Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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929
FXUS62 KRAH 221440
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
1040 AM EDT Sun Oct 22 2017

.SYNOPSIS...
High pressure will extend across the eastern United States through
tonight. Meanwhile, a strong frontal system will approach from the
west and cross the Appalachians and Carolinas late Mon through early
Tue.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1040 AM Sunday...

Little adjustment required to the near term forecast.

Mid/upper level ridge has moved offshore while the sfc ridge axis
remains across our area. Narrow band of fog/low clouds across
portions of the western-southern Piedmont will disperse by mid day.
Expect mostly sunny skies through most of the afternoon, with a
notable increase in high level cloudiness, especially across the
Piedmont. Temperatures on track to reach well into the 70s across
the north, and near 80-lower 80s across the south. These
temperatures are a solid 7-10 degrees above normal.

Clouds will continue to increase and thicken tonight as a s/w
deepens and becomes a closed low over the western TN Valley by early
Monday. Strengthening isentropic upglide ahead of this system may
generate a shower or two late tonight in vicinity of the Yadkin/Pee
Dee River Valley. Southerly flow and thickening cloud cover will
yield overnight temperatures mainly in the 55-60 degree range.

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
As of 330 AM Sunday...

A vigorous cutoff shortwave will lift northeast up the Appalachians
into the mid Atlantic as it is reabsorbed into a longwave trof
digging southeast across the Great Lakes. Low level flow will be
increasing and providing a strong moisture feed into the southern
mountains early Monday, with low level jetting increasing to exceed
50 knots as the flow veers increasingly southerly and begins
marching east ahead of an associated surface cold front. While
instability will be limited by cloudiness and numerous prefrontal
showers, low level convergence in the frontal zone will be very
strong and a line of vigorous convection is expected in the west
during the afternoon, which will move east to reach the Coastal
Plain after midnight Monday night.

The strong low level flow could be translated to the surface by
convective activity, so damaging winds will be possible, especially
in the convective line accompanying the front. In addition, the low
level shear profile would support rotation in stronger storms, so
isolated tornadoes cannot be ruled out. Highs Monday will be mild
despite cloudiness and shower activity due to strong warm air
advection, reaching mostly mid and upper 70s with some lower 70s in
the far western Piedmont. Mixing and warm southerly flow overnight
will maintain mild mins in the mid 50s northwest to lower 60s east.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 233 AM Sunday...

Low level jetting will be moving east of the Coastal Plain early on
Tuesday morning, with drier and cooler air beginning to filter in as
the moisture tap is cut off. Cloudiness will be diminishing, but low
level cold air advection will be delayed until later in the day as
the lagging surface front crosses the area. Highs will have time to
reach mostly low 70s with some upper 60s in the northwest where cold
air advection will begin earlier and there will be additional
potential for stratocumulus accompanying the cool surge. With the
cool air settling into place, mins Tuesday night will fall to the
mid and upper 40s.

An additional reinforcing surge of cool air is expected Wednesday as
strong shortwave energy digs into the Midwest trof, shifting it
across the Ohio Valley, with the axis moving across the south
Atlantic coast Wednesday night. Highs Wednesday and Thursday will be
mostly in the low and mid 60s, with morning mins Thursday morning in
the upper 30s to lower 40s.

Shortwave ridging and return flow as associated surface high
pressure moves offshore will give us a warmup late in the week, with
highs Friday and Saturday mostly in the mid 60s to lower 70s.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
As of 1040 AM Sunday...

Under the continued influence of high pressure along the middle
Atlantic coast, generally VFR conditions are expected to persist for
most of the forecast period, with one exception. Increasingly moist
east to sely low level flow off the Atlantic ocean will favor the
development of IFR-MVFR ceilings mainly at wrn TAF sites (INT/GSO),
and perhaps some visibility restrictions in fog at ern TAF sites
where radiational cooling potential will linger, late tonight-early
Mon.

Outlook: An approaching frontal system will then result in the ewd
progression of a band of IFR-MVFR ceilings, showers and isolated
storms (some possibly severe), and strong/veering winds with height
late Mon and Mon night.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...MWS
NEAR TERM...WSS
SHORT TERM...mlm
LONG TERM...mlm
AVIATION...MWS



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