Severe Thunderstorm Warning 193, NWS Raleigh, NC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
204 PM EDT TUE JUL 17 2007

.SYNOPSIS...
BERMUDA HIGH PRESSURE OFF THE MID ATLANTIC COAST WILL CONTINUE TO
KEEP WARM AND HUMID CONDITIONS WITH SCATTERED AFTERNOON SHOWERS
AND THUNDERSTORMS OVER THE REGION UNTIL THIS WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
SFC ANALYSIS THIS AFTERNOON SHOWS A BOUNDARY IN THE FORM OF A
MOISTURE DISCONTINUITY STRETCHING FROM NORTHERN VA NORTHWEST THROUGH
WV/OH. AHEAD OF THE BOUNDARY DEWPOINTS WERE IN THE MID/UPPER 60S AND
BEHIND THE BOUNDARY DEWPOINTS WERE IN THE 50S. A WEAK PRESSURE
TROUGH STRETCHED FROM EASTERN PA SOUTH THROUGH CENTRAL/EASTERN
VA/NC. A SHEAR AXIS ASSOC/W A WEAK H5 LOW OVER THE LA/MS AREA
EXTENDS NORTHEAST INTO TN. A BROAD H5 TROF WAS LOCATED OVER THE
GREAT LAKES AND NORTHEAST.

A MODIFIED 12Z GSO SOUNDING THIS MORNING SHOWS A MORE FAVORABLE
THERMODYNAMIC ENVIRONMENT FOR CONVECTION THIS AFTERNOON WHEN
COMPARED TO YESTERDAY. 850-500 MB LAPSE RATES ARE STEEPER (JUST OVER
6C/KM...PRIMARILY IN NORTHERN PORTIONS OF THE AREA) FZL AND WBZ
LEVELS ARE A BIT LOWER AND PWAT VALUES ARE HIGHER. SOUNDINGS THIS
AFTERNOON SHOW AROUND 3000 J/KG OF SFC BASED CAPE WITH TEMPS IN
THE LOWER 90S AND DEWPOINTS IN THE UPPER 60S TO ABOUT 70F. THE WIND
SHIFT ALONG THE NC/VA BORDER EARLIER THIS MORNING IS NO LONGER
APPARENT IN SURFACE OBSERVATIONS...AND MSAS STREAMLINES SHOW SFC
CONVERGENCE OVER THE MOUNTAINS AND A PORTION OF THE COASTAL PLAIN.
ALOFT...IT IS DIFFICULT TO DETERMINE WHAT KIND OF UPPER LEVEL
SUPPORT WILL CROSS THE AREA THIS AFTERNOON. THERE ARE HINTS FROM
THE NAM12 OF ENERGY ASSOC/W EITHER THE SHEAR AXIS WEST/SW OF THE
MOUNTAINS OR WEAK SHORTWAVES ALONG THE BASE OF THE BROAD TROF
AFFECTING CENTRAL NC. WILL KEEP CURRENT 40% POPS AS IS FOR THIS
AFTERNOON...EXPECTING SCATTERED SHOWERS AND THUNDERSTORMS AFTER
18Z GIVEN THE AMOUNT OF INSTABILITY THAT WILL BE AVAILABLE AND THE
POTENTIAL FOR WEAK UPPER LEVEL DISTURBANCES ENHANCING CONVECTIVE
COVERAGE. THERE WILL BE A POTENTIAL FOR ISOLATED SEVERE STORMS
TODAY...WITH A PRIMARY THREAT OF DOWNBURSTS WITH DAMAGING WINDS.

OVERNIGHT TONIGHT...THE 12Z NAM12 BRINGS SEVERAL VORT MAXES ACROSS
THE AREA...AND THE 00Z SPC WRF SIMULATED REFLECTIVITY PRODUCT SEEMS
TO LIKE KEEPING CONVECTION GOING DURING THE OVERNIGHT HOURS ACROSS
CENTRAL NC. FCST SOUNDINGS SHOW AMPLE INSTABILITY OVERNIGHT TO
SUPPORT CONVECTION...THEREFORE WILL INCREASE POPS INTO THE CHANCE
RANGE TONIGHT. LOW TEMPS IN THE MID 70S. -VINCENT

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
BROAD TROUGHING ALOFT CONTINUES OVER THE GREAT LAKES AND NORTHEAST
STATES ON WED/THU...WITH THE TROUGH BEGINNING TO AMPLIFY OVER THE
GREAT LAKES BY LATE THU. THE RIDGE ALOFT OFF THE SE COAST ADVECTS
WEST OVER FL AND THE GULF OF MEXICO WED...WEAKENING BY FRI AS THE
UPPER LEVEL TROUGH OVER THE EAST FURTHER AMPLIFIES. AS FAR AS
SENSIBLE WEATHER IS CONCERNED... WED AND THU LOOK SIMILAR TO TODAY
WITH WARM/MUGGY CONDS AND SCATTERED AFTERNOON SHOWERS/STORMS THAT
MAY LINGER PAST SUNSET UNTIL 06Z. GFS/NAM BUFR FCST SOUNDINGS FOR
WED/THU SHOW JUST AS MUCH OR EVEN MORE INSTABILITY THAN WHAT IS
CURRENTLY OUT THERE TODAY...WITH HIGH TEMPS IN THE 90S AND DEWPOINTS
IN THE UPPER 60S TO LOWER 70S. THU APPEARS THE WARMEST DAY DURING
THE SHORT TERM PERIOD...WITH THE LATEST 12Z MAV/MET GUIDANCE BOTH
INDICATING HIGH TEMPS IN THE 93-97F RANGE. ON FRI...THE GFS SHOWS A
VERY UNCHARACTERISTICALLY DEEP TROF FOR JULY AMPLIFYING INTO THE
MID-ATLANTIC...DRIVING A SFC FRONT THROUGH CENTRAL NC DURING EARLY
AFTERNOON. IF THIS FEATURE VERIFIES...IT WOULD LEAD TO AN ENHANCED
CHANCE FOR WIDESPREAD PRECIP ON FRI...AND A CHANCE FOR ORGANIZED
SEVERE WEATHER AS WELL. HIGH TEMPS TRICKY FOR FRIDAY THIS FAR OUT
WITH THE TIMING/PROSPECT OF A FRONTAL PASSAGE AND WIDESPREAD PRECIP
ACROSS THE AREA. AT THIS TIME WILL CONTINUE TO SHOW HIGH TEMPS IN
THE LOWER 90S. -VINCENT

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
TROUGH EXPECTED TO MOVE THROUGH CENTRAL NORTH CAROLINA FRIDAY NIGHT
WITH THE ATMOSPHERE DRYING BEHIND THE TROUGH. BEYOND THAT THE
DURATION OF ANY RAIN FREE PERIOD IS IN DOUBT. FORECAST MODELS ARE
SCATTERED IN THEIR SOLUTIONS KEEPING CONFIDENCE LOW. AT THIS TIME
WILL FOLLOW THE ECMWF MODEL WITH A DIGGING BAGGY 500 MB TROUGH
THAT IS SLIGHTLY PROGRESSIVE. THIS SHOULD PUT TEMPERATURES A BIT
BELOW NORMAL FOR MOST OF THE PERIOD. ANY WIDESPREAD CONVECTION IS
PROBABLY DEPENDENT ON THE COASTAL TROUGH DRIFTING INLAND... WHICH
SOME MODELS ALLOW DUE TO A STRONG RETROGRADING CLOSED UPPER LOW.
ALTHOUGH THIS SOLUTION IS NOT TOTALLY REJECTED...A MOSTLY DRY
FORECAST SEEMS MORE PLAUSIBLE AT THIS TIME.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
BROKEN CEILINGS AROUND 5000 FEET WILL SPREAD NORTH OVER ALL THE
FORECAST AREA. SCATTERED SHOWERS AND THUNDERSTORMS ARE DEVELOPING AT
THIS TIME AND MOVING NORTHEAST. CONVECTION AGAIN EXPECTED TO
DECREASE SHORTLY AFTER SUNSET...BECOMING ISOLATED BEFORE ENDING NEAR
MIDNIGHT. FOG FORECAST IN ROCKY MOUNT... BUT VISIBILITIES WILL FALL
TO IFR BEFORE DAWN IN LOCATIONS RECEIVING WETTING RAIN THIS
AFTERNOON.

AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS ARE FORECAST THROUGH
FRIDAY. MVFR CONDITIONS IN FOG EACH MORNING WITH POCKETS OF IFR/LIFR
CONDITIONS. BEYOND FRIDAY CONFIDENCE IS LOW. AT THIS TIME FORECAST
IS DRY.

&&

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

&&

SYNOPSIS...VINCENT
NEAR TERM...VINCENT
SHORT TERM...VINCENT
LONG TERM...RLH
AVIATION...RLH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RALEIGH NC
436 AM EDT TUE JUL 17 2007

NCZ007>011-021>028-038>043-073>078-083>086-088-089-180845-
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-
436 AM EDT TUE JUL 17 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL NORTH CAROLINA.

.DAY ONE...TODAY AND TONIGHT.

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP DURING
THE AFTERNOON AN EVENING. A FEW STORMS MAY APPROACH OR BECOME SEVERE...
WITH THE POTENTIAL OF PRODUCING DAMAGING WINDS AND LOCALLY HEAVY
RAINFALL.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. HOWEVER THE THREAT
OF SCATTERED SHOWERS AND THUNDERSTORMS DURING THE AFTERNOONS AND
EVENINGS WILL CONTINUE THROUGH SATURDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ENCOURAGED TO STAY TUNED TO POSSIBLE WARNINGS AND
RELAY SEVERE WEATHER INFORMATION TO THE NATIONAL WEATHER SERVICE.

RA

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