Area Forecast Discussion
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FXUS62 KRAH 160103
Area Forecast Discussion
National Weather Service Raleigh NC
803 PM EST Sun Jan 15 2017
High pressure positioned over the northern Mid Atlantic will nose
down into North Carolina tonight, persisting over the region
through Monday night. A cold front will approach from the west
.NEAR TERM /THROUGH TONIGHT/...
As of 310 PM Sunday...
Partly-mostly cloudy skies will become overcast by mid-late evening
with patches of light rain probable over the western Piedmont. This
patchy light rain in response to weak isentropic upglide initiated
by the approach of a mid level s/w. This lift expected to be
maximized during the overnight hours over the Piedmont, mainly
centered in vicinity of the Triad.
A parent sfc high (1030mb) positioned over the northern Mid-Atlantic
will nose southward into eastern NC. The return flow over the cool
stable air mass at the surface coupled with the patches of light
rain will aid to initiate another cold air damming episode
overnight. Min temps should vary from the upper 30s northeast to the
low-mid 40s southwest.
.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 310 PM Sunday...
Monday, ongoing CAD will maintain a low overcast deck through the
morning, with patchy light rain and/or drizzle possible across the
northern counties. Temperatures will be slow to recover, especially
across the north half. An end to the spotty light precip and a
gradually lifting of the ceilings will allow temps to rebound into
the lower 50s across the south and the mid-upper 40s across the
north. If ceilings lift sooner or dissipate, potential for afternoon
temperatures to be 5-6 degrees warmer, primarily across the south.
Monday night, expect variable cloudy skies to persist while another
weak perturbation will approach from the west. This feature may
trigger a patch or two of light rain and/or drizzle, mainly over the
western Piedmont. Min temps in the low-mid 40s.
.LONG TERM /TUESDAY THROUGH SUNDAY/...
As of 220 PM Sunday...
Models continue to come into better agreement with the overall
pattern through Friday. There are still small timing issues and
differences in precip chances/timing over central NC. Generally,
expect multiple rounds of wet weather with dry periods in between.
Timing and amounts are still a challenge. The weather could get very
interesting for late next weekend and early the following week.
Tuesday through Wednesday Night: The wedge will probably linger
through early Tuesday, however the models erode it by the aft/eve as
the return flow from the high offshore and the southerly flow ahead
of the approaching front both increase. Meanwhile aloft, the
remnants of a closed low over the Baja gets absorbed into the
northern stream as a shortwave that swings through the Great Lakes
through and into the Mid-Atlantic Wednesday/Wednesday night. The
wave should be strong enough to dampen/suppress the ridge. The
surface low and attendant front will approach the area Tuesday
night, swinging through by late aft/eve Wednesday. As a result,
expect best chances for rain to be late Tuesday through Wednesday
from west to east. Temperatures will be above normal, slightly cooler
in the NW Tuesday (mid to upper 50s), but otherwise expect highs in
the 60s and lows in the mid 50s Tuesday night. With the expected
frontal passage late Wednesday, overnight lows will be lower, mid
40s north to around 50 degrees south.
Thursday through Friday Night: There is surprising agreement between
the models for this period, though there are some differences, the
pattern is similar. Expect two additional rounds of precipitation
during this time, with a period of dry weather in between. A fleeting
surface high and upper level ridge will move through/build over the
area Thursday while another low moves out of the desert southwest
northeast toward the Great Lakes. The moisture advection into the
Gulf coast states Thursday night combined with the sufficient
forcing from the low will result in another round of rain moving
into the Carolinas from the southwest Friday/Friday Night.
Temperatures should be fairly steady during this time, highs in the
upper 50s to mid 60s and lows in the 40s.
Saturday and Sunday: This part of the forecast period gets quite
interesting and the model agreement make it even more ominous.
Although, this far out it is hard to jump on board completely.
Fingers crossed for some changes. As of the latest model runs, a
strong low will come onshore in the Pacific NW Friday/Friday night
digging a trough south and east toward TX Saturday and Sunday. In
the wake of the low that moves through Central NC Friday night, a
ridge builds aloft over the southeast U.S. while the surface low
strengthens over the Midwest. Very strong southerly flow advects
very warm moist air into the Gulf Coast states late in the weekend.
There is a bit of uncertainty whether a CAD wedge will set up and
hold over NC or not and thus temperatures are low confidence, but do
expect increasing chances for rain late Sunday into early in the
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 800 PM Saturday...
24-hr TAF Period: Ceilings should deteriorate between midnight-
sunrise at all terminals, to MVFR at RDU/FAY/RWI and IFR/LIFR at
INT/GSO. Sub-VFR ceilings are expected to prevail through the day at
most terminals Monday, esp INT/GSO where IFR conditions may persist
through the afternoon, as a warm/moist airmass aloft advects atop a
cold/shallow airmass advecting into the region from the NE, and a
cold air damming wedge develops across the N/NW Piedmont. Expect
light NE/ENE winds to veer to the E at ~5kt overnight, then become
light/variable during the day Monday.
Looking Ahead: 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