Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 180712 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 310 AM EDT THU SEP 18 2014 .SYNOPSIS...A WEAK SURFACE TROUGH WILL EXTEND NORTH-TO-SOUTH OVER THE FOOTHILLS AND WESTERN PIEDMONT TODAY THEN DISSIPATE ON FRIDAY. COOL CANADIAN HIGH PRESSURE CENTERED OVER THE GREAT LAKES TODAY WILL DRIFT EAST AND EXTEND INTO THE CAROLINAS FRIDAY AND SATURDAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 310 AM THURSDAY... TODAY...WATER VAPOR IMAGERY DEPICTS A WEAK MID LEVEL S/W EXITING THE TN VALLEY EARLY THIS MORNING. THIS FEATURE WILL PROGRESS EAST AND CROSS CENTRAL NC LATER THIS MORNING-EARLY AFTERNOON. NOT MUCH IN THE MANNER OF WEATHER ASSOCIATED WITH THIS FEATURE AT THIS TIME. SFC ANALYSIS DEPICTS A WEAK INVERTED SURFACE TROUGH OVER THE WESTERN PIEDMONT. MODEL GUIDANCE MAINTAINS THIS FEATURE IN VICINITY OF THE YADKIN RIVER VALLEY THROUGH TONIGHT. WEAK MOISTURE CONVERGENCE WAS OCCURRING IN VICINITY OF THIS TROUGH AS SFC DEWPOINTS WERE IN THE LOW-MID 60S. THIS POOLING HAS RESULTED IN THE FORMATION OF LOW STRATUS AND FOG EARLY THIS MORNING OVER OUR FAR WESTERN COUNTIES. THIS AREA OF LOW CLOUDS/FOG MAY EXPAND EAST...POSSIBLY AS FAR EAST AS THE TRIANGLE AREA BY DAYBREAK. LATER THIS MORNING...THE APPROACH OF THE MID LEVEL S/W MAY TRIGGER A FEW SHOWERS IN VICINITY OF THE SURFACE TROUGH...MAINLY OVER THE WESTERN-SOUTHERN PIEDMONT. DUE TO MARGINAL INSTABILITY AND WEAK LIFT...BELIEVE THAT COVERAGE WILL BE NO WORSE THAN 20 PERCENT. EARLY MORNING CLOUDINESS WILL GIVE WAY TO PARTLY-MOSTLY SUNNY SKIES WITH MORE SUN THAN CLOUDS ANTICIPATED EAST OF HIGHWAY 1. MAX TEMPS IN THE UPEPR 70S -LOWER 80S. TONIGHT...AVAILABLE LOW LEVEL MOISTURE IN THE WESTERN PIEDMONT...POOLING ALONG THE SFC TROUGH...MAY MAINTAIN A FEW SHOWERS THROUGH THE LATE EVENING HOURS. OTHERWISE AVAILABLE LOW LEVEL MOISTURE MAY CAUSE THE FORMATION OF FOG AND/OR LOW CLOUDS...ESPECIALLY OVER THE PIEDMONT. MIN TEMPS NEAR 60-LOWER 60S.
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&& .SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
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AS OF 310 AM THURSDAY... DRY AIR RIDGE WILL BUILD INTO AND EXTEND ACROSS CENTRAL NC THIS PERIOD. THE DRIEST AIR WILL ENCOMPASS THE NE PIEDMONT AND MOST OF THE COASTAL PLAIN. THE LOW LEVEL EASTERLY FLOW MAY CAUSE MOISTURE TO BANK UP AGAINST THE HIGHER TERRAIN OF WESTERN NC WHICH MAY SPILL INTO OUR FAR WESTERN COUNTIES. THE MOISTURE APPEARS TOO SHALLOW TO SUPPORT ANY SHOWER ACTIVITY PLUS LIFT IS MINIMAL THIS PERIOD. MAX TEMPS SIMILAR TO TODAY IN THE UPPER 70S TO THE LOWER 80S. MIN TEMPS FRIDAY NIGHT IN THE UPPER 50S TO THE LOWER 60S.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/... AS OF 253 PM WEDNESDAY... FRIDAY THROUGH SATURDAY: EASTERN US TROUGH WILL PULL EAST AND OUT TO SEA OUT ON FRIDAY... BUT NOT WITHOUT LEAVING BEHIND A REMNANT MID- LEVEL CIRCULATION TO MEANDER OFF THE SE COAST THROUGH EARLY SUNDAY. AT THE SURFACE...PROGRESSIVE CANADIAN HIGH OVER NEW ENGLAND WILL QUICKLY MOVE EAST OUT INTO THE NORTHERN ATLANTIC...BECOMING ELONGATED AS IT SHIFTS FARTHER OFFSHORE. IN THE WAKE OF THE EXITING TROUGH...HEIGHTS INCREASE OVER THE AREA...WHICH SHOULD KEEP THE MID- LEVEL CIRCULATION OFF THE SE COAST AT BAY AND SECURE DRY CONDITIONS ACROSS CENTRAL NC. AS FAR AS TEMPERATURES...PROGRESSIVE NATURE OF THE PARENT HIGH AND ORIENTATION OF THE ASSOCIATED RIDGE AXIS IS EXPECTED TO YIELD A LONG FETCH OF EAST-NORTHEASTERLY LOW-LEVEL MARITIME FLOW INTO THE AREA AND KEEP THE BRUNT OF THE COOLER AND DRIER AIR TO OUR NORTH...WHILE SUPPORTING PERIODIC PARTLY TO BROKEN CLOUDINESS IN THE WAY OF MORNING STRATUS AND A DIURNALLY ENHANCED CU FIELD. HIGHS IN THE MID 70S NORTH TO AROUND 80 SOUTH. LOWS FRIDAY NIGHT IN THE MID 50S NORTH TO NEAR 60 SOUTH. LOWS SATURDAY NIGHT A GOOD CATEGORY WARMER...IN THE UPPER 50S TO LOWER 60S. SUNDAY THROUGH MONDAY: 40 TO 60 METER HEIGHT FALLS TRAVERSING THE REGION IN ADVANCE OF THE AMPLIFYING UPPER LEVEL TROUGH SWINGING EASTWARD ACROSS THE EASTERN US WILL DRIVE A SURFACE COLD FRONT THROUGH THE AREA MONDAY AFTERNOON. IN ADVANCE OF THE UPPER TROUGH...AFOREMENTIONED MID-LEVEL CIRCULATION/LOW OFF THE SOUTHEAST COAST WILL FINALLY GET KICKED EAST-NORTHEASTWARD...LIFTING UP THE NC COAST AND THEN OUT INTO THE ATLANTIC ON SUNDAY. THE LATEST 12Z/17 GFS IS STRONGER WITH THIS FEATURE AND SUGGEST IT COULD POTENTIALLY ENHANCE THE ONSHORE MARITIME FLOW...POSSIBLY RESULTING IN SLIGHTLY CLOUDIER/COOLER CONDITIONS...MAINLY ACROSS EASTERN PORTIONS OF THE FORECAST AREA ON SUNDAY. OTHERWISE...WITH LOW-LEVEL THICKNESSES PROJECTED TO CLIMB 20 METERS ABOVE NORMAL...HIGHS IN THE LOWER TO MID 80S. THERE ARE SOME MINOR MODEL TIMING DIFFERENCES WITH FROPA ON MONDAY...WITH THE EC A GOOD 12 HOURS FASTER TO PUSH THE FRONT THROUGH THE AREA. GIVEN LIMITED/SHALLOW MOISTURE AVAILABILITY...CONVECTION ALONG THE FRONT WILL NEED TO UTILIZE FAVORABLE DIURNAL TIMING/INSTABILITY TO SUPPORT SLIGHT/SMALL CHANCE POPS MONDAY AFTERNOON/EARLY EVENING. TUESDAY AND WEDNESDAY: BELOW NORMAL TEMPERATURES ARE EXPECTED UNDERNEATH THE EASTERN US TROUGH AND SUPPORTED IN THE LOW-LEVELS BY NORTHERLY FLOW VIA BUILDING STRONG ~1030MB SURFACE HIGH. HIGHS 70 TO 75. LOWS IN THE 50S. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... AS OF 150 AM THURSDAY... CURRENT VFR CONDITIONS ACROSS CENTRAL NC AT 05Z WILL PRETTY MUCH PERSIST OVERNIGHT INTO THE MORNING HOURS. THERE WILL BE A FEW PATCHES OF MVFR/IFR CEILING AND MVFR/IFR VISIBILITY DUE TO GROUND FOG. THE PROBABILITY OF THIS OCCURRING LOOKS HIGHEST IN THE VICINITY OF KFAY. A WEAK SURFACE TROUGH OVER THE WESTERN PIEDMONT AND FOOTHILLS WILL SERVE AS A FOCUS FOR MOISTURE POOLING. THIS FEATURE COUPLED WITH HEATING AND THE PASSAGE OF A WEAK MID LEVEL TROUGH MAY TRIGGER A FEW SHOWERS LATE THIS MORNING INTO THE AFTERNOON. DUE TO EXPECTED SPARSE COVERAGE...WILL OMIT FROM MENTIONING IN THE TRIAD TERMINALS AT THIS TIME. OTHERWISE...EXPECT VFR CONDITIONS WITH CLOUD BASES GENERALLY BET3500-5000FT. LATE TONIGHT INTO EARLY FRIDAY...MAY SEE AREAS OF LOW CLOUDS AND/OR FOG WITH ASSOCIATED MVFR/IFR CONDITIONS. THIS OCCURRENCE LOOKS MORE PROBABLE IN THE KFAY VICINITY. EXPECT VFR CONDITIONS FOR MOST OF FRIDAY THROUGH SUNDAY WITH JUST BRIEF INSTANCES OF EARLY MORNING FOG. AN APPROACHING SURFACE FRONT LATE SUNDAY INTO MONDAY MAY BRING A BRIEF PERIOD OF ADVERSE AVIATION CONDITIONS ON MONDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...CBL AVIATION...WSS

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