Severe Thunderstorm Warning 143, NWS Raleigh, NC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
810 PM EDT TUE JUN 30 2015

.SYNOPSIS...AN INCREASINGLY ACTIVE CYCLONIC FLOW ALOFT WILL PREVAIL
OVER THE REGION THROUGH THE END OF THE WORK WEEK.

&&

.NEAR TERM /TODAY AND TONIGHT/...
AS OF 300 PM TUESDAY...

THE WESTERN HALF OF THE CWA CONTINUES TO BE UNDER A SLIGHT RISK FOR
SEVERE THUNDERSTORMS WITH DAMAGING WINDS THE MOST LIKELY THREAT. THE
SPC HAS ISSUED A MESOSCALE DISCUSSION FOR CENTRAL NC AND INDICATES
THAT A SEVERE THUNDERSTORM WATCH IS POSSIBLE LATER THIS
AFTERNOON/EVENING BUT IT IS UNCLEAR AT THIS TIME HOW CONVECTION
ENTERING UPSTATE SOUTH CAROLINA WILL EVOLVE. SEVERE STORMS ARE
CURRENTLY ONGOING IN THIS AREA WITH SEVERAL REPORTS OF WIND DAMAGE
ALREADY.

WITH A ROBUST SHORTWAVE SUPPLYING THE VORTICITY AND UPPER DIVERGENCE
BEING HELPED BY AN EXITING JET TO THE NORTHEAST...EFFECTIVE SHEAR IN
THE AREA OF CONVECTION HAS BEEN AROUND 30-35 KTS WITH MULTI CELLULAR
CONVECTION STARTING TO EVOLVE INTO LINE SEGMENTS AS OF LAST HOUR.
THIS AMOUNT OF SHEAR IS EXPECTED TO BE MAINTAINED OVER THE NEXT
SEVERAL HOURS BEFORE WEAKENING SLIGHTLY AROUND 00Z. A LOT OF THIS
SHEAR IS WELL OFF THE DECK AND LOW LEVEL SHEAR AND HELICITY VALUES
ARE FAIRLY LOW DURING THE TIME OF CONVECTION LIMITING THE TORNADO
THREAT. ON THE INSTABILITY SIDE OF THINGS...CONVECTION WILL BE
MOVING INTO AN AREA OF 1000-1500 J/KG OF MIXED LAYER CAPE AND
BRINGING WITH IT AN AREA OF 1200-1400 J/KG OF DCAPE. LOW LEVEL LAPSE
RATES AT THIS TIME ARE VERY HIGH WITH A MODERATE 6 DEG/KM OR SO IN
THE MID-LEVELS. WITH CURRENT CONVECTION ALREADY ORGANIZING IT IS NOT
HARD TO ENVISION IT HANGING TOGETHER AS THE VORT MAX MAKES ITS WAY
UP THE PIEDMONT TROUGH. WHILE DIURNAL TIMING MAY NOT YIELD QUITE AS
GOOD OF AN ENVIRONMENT AS THE STORMS ARE CURRENTLY IN...CONFIDENCE
IS FAIRLY GOOD THAT AT LEAST SOME ACTIVITY WILL MOVE INTO THE CWA
FROM THE SOUTHWEST AND PROPAGATE ACROSS THE CWA EXITING SOMETIME
AFTER 5Z OR SO ON WEDNESDAY MORNING. EXPECT THE BEST CHANCE FOR
STRONGER CONVECTION ACROSS THE SOUTHWEST PIEDMONT AND INTO THE
WESTERN SANDHILLS BEFORE STARTING TO WEAKEN AS IT HEADS NORTHEAST.
CONVECTION IS POSSIBLE IN THE TRIAD AS WELL AS ANOTHER LINE OF
STORMS IS BEGINNING TO POP UP ALONG THE FOOTHILLS. ALL OF THIS
ACTIVITY SHOULD TRANSLATE EASTWARD. WHILE THE TRIANGLE MAY NOT GET
THE BRUNT OF THE ACTIVITY...STRONG STORMS ARE CERTAINLY POSSIBLE IN
THIS AREA AS WELL BUT MIGHT BE ON THE NORTHERN FRINGE OF THE
STRONGER ACTIVITY.

OVERNIGHT TONIGHT SKIES SHOULD BEGIN TO CLEAR OUT WITH AN OUTSIDE
CHANCE OF SOME FOG/LOW STRATUS EXISTS IN THE EAST WITH LOWS MID 60S
TO LOWER 70S.

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 300 PM TUESDAY...

ON WEDNESDAY THE UPPER LEVEL TROUGH OVER THE EASTERN CONUS RELAXES A
LITTLE AND A STRONG SURFACE LOW EXITS THE GREAT LAKES REGION TO THE
NORTHEAST AND MOVES INTO SOUTHERN ONTARIO. WITH A GAP IN THE
MOISTURE BEHIND THIS SYSTEM AND AHEAD OF WHAT WILL BE A STRING OF
APPROACHING SHORTWAVES FROM THE MIDWEST...LOOK FOR A RELATIVELY DRY
DAY ON WEDNESDAY WITH AN ISOLATED DIURNAL SHOWER OR THUNDERSTORM
POSSIBLE BUT OTHERWISE DRY. WITH THE BERMUDA HIGH FORCED OFF THE
COAST AND CENTRAL NC SITTING AT THE BASE OF THE UPPER
TROUGH...TEMPERATURES WILL STAY FAIRLY REASONABLE FOR THIS TIME OF
YEAR WITH HIGHS IN THE UPPER 80S NW TO LOW 90S SE. FORECAST
SOUNDINGS DO NOT INDICATE MUCH CHANCE FOR FOG OR LOW STRATUS
THURSDAY MORNING BUT A BROKEN LOW CEILING IS NOT OUT OF THE QUESTION
IN THE EAST BUT CONFIDENCE IN THAT HAPPENING IS VERY LOW AT THIS
TIME.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
AS OF 300 PM TUESDAY...

THE GENERAL OVERALL PATTERN WILL BE DOMINATED BY GENERAL TROUGHINESS
IN THE UPPER LEVELS OVER THE EASTERN U.S. WITH A FEW SHORTWAVE
DISTURBANCES PROGRESSING THROUGH THE AREA. AT THE SURFACE...A WARM
FRONT WILL LIFT NORTH THROUGH NC THURSDAY NIGHT INTO FRIDAY. EXPECT
GENERAL LOW PRESSURE TO LINGER OVER THE SOUTHEAST U.S. AND HIGH
PRESSURE STUCK OVER THE EASTERN GREAT LAKES AND NEW ENGLAND
THEREAFTER. SMALL VARIATIONS IN THIS PATTERN WILL HAVE BIG IMPACTS
ON THE CHANCES...TIMING...AND LOCATION OF CONVECTION...THUS
CONFIDENCE IS NOT TERRIBLY HIGH IN THAT RESPECT. GENERALLY THOUGH...
EXPECT THE USUAL HIGHEST CHANCES IN THE AFT/EVE AND LOWEST
OVERNIGHT/EARLY MORNING. TEMPERATURE WISE: WITH THE EXCEPTION OF
FRIDAY (WHICH FOR NOW APPEARS TO BE THE COOLEST DAY)...HIGHS WILL
GENERALLY BE IN THE UPPER 80S TO LOW 90S THROUGH THE PERIOD...WITH
OVERNIGHT LOWS STEADY IN THE UPPER 60S TO LOW 70S TO SLIGHTLY
INCREASING EARLY NEXT WEEK.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 810 PM TUESDAY...

A BROKEN LINE OF STRONG-SEVERE CONVECTION WILL AFFECT KRDU...KRWI
AND KFAY THROUGH 02Z THEN EITHER EXIT THE REGION OR DIMINISH. IN ITS
WAKE...EXPECT VFR CONDITIONS. AFTER 09Z...THERE MAY BE A SCATTERED
LAYER OF STRATUS WITH BASES 600-1000FT. IF A CEILING DEVELOPS...IT
SHOULD BE BRIEF IN DURATION (LESS THAN AN HOUR).

FOR 12Z WEDNESDAY THROUGH 00Z THURSDAY...EXPECT VFR CONDITIONS AS
CLOUD BASES VARY BETWEEN 4500-6000FT. ANY CONVECTION THAT DEVELOPS
IS EXPECTED TO BE ISOLATED.

FOR THURSDAY AND CONTINUING THROUGH THE HOLIDAY PERIOD...EXPECT AN
UNSETTLED WEATHER PATTERN ACROSS CENTRAL NC AS A SERIES OF UPPER
LEVEL DISTURBANCES INTERACTS WITH THE AVAILABLE MOISTURE AND
INSTABILITY TO GENERATE SCATTERED-NUMEROUS SHOWERS AND T-STORMS AND
ASSOCIATED MVFR CONDITIONS. IN ADDITION...EARLY MORNING STRATUS WITH
LOW END MVFR-IFR CEILINGS WILL LIKELY OCCUR ESPECIALLY FRIDAY
MORNING AND SATURDAY MORNING.

&&

..RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

SYNOPSIS...VINCENT
NEAR TERM...ELLIS
SHORT TERM...ELLIS
LONG TERM...RAH
AVIATION...WSS

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