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000
FXUS62 KRAH 271854
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
255 PM EDT Thu Jul 27 2017

.SYNOPSIS...
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A cold front will approach from the northwest tonight, and cross
our region late Friday night.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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As of 255 PM Thursday...

Little change required to the near term forecast. Highest threat for
scattered convection still appears to be across sections of the
northwest Piedmont through 01Z.

Atmosphere has become moderately unstable as sfc dewpoints have
rebounded into the lower 70s. A pocket of slightly enhanced winds in
the 850-700mb layer is projected to increase the effective bulk
shear in vicinity of the VA border to around 30kts by late
afternoon. This hear coupled with the available buoyancy should lead
to the initiation/maintenance of scattered convection late this
afternoon into the first half of the evening. The convective threat
appears best along and north of I-85, and much less so to the south
and southeast of Raleigh. DCAPE values have improved from what was
expected earlier today, increasing the probability of strong or
locally damaging wind gusts with the stronger storms.

After 01Z, may see isolated/scattered convection drift east into
sections of the northeast Piedmont and northern coastal plain though
the convection should be weaker in intensity. A series of weak
perturbations aloft may maintain a few showers/isolated storms into
the overnight, mainly north of highway 64.
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&&

.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
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As of 255 PM Thursday...

A lingering mid level shear axis overhead is expected to become
reinvigorated late Friday into Friday night with the approach of a
strong s/w diving sewd from the Great Lakes into the northern mid-
Atlantic. This feature will interact with available instability and
shear to produce scattered-numerous convection, essentially from
late Friday morning into Friday night. Effective bulk shear weak at
best at the inset though this is expected to improve by early Friday
evening, leading to a threat for broken/bowing convective segments
and attendant damaging wind threat. This scenario is based on an
atmosphere that will have adequate heating prior to the arrival of
the upper dynamics. The degree of convection overnight tonight
through early Friday morning will play a role in the
coverage/intensity of convection Friday afternoon and evening. If
scattered/numerous showers-storms are in progress early Friday, it
may hinder the ability of the atmosphere to achieve optimum
instability by the time the better dynamics aloft arrive late Friday
into Friday evening, limiting the potential for scattered severe
storms.

A sfc cold front associated with the s/w crossing into the northern
mid Atlantic will approach central NC late Friday, and enter the
Piedmont counties Friday night, slowly edging sewd into early
Saturday. This feature will maintain a decent threat for showers and
a t-storm or two, primarily south and east of Raleigh overnight
Friday night.

High temperatures Friday dependent upon the convective coverage
Friday morning, and when convection re-develops Friday afternoon.
Expect the hottest temperatures to occur across the Sandhills and
southern coastal plain where near 90-lower 90s expected. Extensive
cloud coverage and good potential for scattered convection will
likely hold temperatures in the 80s across the northern Piedmont.
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.LONG TERM /SATURDAY THROUGH THURSDAY/...
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As of 230 PM Thursday...

The surface front will be in vicinity of the coastal plain Saturday
morning, with deep moisture and precip coverage on the decline as
low level flow shifts westerly. As such, will taper off morning PoPs
in the east from 60% to 30% by afternoon, with only slight chances
elsewhere. Initial cool air advection will be underway behind the
front, with highs Saturday ranging from low 80s north to mid 80s
south. The cool air will surge south Saturday night as the upper
trof rotates through, and the strong mid level forcing will spawn
scattered convection Saturday night, mainly across the northeast.
Mins Saturday night will be mostly in the mid 60s, and Sunday`s
highs will be downright pleasant, with lower humidity to accompany
temps mostly in the lower 80s, with some locations in the northeast
perhaps topping out in the upper 70s.

The cutoff low lifts northeast Sunday night and Monday, and the
remainder of the extended at least through Wednesday will be dry as
surface high pressure building into the Ohio Valley delays moisture
return into the area. Gradual extension of the Bermuda high into the
northern Gulf will eventually prevail, beginning with warm air
advection on Wednesday, to be accompanied by the return of moisture
laden air on Thursday. As such, a gradual warm-up is expected through
the week, with highs Monday mostly in the mid 80s, rising into the
upper 80s Tuesday and Wednesday, and back to the upper 80s/lower 90s
on Thursday. Morning mins will follow the trend as well, from mostly
mid 60s Monday morning to around 70 by Thursday morning.
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&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
As of 105 PM Thursday...

While VFR parameters will prevail across much of central NC through
this evening, scattered convection and associated MVFR parameters
will threaten the Triad terminals primarily between 20Z-01Z. While
the bulk of the scattered convection will dissipate by mid evening,
a few showers will likely drift across the northern counties into
the overnight.

Additional scattered convection and associated MVFR parameters
appear likely across central NC Friday through Friday night as a sfc
cold front drifts southward. Areas of MVFR ceilings and a few
showers are possible Saturday as the main upper trough drifts across
the region. A drier, more stable atmosphere and attendant VFR
parameters expected Sunday through Tuesday.

&&

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

&&

$$

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