Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KRAH 011142
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
745 AM EDT FRI AUG 1 2014

.SYNOPSIS...A PROLONGED PERIOD OF UNSETTLED WEATHER CAN BE EXPECTED
THROUGH EARLY NEXT WEEK AS AN UPPER LEVEL TROUGH SLOWLY APPROACHES
FROM THE WEST.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 330 AM FRIDAY...

...LOCALLY EXCESSIVE RAINFALL PROBABLE TODAY THROUGH SATURDAY NIGHT
MAINLY EAST OF HIGHWAY 1...

MOISTURE RICH AIR MASS ADVECTING INTO CENTRAL NC THIS MORNING AS
EVIDENT OF SATELLITE BLENDED TOTAL PRECIP WATER IMAGERY DEPICTING PW
VALUES AROUND 2 INCHES IN VICINITY OF NC/SC BORDER LIFTING SLOWLY
NWD. ALSO...WATER VAPOR IMAGERY DEPICTS A NICE PLUME OF TROPICAL
MOISTURE ORIGINATING IN THE YUCATAN CHANNEL/SOUTHERN GULF EXTENDING
NEWD TO THE SE U.S. COAST. L/W TROUGH OVER THE MS VALLEY DIGGIN SWD
THANKS TO A SERIES OF S/WS DIVING SEWD OVER THE PLAINS STATES THIS
MORNING. LEAD S/W THAT WAS OVER THE SOUTHERN PLAINS/RED RIVER VALLEY
THIS TIME YESTERDAY LIFTING NEWD ACROSS THE SOUTHERN APPALACHIANS
THIS MORNING. THIS FEATURE COUPLED WITH SFC-850MB FLOW OUT OF THE E-
SE (UPSLOPE COMPONENT) WILL FOCUS AREAS OF RAIN (AT TIMES HEAVY)
OVER WESTERN NC...EXTENDING AS FAR EAST AS OUR WESTERN PIEDMONT
COUNTIES THIS MORNING. CLOSER TO THE COAST...AN INVERTED SURFACE
TROUGH WILL SLOWLY RETROGRADE...EVENTUALLY TAKING UP A POSITION OVER
THE INLAND COASTAL PLAIN (JUST EAST OF I-95) LATE THIS AFTERNOON.
THIS FEATURE TOO WILL BE A FOCUS FOR CONVECTIVE DEVELOPMENT THIS
MORNING DUE TO ENHANCE LOW LEVEL SPEED CONVERGENCE.

THIS WILL LEAVE THE HIGHWAY 1 CORRIDOR BRACKETED BY TWO ENHANCED
REGIONS OF PRECIP THIS MORNING WITH SHOWERS AND SCATTERED T-STORMS
TO OUR IMMEDIATE EAST-SE...AND WIDESPREAD RAIN TO OUR WEST-SW. FOR
THIS MORNING...PLAN TO HAVE LIKELY POPS OVER THE EASTERN SANDHILLS
AND SOUTHERN COASTAL PLAIN...AND OVER THE WESTERN PIEDMONT...WITH
HIGH CHANCE POPS ALONG THE HIGHWAY 1 CORRIDOR.

LATER THIS AFTERNOON...S/W WILL EXIT THE SOUTHERN APPALACHIANS. THIS
SHOULD LEAD TO DECREASE IN PRECIP COVERAGE AND INTENSITY OVER OUR
WESTERN PIEDMONT. IN THE EAST...SLOWLY RETROGRADING SFC TROUGH
COUPLED WITH HEATING AND ADDITIONAL LIFT IN THE RIGHT ENTRANCE
REGION OF A 75-80KT 300MB JET SHOULD TRIGGER NUMEROUS SHOWERS WITH
SCATTERED THUNDERSTORMS. POTENTIAL FOR SOME SHOWERS/STORMS TO TRAIN
ACROSS THE SAME LOCATION WHICH WILL LEAD TO LOCALLY HEAVY/EXCESSIVE
RAINFALL. ALSO...A STORM OR TWO WILL HAVE THE POTENTIAL TO BE
STRONG/SEVERE AS BULK SHEAR WILL BE 35-45 KTS (SUPPORTIVE OF
ORGANIZED CONVECTION). INSTABILITY RATHER MEAGER FOR EARLY AUGUST
(MLCAPE 5000-1000 J/KG) BUT SHEAR MORE THAN SUFFICIENT TO OVERCOME
THIS LIMITATION. MAIN WEATHER HAZARD (ASIDE FROM HEAVY RAIN) WILL BE
DAMAGING WIND GUSTS. LOW LEVEL HELICITY WILL BE ENHANCE IN VICINITY
OF THE COASTAL TROUGH SO SOME WEAK ROTATION WILL LIKELY BE OBSERVED.
MAX TEMPS TODAY WILL BE SEVERAL DEGREES BELOW NORMAL DUE TO THE
EXTENSIVE CLOUDINESS AND AREAS OF PRECIP. MAX TEMPS RANGING FROM THE
70S IN THE PIEDMONT OT THE LOWER 80S SANDHILLS/SOUTHERN COASTAL
PLAIN.

TONIGHT...SFC TROUGH WILL CONTINUE TO BE A FOCUS FOR CONTINUED
SHOWER/ISOLATED THUNDERSTORM DEVELOPMENT. THUS POPS WILL BE HIGHER
IN THE COASTAL PLAIN AND SANDHILLS VERSUS THE PIEDMONT. POPS WIL
RANGE FROM LIKELY IN THE EAST-SE...TO CHANCE IN THE FAR WEST-NW.

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
AS OF 330 AM FRIDAY...

THE SLOW MOVING L/W TROUGH TO OUR WEST WILL MAINTAIN THE MOIST AIR
MASS OVER OUR REGION WITH THE SFC TROUGH PROJECTED TO BE ALIGNED SSW-
NNE OVER THE COASTAL PLAIN. MODEL GUIDANCE IN GENERAL AGREEMENT WITH
THE TIMING OF THE NEXT POTENT VORT MAX 9SATURAY AFTERNOON-SATURDAY
EVENING). THIS SUGGEST SHOWERS AND THUNDERSTORMS INCREASING IN
COVERAGE DURING THE AFTERNOON...WANING SOMETIME CLOSE TO MIDNIGHT.
SIMILAR TO FRIDAY...POTENTIAL FOR SHOWERS AND STORMS TO TRAIN OVER
THE SAME LOCATION. IF THIS OCCURS IN THE AREAS THAT GET HIT
TODAY...WILL SEE HIGH AMOUNT OF RUN-OFF LEADING TO FLOODING
ISSUES...PARTICULARLY IN URBAN AREAS AS WELL AS CREEKS/STREAMS.
CONFIDENCE NOT HIGH ENOUGH YET TO ISSUE A FLOOD WATCH BUT ONE MAY
NEED TO BE CONSIDERED. STORM INTENSITY/SEVERITY NOT EXPECTED TO BE
AS MUCH OF A THREAT SATURDAY AS SHEAR VALUES ARE A LITTLE WEAKER.
POPS STILL LIKELY IN THE EAST TRENDING TO HIGH CHANCE IN THE WEST.

ANOTHE DAY OF BELOW NORMAL TEMPS SATURDAY WITH AN UNIFORMED MAX TEMP
FIELD EXPECTED DUE TO EXTENSIVE CLOUD COVERAGE AND MORE
SHOWERS/STORMS EAST VERSUS WEST. MAX TEMPS UPPER 70S/LOWER 80S.
SHOWERS AN STORMS SHOULD TAPER OFF LATE SATURDAY NIGHT WITH BETTER
CHANCES STILL EXPECTED IN VICINITY OF THE STALLED SFC TROUGH IN THE
COASTAL PLAIN. MIN TEMPS UPPER 60S-LOWER 70S.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 315 AM FRIDAY...

THOUGH NWP GUIDANCE INDICATES THE PARENT VORTEX NEAR THE SOUTHERN
TIP OF HUDSON BAY WILL GRADUALLY FILL AND LIFT OUT DURING THE NEXT
COUPLE OF DAYS...A POSITIVELY-TILTED TROUGH ALOFT WILL LINGER FROM
THE FROM THE NE US TO THE LOWER MS VALLEY THROUGH TUE. SOUTHWESTERLY
AND PERTURBED MID LEVEL FLOW WILL CONSEQUENTLY MAINTAIN AN AXIS OF
DEEP MOISTURE CHARACTERIZED PRECIPITABLE WATER VALUES AOA TWO INCHES
OVER THE EASTERN THIRD OF NC (INCLUDING THE RAH COASTAL PLAIN) SUN-
MON...WITH PROGRESSIVELY LOWER VALUES TO AROUND 1.5 INCHES OVER THE
WESTERN PIEDMONT. THE DEEP MOIST AXIS WILL THEN BE SHUNTED OFFSHORE
DURING THE MIDDLE OF THE WEEK...WHEN GUIDANCE SUGGESTS A SUCCESSION
OF SHORTWAVE TROUGHS WILL FORCE THE NORTHERN STREAM PORTION OF THE
TROUGH OFF THE NE AND MID ATLANTIC COAST. THE MOVEMENT OF THE
NORTHERN PORTION OF THE TROUGH SHOULD THEN LEAVE BEHIND TROUGHINESS/
A WEAK UPPER LOW OVER THE GULF COAST STATES THROUGH THE END OF THE
WEEK.

MEANWHILE...IN THE LOW LEVELS AND AT THE SURFACE...THE FRONTAL
ZONE/INVERTED TROUGH WILL LINGER OVER EAST-CENTRAL NC THROUGH
MON...THEN DRIFT EAST AND OFFSHORE IN RESPONSE TO THE EASTWARD
PROGRESSION OF THE NORTHERN PORTION OF THE TROUGH ALOFT.

THE RESULT OF THE EVOLVING PATTERN DESCRIBED ABOVE WILL BE CONTINUED
UNSETTLED CONDITIONS OVER ESPECIALLY THE EASTERN HALF OF THE RAH
FORECAST AREA THROUGH EARLY WEEK. SPECIFICALLY...A CONTINUED LIKELY
PROBABILITY OF SHOWERS AND STORMS ROUGHLY EAST OF US HWY 1 ARE
WARRANTED ON SUN...TAPERING TO CHANCE OVER THE WESTERN PIEDMONT (AND
PERHAPS NOT MUCH OF ANY COVERAGE INVOF AND WEST OF THE YADKIN
RIVER). THAT POP DISTRIBUTION WILL THEN EDGE EASTWARD ON MON...WITH
COVERAGE FOCUSED OVER THE RAH COASTAL PLAIN AND ESPECIALLY POINTS
EASTWARD. MID LEVEL FLOW WILL BE MODEST...15-25 KTS AND RELATIVELY
STRONGEST ON SUN...SUPPORTIVE OF MAINLY MULTI-CELL ORGANIZATION. IN
THE ABSENCE OF STRONGER FLOW AND/OR STEEPER LAPSE RATES ALOFT...
LOCALLY HEAVY RAIN...AMIDST THE CONTINUED HIGH MOISTURE CONTENT
AIR...WILL POSE A PRIMARY HAZARD.

THE DEVELOPMENT OF DRYING WESTERLY FLOW AS THE NORTHERN STREAM MOVES
OFFSHORE BY THE MIDDLE OF THE WEEK WILL FAVOR A RETURN TO MORE
TYPICAL SUMMERTIME CONDITIONS OVER THE CAROLINAS...CHARACTERIZED BY
WARMING TEMPERATURES INTO THE 80S TO NEAR 90 DEGREES - AFTER SUN-MON
TEMPERATURES TRANSITIONING THROUGH THE LOWER TO MIDDLE 80S - AND
ISOLATED TO WIDELY SCATTERED DIURNAL CONVECTION.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
AS OF 745 AM FRIDAY...

HIGH CONFIDENCE OF A PROLONGED PERIOD OF SUB VFR CONDITIONS ACROSS
CENTRAL NC...STARTING TODAY AND PERSISTING THROUGH THE WEEKEND. A
MOIST EAST-SOUTHEAST FLOW NEAR THE SURFACE COUPLED WITH A MOIST SW
FLOW ALOFT WILL MAINTAIN A NEARLY SATURATED AIR MASS THROUGH SUNDAY.
THIS WILL RESULT IN WIDESPREAD MVFR CEILINGS WITH PERIODS OF
IFR/LIFR CEILINGS. THE IFR/LIFR SHOULD MAINLY OCCUR IN THE LATE
NIGHT-EARLY MORNING HOURS.

A SERIES OF UPPER LEVEL DISTURBANCES IN THE FLOW ALOFT WILL TRIGGER
AREAS OF SHOWERS AND A FEW THUNDERSTORMS. THE MOST WIDESPREAD
COVERAGE ANTICIPATED TODAY WITH THE PASSAGE OF A POTENT UPPER LEVEL
SYSTEM...AND AGAIN SATURDAY AFTERNOON-SATURDAY NIGHT WITH THE
APPROACH/PASSAGE OF ANOTHER DISTURBANCE. A FEW STRONG STORMS MAY
OCCUR IN THE VICINITY OF KFAY AND KRWI THIS AFTERNOON AND AGAIN
SATURDAY AFTERNOON AS LOW LEVEL INSTABILITY WILL BE BETTER IN THE
SANDHILLS AND COASTAL PLAIN COMPARED TO THE PIEDMONT.

AVIATION CONDITIONS ARE EXPECTED TO SLOWLY IMPROVE MONDAY INTO
TUESDAY AS THE AIR MASS SLOWLY DRIES OUT AND THE BETTER LIFT FOR
SHOWERS AND THUNDERSTORMS DRIFTS EAST TOWARD THE IMMEDIATE
COASTLINE. STILL...THERE WILL BE PERIODS OF MVFR/IFR CEILINGS DUE TO
RESIDUAL MOISTURE...MAINLY IN THE LATE NIGHT-EARLY MORNINGS HOURS.

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...MWS
AVIATION...WSS



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.