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000
FXUS62 KRAH 192008
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
406 PM EDT Tue Jun 19 2018

.SYNOPSIS...
A ridge of high pressure over the southeastern United States
will shift south but largely persist through the work week. A
cold front will drift int the region on Wednesday and linger
through Thursday before lifting north late Friday.


.NEAR TERM /THROUGH TONIGHT/...
As of 220 PM Tuesday...

...Heat Advisory in Effect through 8 PM this evening and for 11
AM to 9 PM Wednesday for the Sandhills, the southern Coastal
Plain and the eastern Piedmont...

Latest surface analysis shows surface high pressure centered
across the TN Valley with a surface trough extending from the
DELMARVA Peninsula southwest across the eastern Piedmont of the
Carolinas. In addition, a cold front was analyzed from the
eastern shore of VA/MD west across VA into the OH Valley.

The air mass across central NC is moderately unstable with
MLCAPE values averaging between 1000 to 1500 J/Kg, perhaps a
little more across the east/southeast. The atmosphere is warm
today with H5 temperatures around -5C and the warm mid levels
will result in meager mid-level lapse rates of around 5.5. In
contrast, deep mixing has resulted in DCAPE values ranging from
1000-1300 J/kg, greatest in the east.

Satellite imagery shows limited cumulus development this afternoon
with the greatest coverage and depth across the Sandhills and
southern Coastal Plain. The degree of convective development and
more importantly, the evolution and movement of features
developing outside of central NC is difficult. In general, we
still expect less convective coverage than previous days as
larger scale forcing mechanisms are lacking.

However, isolated thunderstorms are likely to develop in the
Sandhills and southern Coastal Plain, especially near the NC/SC
border in a region of slightly better low-level convergence.
Regional radar imagery is already showing scattered
thunderstorms developing across the VA and especially NC
mountains that are moving southeast in the northwest flow aloft.
These storms may impact the western Piedmont later this
evening. Finally, more widespread convection is likely develop
across VA late this afternoon ahead of a southward advancing
cold front. The convection or weakened remnants will move south
and reach the northern Piedmont and Coastal Plain toward
midnight and slip southeast. While the upper flow is weak and
convection will likely be unorganized, there is the potential
for a damaging downburst given the steep low level lapse rates
and high DCAPE. While perhaps limited in coverage, some
convection may still be ongoing late into the evening or early
overnight hours. Lows tonight will range between 73 and 78, near
record high minimums. -Blaes

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 315 PM Tuesday...

The upper-level ridge shifts south on Wednesday and Wednesday
night resulting in falling heights across the Carolinas. As the
ridge shifts south, the westerlies aloft strengthen across the
area and a progressive short wave trough moves from the OH
Valley into the mid-Atlantic during the afternoon and evening.
In addition, the southward advancing cold front across the mid-
Atlantic should have reached the northern/northeastern part of
the CWA by Wednesday morning and stalled with convective
outflow from tonight`s convection likely extending further
southwest into the RAH CWA.

Expect scattered showers and storms to develop again on Wednesday,
with the greatest coverage across the northern and northeastern
portion of the CWA, in proximity to the surface boundary.
Stronger flow aloft will result in 0-6km shear of 20-30 kts
which combined with a weak to moderately unstable air mass,
could result in some storm organization in the form of some
multicells and clusters and the risk of a few strong to severe
storms across the northeastern counties.

Low-level thicknesses and H8 temperature relax a bit on Wednesday
as the ridge shifts south. Highs on Wednesday should range a
couple of degrees cooler than today with highs on Wednesday in
the lower 90s north to mid 90s south. Heat index values will
approach criteria again on Wednesday afternoon across the
southeast. Removed Halifax, Edgecombe, Nash and Franklin from
the advisory tomorrow as the cooler air mass near the front
should hold temps back in those area. Still muggy on Wednesday
night with lows in the 72 to 77 range. -Blaes

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
As of 350 AM Tuesday...

Low-level thicknesses and H8 temps begin to wane Wednesday in
response to the de-amplifying and southward suppression of the the
mid/upper level ridge into the Deep South/eastern GOM. Thus,
highs Wednesday should average a few degrees cooler than
today. Highs ranging from lower 90s north to mid 90s south.
When combined with the 70 degree dewpoints, heat indices across the
Sandhills and southern and central Coastal Plain counties will once
again range between 103 to 107 degrees. As such, we will likely
need to issue another heat advisory on Wednesday for much of the
same area.

Isolated to scattered diurnal convection should once
again develop near the lee surface trough Wednesday afternoon.
The northern/northeastern tier counties have the potential
to see a period of likely pops during the late afternoon/early
evening, where closer proximity to a quasi-stationary west-east
frontal boundary and associated convection/outflow
extending across the Mid-Atlantic region could propagate
south into the area. Enhanced sheared to the north along the front,
could result a few strong to severe storms across the northeastern
counties.

Lows Wednesday night in the lower to mid 70s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
As of 400 PM Tuesday...

Pattern overview: A complex mid-upr level low over the nrn/cntl
Rockies will amplify sewd across the cntl Plains through Thu, then
reach the mid MS Valley by 12Z Fri. Preceding, and influenced by
that low, a portion of a mid level low now over srn TX will
eject/shear shear newd across the TN Valley Thu, and srn and cntl
Appalachians Thu night. The models indicate the parent low
amplifying from the nrn Rockies to the mid MS Valley will then lift
newd across the OH Valley and lwr Great Lakes on Sat, with
associated glancing forcing for ascent and seasonably strong, 30-40
kts of swly mid level flow forecast Sat over cntl NC. Modest, quasi-
zonal to broadly cyclonic flow aloft will then prevail across NC
ahead of a strong nrn stream shortwave trough forecast to sweep off
the Northeast and nrn middle Atlantic coast on Mon. Following
ridging aloft is then forecast to build from the lwr MS Valley to
the cntl Appalachians through the middle of the week.

At the surface, the synoptic frontal zone now draped from the middle
Atlantic coast wwd across the OH Valley, will settle swd and
merge/overtake a preceding lee low over NC Thu, then become quasi-
stationary in the vicinity of cntl/ern NC Thu night-Fri. This
frontal zone will then retreat nwd once again with subsequent
Appalachian-lee troughing through the weekend. A following cold
front is then forecast to cross the srn middle Atlantic states on
Mon, followed by high pressure that may curb the heat and humidity
by Tue. But the likelihood of a front making a complete passage
through NC this time of year is relatively low, as is predictability
in general at Day 7.

Sensible weather: Above average temperatures are most likely to be
interrupted behind the aforementioned two (partial) frontal
passages, on Fri and Tue. Precipitation/convective chances will also
be maximized along those fronts, particularly late Thu-Fri.
Environmental shear in the presence of the front Fri may also favor
a semi-organized storm mode and marginal risk of severe weather
during that time. Mainly diurnal convection, with slight to low
chances, is otherwise anticipated throughout the period.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
As of 205 PM Tuesday...

24 Hour TAF Period: Isolated thunderstorms will develop near the
NC/SC border this afternoon, potentially impacting the FAY terminal
through early this evening. In addition, scattered thunderstorms
developing across the NC/VA mountains may drift southeast into the
northwestern and northern Piedmont later this evening. Finally, more
widespread convection is likely develop across VA late this
afternoon and move south with the weakening remnants pushing into
the northern Piedmont and Coastal Plain after midnight with possibly
VFR CIGs and a small chance of convection. Outside of these lower
end possibilities, VFR conditions are expected across most of the
area through the TAF period. There is a limited threat of some SCT-
BKN stratus or patchy fog across the northeast toward daybreak as
well.

Outlook: The chances of adverse aviation conditions with scattered,
mainly afternoon and evening showers and thunderstorms will increase
on Wednesday through the weekend as a cold front approaches and then
lingers near or just north of the region. -Blaes

&&

.CLIMATE...
Max temperature and high-minimum temperature records...

GSO:
          REC             HI
DAY       MAX    YR      MIN     YR

06/19     100    1944     77    1970
06/20     100    1924     75    2009
06/21     100    1933     75    1924
06/22     100    1914     75    1981

-------------------------------------

RDU:
          REC              HI
DAY       MAX     YR      MIN     YR

06/19     102    1944      73    2010
06/20     102    1887      77    1924
06/21     101    1933      75    1933
06/22     100    1981      78    1933

-------------------------------------

FAY:
          REC             HI
DAY       MAX    YR       MIN     YR

06/19     102    1944      77    2017
06/20     102    1970      77    2009
06/21     105    1933      84    1928
06/22     101    1990      84    1928

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT this evening for NCZ010-011-
026>028-041>043-075>078-084>086-088-089.
Heat Advisory from 11 AM to 8 PM EDT Wednesday for NCZ041>043-
075>078-085-086-088-089.

&&

$$
SYNOPSIS...BLAES
NEAR TERM...BLAES
SHORT TERM...BLAES
LONG TERM...MWS
AVIATION...BLAES
CLIMATE...KCP