Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 151757 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1255 PM EST MON DEC 15 2014 .SYNOPSIS...HIGH PRESSURE OVER THE AREA WILL SLIDE OFFSHORE TODAY IN ADVANCE OF A COLD FRONTAL PASSAGE FROM THE WEST ON TUESDAY. HIGH PRESSURE WILL THEN BUILD INTO THE AREA THROUGH FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 955 AM MONDAY... THE UPPER RIDGE IS DIRECTLY OVERHEAD THIS MORNING AND THE ASSOCIATED SURFACE HIGH IS CENTERED OVER THE NORTHERN COASTAL PLAIN. THIS DEEP LAYER RIDGE WILL SHIFT EAST TODAY AHEAD OF A HEIGHT FALLS OVER MIDWEST AND A LOW PRESSURE SYSTEM OVER THE MID MISSISSIPPI RIVER VALLEY. LITTLE CHANGE NEEDED TO THE NEAR TERM FORECAST...AS THE LEAD BAND OF CIRRUS CURRENTLY MOVING INTO WESTERN NC WILL HAVE LITTLE IMPACT IF AFTERNOON TEMPS. THE 1339M H10-H85 THICKNESS OBSERVED AT KGSO (12Z) IS 6M LOWER THAN THAT OF SUNDAY MORNING. LIGHT SOUTHERLY WIND THIS AFTERNOON SHOULD COMPENSATE AND HIGHS WILL BE WITHIN A DEGREE OR TWO OF SUNDAY`S VALUES... 59-63. -BLS ADVECTION OF WARM MOIST AIR INTO THE REGION WITHIN A BROAD UPPER LEVEL DIFFLUENCE ZONE WILL SUPPORT THICKENING CLOUD COVER AFTER MIDNIGHT ALONG WITH THE EASTWARD TRANSLATION OF A BROKEN BAND OF SHOWERS TOWARDS THE TRIAD AOA DAYBREAK. OTHERWISE...MILDER OVERNIGHT LOWS OWING TO THE CLOUD COVER AND LIGHT SOUTHERLY BREEZE. LOWS IN THE UPPER 30S TO LOWER 40S. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 235 AM MONDAY... WEAKENING SOUTHERN STREAM TROUGH WILL ASSUME A NEGATIVE TILT AS IT MOVES EAST-NORTHEASTWARD ACROSS THE EASTERN GREAT LAKES AND THEN INTO THE NORTHEAST AND NEW ENGLAND TUESDAY NIGHT...EVENTUALLY GETTING GETTING COMPLETELY ABSORBED BY THE NORTHERN STREAM TROUGH DIVING SOUTHEASTWARD OUT OF MANITOBA/ONTARIO. THE ONGOING PRE-FRONTAL BAND OF SHOWERS ACROSS WESTERN NC EMBEDDED IN THE LLJ ASSOCIATED WITH THE WARM CONVEYOR BELT WILL TRANSLATE EASTWARD THROUGH THE AFTERNOON...EXITING THE COASTAL PLAIN CORRIDOR AOA 21Z. TRAILING SFC COLD FRONT...WHICH IS PROGGED TO MOVE THROUGH THE AREA BETWEEN 21Z TO 06Z TIME...WILL ACTUALLY CROSS THE AREA WITH VERY LITTLE FANFARE...WITH MODELS SHOWING LITTLE TO NO PRECIP/SHOWERS ALONG THE ACTUAL FRONT. LITTLE TO NO INSTABILITY ALONG WITH A DISCONNECT BETWEEN THE LOWER AND MID/UPPER LEVEL SATURATION AND LIFT WILL RESULT IN LIGHT QPF AMOUNTS OF LESS THAN A TENTH OF AN INCH OR LESS. FOR THE SAME REASONING HAVE CHOSEN TO KEEP POPS AT HIGH CHANCE. TEMPERATURES...HIGHS TUESDAY DEPENDENT UPON EXTENT OF SHOWER COVERAGE. HOWEVER...GIVEN LATE ARRIVAL OF COLD FRONT...EXPECT ANOTHER DAY OF ABOVE NORMAL TEMPERATURES. HIGHS RANGING FROM MID/UPPER 50S TO LOWER 60S SOUTH. LOWS TUESDAY NIGHT IN THE UPPER 30S NW TO LOWER 40S SE. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 230 AM MONDAY... WEDNESDAY THROUGH THURSDAY NIGHT: HIGH PRESSURE WILL RIDGE INTO THE REGION THROUGH THURSDAY. THE FLOW ALOFT WILL BECOME MORE ZONAL FOR THIS PERIOD...WITH GENERALLY WEST-NORTHWEST FLOW OVER CENTRAL NC. EXPECT DRY WEATHER TO DOMINATE DURING THIS TIME WITH CLEAR TO PARTLY CLOUDY SKIES. HIGHS IN THE UPPER 50S TO LOW 60S WEDNESDAY... DECREASING SLIGHTLY FOR THURSDAY...LOW TO MID 50S. OVERNIGHT LOWS MAINLY IN THE LOW TO MID 30S EXPECTED. FRIDAY AND FRIDAY NIGHT: SURFACE HIGH PRESSURE WILL LINGER OVER THE REGION ON FRIDAY AND THE WEATHER IS EXPECTED TO REMAIN DRY INTO THE OVERNIGHT HOURS...ALTHOUGH CLOUD COVER WILL INCREASE THROUGH THE DAY FRIDAY. HIGHS WILL BE SIMILAR TO THURSDAY...LOW TO MID 50S. THE INCREASED CLOUD COVER MAY YIELD LOWS A FEW DEGREES HIGHER THAN PREVIOUS NIGHTS...GENERALLY IN THE MID 30S. SATURDAY THROUGH SUNDAY: THERE IS STILL QUITE A BIT OF DEVIATION IN THE MODELS WITH THE DEVELOPMENT OF THE NEXT LOW PRESSURE SYSTEM THAT IS EXPECTED TO IMPACT CENTRAL NC ON SATURDAY. HOWEVER...BOTH AGREE THAT A SURFACE LOW WILL DEVELOP OVER THE GULF COAST ON FRIDAY AND MOVE GENERALLY EAST OR NORTHEAST ON SATURDAY. MEANWHILE ALOFT...A TROUGH WILL DIG OVER THE MIDWEST...DEEPER/MORE AMPLIFIED AND A BIT SLOWER IN THE ECMWF VERSUS THE QUICKER AND LESS AMPLIFIED GFS SOLUTION. THE ECMWF CONTINUES TO BE THE WETTER SOLUTION...HOWEVER BOTH MODELS GENERATE PRECIP OVER THE AREA ON SATURDAY AND INTO SATURDAY NIGHT...AND MOVING OUT OF CENTRAL NC BY SUNDAY AFTERNOON. GIVEN THE CONTINUED MODEL DIFFERENCES AND UNCERTAINTY...CONFIDENCE IN THE SPECIFIC DETAILS IN THIS PART OF THE FORECAST REMAINS SOMEWHAT LOW...BUT THERE IS RELATIVELY HIGH CONFIDENCE THAT THERE WILL BE PRECIP ON SATURDAY AND INTO SATURDAY NIGHT. WHETHER THERE WILL BE ANY P-TYPE OR SEVERE WEATHER CONCERNS WILL LARGELY DEPEND ON THE POSITION AND TIMING OF THE LOW AS IT PROGRESSES INTO THE REGION. GIVEN THE DIFFERENCES...UNCERTAINTY...AND LOW CONFIDENCE NOTED ABOVE...WILL REFRAIN FROM GOING THROUGH EVERY POSSIBLE SCENARIO AND JUST NOTE TWO THINGS. FIRST...ANY P-TYPE CONCERNS WOULD BE LIMITED TO THE FAR NORTH AND WEST EARLY SATURDAY MORNING AT THE ONSET OF PRECIP...ALTHOUGH FOR NOW KEEP TEMPS JUST ABOVE FREEZING AND THE PRECIP LIQUID. SECOND...IF THERE IS A THREAT FOR SEVERE WEATHER...IT WOULD LARGELY BE LIMITED TO THE FAR SOUTHEAST...BUT FOR NOW MENTION OF THUNDER IS LEFT OUT OF THE FORECAST. TEMPERATURES WILL ALSO HINGE ON HOW THIS SYSTEM DEVELOPS AND THUS CONFIDENCE IS LOW IN THAT ASPECT OF THE FORECAST AS WELL...BUT FOR NOW EXPECT HIGHS IN THE LOW 40S TO LOW 50S FROM NW TO SE ON SATURDAY...LOWS GENERALLY IN THE MID 30S. SLIGHTLY WARMER ON SUNDAY...HIGHS IN THE MID 40S TO AROUND 50 DEGREES...COOLER OVERNIGHT...LOWS IN THE LOW TO MID 30S. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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AS OF 1255 PM MONDAY... HIGH PRESSURE CONTINUES TO DOMINATE THIS AFTERNOON WITH VFR CONDITIONS AND A LIGHT WIND THAT WILL SLOWLY BECOME SOUTHERLY THIS EVENING. MOISTURE WILL BEGIN TO INCREASE MORE READILY TONIGHT AHEAD OF A FRONTAL SYSTEM MOVING THROUGH THE TN VALLEY. HOWEVER... CONFIDENCE IN VFR CONDITIONS IS HIGH THROUGH 06Z. AFTER 06Z...SOME MODELS INDICATE VERY SHALLOW MOISTURE ACROSS THE COASTAL PLAIN THAT MAY RESULT IN PATCHY FOG/LOW CLOUDS PRIOR TO 12Z. A BAND OF SHOWERS WILL THEN MOVE INTO THE WESTERN PIEDMONT AFTER 12Z...WHICH SHOULD RESULT IN MAINLY MVFR CEILINGS AS IT MOVES WEST TO EAST ACROSS THE AREA BETWEEN 12Z AND 21Z. OUTLOOK...ONCE A BAND OF SHOWERS MOVES EAST OF THE AREA TUESDAY AFTERNOON...A COLD FRONT WILL PUSH EAST THROUGH CENTRAL NC...WITH DRIER AIR AND VFR CONDITIONS RETURNING TUESDAY NIGHT. THE NEXT CHANCE OF WIDESPREAD SUB-VFR CONDITIONS WILL BE DURING THE UPCOMING WEEKEND.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...CBL NEAR TERM...CBL/BLS SHORT TERM...CBL LONG TERM...KC AVIATION...BLS

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