bring increasing rain
chances beginning Sunday night.
.NEAR TERM /today through tonight/...
-- Changed Discussion --As of 205 AM Friday...
Another quiet day with high pressure building in at the surface from
the NW, and rising heights aloft as the axis of the broad mid level
ridge shifts eastward over the Southeast states. Forecast soundings
unanimously show a dry and stable column, with the only clouds
likely to be a few high thin clouds resulting from minor high level
moisture within a fast mid-upper flow across the region. Slightly
below normal thicknesses projected today balanced by abundant
sunshine should yield highs close to normal, from the mid 50s to
around 60. High thin clouds will continue to stream into the area
tonight as blowoff from TX convection tops the broad ridge and
srreams into the region. Lows 30-36 under fair skies with light
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.SHORT TERM /Saturday through Saturday night/...
-- Changed Discussion --As of 240 PM Thursday...
The surface ridge, centered over the central Miss Valley early Sat,
shifts NE through the Great Lakes region through Sat night while
continuing to extend SE through NC. Pieces of energy emanating from
the deep low over NW Mexico will slowly break down the ridge as they
ride along its top into NC, resulting in slowly thickening and
lowering clouds, particularly Sat night. Expect mostly sunny skies
early Sat to trend to partly sunny in the afternoon, then to cloudy
Sat night from SW to NE as moist upglide strengthens and deepens in
the mid levels. Expect no pops, however, as the column remains quite
dry below 700 mb. Thicknesses should be slightly lower Sat than on
Fri, suggesting cooler highs in the lower to mid 50s. Increasing
clouds should limit radiational cooling in the SW CWA Sat night,
lesser so in the NE, so expect lows to range from the mid 30s NE to
around 40 SW. -GIH
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.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
As of 335 PM Thursday...
The extended forecast will be characterized by a series of
shortwaves progressing through the central U.S. Though the model
solutions are in much better agreement for Sunday through Tuesday,
significant model differences arise thereafter. As a result,
forecast confidence beyond Tuesday is quite low.
Sunday through Tuesday: An upper level cut-off low over NW Mexico
will usher a good amount of moisture into the Gulf Coast states and
southeast U.S. Sunday while a weak ridge lingers over the east
coast. Meanwhile, a northern stream shortwave over the Midwest will
progress eastward, though the impact it will have on the ridge is a
bit uncertain and will have an impact on the northeastward extent of
the Pacific moisture. The better chance for rain to move into the
region will come Monday and Tuesday as the aforementioned low starts
to move northeast through the Midwest and interacts with another
shortwave traversing a strengthening trough over the Rockies. The
advection of additional moist air being picked up off the Gulf in
the southwesterly flow will result in increasing chances for rain
over the Carolinas. Highs Sunday will still be somewhat cool, upper
40s to low 50s before warming up into the mid to upper 50s Monday
and Tuesday. Lows will generally be in the upper 30s to low 40s.
Wednesday and Thursday: The low should be absorbed into the northern
stream flow by late Tuesday/Tuesday night and the rain should exit
to the east Tuesday night. Though the upper level patterns appear
similar on Wednesday and Thursday, the difference in the strength
and location of the next low/trough is significant. As a result,
forecast uncertainty is high with respect to both weather and
temperatures. Per the GFS...Central NC could get a quick shot of
rain followed by strong cold advection and the chance to see lows in
the low to mid 20s Thursday night. Conversely...the ECMWF is
stronger and slower with the system and given the latest solution,
the rain would be delayed until late Thursday/Thursday night. For
now, will keep this period dry with highs in the mid 50s to low 60s
and lows decreasing from 40s Wednesday night to 20s and 30s Thursday
.AVIATION /06Z Friday through Tuesday/...
As of 1235 AM Friday...
High confidence in VFR conditions for the next 24 hours. High
pressure will continue to build into the region, with deep dry air
as mid level ridging shifts over the Southeast states. Only a few
thin high clouds are expected across the area today through tonight,
and low humidities will result in VFR vsbys. Surface winds will be
light from the NW through daybreak, then from the W or WNW at 8-12
kts through sundown, and light from the NW again tonight.
Looking beyond 06z Sat: High clouds will steadily increase and
thicken with lowering bases to around 10 000 ft AGL through Sat
night, and to around 5 000 ft AGL Sunday with light rain spreading
in late from the SW as an upper level disturbance approaches from
the SW and a surface frontal zone moves in from the south.
Confidence is high that conditions will deteriorate further to IFR
Sunday night and remain poor at IFR or LIFR Monday into Tuesday with
periods of rain and potential low level wind shear. -GIH