Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 150139
Area Forecast Discussion
National Weather Service Raleigh NC
839 PM EST Sat Jan 14 2017
Cool high pressure at the surface will drift offshore tonight.
A cold front will drop southward across central NC on Sunday,
followed by another chilly surface high pressure Sunday night
.NEAR TERM /THROUGH TONIGHT/...
As of 300 PM Saturday...
Little change in our sensible weather tonight. Abundant low level
moisture will aid to maintain a deck of stratus across the region
this evening. A passage of a mid level perturbation late this
evening/overnight will veer the low/mid level flow to a more wly
direction. The downslope component to the flow will help to disperse
the low level clouds. This partial clearing may potentially lead to
the development of fog with pockets of dense fog possible.
Confidence however is not high enough to mention in the forecast nor
issue an advisory. Temperatures tonight will either hold steady or
fall ever so slowly. Min temps will generally be in the mid 40s.
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
AS OF 300 PM Saturday...
Sunday, a strong s/w will cross southern New England/northern Mid-
Atlantic region. The sfc cold front attendant with this feature will
enter our northeast counties by early afternoon and drive southwest,
exiting our southern Piedmont shortly after sunset. Similar to the
last frontal passage, very little if any rain will occur ahead or
along the front. In fact, skies Sunday will be variably cloudy with
peaks of sunshine probable, especially across the Sandhills and
southern coastal plain. This may lead to a wide range in high
temperatures Sunday afternoon, varying from near 50/lower 50s far
northeast to the lower 60s southwest. if sunshine is more prevalent
than current thinking, afternoon temps may end up 3-5 degrees warmer
Sunday night, a dry air sfc ridge will build south along the
Carolina coast. Meanwhile the the flow in the 925-850mb layer will
be veering to a south-southwesterly direction as a waa regime
commences. This will lead to the development of another stratus
layer along with patches of light rain, primarily over the western
Piedmont. This set-up will initiate a hybrid cold air damming event.
Min temps Sunday night will vary from the upper 30s northeast to the
low-mid 40s southwest.
.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 300 PM Saturday...
A 1030-1032 mb surface high will settle over the New England coast
Monday resulting in a CAD wedge over northern and western NC. The
high will shift off the Mid-Atlantic coat Monday night, but the
wedge will remain over northwest portions of the area through
Tuesday, as the return flow from the high offshore and increasing
southerly flow ahead of the approaching front won`t erode it before
then. Meanwhile aloft, the closed low over the Baja will swing
northeast into the Midwest by Monday and toward the Great Lakes
through Monday Night. The aforementioned low will get absorbed in
the northern stream Tuesday while a lingering trough/low remains of
the southwest U.S. The strength of the low/shortwave as it moves
through the Great Lakes and the high ridging over the southeast U.S.
will play an important part in how the weather plays out over
Central NC Tuesday through Thursday. It is even uncertain at this
time when the actual frontal passage will occur. Given all the
uncertainty, the forecast confidence is very low at this time, with
respect to both temperatures and precipitation.
The secondary southern stream low will progress eastward Thursday
through Saturday as a strong upper low approaches the Northwest U.S.
coast, digging a very deep trough over the western U.S. Although
confidence is low, it does appear that another round of
precipitation will occur as the low moves eastward in the Mid-
Atlantic late in the week/early weekend, but exactly when and how
much is far to uncertain to specify at this time.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --AS OF 840 PM Saturday...
MVFR ceilings have steadily eroded from west-east this evening,
scattering out to VFR at all terminals except KRWI where BKN/OVC
ceilings ~1500 ft AGL persisted as of 01Z. Expect RWI to scatter out
to VFR by ~03Z. Expect VFR conditions to prevail for the remainder
of tonight through noon Sunday, though eastern terminals could see
sub-VFR conditions in the form of fog for several hrs prior to
sunrise (08-12Z), particularly the RWI terminal. MVFR ceilings are
expected to return Sunday afternoon/evening in the wake of a back-
door cold front as high pressure into central NC from the N/NE.
MVFR ceilings will persist Sunday night into Monday, when conditions
will likely deteriorate to IFR at the RDU terminal and IFR/LIFR at
the INT/GSO terminals as southerly low-level return flow develops
atop the shallow sfc ridge extending SW into central NC, resulting
in the development of a cold air damming wedge. Conditions may
briefly improve on Tue as the CAD wedge weakens in response to
strengthening southerly flow in advance of a cold front approaching
from the west, before deteriorating Tue night into Wed as low
ceilings/rain overspread the region along/ahead of the cold front,
which is expected to cross central NC Wed afternoon. VFR Conditions
will return to all terminals in the wake of the cold front Wed night
and Thursday. -Vincent
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