FXUS62 KRAH 100534 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1235 AM EST WED FEB 10 2010 .SYNOPSIS... A STRONG LOW PRESSURE SYSTEM ALOFT WILL MOVE INTO VIRGINIA WEDNESDAY...PRODUCING VERY WINDY CONDITIONS IN NORTH CAROLINA DURING THE DAY WEDNESDAY. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... AS OF 930 PM... LITTLE CHANGE TO FORECAST. WIDESPREAD RAINS HAVE EXITED THE WESTERN PIEDMONT... AND ANY FUTURE PRECIPITATION TONIGHT BEHIND THE EXITING RAIN SHIELD WILL BE BRIEF AND SCATTERED. SLIGHT CHANCE POPS ARE LOCATED NORTH OF HIGHWAY 64 UNTIL JUST AFTER MIDNIGHT WHERE THE BEST MOISTURE AND DYNAMICS ARE LOCATED. MODELS IN GOOD AGREEMENT IN CREATING A DEEP MIXED LAYER BEFORE DAWN WHICH WILL TAP INCREASING WINDS ALOFT. WITH WINDS AT THE TOP OF THIS LAYER APPROACHING 35 KNOTS... GUSTS TO 35 MPH EXPECTED AT THE SURFACE. IMPRESSIVE COOLING RIDING INTO NORTH CAROLINA ON THESE WINDS. HOWEVER PRECIPITATION AND MOISTURE WILL EXIT BEFORE TEMPERATURES FALL ENOUGH ALOFT FOR NONLIQUID PRECIPITATION. THE TIMING OF FREEZING TEMPERATURES MAY PLAY A POSSIBLE ROLE IN SLICK SPOTS DEVELOPING NEAR DAWN. MAIN AREA OF CONCERN IS ROUGHLY ROXBORO TO NORTH OF DURHAM TO ASHEBORO AND POINTS WEST. TEMPERATURES ALWAYS DIFFICULT IN A STRONG ADVECTION CASE. MODELS ARE FREQUENTLY TOO COLD WITH NORTHWEST TO WEST FLOW AND DO NOT SEEM TO FULLY MODEL THE BLOCKING IMPACT OF THE MOUNTAINS. HOWEVER TAKING THIS INTO ACCOUNT... BELIEVE TEMPERATURES WILL DROP INTO THE MID 20S IN THE NORTHWEST PIEDMONT BY 9 AM. DEW POINTS ARE EXPECTED TO FALL INTO THE TEENS BY THIS TIME... AND STRONG DRYING OF ROADS MAY MAKE BLACK ICE A NON-ISSUE. WILL ONLY MENTION IN THE WEATHER OUTLOOK PRODUCT AT THIS TIME FOR THE ABOVE OUTLINED AREA. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... AS OF 250 PM TUESDAY... HIGH WIND WARNING IN EFFECT FOR ALL OF CENTRAL NORTH CAROLINA ON WEDNESDAY. MODELS CONTINUE TO ADVERTISE A DEEP MID AND UPPER LEVEL LOW CROSSING SOUTHERN VA WEDNESDAY...AIDING TO RAPIDLY INTENSIFY SURFACE LOW OFF THE NORTHERN MID ATLANTIC COAST. 12Z MODELS CONSISTENT WITH 00Z COUNTERPARTS IN DEPICTING STRATOSPHERIC INTRUSION INTO THE BOUNDARY WEDNESDAY...HELPING TO MIX VERY STRONG WINDS TOWARDS THE SURFACE. MODEL SOUNDINGS SUGGEST WINDS 53 TO 58 KNOTS AT THE TOP OF THE MIX LAYER. HAVE NOT SEEN WINDS THIS STRONG IN A WHILE. WILL LIKELY NOT REALIZE WINDS THIS STRONG AT THE SURFACE BUT STEEP LOW LEVEL LAPSE RATES SHOULD SUPPORT WIND GUSTS 40 TO 45 KNOTS...ESPECIALLY ACROSS THE NORTH. TOPSOIL REMAIN SATURATED WITH LITTLE DRYING ANTICIPATED. THIS SUPPORTS IDEA OF NUMEROUS DOWNED TREES AND A FEW POWER LINES. THUS...WILL UPGRADED HIGH WIND WATCH TO A WARNING FOR THE ENTIRE AREA. WILL STAY ON THE COOL SIDE OF MOS GUIDANCE DUE TO STRONG LOW LEVEL COLD AIR ADVECTION...OFFSET SOMEWHAT BY DOWNSLOPE COMPONENT/ADIABATIC WARMING. HIGHS MID 30S NORTH TO LOWER 40S SOUTH. TEMPERATURES COMBINED WITH WINDS WILL PRODUCE WIND CHILLS IN THE 20S. WEDNESDAY NIGHT...WINDS WILL SLOWLY SUBSIDE BUT REMAIN BLUSTERY. SKIES WILL REMAIN CLEAR TO PARTLY CLOUDY. IN SPITE OF MIXING...850MB THERMAL TROUGH IMMEDIATELY NORTHWEST OF FORECAST AREA. LEANED TOWARD THE COOL END OF MOS BUT COULD SEE MINIMUM TEMPERATURES 2 TO 3 DEGREES COOLER IF LIGHTER WINDS OCCUR. && .LONG TERM /THURSDAY THROUGH TUESDAY/... AS OF 300 PM TUESDAY... THE EXTENDED FORECAST WILL CONTINUE TO FEATURE TEMPERATURES BELOW NORMAL. CURRENTLY...NO DAY IN THE EXTENDED FORECAST SHOWS A HIGH OR LOW AT OR ABOVE NORMAL. THURSDAY THROUGH FRIDAY...SURFACE WINDS SHOULD STILL BE GUSTY INTO THE DAY THURSDAY...ESPECIALLY AFTER DIURNAL MIXING TAKES PLACE...WITH 925 MILLIBAR WINDS NEAR 40 KNOT AROUND 12Z THURSDAY...DIMINISHING TO 30 KNOT LATE IN THE DAY. DID NOT FORECAST WINDS REALLY HIGH YET...TO 40 MPH...AS BUFR SOUNDINGS AND 925 MILLIBAR WINDS SHOW A FAIRLY RAPID DECREASE IN GUST POTENTIAL BETWEEN 12Z AND 18Z... BUT TRENDS WILL HAVE TO BE MONITORED AS THE GRADIENT REMAINS TIGHT THROUGHOUT MUCH OF THE DAY. WINDS WILL DIMINISH THURSDAY NIGHT AND BE MARKEDLY LOWER FRIDAY AS 925 MILLIBAR WINDS FALL TO 10-15 KNOT FOR MUCH OF THE DAY. 1000-850MB THICKNESSES REMAIN COOL...SHOWING HIGHS ONLY IN THE UPPER 30S IN THE TRIAD THURSDAY AND IN THE LOWER 40S IN THE SAME LOCATION FRIDAY. ELSEWHERE...THIS SHOULD TRANSLATE TO HIGHS IN THE LOWER TO MID 40S. MIXING ON THE GFS IS BETTER FRIDAY COMPARED TO THE NAM... BUT DEGREE OF HIGH CLOUDS AHEAD OF THE NEXT LOW PRESSURE SYSTEM TO AFFECT THE SOUTHEAST IS MUCH MORE PRONOUNCED ON THE GFS...WITH ITS UPPER-LEVEL MOISTURE...COMPARED TO THE NAM. THERE COULD ALSO BE A FEW HIGH CLOUDS IN THE STRONG WINDS ALOFT EARLY THURSDAY...MAINLY CENTRAL AND WEST...AND 300MB WINDS ARE FORECAST TO EXCEED 150 KNOT THURSDAY. THE MODEL TRENDS FROM THE ECMWF HAVE FORECAST LATE-WEEK LOW PRESSURE OVER THE SOUTHEAST FARTHER NORTH...WHILE THE GFS HAS TRENDED DRIER AND FARTHER SOUTH. THE GFS OVERALL HAS TRENDED WEAKER WITH THE GULF LOW AND STRONGER WITH SURFACE HIGH PRESSURE FOR LATE IN THE WEEK...AND RELATIVE TO THE ECMWF...THE GFS IS STRONGER WITH THE HIGH AND WEAKER WITH THE LOW. QPF WITH THE GFS IS ZERO OVER CENTRAL NORTH CAROLINA...WHILE THE FARTHER NORTH ECMWF SHOWS LIGHT PRECIPITATION JUST BARELY REACHING THE SOUTH TIER OF CENTRAL NORTH CAROLINA COUNTIES LATE FRIDAY NIGHT INTO EARLY SATURDAY. FOR WHAT IT IS WORTH...THE DGEX IS WELL SOUTH...CLOSER TO THE GFS IN TRACK BUT STRONGER WITH LOW PRESSURE...KEEPING PRECIPITATION SOUTH OF CENTRAL NORTH CAROLINA. WHILE THE SYSTEM BEARS WATCHING...AS ANY PRECIPITATION THAT OCCURS WITH THIS WOULD BE IN THE FORM OF LIGHT SNOW BASED ON COLD THICKNESSES...BASED ON THE CURRENT CONSENSUS TRACK OF LOW PRESSURE WILL CONTINUE A DRY FORECAST. DURING THE REST OF THE EXTENDED PERIOD...WHILE THE FORECAST WILL STILL BE DRY...THERE IS SOME CONCERN ABOUT A MODERATELY-STRONG SHORTWAVE OR TWO IN THE NORTHWEST FLOW THAT WILL MOVE ACROSS CENTRAL NORTH CAROLINA. THE GFS SUPPORTS TWO OF THESE...ONE BEHIND THE SOUTHEAST LOW LATE FRIDAY NIGHT AND EARLY SATURDAY...AND ANOTHER SUNDAY NIGHT INTO EARLY MONDAY. THE ECMWF IS MORE SUPPORTIVE OF THE LATTER...AND IT APPEARS LIKELY THAT IN SOME PART OF THIS PERIOD... WITH THE PERSISTENCE OF THE UPPER LOW PRESSURE OVER SOUTHEAST CANADA AND A RIDGE IN THE WEST WITH THE GENERAL NORTHWEST FLOW RIGHT THROUGH THE MID-ATLANTIC AND CAROLINAS...AT LEAST ONE MODESTLY STRONG SHORTWAVE WILL MOVE OVER OR NEAR CENTRAL NORTH CAROLINA. ANY PRECIPITATION SHOULD BE LIGHT...BUT GIVEN THE COLD AIR THAT WILL BE IN PLACE...ANY PRECIPITATION WOULD ALMOST CERTAINLY BE FROZEN PARTICULARLY IF THE TIMING IS AT NIGHT. WILL REFRAIN FROM INTRODUCING A SLIGHT CHANCE OR CHANCE OF SNOW SHOWERS WITH A NOCTURNAL TIMING OUT TO THE SIXTH OR SEVENTH DAY...BUT WILL INCREASE CLOUD COVER FOR A COUPLE OF PERIODS WHERE THE CONSENSUS SUPPORTS AT LEAST A WAVE MOVING OVER OR NEAR THE AREA. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 1230 AM WEDNESDAY... THE WIDESPREAD LIFR/IFR CONDITIONS...ASSOCIATED WITH A STABLE COLD AIR DAMMING WEDGE AND A STRENGTHENING AREA OF LOW PRESSURE ALONG THE NORTH CAROLINA COAST...WILL QUICKLY SCOUR OUT BY 08Z TO 10Z AS A STRONG COLD FRONT PUSHES THROUGH THE AREA. THEREAFTER...THE PRIMARY AVIATION CONCERN WILL BE VERY STRONG CROSSWINDS OF RUNWAYS ORIENTED SW TO NE AS SUSTAINED WEST/NW WINDS OF 25-30 KNOTS... WITH FREQUENT GUSTS TO 40-45 KNOTS ARE EXPECTED BY MID/LATE MORNING. SPORADIC GUSTS UP TO 50 KNOTS WILL BE POSSIBLE AT THE INT/GSO/RDU/RWI TAF SITES...PARTICULARLY IN THE 17-21Z PERIOD WED AFTERNOON. 00Z THURSDAY THROUGH SUNDAY: STRONG NORTHWEST WINDS WILL GRADUALLY SUBSIDE WEDNESDAY NIGHT. VFR CONDITIONS ARE EXPECTED THURSDAY THROUGH SUNDAY. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... HIGH WIND WARNING FROM 6 AM TO 9 PM EST WEDNESDAY FOR NCZ007>011-021>028-038>043-073>078-083>086-088-089. && $$ SHORT TERM...WSS LONG TERM...DJF AVIATION...CBL/VINCENT