Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 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

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