Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 071840 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 235 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 1110 AM TUESDAY... MORNING ANALYSIS SHOWS THE LOWER AND MID LEVEL TROUGH AXIS SHIFTING EAST ACROSS CENTRAL NC. THE AIR MASS ACROSS CENTRAL NC HAS DRIED CONSIDERABLY IN THE PAST 24 HOURS WITH PW VALUES NEAR 1.1 INCHES IN THE WESTERN PIEDMONT AND 1.6 INCHES IN THE EAST. STRATUS THIS MORNING WAS RATHER LIMITED AND MOST OF THE AREA WAS RECEIVING FULL SUN AS OF MID MORNING. FOCUS FOR CONVECTION TODAY IS GENERALLY CONFINED TO THE EASTERN PIEDMONT AND SANDHILLS...EAST OF THE SURFACE TROUGH AND EASTWARD OF THE SHIFTING LOWER AND MID LEVEL SHEAR AXIS. NWP GUIDANCE SUGGESTS ONLY WEAK INSTABILITY WITH THE INSTABILITY GREATEST ACROSS THE COASTAL PLAIN AND SANDHILLS. MID LEVEL LAPSE RATES ARE PRETTY ANEMIC...RANGING AROUND 5.5 DEG C/KM. GIVEN THIS...CONVECTIVE COVERAGE WILL BE LIMITED AS NOTED BY LATEST CONVECTION ALLOWING MODELS. WILL KEEP POPS CONFINED TO THE SLIGHT CHANCE RANGE AND LOCATED IN THE EAST. HIGHS TODAY WILL BE A FEW DEGREES WARMER THAN MONDAY WITH THICKNESS VALUES VALUES AT GSO 18M WARMER THAN YESTERDAY. HIGHS IN THE 89 TO 94 RANGE LOOK ON TARGET. ANY CONVECTION SHOULD DIMINISH JUST AFTER SUNSET. LOWS WILL RANGE IN THE UPPER 60S AND LOWER 70S. -BLAES && .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 650 AM TUESDAY... OTHER THAN SOME ISOLATED AREAS OF LIMITED VSBY....VFR CONDITIONS PREVAIL THIS MORNING. SCATTERED CU WITH BASES IN THE 4-5K FT FT RANGE WILL DEVELOP FOR THE AFTERNOON HOURS...BUT WITH DRIER AIR OVER WESTERN NC...ONLY WIDELY SCATTERED SHOWERS AND ISOLATED STORMS ARE EXPECTED OVER THE COASTAL PLAIN...PRIMARILY IN THE VICINITY OF KFAY AND/OR KRWI AFTER 18Z. VFR CONDITIONS ARE THEN EXPECTED TONIGHT. OUTLOOK...MOSTLY VFR CONDITIONS THROUGH THE END OF THE WEEK AS HIGH PRESSURE DOMINATES THE REGION. SOME AFTERNOON STORMS ARE POSSIBLE EACH DAY...ALONG WITH EARLY MORNING VSBY RESTRICTIONS. && ..RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BLAES NEAR TERM...BLAES SHORT TERM...BLAES LONG TERM...MLM AVIATION...22

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