Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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943 FXUS62 KRAH 090325 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1025 PM EST MON FEB 8 2016 .SYNOPSIS... A SERIES OF DISTURBANCES WILL ROTATE ACROSS THE CAROLINAS AND MIDDLE ATLANTIC STATES THROUGH TUE...IN CYCLONIC FLOW ALOFT AROUND AN ANOMALOUSLY STRONG MID-UPPER LEVEL LOW OVER THE LOWER GREAT LAKES AND OH VALLEY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1025 PM MONDAY... A LEAD COLD FRONT AND BAND OF SHOWERS THAT PRODUCED PEAK WIND GUSTS OF 34 KTS AT FAY; 35 KTS AT FBG; AND 37 KTS AT POB...HAS MOVED EAST OF CENTRAL NC THIS EVENING. WHILE THE ASSOCIATED LEAD SHORTWAVE TROUGH WILL LIFT NORTHEAST THROUGH EASTERN NC/VA AND MAINTAIN A CHANCE OF SHOWERS THERE TONIGHT...THOSE ARE EXPECTED TO REMAIN EAST OF CENTRAL NC. HOWEVER...WV SATELLITE IMAGERY DEPICTS ANOTHER COMPACT CIRCULATION DIGGING ACROSS THE LOWER OH VALLEY THIS EVENING...AND THIS FEATURE AND THE ACCOMPANYIGN SURFACE COLD FRONT ARE FORECAST TO MOVE INTO THE CENTRAL APPALACHIANS BY 12Z TUE. FORCING FOR ASCENT DOWNSTREAM OF THE MID-UPPER FEATURE...ACROSS VA AND NC...IN CONJUNCTION WITH VERY STEEP LAPSE RATES IN EXCESS OF 7.5 C/KM THROUGH A VERY DEEP LAYER (FROM THE SURFACE TO 500 MB) SAMPLED BY THE 00Z GSO RAOB...WILL RESULT IN SCATTERED SNOW SHOWERS AND FLURRIES OVERNIGHT...PARTICULARLY ACROSS THE NORTHERN PIEDMONT/IN CLOSEST PROXIMITY TO THE AFOREMENTIONED COMPACT DISTURBANCE APPROACHING FROM THE WNW. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 315 PM MONDAY... THE DEEP UPPER TROUGH TO OUR WEST WILL MAKE ITS WAY OVERHEAD ON TUESDAY...WITH A DISTURBANCE WITHIN THE TROUGH FORECAST TO SWING ACROSS VA AND NORTHERN NC DURING THE AFTERNOON. STEEP LAPSE RATES ALOFT...ALONG WITH THE STRONG DCVA AND MOISTENING BETWEEN 5-10K FEET(COINCIDENT WITH THE ICE NUCLEATION ZONE)...MAY LEAD SOME ISOLATED SHOWERS NEAR THE NC/VA BORDER....ESPECIALLY LATER IN THE DAY FROM ROXBORO TO ROANOKE RAPIDS. HOWEVER...MODELS CONTINUE TO INDICATE MUCH BETTER COVERAGE NORTH OF THE BORDER AND THE ECMWF IS THE ONLY MODEL TO INDICATE ANY QPF IN THE NORTHERN COASTAL PLAIN. HIGHS WILL REACH THE UPPER 30S WEST TO MID 40S EAST...BUT DEWPOINTS IN THE LOWER 20S WOULD PUSH WETBULB PROFILES COLD ENOUGH TO SUPPORT SNOW SHOWERS OR FLURRIES. COLD ADVECTION WILL CONTINUE TUESDAY NIGHT BEHIND THE ARCTIC FRONT...WITH TEMPS FALLING INTO THE LOW/MID 20S. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... AS OF 400 PM MONDAY... COLD MID-LATE WEEK...AND EVEN COLDER --PERHAPS RECORD SO-- THIS WEEKEND...WITH A COUPLE OF OPPORTUNITIES FOR PRECIPITATION (LATE FRI- FRI NIGHT AND LATE MON-TUE). A HIGHLY AMPLIFIED PATTERN CHARACTERIZED BY A STRONG WESTERN NOAM RIDGE AND EASTERN NOAM TROUGH WILL UNDERGO A BRIEF RELAXATION LATE IN THE WEEK...IN ADVANCE OF A POLAR VORTEX THAT WILL SETTLE ACROSS SOUTHEAST CANADA AND NEW ENGLAND...AND EFFECTIVELY RE-AMPLIFY THE FLOW...THIS WEEKEND. A PROGRESSIVE PACIFIC TROUGH WILL THEN FLATTEN THE WESTERN NOAM RIDGE SUN-MON. WITHIN THE NW FLOW ALOFT...SHEAR VORTICITY AND ASSOCIATED LOW AMPLITUDE TROUGHS WILL AMPLIFY INTO THE BASE OF THE TROUGH OVER THE EASTERN STATES MID-LATE WEEK...WITH EACH SUPPORTING AN AREA OF LIGHT PRECIPITATION STREAKING SOUTHEASTWARD FROM THE NORTHERN PLAINS TO THE CENTRAL-SOUTHERN APPALACHIANS. THE MODELS SUGGEST THE LEAD DISTURBANCE WILL HAVE A MORE LIMITED MOISTURE SUPPLY AND LITTLE LOW LEVEL SUPPORT FOR THE MAINTENANCE OF PRECIPITATION EAST OF THE APPALACHIANS ON THU...WHILE THE SECOND WILL BE ACCOMPANIED BY A LOW- MID LEVEL WAA REGIME AND CONSEQUENTLY HAVE A BETTER CHANCE OF SUPPORTING A BRIEF PERIOD OF LIGHT PRECIPITATION...MOST LIKELY IN THE FORM OF SNOW...OR A RAIN/SNOW MIX ACROSS THE SOUTHERN COUNTIES...CENTERED AROUND FRI EVENING. A POTENTIALLY MORE SIGNIFICANT SYSTEM WILL ACCOMPANY THE AFOREMENTIONED PACIFIC TROUGH...AS THE AFOREMENTIONED POLAR VORTEX SUPPRESSES THE NORTHERN STREAM/PROMOTES CONFLUENT FLOW ALOFT...WHICH WOULD SUPPORT THE SOUTHEASTWARD MAINTENANCE OF A 1040-1045 MB HIGH FROM THE ARCTIC. WHILE THIS WOULD YIELD INITIALLY JUST NEAR RECORD COLD CONDITIONS FOR THE WEEKEND...THE EASTWARD MIGRATION OF THE PACIFIC TROUGH AND AN INCREASINGLY ACTIVE SOUTHERN STREAM WOULD RAISE THE PROBABILITY OF STREAM INTERACTION...AND STORMINESS AND APPALACHIAN COLD AIR DAMMING...MON-TUE. && .AVIATION /00Z FRIDAY THROUGH SATURDAY/... AS OF 730 PM MONDAY... A BAND OF SHOWERS WITH GUSTY WINDS AND MVFR CONDITIONS IS CURRENTLY MOVING ACROSS CENTRAL NC THIS EVENING... IN ADVANCE OF A SURFACE COLD FRONT. THE BAND OF SHOWERS HAS JUST MOVED TO THE EAST OF KFAY AND KRDU THIS EVENING... WITH ONLY KRWI STILL EXPERIENCING THE PRECIP AND THREAT OF GUSTY WINDS AND SUB VFR CONDITIONS (GENERALLY WIND GUSTS IN THE 25 TO 35 MPH RANGE POSSIBLY... WITH MVFR CONDITIONS POSSIBLE). THE MAIN SURFACE COLD FRONT WILL CROSS THE AREA THIS EVENING INTO EARLY TUESDAY MORNING... ENDING ANY LINGERING THREAT OF ISOLATED SHOWERS AND SUB-VFR CONDITIONS. WESTERLY WINDS WILL INCREASE TO 9-12KT AND GUSTS TO AROUND 18 TO 23 KTS ON TUESDAY... WITH POSSIBLY SOME CIGS AT AROUND 4 TO 5 KFT ALONG WITH MAYBE A FEW SPRINKLES OR FLURRIES. OUTLOOK...WEDNESDAY AND THURSDAY WILL FEATURE VFR CONDITIONS WITH GUSTY NORTHWEST WINDS OF 20-25 KTS. THE NEXT CHANCE OF SUB-VFR CONDITIONS WILL COME FRIDAY AS A WEAK LOW PRESSURE SYSTEM CROSSES THE AREA. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...2 NEAR TERM...2 SHORT TERM...SMITH LONG TERM...2 AVIATION...7/SMITH

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