Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 300117 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 915 PM EDT FRI MAY 29 2015 .SYNOPSIS...HIGH PRESSURE CENTERED OVER THE WESTERN ATLANTIC WILL EXTEND INTO THE REGION THROUGH SATURDAY. A COLD FRONT WILL DROP INTO THE MID ATLANTIC AND SOUTHERN APPALACHIANS ON SUNDAY AND MOVE INTO THE CAROLINAS ON MONDAY AND TUESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 915 PM FRIDAY... VERY DRY AIR IN THE MID LEVELS MIXED TO THE SURFACE OVER THE SANDHILLS AND PORTIONS OF THE EASTERN PIEDMONT AND COASTAL PLAIN THIS AFTERNOON AND EARLY EVENING. DEW POINTS WERE 10-20 DEGREES LOWER THAN 24 HOURS AGO. THEY BOTTOMED OUT IN THE UPPER 40S OVER PORTIONS OF THE SANDHILLS AND EVEN MID 50S AT RDU. THIS MIXING OCCURRED AT STRONG BERMUDA HIGH PRESSURE BUILT BACK WESTWARD OVER INTERIOR NC/SC. THIS EFFECTIVELY PUSHED THE DEEPER MOISTURE BACK WESTWARD INTO WESTERN NC. THERE WERE LOCALIZED 1 TO 1.5 INCH RAIN TOTALS IN THE NW PART OF NC INCLUDING THE WINSTON-SALEM AREA WITH THE SLOW MOVING THUNDERSTORMS THIS AFTERNOON. FOR THE REMAINDER OF THE NIGHT... MAINLY CLEAR SKIES ARE EXPECTED UNTIL LATER TONIGHT. STRATUS MAY ADVECT INLAND INTO THE COASTAL PLAIN WITH THE ONSHORE FLOW. A FEW STRATUS MAY ALSO AFFECT THE NW ZONES WHERE DEEPER MOISTURE IS IN PLACE. OTHERWISE... LOWS GENERALLY 63-68. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 315 PM FRIDAY... SATURDAY AND SATURDAY NIGHT: SURFACE HIGH PRESSURE BUILDS BACK IN A LITTLE FURTHER THAN RECENT DAYS AND THE UPSHOT IS POSSIBLY A DRIER DAY IN THE TRIAD THAN PREVIOUS AFTERNOONS. WILL STILL CARRY A SLIGHT CHANCE OF SHOWERS IN THE WEST TOMORROW BUT CONTINUED MINIMAL SHEAR AND EVEN LESS INSTABILITY THAN TODAY DONT BODE WELL FORE CONVECTION PROSPECTS. THIS IS BACKED UP BY CAMS WHICH SHOW MINIMAL ACTIVITY TOMORROW AFTERNOON. INSTEAD EXPECT ANOTHER DAY OF WARM RETURN FLOW WITH HIGHS AGAIN MOSTLY IN THE UPPER 80S. LOWS SATURDAY NIGHT IN THE MIDDLE 60S ONCE AGAIN. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 325 PM FRIDAY... A LARGE SCALE PATTERN CHANGE IS AFOOT...WHEREIN THE WRN ATLANTIC RIDGE WILL FINALLY GIVE WAY TO A SOUTHWARD DIP IN THE WESTERLIES OVER THE CONUS. THIS WILL BRING IMPROVING CHANCES FOR MUCH-NEEDED RAINFALL BEGINNING EARLY IN THE WORK WEEK. THE VAST MAJORITY OF CENTRAL NC HAS SEEN VERY LITTLE RAIN IN THE LAST COUPLE OF WEEKS... BETWEEN 1 AND 2 INCHES BELOW NORMAL IN THE LAST 14 DAYS ACCORDING TO WATER.WEATHER.GOV/PRECIP/. SUNDAY SHOULD BE OUR LAST STEAMY BUT MOSTLY DRY DAY. THE APPROACHING COLD FRONT IS EXPECTED TO STRETCH ACROSS THE MASON DIXON LINE DOWN THROUGH ERN KY LATE SUN... WITH ITS ASSOCIATED MID LEVEL TROUGH EXTENDING FROM THE GREAT LAKES TO THE LOWER MISS VALLEY AS THE WRN ATLANTIC RIDGE HOLDS ON FOR ONE MORE DAY. LATEST MODEL OUTPUT SHOWS SCATTERED TO NUMEROUS SHOWERS/STORMS POPPING UP BY AFTERNOON OVER THE HIGHER TERRAIN TRACKING TO THE NE WITHIN THE WEAK MEAN STEERING FLOW AROUND THE RIDGE. THIS CONVECTION IS EXPECTED TO WEAKEN DURING THE EVENING BUT EASE EASTWARD INTO THE NORTHWEST CWA SUN NIGHT... FOLLOWING THE PROGRESSION OF THE NRN PORTION OF THE MID LEVEL TROUGH INTO THE NORTHEAST STATES THROUGH MON. THE REST OF THE CWA SHOULD REMAIN MOSTLY DRY (ALTHOUGH AN ISOLATED SLOW-MOVING CELL OR TWO IS CERTAINLY POSSIBLE) GIVEN THE SOMEWHAT DRY LOW LEVELS (LIMITING CAPE) AND DRY AIR THROUGH THE COLUMN (BELOW NORMAL PW OVER ERN HALF OF CWA). HIGHS SUN 85-90. LOWS SUN NIGHT MAINLY IN THE UPPER 60S WITH CONVECTIVE DEBRIS CLOUDS AND A SMALL CHANCE OF SHOWERS OVER THE NRN/WRN CWA OVERNIGHT. WHILE WE SHOULD SEE A PIEDMONT TROUGH FORMING (OR BECOMING BETTER DEFINED) OVER THE CWA MON... MODELS ARE KEEPING A THERMAL RIDGE ACROSS OUR AREA WITH THE FRONTAL ZONE HOLDING TO OUR NW THROUGH THE DAY... A FUNCTION OF THE SLOW SPEED AND LOW AMPLITUDE OF THE MID LEVEL TROUGH TO OUR WEST. WE`LL NEED TO WAIT FOR ADDITIONAL ENERGY TO DROP FROM SW ONTARIO DOWN THROUGH THE GREAT LAKES STARTING MON IN ORDER FOR THE TROUGH TO MAKE ANY MEANINGFUL EASTWARD PROGRESS. ALL OF THIS WILL SERVE TO DELAY COOLING INTO NC UNTIL THE SURFACE FRONT DROPS INTO NC TUE NIGHT OR EARLY WED. BOTH MOISTURE AND FORCING FOR ASCENT WILL DEEPEN AND INCREASE AHEAD OF THE FRONT... AND BY LATE MON AFTERNOON WE SHOULD SEE GOOD COVERAGE OF SHOWERS AND STORMS PARTICULARLY OVER THE WRN AND SW CWA WHERE LOW LEVEL MOISTURE POOLING SHOULD BE GREATEST. COVERAGE AND INTENSITY WILL WANE MON NIGHT WITH LOSS OF HEATING... BUT NOT GO AWAY ENTIRELY GIVEN THE PERSISTENCE OF ELEVATED INSTABILITY OVERNIGHT AND ABOVE-NORMAL PW. MODERATE INSTABILITY AND HIGH MOISTURE SHOULD PERSIST AREAWIDE TUE... SUPPORTING ABOVE NORMAL CHANCES FOR SHOWERS AND STORMS (50- 60%). EXPECT HIGH COVERAGE AGAIN WED ACROSS ALL BUT THE NW AS THE FRONT SETTLES INTO THE NRN/WRN CWA. THE GFS/ECMWF SOLUTIONS DIVERGE WITH THE LATTER SHOWING A DEEPER TROUGH JUST TO OUR IMMEDIATE WEST TUE AND SHIFTING OVER THE ERN STATES WED... WHILE THE GFS KEEPS THE STREAMS UNPHASED WITH A CUTOFF MID LEVEL LOW OVER THE LOWER MISS VALLEY. PREFER THE WEAKER-FLOW GFS WITH THE FRONT LOITERING ACROSS ERN AND SRN NC THROUGH THU/FRI... AS THE ONCE-COOL SURFACE HIGH CENTERED OVER THE ERN GREAT LAKES EARLY WED MODIFIES AND STARTS TO DRIFT OFF THE NORTHEAST COAST BY FRI. THE FRONT SHOULD BE MOSTLY WASHED OUT AND BE OVERTAKEN BY COASTAL INVERTED TROUGHING OVER THE SOUTHEAST COAST. WILL TREND POPS TOWARD MORE CLIMATOLOGICALLY NORMAL VALUES THU/FRI -- 25-35% CHANCES MAINLY IN THE EAST AND SOUTH -- GIVEN THE DECREASING DEEP LAYER SHEAR AND WEAKENING FORCING FEATURES. DESPITE WHAT SHOULD BE A PERIOD OF MOSTLY CLOUDY SKIES FROM CONVECTIVE DEBRIS AND LIFTING MORNING STRATUS ON MON... WE SHOULD SEE ENOUGH HEATING WITHIN THE WARM SECTOR TO PUSH TEMPS UP TO HIGHS FROM THE MID 80S TO AROUND 90 (COOLEST NW AND FAR NORTH). HIGH TEMPS SHOULD SLIP BACK CLOSER TO NORMAL TUE GIVEN THE EXPECTED CONSIDERABLE CLOUDINESS... WITH THESE CLOUDS EQUATING TO MILD/HUMID OVERNIGHT LOWS THROUGH TUE NIGHT. SLIGHTLY BELOW NORMAL TEMPS WED... THEN TRENDING BACK TOWARD NEAR OR SLIGHTLY ABOVE NORMAL THU/FRI AS THE FRONT WASHES OUT AND THE RESIDENT AIR MASS MODIFIES. -GIH && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... AS OF 835 PM FRIDAY... 24-HR TAF PERIOD: ASIDE FROM A POTENTIAL FOR SUB-VFR CEILINGS OR FOG DURING THE PRE-DAWN/EARLY MORNING HOURS (08-13Z)...PRIMARILY AT THE INT/GSO TERMINALS...VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE TAF PERIOD IN ASSOC/W A PERSISTENT UPPER LEVEL RIDGE ALONG THE EASTERN SEABOARD. LOOKING AHEAD: ASIDE FROM A POTENTIAL FOR SUB-VFR CEILINGS/FOG DURING THE EARLY MORNING (08-13Z) AND CONVECTION DURING THE LATE AFT/EVE (20-01Z)...PRIMARILY AT THE INT/GSO TERMINALS...EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE WEEKEND. CHANCES FOR EARLY MORNING STRATUS/FOG AND AFT/EVE CONVECTION WILL INCREASE AT ALL TERMINALS (PARTICULARLY INT/GSO) MONDAY INTO TUESDAY AS THE UPPER LEVEL RIDGE WEAKENS AND A SLOW-MOVING UPPER LEVEL TROUGH APPROACHES THE CAROLINAS/MID-ATLANTIC FROM THE WEST. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BLAES NEAR TERM...ELLIS SHORT TERM...ELLIS LONG TERM...HARTFIELD AVIATION...VINCENT

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