Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 011453
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1053 AM EDT FRI AUG 1 2014

.SYNOPSIS...
UNSETTLED WEATHER AND UNSEASONABLY COOL TEMPERATURES WILL
CONTINUE THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM FRIDAY...

RADAR AND SATELLITE PRESENTATION THIS MORNING TELLS THE STORY OF
A VORT MAX MOVING THROUGH THE WESTERN PIEDMONT PRODUCING LOCALLY
HEAVY RAIN THIS MORNING...MAINLY IN THE SOUTHWEST PIEDMONT.
MEANWHILE A MOISTURE PLUME OFF OF THE ATLANTIC HAS CAUSED HEAVY
RAIN ACROSS EASTERN NC AND THIS SHOULD BE THE EVOLVING AREA OF
FOCUS THIS AFTERNOON. CENTRAL NC AND THE TRIANGLE IN PARTICULAR
HAVE BEEN LEFT OUT AT THIS TIME AND WILL CONTINUE TO BE IN A
PRECIPIATION MINIMUM FOR THE REST OF THE MORNING AND PROBABLY INTO
THE AFTERNOON. THAT BEING SAID THERE IS STILL 1.8 INCHES OF
PRECIPITABLE WATER OVER THIS AREA. WITH THE LACK OF RAIN THIS
MORNING SOME POTENTIAL INCREASED INSOLATION...ESPECIALLY IN THE
SOUTH CENTRAL COUNTIES...HAS CAUSED AN INCREASE IN
INSTABILITY...AND DOWNDRAFT CAPE IN PARTICULAR AS SEEN ON THE SPC
MESO-ANALYSIS. THIS COULD HELP SET UP SOME DIFFERENTIAL HEATING
BOUNDARIES WHICH COULD BE A FOCUS FOR SOME STRONGER CONVECTION
THIS AFTERNOON. ADD TO THAT 35-40 KTS OF EFFECTIVE SHEAR AND 100
M2S2 OF EFFECTIVE HELICITY AND IT IS NO SURPRISE THAT WE HAVE
STARTED TO SEE ROTATION IN SOME CELLS THIS MORNING.

TO SUMMARIZE THE HEAVY RAIN THREAT SHOULD SHIFT FROM THE WESTERN
PIEDMONT THIS MORNING TO THE COUNTIES EAST OF I-95 THIS AFTERNOON.
THE AREA IN BETWEEN WILL SEE A MINIMUM OF PRECIPITATION BUT MAY
END UP WITH THE BEST CHANCE OF A STRONG OR SEVERE THUNDERSTORM
THIS AFTERNOON WITH DAMAGING WINDS THE PRIMARY THREAT AND A NON-
ZERO THREAT OF AN ISOLATED TORNADO. MAX TEMPERATURES WILL BE HARD
TO PREDICT BASED ON REALIZED INSOLATION BUT IN GENERAL MID 70S TO
LOW 80S NW TO SE WITH AN ISOLATED 85 DEGREES POSSIBLE SOMEWHERE
ACROSS THE SOUTH THIS AFTERNOON.

RAIN SHOULD CONTINUE INTO THE EVENING AND OVERNIGHT TONIGHT WITH
THE FOCUS ACROSS THE EAST BUT THERE COULD BE A LULL IN THE PRECIP
AS HINTED AT BY SOME OF THE CONVECTIVE ALLOWING MODELS DURING THE
OVERNIGHT HOURS INTO EARLY SATURDAY MORNING BEFORE ANOTHER WAVE OF
SHOWERS AND THUNDERSTORMS IS EXPECTED NEAR DAYBREAK. AN AREAL
FLOOD WARNING HAS BEEN POSTED FOR EXTREME EASTERN COUNTIES THROUGH
SUNDAY NIGHT WITH A FOCUS ON FLOODING MAINLY LATER IN THE PERIOD.
NO WIDESPREAD FLOODING IS ANTICIPATED UNTIL POSSIBLY LATER IN THE
WEEKEND. LOWS IN THE MID 60S TO LOWER 70S.

&&

.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...
FLOOD WATCH THROUGH SUNDAY EVENING FOR NCZ028-043-078-088-089.

&&

$$
SYNOPSIS...ELLIS
NEAR TERM...ELLIS
SHORT TERM...WSS
LONG TERM...MWS
AVIATION...WSS



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