Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
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FXUS62 KRAH 011115
Area Forecast Discussion
National Weather Service Raleigh NC
615 AM EST Thu Dec 01 2016
-- Changed Discussion --A cold front will move east of the area early this morning. High
pressure will then build over the Eastern U.S. from the west through
the upcoming weekend. An approaching upper level disturbance and
increasing moist flow from the Atlantic and Gulf will bring
increasing rain chances beginning Sunday night.
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.NEAR TERM /today through tonight/...
As of 225 AM Thursday...
The cold front has just cleared the northwest CWA, where clouds have
cleared out, winds have taken on a primarily westerly component, and
dewpoints have fallen into the 40s. Such changes will progress
steadily eastward for the balance of the night, with the remaining
light showers over the eastern Carolinas including our far SE
sections (oriented along the departing 850 mb jet) ending in the
next few hours. The continental surface high that will build in
behind the front from the WSW today is sufficiently modified such
that this initial post-front drop in temps won`t be extreme, with
slightly above normal thicknesses supporting seasonably mild highs
of 59-68 under plentiful sunshine and lighter (yet still
periodically gusty) winds. 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 /12Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --As of 615 AM Thursday...
Conditions have improved to VFR across Central NC, and this is
likely to persist for the next 24 hours. The surface cold front is
currently shifting eastward into the Coastal Plain and should be
exiting the forecast area by mid morning. Surface winds from the SW
ahead of the front shift to WNW behind the front, and should hold at
or under 10 kts today with infrequent gusts to 15-20 kts. Winds will
diminish further after 22z, with VFR conditions holding through
tonight as dry high pressure builds in from the WSW.
Looking beyond 12z early Fri morning, VFR conditions will hold well
into the weekend as the ridge of high pressure builds into the area.
High clouds will spread in from the WSW on Sunday, and these clouds
will thicken with lowering bases to MVFR then IFR Sunday night as an
upper level disturbance approaches from the WSW, in conjunction with
increasing low level moisture from the Atlantic and Gulf. MVFR to
IFR cigs/vsbys will persist through Monday with light rain
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