Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 071922
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
320 PM EDT TUE JUL 7 2015

.SYNOPSIS... AN UPPER TROUGH ACROSS THE SOUTHERN APPALACHIANS WILL
LIFT AWAY FROM THE REGION TODAY. A RIDGE OF HIGH PRESSURE WILL THEN
DEVELOP OVER THE SOUTHEAST AND STRENGTHEN THROUGH THE REMAINDER OF
THE WORK WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 320 PM TUESDAY...

LATEST SURFACE ANALYSIS SHOWS A WEAK TROUGH EXTENDING SOUTH ACROSS
THE PIEDMONT OF THE CAROLINAS. LATEST WV IMAGERY INDICATES THE SLOW
MOVING SHEAR AXIS ALOFT IS STILL LOCATED ACROSS THE WESTERN PIEDMONT
AND IT WILL LIKELY BE LATE THIS EVENING OR OVERNIGHT UNTIL THIS
FEATURE EXITS CENTRAL NC. DEW POINTS RANGE IN THE UPPER 60S TO LOWER
70S. THE AIR MASS ACROSS CENTRAL NC IS WEAKLY UNSTABLE ACROSS THE
WESTERN PIEDMONT WITH MLCAPE VALUES INCREASING TO AROUND 1500 J/KG
IN THE EASTERN PIEDMONT AND SANDHILLS. MID LEVEL LAPSE RATES ARE
PRETTY ANEMIC...RANGING AROUND 5.5 DEG C/KM. STILL IT SHOULD BE
NOTED THAT THE AIR MASS ACROSS CENTRAL NC HAS DRIED CONSIDERABLY IN
THE PAST 24 HOURS WITH PW VALUES NEAR 1.3 INCHES IN THE WESTERN
PIEDMONT AND 1.6 INCHES IN THE EAST.

VISIBLE SATELLITE IMAGERY SHOWS A WIDESPREAD CUMULUS FIELD ACROSS
THE CAROLINAS WITH THE DEEPEST VERTICAL DEVELOPMENT LOCATED ALONG
THE COAST IN THE VICINITY OF THE SEA BREEZE...ACROSS THE NORTHERN
MOUNTAINS OWING TO DIFFERENTIAL HEATING WITH JUST A FEW SHOWERS
ACROSS CENTRAL NC. THE COVERAGE OF THESE SHOWERS WILL INCREASE A BIT
DURING NEXT FEW HOURS BUT GIVEN THE LIMITED FORCING FOR ASCENT AND
MODEST INSTABILITY...COVERAGE SHOULD REMAIN LIMITED. THE CONVECTION
WILL MOVE OFF TO THE NORTHEAST WITH THE OVERALL REGION OF SHOWERS
GENERALLY TRANSITIONING EAST. WILL KEEP POPS CONFINED TO THE SLIGHT
CHANCE RANGE AND GENERALLY LOCATED ALONG AND EAST OF U.S. ROUTE 1.
THE PRECIPITATION SHOULD WANE WITHIN A FEW HOURS OF SUNSET. LOWS
TONIGHT WILL RANGE FROM 68 NEAR THE VA BORDER TO 73 NEAR THE SC
BORDER WITH A LIGHT SOUTHWEST WIND.
-BLAES/CAMPBELL
&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 235 PM TUESDAY...

THE SUBTROPICAL RIDGE WILL STRENGTHEN DURING THE PERIOD WITH RISING
HEIGHTS AND THICKNESSES. A SHORTWAVE TROUGH IN THE GREAT LAKES EARLY
WEDNESDAY SHEARS NORTHEAST ATOP THE RIDGE ON WEDNESDAY. THE
ASSOCIATED COLD FRONT SETTLES NORTH OF OUR AREA IN AN EAST TO WEST
AXIS ACROSS THE MID ATLANTIC AND OHIO VALLEY. WITH THE UPPER FLOW
PARALLEL TO THE FRONTAL POSITION IS UNLIKELY TO MAKE MUCH
SOUTHWARD PROGRESS. A SERIES OF UPPER-LEVEL DISTURBANCES IS PROGGED
TO RIDE AROUND THE RIDGE IN PROXIMITY OF THE FRONT ON WEDNESDAY INTO
THURSDAY ENHANCING AREA OF CONVECTION TO OUR NORTHWEST AND NORTH.

THE AIR MASS ACROSS CENTRAL NC WILL BE SLIGHTLY MORE UNSTABLE THAN
PREVIOUS DAYS...ESPECIALLY IN THE EASTERN PIEDMONT AND SANDHILLS.
PRECIPITABLE WATER VALUES ALSO REBOUND AND RANGE BETWEEN 1.6 AND 1.9
INCHES BY LATE WEDNESDAY. THE RESULT WILL BE AN AIRMASS MORE
THERMODYNAMICALLY FAVORABLE FOR CONVECTION BUT STILL LACKING A WELL
DEFINED TRIGGER. CONVECTION WILL LIKELY INITIATE IN LOCALIZED
CONVERGENCE FROM DIFFERENTIAL HEATING AND NEAR THE SEABREEZE IN THE
EARLY TO MID AFTERNOON. MOST CONVECTION ALLOWING MODELS CONTINUE
SUGGEST THAT CONVECTION THAT ORIGINATES IN THE MOUNTAINS MAY
ORGANIZE INTO A BROKEN OUTFLOW DOMINATED CONVECTIVE LINE THAT MOVES
INTO CENTRAL NC VERY LATE IN THE AFTERNOON AND EVENING. BULK SHEAR
VALUES ARE PROGGED TO BE WEAK...LIKELY RANGING BETWEEN 10 AND 15 KTS
INDICATIVE OF POOR STORM ORGANIZATION AND LIMITED SEVERE WEATHER
THREAT. STILL...WE HAVE ADJUSTED POPS UPWARD SLIGHTLY AND ATTEMPTED
TO INCLUDE THE ABOVE STORM MORPHOLOGY IN THE POP GRIDS. HIGHS WILL
RANGE BETWEEN 89 IN THE TRIAD TO 95 IN THE SANDHILLS. LOWS WILL
RANGE BETWEEN 68 AND 73. -BLAES
&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
AS OF 155 PM TUESDAY...

ON THURSDAY...THE SUBTROPICAL RIDGE RETROGRADING ACROSS THE
SOUTHEAST WILL SUPPRESS THE WESTERLIES WELL NORTH OF THE
AREA...LEAVING US ONLY A SLIGHT CHANCE OF CONVECTION ACROSS THE
NORTHERN TIER COUNTIES. HIGHS ARE STILL ON TRACK FOR LOW AND MID 90S
WITH STRONG INSOLATION. AMPLIFICATION OF THE UPPER RIDGE INTO THE
MIDWEST WILL TIP THE FLOW NORTHWESTERLY ON FRIDAY...PROVIDING
FAVORABLE STEERING FLOW FOR ADVECTION OF UPSTREAM CONVECTION ACROSS
THE OHIO VALLEY INTO THE NORTHERN TIER COUNTIES...WITH SLIGHTLY
BETTER CHANCES (ALBEIT STILL A CLIMATOLOGICAL 30 PERCENT) IN THE
NORTHEAST PIEDMONT AND NORTHERN COASTAL PLAIN. NO CHANGE OF
AIRMASS...BUT INCREASED DEBRIS CLOUDINESS IN THE NORTHWEST FLOW
ACROSS THE NORTHERN TIER COULD NIP A COUPLE OF DEGREES OFF THE
AFTERNOON HIGH...WILL MAINTAIN A FORECAST OF AROUND 90 NORTH TO 96
SOUTH.

RIDGE CONTINUES TO BUILD IN THE MIDWEST OVER THE WEEKEND...RESULTING
IN STRONGER NORTHWEST FLOW. THIS WILL MAINTAIN A POP GRADIENT
FAVORING THE NORTHEAST...WHILE THE SOUTHWEST PIEDMONT COULD BE DRY
THROUGH TUESDAY. IN ADDITION...THE CHANCE FOR NON-DIURNAL CONVECTION
WILL BE INCREASING DUE TO THE POTENTIAL FOR IMPULSES ORIGINATING
FROM DIURNALLY ENHANCED MCS ACTIVITY OVER THE OHIO VALLEY TO MOVE
INTO THE AREA OVERNIGHT. IT IS DIFFICULT TO PINPOINT A MORE
FAVORABLE TIME SLOT FOR INCREASED CONVECTIVE ACTIVITY AT THIS POINT
GIVEN LOW CONFIDENCE IN FORECASTING UPSTREAM MESOSCALE
FEATURES...THUS WILL MAINTAIN NEAR CLIMATOLOGICAL POPS FOR THE
MEANTIME. SIMILARLY...HIGHS EACH DAY WILL BE PERSISTENCE BARRING
DEBRIS CLOUDINESS AND EARLY DAY CONVECTION...IN THE LOW TO MID
90S...WITH SOME UPPER 90S POSSIBLE IN THE SOUTH.

&&

.AVIATION /12Z TUESDAY THROUGH FRIDAY/...
AS OF 135 PM TUESDAY...

VFR CONDITIONS ARE GENERALLY EXPECTED THROUGH THE 24 HOUR TAF
PERIOD. A FAIRLY WIDESPREAD CUMULUS FIELD HAS DEVELOPED WITH BASES
AROUND 4500 FEET. ISOLATED SHOWERS AND PERHAPS A THUNDERSTORM WILL
DEVELOP ACROSS THE EASTERN PIEDMONT...SANDHILLS AND COASTAL PLAIN
THIS AFTERNOON POSSIBLY AFFECTING THE KRWI AND KFAY TERMINALS. WILL
EXCLUDE MENTION OF A THUNDERSTORM BUT KEEP A TEMPO FOR A SHOWER.
CHANCES OF PRECIPITATION ARE LESS AT KRDU AND MINIMAL IN THE TRIAD
AT KINT AND KGSO. ANY SHOWER ACTIVITY AND THE CUMULUS WILL DIMINISH
JUST AFTER SUNSET. FAIR WEATHER IS EXPECTED OVERNIGHT WITH JUST A
LIMITED THREAT OF SOME MVFR STRATUS TOWARD DAYBREAK AT KFAY AND
KRWI. WITH LIMITED PRECIPITATION EXPECTED AND A LOT OF NWP
SPREAD...HAVE OPTED TO EXCLUDE STRATUS FROM THE TAFS FOR NOW GIVEN
THE LOW CONFIDENCE OF OCCURRENCE. LOW LEVEL FLOW AT THE TOP OF THE
LOW LEVEL INVERSION INCREASES OVERNIGHT WITH A SOUTHWESTERLY WIND AT
25-30KTS AT 1500 FT JUST OUTSIDE OF LLWS CRITERIA SO WILL OMIT THAT
FROM THE TAF AS WELL. THE FIRST HALF OF WEDNESDAY WILL FEATURE VFR
CONDITIONS WITH THE REDEVELOPMENT OF SCT CUMULUS AT AROUND 4-5KT AND
SOME MID-HIGH LEVEL BKN DEBRIS CLOUDINESS FROM UPSTREAM CONVECTION.

OUTLOOK...A RIDGE OF HIGH PRESSURE WILL BUILD OVER THE SOUTHEAST
THROUGH THE PERIOD SETTING UP A TYPICAL SUMMERTIME PATTERN. VFR
CONDITIONS ARE EXPECTED TO DOMINATE OUTSIDE OF MAINLY ISOLATED
AFTERNOON OR EVENING THUNDERSTORMS AND PATCHY FOG AROUND DAYBREAK.
-BLAES

&&

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

&&

$$

SYNOPSIS...BLAES
NEAR TERM...BLAES/CAMPBELL
SHORT TERM...BLAES
LONG TERM...MLM
AVIATION...BLAES



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