Special Weather Statement, NWS Raleigh, NC

Area Forecast Discussion
National Weather Service Raleigh NC
345 PM EDT Mon Jun 19 2017

.SYNOPSIS...
A cold front will track east across the mountains this evening, then
stall over the Carolinas tonight. The front will gradually dissipate
over the region on Tuesday.

&&

.NEAR TERM /Today and Tonight/...
As of 200 PM Monday...

Overview: A cold front attendant a vertically stacked cyclone in
vicinity of Hudson Bay will track east across the southern
Appalachians this aft/eve, then stall over central NC tonight. Broad
cyclonic flow aloft will develop over the region this afternoon into
tonight as an upper level trough over the upper Great Lakes
progresses eastward into the OH Valley (this aft/eve) and northern
Mid-Atlantic (tonight). Expect an increasing potential for DPVA
attendant small amplitude waves as cyclonic flow aloft becomes
established this evening/tonight.

Environment: An extremely moist airmass is in place across central
NC today, with surface dewpoints ranging from 72-75F and 925 mb
dewpoints near ~20C (68F). Despite the presence of weak mid-level
lapse rates, rich low-level moisture and strong diurnal heating
(highs ranging from the mid/upper 80s W/NW to lower 90s E/SE) will
yield 1500-2500 J/kg of MLCAPE by peak heating. As of 17Z, CINH had
entirely eroded and moderate diurnal destabilization (1500-2000 J/kg
MLCAPE) had been achieved over most of central NC. Isolated
convection cannot be ruled out anywhere through mid-afternoon in
assoc/w mesoscale features such as differential heating boundaries,
the seabreeze and/or outflow from convection that develops along the
seabreeze. The relative best forcing will not arrive until late this
evening/tonight (21-06Z) when the SFC-925 front progresses into the
western Piedmont and small amplitude waves /DPVA/ become more likely
as cyclonic flow aloft strengthens over the region.

Hazardous Weather: Portions of central NC (primarily along/west of
Hwy 1) are in a slight risk for severe thunderstorms this afternoon
and evening. Strengthening westerly wind shear (25-35 knots by 21-
00Z) suggests multicellular organization will predominate, though
transient supercellular organization cannot be ruled out. As
activity develops along the front and/or on the eastern slopes of
the Appalachians by late afternoon, expect convection to grow
upscale via outflow as it progresses across the western Piedmont
toward the Hwy 1 corridor. Moderate instability, moderate DCAPE (750-
1000 J/kg), and high PWAT (~2.00") suggest severe downbursts will be
possible in association with any deep convection this afternoon and
evening, with the greatest potential along/west of Hwy 1 where cold
pool consolidation is most likely to occur in vicinity of peak
heating. Torrential rainfall can be expected with any deep
convection this afternoon through tonight (rainfall rates 1-3" per
hour). Isolated flash flooding will be possible in areas repeatedly
affected by convection, particularly urban, low-lying, and other
flood prone locations. -Vincent

&&

.SHORT TERM /Tuesday and Tuesday night/...
As of 200 PM Monday...

The cold front progressing into the region late this evening is
expected to stall over central NC tonight and persist during the day
Tue, amidst broad cyclonic flow aloft and rich moisture (PWAT
~2.00"). With the above in mind, expect numerous showers/storms in
vicinity of the stalled front Tue/Tue night, primarily east of Hwy 1
and south of Hwy 64. Little potential for convection is expected
north of the front in the far N/NW Piedmont near the VA border where
a drier airmass (PWAT ~1.50" and dewpoints in the lower 60s) is
progged to be in place during the day Tue. However, even in the
northern Piedmont, isold to sct convection will be possible AOA ~00Z
as the front washes out and moisture returns N/NW toward the
Appalachians. With cloud cover and convection, expect highs in the
lower 80s across most of central NC. Lows Tue night should range
from the mid 60s far N/NW to lower 70s far S/SE. -Vincent

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 345 PM EDT Monday...

On the southern periphery of the northern stream trough extending
from Quebec south into the Mid-Atlantic states, a quasi-stationary
frontal zone extending across eastern NC is expected to wash
out/dissipate across the area on Wednesday. The high ~2.0" PWAT
plume is forecast  to shift east and offshore early in the day, with
models showing only weak instability developing across the area
Wednesday afternoon, perhaps hindered by earlier/ongoing morning
convection and associated widespread cloudiness. Wouldn't be
surprise if central NC ended up seeing the best rain chances in the
morning, with pops actually decreasing by the afternoon, especially
west of Interstate-95. Daytime temperatures will be tempered by
clouds and rain chances. Highs in the lower to mid 80s. Lows in the
mid 60s around 70.

May see a brief reprieve from convection/rain on Thursday before
daily rain chances ramp up again Friday and continuing through the
weekend, fueled by strong tropical moisture transport feed and upper
disturbances(potentially convectively induced) between a tropical
low over east Texas/Lower MS Valley(disturbance currently near the
Yucatan Peninsula)and the subtropical high over the western Atlantic.
Eventually the low/remnant circulation center, is forecast to get
picked by the westerlies and attendant sfc cold front approaching
from the west Sunday and into Monday. This set up could lead
to a multi-day heavy rain event with the potential for flooding
across central NC for Friday through Sunday. Will continue to
monitor this heavy rain threat in the days to come. Temperatures
will be greatly influenced by convective rain chances, with highs
ranging from mid 80s to around 90. Lows in upper 60s to lower 70s.

&&

.AVIATION /18Z Monday through Saturday/...
As of 130 PM Monday...

24 Hour TAF period: VFR ceilings (3000-4000 ft AGL) were present
over most of central NC early this afternoon. S/SW winds sustained
at 10-15 mph will gust up to 20-25 mph at times this afternoon and
evening. All terminals are expected to be affected by showers and
thunderstorms late this aft/eve into tonight as a cold front
progresses east of the mountains into the western Piedmont. The
overall best chance for showers/storms will fall roughly between 21Z
this afternoon and 06Z tonight, though convection could persist into
the 06-12Z time frame at eastern terminals. Isolated severe
thunderstorms capable of producing WSW wind gusts up to 50 knots
will be possible between 21-03Z, primarily at the INT/GSO/RDU
terminals.

Looking ahead: The aforementioned front is expected to stall over
central NC tonight, then gradually wash out during the day Tuesday.
Sub-VFR ceilings cannot be ruled out during the pre-dawn /early
morning/ hours each day this week. Diurnal convection will be
possible both Tue/Wed, though primarily at eastern terminals. Early
morning stratus and diurnal convection could potentially affect all
terminals Wed-Sat, though confidence is lower than avg. -Vincent

&&

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

&&

SYNOPSIS...Vincent
NEAR TERM...Vincent
SHORT TERM...Vincent
LONG TERM...CBL
AVIATION...Vincent

Hazardous Weather Outlook...UPDATED
National Weather Service Raleigh NC
808 AM EDT Mon Jun 19 2017

NCZ007>011-021>028-038>043-073>078-083>086-088-089-201215-
Person-Granville-Vance-Warren-Halifax-Forsyth-Guilford-Alamance-
Orange-Durham-Franklin-Nash-Edgecombe-Davidson-Randolph-Chatham-Wake-
Johnston-Wilson-Stanly-Montgomery-Moore-Lee-Harnett-Wayne-Anson-
Richmond-Scotland-Hoke-Cumberland-Sampson-
808 AM EDT Mon Jun 19 2017

This Hazardous Weather Outlook is for central North Carolina.

.DAY ONE...Today and Tonight.

There is a slight risk for severe thunderstorms across central North
Carolina late this afternoon and evening. Showers and thunderstorms
will develop along and ahead of a cold front as it tracks east of the
mountains later today. Isolated severe thunderstorms capable of
producing damaging wind gusts and hail up to the size of quarters
will be possible as activity progresses east across central North
Carolina late this afternoon and evening, primarily between 3 pm
this afternoon and 11 pm this evening.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Heavy rain will be possible early this week and again late this week
into this weekend. Isolated flash flooding will be possible in areas
repeatedly affected by heavy rain.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening.

Special Weather Statement
National Weather Service Raleigh NC
311 PM EDT MON JUN 19 2017

NCZ041-192000-
Wake NC-
311 PM EDT MON JUN 19 2017

...A strong thunderstorm will affect portions of central Wake County
Until 400 PM EDT...

At 311 PM EDT, Doppler radar was tracking a strong thunderstorm 4
miles west of Garner, or 7 miles southeast of Cary, moving northeast
at 25 mph.

Wind gusts up to 50 mph will be possible with this storm.

Locations impacted include...
Raleigh, Cary, Wake Forest, Garner, Knightdale, Rolesville, Lake
Wheeler, Falls Lake Boat Ramp, Purnell and Lake Benson.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Seek shelter in a nearby building or vehicle. Wind gusts as high as
50 mph are capable of knocking down small or weakened trees and
blowing around trash cans, potted plants, lawn furniture and other
light outdoor objects.

Torrential rainfall is occurring with this storm. If driving, slow
down and exercise additional caution to avoid hydroplaning.

&&

LAT...LON 3599 7846 3598 7843 3594 7839 3593 7835
      3592 7835 3563 7862 3561 7869 3566 7880
      3572 7881 3605 7863
TIME...MOT...LOC 1911Z 210DEG 22KT 3571 7871

VINCENT

Special Weather Statement
National Weather Service Raleigh NC
315 PM EDT MON JUN 19 2017

NCZ041-042-077-192000-
Johnston NC-Harnett NC-Wake NC-
315 PM EDT MON JUN 19 2017

...A strong thunderstorm will affect portions of west central
Johnston...northeastern Harnett and south central Wake Counties
Until 400 PM EDT...

At 314 PM EDT, Doppler radar was tracking a strong thunderstorm 4
miles northeast of Lillington, moving northeast at 20 mph.

Wind gusts up to 50 mph will be possible with this storm.

Locations impacted include...
Lillington, Clayton, Angier, Coats, Coats Crossroads, Buies Creek and
Raven Rock State Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Seek shelter in a nearby building or vehicle. Wind gusts as high as
50 mph are capable of knocking down small or weakened trees and
blowing around trash cans, potted plants, lawn furniture and other
light outdoor objects.

Torrential rainfall is occurring with this storm. If driving, slow
down and exercise additional caution to avoid hydroplaning.

&&

LAT...LON 3536 7877 3537 7881 3544 7887 3547 7888
      3550 7884 3563 7864 3566 7857 3568 7850
      3565 7846 3555 7838 3552 7838 3548 7842
      3537 7869
TIME...MOT...LOC 1914Z 235DEG 18KT 3545 7876

VINCENT

Special Weather Statement
National Weather Service Raleigh NC
359 PM EDT MON JUN 19 2017

NCZ026-027-192045-
Nash NC-Franklin NC-
359 PM EDT MON JUN 19 2017

...A strong thunderstorm will affect portions of western Nash and
eastern Franklin Counties Until 445 PM EDT...

At 359 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles south of Bunn, or 16 miles southwest of Nashville, moving
northeast at 35 mph.

Wind gusts up to 50 mph will be possible with this storm.

Locations impacted include...
Nashville, Bunn, Red Oak, Spring Hope, Middlesex, Castalia, Pilot and
Aventon.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Seek shelter in a nearby building or vehicle. Wind gusts as high as
50 mph are capable of knocking down small or weakened trees and
blowing around trash cans, potted plants, lawn furniture and other
light outdoor objects.

&&

LAT...LON 3621 7801 3618 7798 3619 7797 3618 7795
      3619 7794 3618 7793 3619 7792 3617 7792
      3616 7790 3614 7789 3614 7782 3583 7810
      3577 7819 3579 7824 3587 7828 3590 7831
      3622 7807
TIME...MOT...LOC 1959Z 218DEG 29KT 3587 7822

VINCENT

Special Weather Statement
National Weather Service Raleigh NC
400 PM EDT MON JUN 19 2017

NCZ010-026-192030-
Franklin NC-Warren NC-
400 PM EDT MON JUN 19 2017

...A strong thunderstorm will affect portions of Franklin and
southwestern Warren Counties Until 430 PM EDT...

At 400 PM EDT, Doppler radar was tracking a strong thunderstorm 5
miles southwest of Louisburg, moving northeast at 40 mph.

Wind gusts up to 50 mph will be possible with this storm.

Locations impacted include...
Louisburg, Youngsville, Centerville, Afton and Ingleside.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Seek shelter in a nearby building or vehicle. Wind gusts as high as
50 mph are capable of knocking down small or weakened trees and
blowing around trash cans, potted plants, lawn furniture and other
light outdoor objects.

&&

LAT...LON 3638 7814 3631 7800 3623 7803 3596 7828
      3594 7835 3601 7847 3604 7849 3607 7847
      3639 7820
TIME...MOT...LOC 2000Z 214DEG 36KT 3604 7837

VINCENT

Special Weather Statement
National Weather Service Raleigh NC
414 PM EDT MON JUN 19 2017

NCZ042-077-192115-
Johnston NC-Harnett NC-
414 PM EDT MON JUN 19 2017

...a strong thunderstorm will affect portions of southern Johnston
and southeastern Harnett Counties Until 515 PM EDT...

At 411 PM EDT, Doppler radar was tracking a strong thunderstorm near
Dunn, or 8 miles east of Lillington, moving east at 25 mph.

Wind gusts up to 45 mph will be possible with this storm.

Locations impacted include...
Smithfield, Dunn, Benson, Micro, Selma, Erwin, Coats, Four Oaks, Pine
Level and Coats Crossroads.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Seek shelter in a nearby building or vehicle. Wind gusts as high as
45 mph are capable of knocking down small or weakened trees and
blowing around trash cans, potted plants, lawn furniture and other
light outdoor objects.

Locally heavy rain may also result in minor flooding of creeks,
streams, and areas of poor drainage.

&&

LAT...LON 3532 7882 3543 7875 3561 7850 3557 7821
      3535 7817 3534 7822 3533 7823 3530 7853
      3532 7854 3529 7859 3527 7871
TIME...MOT...LOC 2011Z 250DEG 22KT 3537 7867

26

Special Weather Statement
National Weather Service Raleigh NC
440 PM EDT MON JUN 19 2017

NCZ007>010-024-025-040-041-076-192130-
Lee NC-Chatham NC-Vance NC-Durham NC-Wake NC-Person NC-Warren NC-
Granville NC-Orange NC-
440 PM EDT MON JUN 19 2017

...A ragged line of showers and scattered strong thunderstorms will
affect portions of central Lee... eastern Chatham...Vance...
Durham...northwestern Wake...southern Person...northern
Warren...Granville and southern Orange Counties Until 530 PM EDT...

At 435 PM EDT, Doppler radar was tracking a line of showers and
thunderstorms stretching from Sanford in Lee county north across
Durham all the way to the Virginia border north of Oxford. These
storms were moving northeast at 30 mph.

Wind gusts up to 40 mph and very heavy rain may be expected with
stronger storms. Evening commuters should be alert for reduced
visibility in heavy rain and water on the road. Slow down to avoid
hydroplaning.

Locations impacted include...
West Raleigh, Durham, Cary, Chapel Hill, Sanford, Henderson, Oxford,
Creedmoor, Pittsboro and Carrboro.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If on or near Jordan Lake and Falls Lake, be alert for these storms
and be prepared to seek safety.  Do not be caught on the water in a
thunderstorm.

&&

LAT...LON 3653 7817 3539 7919 3548 7936 3548 7935
      3550 7934 3552 7935 3552 7940 3654 7865
      3655 7823
TIME...MOT...LOC 2035Z 218DEG 26KT 3601 7881

13