Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 160817
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
317 AM EST Mon Jan 16 2017

.SYNOPSIS...
High pressure to the northeast will set up cold air damming over
central NC through Monday before a low pressure system approaches
the area midweek.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 317 AM Monday...

Light rain is ongoing across the US-70 corridor early this morning
being caused by some low level isentropic lift as surface high
pressure over the northeast will move southward into an in-situ
damming scenario. This will keep low ceilings locked in for much of,
if not all of the day today and well into the evening. Southern and
eastern locales have the best chance of seeing a return to VFR
conditions today but otherwise expect at least MVFR ceilings to
persist throughout the day. High resolution models keep
precipitation sporadic throughout the day with perhaps the best
chances occurring in the northeast. Expect periods of drizzle and
light rain on and off throughout the day. Temperatures will be
dependent upon the strength of the damming but as is usually the
case with CAD scenarios, we will under cut guidance temperatures
quite a bit. Expect upper 40s to low 50s for highs with lows Tuesday
morning in the low to mid 40s.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 317 AM Monday...

On Tuesday the in-situ CAD will break down and attention will turn
to the west where a low pressure system will track through the Ohio
Valley and into the great lakes region. This will put central NC in
the warm sector ahead of a cold front stretching through Tennessee
and into the lower Mississippi Valley. While a moist airmass will be
in place, there wont be a lot of dynamics to force any real
precipitation threat so expect a slight chance of light showers but
nothing more as main precipitation associated with the approaching
front will remain northwest of the forecast area. High temperatures
will increase considerably into the low to middle 60s from north to
south with lows Wednesday morning only dropping into the low to mid
50s.

&&

.LONG TERM /Wednesday through Sunday/...
As of 310 AM Monday...

This period will feature warm temps and alternating wet and dry
days. Polar air will remain bottled up well to our north, affecting
only eastern Canada and Maine, leaving NC in a mild pattern with low
level thicknesses staying well above seasonal normals. A very wavy
and progressive flow across the southern CONUS will bring bouts of
unsettled weather reminiscent more of early spring than of the heart
of winter.

Wed/Wed night: Areas of rain should be ongoing Wed morning, ahead of
a small but potent shortwave trough that moves from the Ohio Valley
ESE across VA/NC Wed/Wed night. An occluded frontal system ahead of
this wave will shift over and off the mid-Atlantic coast, dragging a
cold front slowly SSE through the state late in the day. Mild WSW
flow ahead of this front should equate to highs in the mid 60s to
near 70 despite abundant cloud cover. Expect good chance to likely
pops, weighted early in the day, exiting to the east in the
afternoon. Cooler lows are likely Wed night with fair skies post-
front, although lows will still be above normal, in the lower to mid
40s.

Thu/Thu night: A brief dry period is expected as the front settles
to our south and a weak continental high builds over the area from
the west, beneath a prominent mid level ridge sitting between the
aforementioned exiting wave and ahead of another strong low/wave
shifting through the central and southern Plains Thu. Fair skies Thu
with increasing clouds late Thu into Thu night. Highs in the upper
50s to lower 60s. Lows in the lower to mid 40s.

Fri/Fri night: High coverage of rain appears likely to return by Fri
morning, as the Plains low/trough tracks ENE, deamplifying but
taking on a negative tilt as it crosses the Mid-South then Ohio
Valley/mid-Atlantic region. Passage of this wave should draw the
surface front back northward as a warm front, with another short
period of shortwave ridging following for Fri night. Highs in the
upper 50s to mid 60s and lows in the mid-upper 40s.

Sat into Sun: The mid level ridging holds over the Southeast on Sat,
along with a light SW low level flow into NC. Models hint at a
potential secondary frontal zone along the Gulf Coast that would, if
it occurs, provide a focus for convection, effectively shutting off
any moisture influx into NC. As such, Sat should be a generally dry
day, with temps once again above normal, peaking in the upper 50s to
lower 60s. By Sun, however, the active southern stream culminates in
a deepening low over the Southern Plains, Gulf States and Mid-
South/W Ohio Valley, with a strong negatively tilted trough
approaching our area from the W and SW. The op GFS and ECMWF differ
a bit with timing but both indicate this general pattern, with a
strong surface low over the mid Miss Valley, a possible occlusion
moving into the western Carolinas, and warm frontogenesis across the
Carolinas. This has the potential to bring a threat of strong storms
late Sun into Sun night. Of course, at this far range, the details
cannot be pinned down, and there is still plenty of uncertainty. But
the op models do have support from the CFS, and the GFS and ECMWF
are fairly close in solution at this range, very surprising
considering that the pertinent features of this pattern are still
well out over the western Pacific and SE Asia and should not, by all
accounts, be very well sampled. Temps should remain above normal
through the weekend. -GIH

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 1244 AM Monday...

24 Hour TAF period: MVFR ceilings beginning to show up across the
CWA this morning and conditions are expected to continue to
deteriorate with IFR conditions if not LIFR ceilings to begin to
show up at least at the Triad sites if not all as in-situ cold air
damming begins to set in across the NW Piedmont. expect light winds
out of the northeast or east through the period. Ceilings are not
expected to lift beyond MVFR levels in most locations on Monday with
the exception of KRWI and possibly KFAY late in the day. Otherwise
will maintain MVFR conditions through the end of the TAF period.
Some light rain will also be possible.

Long term: An active pattern will see several systems cross the area
next week. While no winter precipitation is expected, adverse
aviation conditions due to low ceilings and visibilities are
expected.

&&

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

&&

$$

SYNOPSIS...Ellis
NEAR TERM...Ellis
SHORT TERM...Ellis
LONG TERM...Hartfield
AVIATION...Ellis



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