Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 190554 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 150 AM EDT SUN APR 19 2015 .SYNOPSIS...A WARM FRONT WILL PUSH INTO OUR REGION FROM THE SOUTH TODAY. LOW PRESSURE WILL TRACK ALONG THE APPALACHIANS THIS EVENING AS THE WARM FRONT MOVES NORTHWARD INTO VIRGINIA. A COLD FRONT SHOULD SURGE SOUTHEAST ACROSS NC MONDAY AFTERNOON AND EVENING. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1040 PM SATURDAY... BENEATH MID-UPPER LEVEL SHORTWAVE RIDGING...A W-E ORIENTED NEARLY STATIONARY FRONT - ONE THAT SEPARATED SURFACE DEWPOINTS IN THE MIDDLE TO UPPER 60S OVER MOST OF THE SE US FROM 40S AND 50S OVER VA - WAS ANALYZED ACROSS CENTRAL NC AT 02Z...WHILE A STRONGER COLD FRONT WAS ANALYZED OVER SOUTHERN PA. NUMEROUS OUTFLOW BOUNDARIES FROM CONVECTION THAT INITIATED OVER THE FRONT OVER CENTRAL NC SAT AFTERNOON REMAIN ACROSS OUR AREA...THE MOST NOTABLE OF WHICH HAS MAINTAINED SCATTERED...WESTWARD-PROPAGATING SHOWERS AND STORMS FROM NEAR KRWI TO NEAR FIVE COUNTY STADIUM. THE MAIN THREAT FROM THIS CONVECTION WILL BE HEAVY RAIN OWING TO THE RELATIVELY SLOW MOVEMENT/OUTFLOW PROPAGATION AMIDST WEAK INSTABILITY SAMPLED BY THE 00Z KGSO AND KMHX RAOBS...AND SUPPORTED BY MORE RECENT SPC MESO- ANALYSIS DATA. A SEPARATE AREA OF WEAKER SHOWERS HAVE BEEN MAINTAINED OVER THE SOUTHERN HALF OF THE FORECAST AREA...IN ASSOCIATION WITH A NEARLY STATIONARY 850-700 MB TROUGH/SHEAR AXIS EVIDENT IN BOTH THE 12Z/18TH AND 00Z/19TH RAOB DATA. NWP GUIDANCE SUGGESTS THIS TROUGH AXIS WILL RETREAT NORTH INTO THE WESTERN CAROLINAS AND BECOME ORIENTED INCREASINGLY NW-SE WITH TIME. WHILE SCATTERED SHOWERS OR AN ISOLATED THUNDERSTORM OR TWO WILL CONTINUE TO PERCOLATE INVOF THE E-W SFC BOUNDARY...GUIDANCE SUGGESTS IT WILL BE THE 850-700 MB TROUGH AXIS - IN A ZONE OF INCREASINGLY CONFLUENT FLOW IN THAT LAYER - THAT WILL FOCUS MORE NUMEROUS SHOWERS OVERNIGHT INTO EARLY SUN...WHICH WILL INCLUDE THE SOUTHERN AND WESTERN PIEDMONT AND SANDHILLS OF NC. LOWS MOSTLY IN THE 60S...THOUGH SOME UPPER 50S WILL BE POSSIBLE OVER THE NORTHERN COASTAL PLAIN AND FAR NE PIEDMONT...WHERE SOME OF THE DRIER LOW LEVEL AIR OVER VA WILL LIKELY FILTER INTO OVERNIGHT. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 330 PM SATURDAY... SUNDAY...AN INCREASINGLY MOIST AIR MASS (PRECIP WATER VALUES 1.5-1.7 INCHES PROBABLE BY AFTERNOON) COUPLED WITH DECENT CONVERGENCE IN THE LOWER LEVELS AND INCREASING DIVERGENCE ALOFT (DUE TO THE NOSE OF 300MB JET CROSSING THE NORTHERN GULF) WILL CAUSE SHOWERS TO OVERSPREAD CENTRAL NC FROM THE SW. LOW LEVEL WIND WILL HAVE AN UPSLOPE COMPONENT OVER THE WESTERN PIEDMONT...SUGGESTING A SUSTAINED PERIOD OF SHOWERS WITH MODERATE TO BRIEFLY HEAVY RAINFALL RATES LIKELY. WHILE NOT ANTICIPATING WIDESPREAD FLOODING ISSUES AT THIS TIME...PROLONGED MODERATE RAINFALL IN THE URBANIZED AREAS OF THE TRIAD COULD LEAD TO STREET FLOODING ALONG WITH SIGNIFICANT RISES ALONG AREAS CREEKS AND STREAMS. WILL REFRAIN FROM ISSUING A FLASH FLOOD WATCH AT THIS TIME AS BEST LIFT PROJECTED TO OCCUR OVER THE FOOTHILLS/HIGHER TERRAIN OF WESTERN NC. LATEST MODEL GUIDANCE HAS TRENDED MORE UNSTABLE LATE SUNDAY-SUNDAY EVENING ACROSS THE SOUTHERN HALF OF CENTRAL NC WITH BULK SHEAR INCREASING 35-40KTS AND MLCAPE 500-1000J/KG(NAM). WHILE CANNOT RULE OUT THE POTENTIAL FOR AN ISOLATED STRONG/SEVERE STORM SUNDAY NIGHT OVER THE SOUTHERN COUNTIES...FEEL THAT SEVERE POTENTIAL BETTER FARTHER SOUTH ACROSS GA/SOUTHERN SC WHERE ATMOSPHERE WILL HAVE A BETTER CHANCE TO DESTABILIZE. WIDESPREAD SHOWERS AND OVERCAST SKIES SHOULD LIMIT TEMP RECOVERY SUNDAY. HIGH TEMPS SHOULD VARY FROM THE MID 60S-LOWER 70S FAR SOUTH- SOUTHEAST OTHERWISE...SHOULD SEE SHOWER DECREASING IN COVERAGE AND INTENSITY SUNDAY NIGHT FROM THER SW AS MID LEVEL S/W LIFTS NEWD INTO THE NORTHERN MID ATLANTIC. THE APPROACH OF YET ANOTHER S/W (VERY POTENT) TOWARD DAYBREAK MONDAY WILL CONTINUE A THREAT SHOWERS OVERNIGHT. MIN TEMPS 60-65. MON/MON NIGHT: WILL HOLD ONTO JUST A FEW HOURS OF SHOWERS IN THE FAR NE EARLY MON MORNING... CONSIDERING THAT THE MODELS HAVE BEEN TRENDING A BIT FASTER TO MOVE PRECIP OUT OF CENTRAL NC... AND WILL FOLLOW WITH A PERIOD OF NO POPS FOR MID TO LATE MORNING... UNTIL THE ONSET OF CONVECTION. STILL LOOKS LIKE A GOOD PROBABILITY OF STRONG TO SEVERE STORMS MON AFTERNOON INTO EARLY EVENING WITH A FEW SUPERCELLS POSSIBLE. WE`LL BE FULLY IN THE WARM SECTOR WITH WARM MOIST AIR NEAR THE GROUND AND A GOOD PUNCH OF MID LEVEL DRY AIR COMING IN FROM THE SW. LATEST MODEL RUNS ARE SHOWING A LITTLE BETTER INSTABILITY THAN YESTERDAY`S RUNS FOR MON AFTERNOON... WITH MUCAPE OF 1000-2000 J/KG ON THE GFS AND 1500-3000 J/KG ON THE NAM... AND SREF MEAN MLCAPE VALUES PEAKING AT 1200-1500 J/KG... ALTHOUGH THE DEEP LAYER SHEAR STILL LOOKS MARGINAL AT AROUND 30 KTS. NAM/GFS BUFR SOUNDINGS SHOW A WEAK CAP LOCATED BETWEEN 1 AND 2 KM AGL IN THE MORNING... BREAKING EARLY IN THE AFTERNOON... AND ONCE IT DOES... CONVECTION SHOULD DEVELOP AND BECOME VIGOROUS QUICKLY WITH BROAD AND DEEP CAPE IN THE MID-UPPER LEVELS. DYNAMIC FORCING FOR ASCENT WILL BE PRESENT AS WELL WITH STRONG UPPER DIVERGENCE IN THE LEFT EXIT REGION OF A 140 KT SUBTROPICAL JET... AND A SHOT OF MID LEVEL DPVA AS THE TROUGH AXIS ROTATES UP THROUGH THE AREA. WILL MAINTAIN A MENTION IN THE HAZARDOUS WEATHER OUTLOOK OF DAMAGING WIND AS THE PRIMARY THREAT GIVEN THE ABUNDANCE OF DRY AIR 700-300 MB... HOWEVER THE EXPECTED CAPE IN THE -10C TO -30C LAYER APPEARS SUFFICIENT TO SUPPORT LARGE HAIL IF WE CAN GET ENOUGH MOISTURE ALOFT. THICKNESSES ARE PROJECTED TO START THE DAY AROUND 20 M ABOVE NORMAL... SO HIGHS IN THE UPPER 70S TO MID 80S (NW TO SE) LOOK ATTAINABLE WITHIN GOOD WARM AIR ADVECTION. WILL TREND OUT SHOWERS/STORMS IN THE MID-LATE EVENING FROM WEST TO EAST... WITH COLD FRONTAL PASSAGE EXPECTED LATE OVERNIGHT. LOWS FROM THE LOWER 50S NW TO AROUND 60 SE. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 100 AM SUNDAY... ...DRIER CONDITIONS FOR MUCH OF THE UPCOMING WEEK... THE MAIN COLD FRONT WILL BE OFFSHORE BY 12Z/TUE. COOL AND DRY ADVECTION WILL OVERSPREAD CENTRAL AND EASTERN NORTH CAROLINA TUESDAY AS THE SURFACE HIGH SHIFTS EAST ALONG THE GULF COAST STATES. HIGHS SHOULD STILL REACH 70-75 IN MOST AREAS EXCEPT UPPER 60S IN THE NORTHWEST PIEDMONT INCLUDING WINSTON-SALEM AND GREENSBORO. BREEZY W-NW WINDS AT 10-20 MPH ARE EXPECTED FROM MID MORNING THROUGH THE AFTERNOON... DIMINISHING LATE AFTERNOON. THE SURFACE HIGH PRESSURE WILL PUSH EAST ALONG THE SE STATES THEN OFFSHORE TUESDAY NIGHT AND WEDNESDAY. THIS OCCURS AS A DRY COLD FRONT IS FORECAST TO APPROACH THE REGION WEDNESDAY AFTERNOON DRIVEN BY THE NW FLOW ALOFT. A RETURN SW SURFACE FLOW SHOULD COMMENCE FROM THE TENNESSEE VALLEY NORTHEAST ACROSS THE CENTRAL APPALACHIANS AND NW NC TUESDAY NIGHT. THE SW RETURN FLOW WILL ARRIVE OVER THE REST OF NORTH CAROLINA WEDNESDAY. THERE WILL BE LITTLE TO NO GULF MOISTURE RETURN OUT AHEAD OF THIS FRONT WITH ONLY SOME MID AND HIGH CLOUDINESS EXPECTED. THEREFORE... EXPECT PARTLY CLOUDY SKIES TUESDAY NIGHT AND PARTLY SUNNY WEDNESDAY. LOWS IN THE MID 40S. HIGHS IN THE LOWER TO MID 70S WEDNESDAY. THE COLD FRONT IS EXPECTED TO STALL JUST TO OUR SOUTH ON WEDNESDAY NIGHT AND THURSDAY BEFORE THE NEXT SURGE OF ENERGY IN THE WNW FLOW ALOFT EVENTUALLY DRIVES ANOTHER COLD FRONT TOWARD THE AREA LATE THURSDAY. THE GULF AND ATLANTIC APPEAR TO BE CUT OFF DURING THIS TIME IN THE PREDOMINATELY WESTERLY FLOW - HOWEVER HARD TO TIME ENERGY ALOFT MAY BRING A SMALL CHANCE OF LIGHT SHOWERS LATE WED NIGHT AND THURSDAY. WE WILL ONLY CARRY A SLIGHT CHANCE AT THE CURRENT TIME DUE TO THE LACK OF AVAILABLE MOISTURE EXPECTED. LOWS AND HIGHS SHOULD RETURN TO NORMAL (LOWER TO MID 50S/LOWER TO MID 70S) INTO THURSDAY. FRIDAY AND SATURDAY... DRY CONDITIONS SHOULD CONTINUE THROUGH LATE WEEK BEHIND THE COLD FRONT THURSDAY. HOWEVER... LOW CONFIDENCE OF TIMING AND STRENGTH OF A POTENTIAL SOUTHERN BRANCH SYSTEM TOWARD THE WEEKEND INCREASING THE CHANCE OF SHOWERS BY SATURDAY. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... AS OF 150 AM SUNDAY... 24 HOUR PERIOD: CIGS WILL DROP TO MVFR... THEN IFR... AT KINT AND KGSO BETWEEN 09Z AND 12Z... AND PROGRESS NORTHEAST THROUGH THE MORNING AS RAIN AND EMBEDDED HEAVY RAIN SHOWERS OVERSPREAD THE AREA AHEAD OF A WARM FRONT. THE HEAVIEST RAIN WITH ISOLATED THUNDERSTORMS WILL LIKELY OCCUR BETWEEN 21Z/SUN AND 03Z/MON WHEN LIFR CIGS/VSBYS CAN BE EXPECTED. THE HEAVY RAIN WILL PUSH NORTH OF THE REGION BETWEEN 03Z-07Z/MON... LEAVING WIDESPREAD IFR/MVFR CEILINGS THROUGH 12Z/MON. VFR CONDITIONS ARE EXPECTED MONDAY. HOWEVER... A COLD FRONT WILL BRING MVFR CIGS DURING THE MID TO LATE AFTERNOON. SW WINDS 15-25KT WILL PRECEDE THE FRONT... SHIFTING TO THE WEST DURING THE EVENING AT 10KT. SCATTERED CIGS/VSBYS OF IFR TO MVFR WILL OCCUR IN SHOWERS AND THUNDERSTORMS MONDAY AFTERNOON AND EVENING UNTIL THE FRONT PASSES. A RETURN TO VFR CONDITIONS ARE FORECAST FOR LATE MONDAY NIGHT THROUGH THURSDAY AS HIGH PRESSURE BUILDS IN. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BADGETT NEAR TERM...RAH SHORT TERM...WSS LONG TERM...BADGETT AVIATION..BADGETT

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