Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 011920
Area Forecast Discussion
National Weather Service Raleigh NC
220 PM EST Thu Dec 1 2016
A departing cold front will push off the Southeast coast today.
High pressure will build over the Eastern U.S. from the west today
into the weekend. Upper level disturbances will approach the
eastern U.S. from the north and west on Sunday and from the
southwest on Monday bringing an increasing chance of precipitation
for late Sunday and again late Monday into Tuesday.
.NEAR TERM /THROUGH TONIGHT/...
As of 1115 AM Thursday...
The latest surface analysis shows the cold front now moving off
the Carolina coast as of 16Z. A much drier air mass is moving
into the region as noted by surface dew points that are falling
through the 40s into the 30s as of late morning compared to dew
points in the 60s to near 70 observed 24 hours ago. Deep layer
moisture is also reduced with the precipitable water value at
KGSO from this morning`s 12Z sounding at 0.32 inches. Given large
scale subsidence today and the drier atmosphere, skies will be
clear and sunny today. Cold advection behind the front is not
terribly robust so highs will be cooler than Wednesday but still
above normal. Given the warm start in the east where the front
exited, only a few hours ago, will adjust highs in the central
and southern Coastal Plain upward several degrees into upper 60s.
Highs will range in the lower to mid 60s elsewhere. Northwest
winds will range around 8 to 14 MPH with a few gusts to near 20
The generally clear skies will continue through tonight; however,
a weak shortwave trough located over the Front Range early this
morning is projected to track quickly across VA tonight,
potentially bringing a few high thin clouds as mid level winds
remain rather brisk. Overall, though, expect fair skies at most
overnight, with a slackening MSLP gradient yielding light winds.
Expect lows of 32-39. -GIH
.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
As of 240 AM Thursday...
Forecast soundings show deep dry and stable air across Central NC on
Friday, with a fairly flat and fast mid level flow and high pressure
still building in at the surface, leading to generally sunny skies.
As this southern stream surface high begins to merge with the larger
Canadian high to its NNW, low level thicknesses will drop further on
Friday, to around 10-15 m below normal, so temps should follow suit
with below normal highs of 53-60. High clouds are expected to being
increasing Friday night, spreading in ahead of convection over TX
and the lower Miss Valley (ahead of the digging low over NW Mexico).
These initial high clouds should be thin however as they encounter
the destructive effects of broad ridging over the Gulf States and
Southeast, and thus they should do little to impede radiational
cooling. Lows 30-35. -GIH
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 312 AM Thursday...
The long term will start out dry and cool as high pressure moves
across the Ohio Valley and into the mid-Atlantic states on Saturday
and Saturday night. Expect high temperatures to top out in the low
50s on Saturday with lows in the mid 30s.
Sunday will be a more active and colder day as the high initially
sets up over the eastern half of the state and some lower thickness
values sink down from the north causing highs to be right around 50
degrees with an overcast low to mid level cloud deck. Later in the
day a somewhat disorganized inverted trough pushes northward out of
the deep south and isentropic lift begins to increase Sunday night
as a low tries to develop just offshore. This will lead to
precipitation chances increasing on Sunday with the bulk of the
precipitation with this wave occurring Sunday night and Monday
morning. Expect anywhere form a couple of tenths of rain across the
north to closer to a half inch in the south.
Monday could see a lull in the precipitation between the exiting
wave and a much larger system approaching from the southwest which I
will talk more in depth about in a minute but for Monday a weak high
passing to the north could help to get that pause in precipitation,
especially across the north. Temperatures will be a little warmer as
thicknesses increase. Highs in the low to mid 50s. Lows Monday night
in the upper 30s to near 40 degrees.
Precipitation chances will pick up significantly on Tuesday as
models are in agreement on a Miller B scenario with two low pressure
systems coming at us from the southwest, one will eventually move up
the Carolina coast with the second through the Tennessee Valley.
Diverging upper level flow will move the two lows further apart as
they pass over us but that divergence aloft will also provide some
good lift that will most likely make Tuesday a wash with early
precipitation estimates between an inch and an inch and a half of
rain possible from early Tuesday morning through early Wednesday.
Highs Tuesday in the mid 50s with lows in the low to mid 40s.
Wednesday should see the return of mostly dry weather as the system
lingers offshore. Warmer with highs in the mid to upper 50s across
the NW piedmont and lower 60s in the southeast.
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --As of 220 PM Thursday...
High confidence of VFR conditions through the 24 hour TAF period.
Surface high pressure and a dry airmass will lead to mainly clear
skies and fair weather through Friday afternoon. Westerly surface
winds this afternoon at 6 to 12kts with gusts to 15kts at times
will become light northwesterly overnight before backing to more
westerly on Friday.
Looking beyond the 24 hour TAF period... Fair weather is expected
to continue into the weekend as surface high pressure builds into
the region. Mid and high level cloudiness will increase and
thicken on Saturday and lower and thicken into early Sunday. A
series of upper level disturbances will bring increasing chances
of adverse aviation conditions into the area late Sunday and then
late Monday especially Tuesday. -Blaes
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