Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281912 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 312 PM EDT FRI AUG 28 2015 .SYNOPSIS...HIGH PRESSURE WILL EXTEND IN TO THE AREA FROM THE NORTH THROUGH SATURDAY. AN UPPER LEVEL DISTURBANCE WILL MOVE NORTHWARD ALONG THE APPALACHIANS ON SUNDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 307 PM FRIDAY... AREA IS UNDER A QUASI-ZONAL FLOW ALOFT... WHILE A WEAK UPPER LEVEL LOW HAS DEVELOPED OVER THE NORTHERN GULF. AT THE SURFACE... HIGH PRESSURE OVER THE MIDATLANTIC IS EXTENDING IN TO THE AREA. DRY AIRMASS IS IN PLACE WITH PWS UNDER AN INCH ACROSS THE AREA. MAINLY CLEAR SKIES EXPECTED TONIGHT... LOWS IN THE LOW 60S. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... AS OF 309 PM FRIDAY... SHORTWAVE WILL MOVE INTO THE MIDWEST... AND THE UPPER LOW WILL BEGIN TO SLOWLY LIFT NORTHWARD AND WEAKEN. SURFACE HIGH MOVES EASTWARD TO THE MIDATLANTIC COAST... AND WINDS WILL BECOME MORE SOUTHEASTERLY SATURDAY NIGHT... BEGINNING A GRADUAL INCREASE IN MOISTURE ACROSS THE AREA. CONDITIONS WILL REMAIN DRY... BUT WITH INCREASING CLOUDS ASSOCIATED WITH THE UPPER LOW. HIGHS IN THE UPPER 80S AND LOWS IN THE MID 60S. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 355 AM FRIDAY... THE MODELS INDICATE THAT A CLOSED LOW CENTERED NEAR THE CENTRAL GULF COAST THIS MORNING WILL EJECT NORTHEASTWARD AS A SHORTWAVE TROUGH THROUGH THE SOUTHERN AND CENTRAL APPALACHIANS SUN-SUN NIGHT...WITH THE PAST COUPLE OF RUNS OF THE ECMWF OUT-PACING THE PREFERRED AMERICAN MODELS BY 6-12 HOURS WITH THE TIMING OF THIS FEATURE. THE ASSOCIATED FORCING FOR ASCENT WILL OVERSPREAD THE WESTERN CAROLINAS DURING PEAK HEATING...OR SHORTLY THEREAFTER WITH NORTHEASTERN EXTENT INTO THE NC SOUTHERN AND WESTERN NC PIEDMONT...WHICH IN CONJUNCTION WITH BOTH GRADUALLY INCREASING DEEP MOISTURE IN SW FLOW AND A WEAKENING CAP ALOFT...SHOULD PROVE SUPPORTIVE OF SCATTERED SHOWERS AND STORMS INVOF THE YADKIN RIVER AND ESPECIALLY WEST/IN THE MOUNTAINS...WHERE LOWER LEVEL FORCING/DIFFERENTIAL HEATING WILL BE MORE LIKELY TO COMPENSATE FOR A STILL RELATIVELY DRY BOUNDARY LAYER CHARACTERIZED BY SFC DEWPOINTS IN THE LOW-MID 60S. SOME OF THIS ACTIVITY COULD LINGER OVERNIGHT OVER THE PIEDMONT...AS THE S/W TROUGH TRACKS INTO WESTERN NC. NEAR CLIMO TEMPERATURES IN THE MID-UPPER 80S AND MID-UPPER 60S. THE MODELS CONTINUE TO SUGGEST ADDITIONAL SHORTWAVE ENERGY WILL AMPLIFY INTO THE SOUTHERN PLAINS TO LOWER-MID MS VALLEY AND EFFECTIVELY CAUSE THE PATTERN ALOFT TO RETROGRADE (DISCONTINUOUSLY)...AND CONSEQUENTLY ALLOW THE SUB-TROPICAL RIDGE BULGE WESTWARD ALONG THE SOUTHEAST US COAST. AT THE SAME TIME...A SEPARATE RIDGE ALOFT IS FORECAST TO BUILD ACROSS THE OH VALLEY AND GREAT LAKES...AND THE RESULT IN RECENT MODEL RUNS IS A SLOWER AND MORE WEST AND SOUTHWARD SUPPRESSED TRACK OF ERIKA. ANY ASSOCIATED TROPICAL MOISTURE OR AFFECTS ON CENTRAL NC WOULD LIKELY NOT OCCUR UNTIL MID-WEEK...AND EVEN THAT WILL BE CONDITIONAL ON 1) ERIKA NOT DISSIPATING ENTIRELY AS IT TRACKS WEST OR NORTHWEST THROUGH A HOSTILE ENVIRONMENT DURING THE NEXT DAY OR TWO...AND 2) THE AFOREMENTIONED BUILDING RIDGE NOT COMPLETELY SUPPRESSING THE SYSTEM --OR WHAT IS LEFT OF IT-- SOUTH AND WEST OF OUR REGION THROUGHOUT THE FORECAST PERIOD. GIVEN THE UNCERTAINTY AND POSSIBLE MINIMAL AFFECT FROM ERIKA...HAVE TRENDED THE FORECAST TOWARD CLIMO FOR THE UPCOMING WEEK...WITH SLIGHT-CHANCE DIURNAL POP AND TEMPERATURES NEAR TO SLIGHTLY ABOVE AVG. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AS OF 145 PM FRIDAY... 24 HOUR PERIOD: VFR CONDITIONS WILL PREVAIL AS HIGH PRESSURE EXTENDS IN TO THE REGION FROM THE MIDATLANTIC. OUTLOOK: VFR CONDITIONS REMAIN LIKELY. MAINLY DIURNAL SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE SUNDAY THROUGH MIDWEEK AS MOISTURE INCREASES ACROSS THE AREA. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...30 NEAR TERM...30 SHORT TERM...30 LONG TERM...26 AVIATION...30

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