000 FXUS62 KRAH 250233 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 925 PM EST TUE NOV 24 2009 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OVER NORTH CAROLINA THROUGH WEDNESDAY. A MILDER SOUTHWEST FLOW WILL DEVELOP THURSDAY AHEAD OF A DRY COLD FRONT. THIS FRONT WILL PUSH EAST THROUGH THE REGION LATE THURSDAY AND THURSDAY NIGHT. WINDY AND COLDER WEATHER IS EXPECTED FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 925 PM TUESDAY... THE SURFACE RIDGE AXIS CONTINUED TO EXTEND FROM NY STATE S-SW ACROSS NC/SC THIS EVENING. ALONG AND EAST OF THE AXIS... THE SURFACE WINDS WERE LIGHT FROM THE NNE. WEST OF THE AXIS... THE SURFACE WINDS WERE LIGHT FROM THE SE-S. THERE WERE SOME BREAKS THIS AFTERNOON OVER AND WEST OF THE RIDGE AXIS... OTHERWISE IT REMAINED OVERCAST THROUGH THE DAY. OVERCAST SKIES HAVE RETURNED TO ALL AREAS THIS EVENING. THE LATEST UPPER AIR DATA AND RAOB INFORMATION INDICATE VERY DRY AIR IN THE MID AND UPPER LEVELS... WITH THE RESIDUAL STABLE MOIST LAYER IN THE LOWER LEVELS (5K FEET AND BELOW). A STRONG INVERSION WAS LOCATED AT 5K. THE FLOW FROM THE SURFACE TO 5K FEET INDICATED GOOD VEERING AND WARM AIR ADVECTION. THIS SUGGESTS THE STRATUS AND STRATOCUMULUS WILL PERSIST THROUGH THE NIGHT. THE CEILING SHOULD DISRUPT DENSE FOG DEVELOPMENT NEAR THE SURFACE. THE TEMPERATURES OVERNIGHT WILL ALSO FALL ONLY SLIGHTLY FROM THE CURRENT READINGS IN THE LOWER TO MID 50S. POP OVERNIGHT SHOULD BE ALMOST NIL. HOWEVER... THERE HAVE BEEN SOME SPRINKLES OVER CENTRAL SC ASSOCIATED WITH WHAT APPEARS TO BE THE TAIL END OF A H85 WARM FRONT EXTENDING FROM IL/KY SE INTO SC. THIS H85 WARM FRONT SHOULD NUDGE NE OVERNIGHT AND COULD BRING A SPRINKLE. WE WILL LEAVE OUT MENTION IN THE FORECAST SINCE IT IS NOT ANTICIPATED TO BE MEASURABLE. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 PM TUESDAY... LEAD SHORTWAVE TROUGH CURRENTLY OVER IA AND MZ WILL FILL AS IT LIFTS NE ACROSS THE EASTERN GREAT LAKES AND INTO NE US. THE ATTENDANT WEAK LOW-LEVEL TROUGH PASSAGE WILL PUSH EAST ACROSS THE AREA ON WEDNESDAY. VERTICAL MIXING ALONG THE TROUGH PASSAGE WILL AIDE IN ERODING THE SHALLOW COOL WEDGE DOME WITH DIABATIC SURFACE HEATING CONTRIBUTING AS WELL. EXPECT TO SEE A SW TO NE CLEARING TREND...WITH NE SECTIONS POSSIBLY DELAYED UNTIL THE LATE AFTERNOON...~21Z. MEANWHILE..THERE IS GOOD AGREEMENT THAT THE OLD BAROCLINIC ZONE OFF THE SE COAST WILL UNDERGO NEW FRONTOGENESIS... REMAINING OFFSHORE THROUGH THE PERIOD. EXPECT HIGHS IN THE LOWER 60S TO UPPER 50S...WITH THE WARMEST READINGS ACROSS SOUTHERN AND WESTERN ZONES WHERE THE EARLIEST BREAKS ARE EXPECTED. CLEAR SKIES AND LIGHT WINDS WEDNESDAY EVENING MAY PROMOTE SOME PATCHY DENSE FOG WEDNESDAY NIGHT...PARTICULARLY ACROSS THE WESTERN PIEDMONT WHERE SOME OF THE HEAVIEST RAINFALL WAS OBSERVED EARLIER THIS WEEK. ALSO...PRESSURE GRADIENT MAY TIGHTEN JUST ENOUGH IN THE EAST AS AN AREA OF LOW PRESSURE TRACKS UP THE NC COAST TO IMPEDE FOG DEVELOPMENT ACROSS THE COASTAL PLAIN REGION. OVERNIGHT LOWS IN THE LOWER TO MID 40S. && .LONG TERM /THURSDAY THROUGH TUESDAY/... AS OF 215 PM TUESDAY... THURSDAY THROUGH FRIDAY NIGHT: A COLD FRONT IS EXPECTED TO MOVE THROUGH THE REGION ON THURSDAY NIGHT. DESPITE FAIRLY DECENT UPPER LEVEL FORCING (STRONG UPPER LOW...INCREASING UPPER LEVEL DIVERGENCE ASSOCIATED WITH THE LEFT EXIT REGION OF THE SUBTROPICAL JET)...LACK OF SIGNIFICANT MOISTURE WILL RESULT IN A MOSTLY DRY FRONTAL PASSAGE. THE ONLY EXCEPTION MAY BE THE NORTHERN CWA...WHERE SLIGHT CHANCE POPS WHERE MAINTAINED DUE TO THE PROXIMITY OF THE UPPER LOW. BEHIND THE FRONT ON LATE THURSDAY NIGHT AND INTO FRIDAY...THE PRESSURE GRADIENT WILL INCREASE SIGNIFICANTLY. AS A RESULT...AM EXPECTING SUSTAINED WINDS AROUND 15 MPH WITH FREQUENT GUSTS OVER 25 MPH. THICKNESS VALUES IN THE 1340 TO 1350M RANGE ON THURSDAY AHEAD OF THE FRONT WILL LEAD TO HIGH TEMPS GENERALLY IN THE LOW TO MID 60S. BEHIND THE FRONT ON FRIDAY...WITH STRONG COLD AIR ADVECTION IN PLACE...THICKNESSES WILL DROP INTO THE 1305 TO 1315M RANGE AND THEREFORE TEMPS WILL BE COOLER...GENERALLY LOW TO MID 50S. TEMPS ON THURSDAY NIGHT ARE EXPECTED TO BE IN THE UPPER 30S TO LOW 40S AS THE BOUNDARY LAYER REMAINS WELL MIXED DUE TO THE BREEZY CONDITIONS. SATURDAY THROUGH SUNDAY NIGHT: SURFACE HIGH PRESSURE/RIDGING ALOFT WILL GRADUALLY SETTLE OVERHEAD FOR THE WEEKEND...BEFORE EVENTUALLY SHIFT OFFSHORE BY EARLY NEXT WEEK. LOWS ON SATURDAY AND SUNDAY MORNING ARE EXPECTED TO BE IN THE 30S AREAWIDE...WITH NEAR FREEZING TEMPS POSSIBLE GENERALLY EAST OF THE TRIANGLE. THE SURFACE RIDGE IS PROGGED TO BE DIRECTLY OVERHEAD ON SUNDAY MORNING...HOWEVER CIRRUS CLOUDS FROM AN APPROACHING SOUTHERN STREAM TROUGH MAY HINDER OPTIMAL RADIATIONAL COOLING. TEMPERATURES WILL GRADUALLY MODERATE TO NEAR 60 DEGREES BY SUNDAY. MONDAY AND TUESDAY: MODELS DIVERGE SIGNIFICANTLY DURING THIS POINT IN THE FORECAST WITH RESPECT TO TIMING AND LOCATION OF THE NEXT SYSTEM...REGARDLESS A STRONG SYSTEM LOOKS TO TAKE AIM AT THE REGION BY THE MIDDLE OF NEXT WEEK. THE 12Z GFS IS MUCH FASTER AND FURTHER SOUTH THAN THE 00Z ECMWF...WITH THE SYSTEM AFFECTING THE REGION BY MID DAY MONDAY ACCORDING TO THE GFS. THIS WILL HAVE TO MONITORED CLOSELY AS THIS COULD BE A SIGNIFICANT RAINFALL PRODUCER AS WELL AS A POTENTIAL SEVERE WEATHER MAKER ACROSS THE SOUTH AND POSSIBLY A PORTION OF THE CAROLINAS. GENERALLY WENT A MIDDLE OF THE ROAD SOLUTION AND SHOWED AN INCREASE IN PRECIP CHANCES FOR MONDAY AND TUESDAY...BUT AM STILL WELL BELOW GUIDANCE DUE TO THE MODEL UNCERTAINTY. && .AVIATION /00Z WEDNESDAY THROUGH SATURDAY/... AS OF 645 PM TUESDAY... A MOIST COLD AIR DAMMING AIR MASS WILL LINGER OVER CENTRAL NC THROUGH THE OVERNIGHT HOURS. CEILINGS VARY FROM HIGH MVFR IN THE TRIAD TO IFR IN SOUTHEASTERN NC THIS EVENING. SOMEWHAT OF A LOW CONFIDENCE FORECAST FOR EXACTLY HOW LOW CEILINGS WILL DROP OVERNIGHT...AS MODEL GUIDANCE HAS STRUGGLED WITH THE CURRENT AMOUNT OF LOW LEVEL MOISTURE. WITH A WEAK PRESSURE GRADIENT OVER NC...WINDS WILL CONTINUE TO BECOME VERY LIGHT TO CALM...WHICH WILL ALLOW CEILINGS TO LOWER TO IFR WITH SUCH A MOIST BOUNDARY LAYER. PARTIAL CLEARING IN THE NORTHWEST PIEDMONT EARLIER THIS AFTERNOON HAS LEFT A THINNER LAYER OF STRATUS OVER THAT AREA...WHICH MAY ALLOW FOR MORE COOLING AND PROMOTE FOG DEVELOPMENT...ALTHOUGH AT LEAST MVFR VISIBILITIES WILL PREVAIL AT ALL TERMINALS AFTER MIDNIGHT. ON WEDNESDAY...WINDS ABOVE THE SURFACE WILL BECOME WESTERLY AND SURFACE WINDS WILL TURN TO SOUTHWESTERLY...ALLOWING CEILINGS TO SCOUR AS A WEAK TROUGH CROSSES CENTRAL NC. VFR CONDITIONS WILL COME FIRST TO THE TRIAD..POTENTIALLY BY NOONTIME....SPREADING EAST BY LATER IN THE AFTERNOON. LOOKING AHEAD... WITH CLEARING SKIES AND WEAK WINDS...FOG MAY DEVELOP AGAIN ON WEDNESDAY NIGHT AND THURSDAY MORNING. A COLD FRONT WILL CROSS THE AREA ON THURSDAY...AND A STRONG PRESSURE GRADIENT BEHIND THE FRONT WILL LEAD TO WINDS OF 15 TO 20 MPH WITH GUSTS UP TO 30 MPH ON FRIDAY...RESULTING IN SIGNIFICANT CROSSWIND FLOW AT SW TO NE ORIENTED RUNWAYS. VFR CONDITIONS ARE THEN EXPECTED TO PERSIST AS DEEP LAYER RIDGING PERSISTS THROUGH THE WEEKEND. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...CBL/BADGETT NEAR TERM...CBL/BADGETT SHORT TERM...CBL LONG TERM...KRR AVIATION...SMITH