Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 240702 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 301 AM EDT THU APR 24 2014 .SYNOPSIS...HIGH PRESSURE WILL BUILD SOUTH ACROSS THE MIDDLE ATLANTIC STATES TODAY...THEN OFFSHORE TONIGHT. A WARM FRONT WILL LIFT NORTH THROUGH NC AND VA FRIDAY MORNING...FOLLOWED BY THE PASSAGE OF A COLD FRONT FRIDAY EVENING. && .NEAR TERM /THROUGH TONIGHT/... AS OF 245 AM THURSDAY... A REINFORCING BACKDOOR COLD FRONT...EVIDENT AS A RADAR FINE LINE ON KAKQ/KRAX/KMHX BETWEEN 00-06Z...HAD SETTLED INTO THE SOUTHERN COASTAL PLAIN/SANDHILLS/SOUTHERN PIEDMONT DURING THE PAST HOUR OR TWO. THIS BOUNDARY MARKS THE LEADING EDGE OF A 1021 MB HIGH OVER EASTERN MI...WHICH WILL BUILD SOUTH ACROSS THE MIDDLE ATLANTIC STATES TODAY...AND RESULT IN TEMPERATURES 2-3 DEGREES COOLER THAN THOSE OF WED. SKIES WILL BE SUNNY TO START...BECOMING MOSTLY TO PARTLY SO FROM SOUTH TO NORTH...AS A RESULT OF A BAND OF 10-15 THOUSAND FT MOISTURE OVER THE UPPER MIDWEST AND OH VALLEY FORECAST TO SKIRT IN NW MID LEVEL FLOW MAINLY THE NORTHERN HALF OF THE FORECAST AREA THIS AFTERNOON. OTHERWISE SOME PASSING THIN CIRRUS OVER THE TN VALLEY THIS MORNING WILL ARRIVE AREA-WIDE ABOUT THE SAME TIME. THE SURFACE RIDGE AXIS WILL HAVE SHIFTED OFFSHORE BY THIS EVENING AND PROMOTE A DEVELOPING RETURN/SOUTHERLY FLOW (PARTICULARLY JUST ABOVE A STABLE/NOCTURNAL INVERSION)...AND CONSEQUENTLY ALLOW THE SURFACE BOUNDARY TO RETREAT NORTH AS A WARM FRONT IN ADVANCE OF A SHORTWAVE TROUGH ALOFT AND ATTENDANT SURFACE LOW LIFTING TOWARD THE OH VALLEY/LOWER GREAT LAKES. THE APPROACH AND PASSAGE OF THE BOUNDARY VERY LATE TONIGHT THROUGH EARLY FRI WILL RESULT IN THE DEVELOPMENT OF STRATUS...LOWEST AND WITH GREATEST COVERAGE OVER THE WESTERN/SOUTHERN PIEDMONT. SCATTERED ELEVATED SHOWERS ARE ALSO APT TO DEVELOP NORTHWARD WITH THE PASSAGE OF THE FRONT...AS MOISTENING AT THE NOSE OF THE LLJ AND INVOF THE BOUNDARY DRIVE WEAK/SHALLOW ELEVATED INSTABILITY AMIDST A LIFT-INDUCING REGIME OF LOW LEVEL WAA AND HEIGHT FALLS ALOFT (AHEAD OF THE AFOREMENTIONED SHORTWAVE TROUGH). WIDE RANGING LOWS FROM THE MID 40S IN CLOSEST PROXIMITY TO THE DEPARTING SFC RIDGE AXIS AND PERIODS OF CALM OVER THE COASTAL PLAIN...TO LOWER 50S OVER THE SOUTHERN PIEDMONT. && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
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AS OF 300 AM THURSDAY... FRIDAY AND FRIDAY NIGHT: A DEAMPLIFYING SHORTWAVE TROUGH WILL APPROACH AND CROSS THE REGION DURING THE DAY ON FRIDAY...WITH THE ASSOCIATED TRAILING WEAK COLD FRONT EXPECTED TO MOVE THROUGH THE REGION FRIDAY AFTERNOON/EVENING. AS A RESULT...PRECIP CHANCES WILL INCREASE FROM WEST TO EAST FRIDAY MORNING...BEFORE GRADUALLY DECREASING DURING THE EVENING HOURS. THERE ARE STILL SEVERAL DIFFERENCES IN THE MODELS...MOST NOTABLY BEING THE STRENGTH/TIMING OF THE SHORTWAVE ENERGY...WHICH WILL HAVE IMPLICATIONS ON OUR PRECIP AND SUBSEQUENT SEVERE THREAT. THE GFS MOVES THE WEAK ENERGY ACROSS THE AREA EARLY IN THE DAY...WHILE THE ECMWF IS STRONGER/DEEPER WITH THIS FEATURE AND THEREFORE SOMEWHAT SLOWER IN ITS PROGRESSION (WITH THE NAM BEING IN THE MIDDLE). WITH THE EARLIER ARRIVAL OF THE SHORTWAVE (PER GFS)...SHOWERS SHOULD BE ONGOING DURING THE MORNING AHEAD OF THE APPROACHING SURFACE FRONT... THUS LIMITING THE AFTERNOON DESTABILIZATION. IN ADDITION...OUR AREA WOULD BE ON THE SUBSIDENT SIDE OF THE SHORTWAVE BEFORE THE FRONT MOVES THROUGH. ALL OF THIS WOULD LEAD TO A LIMITED SEVERE WEATHER THREAT. HOWEVER...WITH THE SLOWER PROGRESSION...FEATURES COULD LINE UP MORE FAVORABLY...ESPECIALLY ACROSS THE EASTERN HALF OF THE FORECAST AREA. THIS WILL CONTINUED TO BE CLOSELY MONITORED OVER THE NEXT COUPLE OF DAYS. NEVERTHELESS...EVEN THE GFS INDICATES SOME MARGINAL INSTABILITY (MOSTLY ACROSS THE EAST) AS TEMPS RISE TO NEAR 80 DEGREES AND THEREFORE CANNOT RULE OUT AN ISOLATED STRONG TO SEVERE STORM. SATURDAY THROUGH SUNDAY NIGHT: DRY WEATHER WITH SEASONABLE TEMPERATURES WILL ENSUE FOR THE WEEKEND IN THE WAKE OF THE COLD FRONT FRIDAY NIGHT AS A MILD SURFACE HIGH SURFACE BUILDS INTO THE AREA LOWER MS VALLEY/NORTHERN GULF COAST STATES. A COMPACT UPPER LOW/TROUGH OVER THE UPPER GREAT LAKES WILL MOVE EASTWARD-SOUTHEASTWARD THROUGH SOUTHERN NEW ENGLAND ON SUNDAY. ATTENDANT HEIGHT FALLS ALOFT ACROSS THE NORTHERN MID-ATLANTIC STATES WILL ATTEMPT TO DRIVE A BACK-DOOR COLD FRONT SOUTHWARD INTO THE AREA ON SUNDAY...BUT GIVEN S/W RIDGE ALOFT BUILDING IN FROM THE WEST...THINK THIS WIL CURTAIL SOUTHWARD PUSH OF THE FRONT...WITH EXPECTATIONS OF THE FRONT STALLING NORTH OF THE AREA. HIGHS IN THE 70S. LOWS IN THE 50S.
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&& .LONG TERM /MONDAY THROUGH SATURDAY/... AS OF 300 AM THURSDAY... AN ACTIVE AND UNSETTLED WEATHER PATTERN LOOKS TO BE SETTING UP ANYWHERE FROM THE SOUTHERN PLAINS EASTWARD FOR AT LEAST THE FIRST HALF OF NEXT WEEK..IF NOT LONGER OWING TO THE BLOCKING PATTERN OVER THE SOUTHEAST CANADA TOWARDS GREENLAND THAT WILL HAMPER THE EASTWARD PROGRESSION OF A STRONG CLOSED LOW FROM THE SOUTHWEST INTO THE CENTRAL CONUS. REGARDING SENSIBLE WEATHER IMPACTS...WHILE MODEL SPREAD IS CURRENTLY TOO HIGH TO ELABORATE ON FORECAST SPECIFICS/DETAILS...GIVEN SUCH A POTENT SYSTEM WITH A HIGH LIKELIHOOD OF DEEP GULF MOISTURE TRANSPORT NORTHWARD INTO THE AREA DURING THE CLIMATOLOGICALLY FAVORED SPRING CONVECTIVE SEASON OF LATE APRIL/EARLY MAY...CENTRAL NC WILL HAVE TO BE ON THE LOOKOUT FOR THE POSSIBILITY OF EXCESSIVE RAINFALL AND SEVERE STORMS MONDAY THROUGH WEDNESDAY. PROSPECTS OF WIDESPREAD CLOUDS AND PRECIP WILL KEEP TEMPERATURES NEAR NORMAL. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 300 PM WEDNESDAY... HIGH PRESSURE OVER THE AREA ON SUNDAY WILL RESULT IN QUIET WEATHER FOR CENTRAL NC...WITH TEMPS NEAR TO SLIGHTLY ABOVE NORMAL. THE HIGH WILL SHIFT OFFSHORE LATE SUNDAY INTO MONDAY AHEAD OF A STRONG SYSTEM THAT WILL LIKELY BE A BIG SEVERE WEATHER MAKER FOR THE CENTRAL CONUS OVER THE WEEKEND AND EARLY NEXT WEEK. THERE IS STILL A LOT TO BE WORKED OUT WITH REGARD TO THE DETAILS OF THIS SYSTEM...THEREFORE FORECAST UNCERTAINTY REMAINS HIGH. OVERALL THIS CUTOFF LOW WILL SLOWLY MAKE ITS WAY EAST THROUGH THE MIDDLE OF NEXT WEEK...WITH OUR BEST PRECIP CHANCES LOOKING TO BE ON TUESDAY...ALTHOUGH SOME OVERRUNNING PRECIP WILL BEGIN EARLY MONDAY MORNING. TEMPS SHOULD BE NEAR TO SLIGHTLY BELOW NORMAL...BUT WILL ULTIMATELY DEPEND ON THE AMOUNT/TIMING OF CLOUDS/PRECIP. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... AS OF 155 AM THURSDAY... HIGH PRESSURE WILL BUILD SOUTH FROM THE GREAT LAKES AND RESULT IN A HIGH CONFIDENCE OF VFR CONDITIONS THROUGH THE TAF PERIOD. IN ANTICYCLONIC FLOW AROUND THE HIGH...NNE SURFACE WINDS THIS MORNING WILL BECOME LIGHT AND VARIABLE BENEATH THE RIDGE AXIS BY MIDDAY... THEN LIGHT SOUTHERLY...THIS AFTERNOON AT TRIAD TERMINALS...AND THIS EVENING ELSEWHERE. PASSING MID CLOUDS (BETWEEN 10 AND 15 THOUSAND FEET) IN WNW FLOW ALOFT WILL SKIRT THE NORTHERN PIEDMONT THIS AFTERNOON. OUTLOOK: THE DEVELOPING SOUTHERLY RETURN FLOW AND ASSOCIATED APPROACH OF A SURFACE WARM FRONT FROM THE SOUTH WILL RESULT IN THE DEVELOPMENT OF IFR-MVFR STRATUS LATE TONIGHT AND EARLY FRI...LOWEST AND MOST LIKELY AT TRIAD TERMINALS. THE PASSAGE OF THE WARM FRONT WILL ALSO SUPPORT SCATTERED SHOWERS FRI MORNING...FOLLOWED BY A BREEZY SW SURFACE WIND AND ANOTHER ROUND OF SCATTERED SHOWERS - AND THUNDERSTORMS - ALONG AND AHEAD OF A COLD FRONT FRI AFTERNOON AND EVENING. UNSETTLED WEATHER WILL RETURN AGAIN EARLY NEXT WEEK..AND WILL LIKELY LINGER THROUGH MID-WEEK. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...KRD/CBL LONG TERM... CBL AVIATION...MWS

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