000 FXUS62 KRAH 130843 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 330 AM EST WED FEB 13 2008 .SYNOPSIS... A WARM FRONT WILL REMAIN NEARLY STATIONARY ACROSS CENTRAL NORTH CAROLINA INTO THIS MORNING. A COLD FRONT WILL MOVE SLOWLY THROUGH CENTRAL NORTH CAROLINA LATE THIS AFTERNOON THROUGH EARLY EVENING. HIGH PRESSURE WILL MOVE FROM THE TENNESSEE VALLEY ACROSS OUR AREA TO THE MID ATLANTIC COAST LATE TONIGHT THROUGH THURSDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 220 AM WEDNESDAY... THE SYNOPTIC PATTERN IS EVOLVING LARGELY AS EXPECTED EARLY THIS MORNING... WITH THE FULL LATITUDE MID LEVEL TROUGH AMPLIFYING OVER THE MISS VALLEY THEN SHARPENING AS IT SWINGS THROUGH NC TONIGHT. SEVERAL WEAK LOWS EXIST ALONG THE COLD FRONT... CURRENTLY RUNNING FROM E OH TO E TN TO S MS... AND ANOTHER LEE LOW APPEARS TO BE FORMING ALONG THE WEDGE FRONT OVER UPSTATE SC INTO THE SRN NC FOOTHILLS. DESPITE PRECIPITATION FALLING THROUGH 10-15C AIR JUST 0.5-1.0 KM ALOFT... THE STABLE WEDGE REMAINS LOCKED IN OVER THE WESTERN PIEDMONT WHERE SURFACE TEMPS HOLD IN THE LOW-MID 30S. THE WEDGE FRONT HAS MOVED LITTLE IN THE LAST SEVERAL HOURS... STRETCHING FROM JUST SE OF WADESBORO / SANFORD / RALEIGH / HALIFAX. AS ONE MIGHT EXPECT... THE LARGE SCALE MODELS ARE DEPICTING THE DETAILS OF THE WEDGE REGIME POORLY. THE RUC13 IS DOING MUCH BETTER AND IT INDICATES THAT THE STABLE POOL WILL NOT BECOME DISLODGED FROM THE FAR NW PIEDMONT PRIOR TO COLD FRONT PASSAGE. 925-850 MB WINDS ARE FROM THE SOUTH... NEARLY PARALLEL TO THE WEDGE FRONT... AND ARE EXPECTED TO VEER TO WSW AS A LOW LEVEL TROUGH... LOCATED ALONG THE AL/GA BORDER AT 00Z... PIVOTS NORTHEAST AND THROUGH THE CWA LATER THIS MORNING. ALL OF THIS MEANS THAT TEMPERATURES IN THE TRIAD ARE ONLY EXPECTED TO RISE THROUGH THE 30S... AND THAT MAY BE OPTIMISTIC... BEFORE THE COLD FRONT PUSHES THROUGH TOWARD MIDDAY... AND THE POSSIBLE DEVELOPMENT OF THE LEE LOW ALONG THE WEDGE FRONT WOULD ONLY REINFORCE THIS IDEA. TEMPERATURES IN THE SOUTHEAST HOWEVER WILL UNDOUBTEDLY HOLD IN OR RISE THROUGH THE LOW-MID 60S AS INTENSE LOW LEVEL WARM AIR ADVECTION PERSISTS. REGARDING RAIN CHANCES AND THE RISK OF SEVERE STORMS... LATEST GUIDANCE AND TRENDS ARE ON PACE WITH THE FORECAST WITH WIDESPREAD RAIN... OCCASIONALLY MODERATE AS PRECIPITABLE WATER VALUES ARE OVER 200% OF NORMAL... LASTING THROUGH THE MORNING. DYNAMIC FORCING IS STRONG WITH MODEL WIND PROGS ON THE 1.5 PVU SURFACE DEPICTING IDEALLY JUXTAPOSED POLAR AND SUBTROPICAL JETS OVER NC THIS MORNING... HOWEVER THE CHANCES OF STRONG CONVECTION AND ISOLATED SEVERE STORMS TODAY ARE HIGHLY RELIANT ON THE DEGREE OF POTENTIAL INSTABILITY. 00Z REGIONAL SOUNDINGS AND LATEST RUC-ADJUSTED PLOTS FROM SPC SHOW JUST 100 J/KG OF CAPE OR LESS (AND THIS IS ELEVATED POTENTIAL INSTABILITY WEST OF THE WEDGE FRONT) ALTHOUGH ANY ADDITIONAL BOUNDARY LAYER WARMING WILL PUMP UP THESE NUMBERS QUICKLY IN THE WARM SECTOR... AND BUFR SOUNDINGS AT FAY SHOW A FEW HUNDRED J/KG OF CAPE BY THIS AFTERNOON. OF COURSE THE LOW LEVEL STORM RELATIVE HELICITY IS OVER 500 M2/S2 NEAR AND NW OF THE WEDGE FRONT... SO IF WE CAN GET ANY DISCRETE CONVECTIVE ELEMENTS GOING... THEY`LL NEED TO BE WATCHED FOR QUICK SPINUP IF THEY TRAVERSE THIS ZONE OF HIGH VORTICITY. WILL ALSO NEED TO WATCH NEAR A SURFACE LOW CENTER EXPECTED TO SPIN UP OFF THE SC COAST THIS MORNING... ASSOCIATED WITH A MID LEVEL VORTICITY MAX NOTED ON WATER VAPOR IMAGERY TRACKING UP THE COAST. LATER TODAY... AS THE 80+ KT 500 MB JET WRAPS AROUND THE MID LEVEL LOW UP INTO ERN NC... HODOGRAPHS WILL BECOME STRONGLY LINEAR WITH 60+ KTS OF DEEP LAYER SHEAR... AND A FEW BOWING SEGMENTS MAY PRODUCE DAMAGING WIND GUSTS... MAINLY ALONG/EAST OF I-95 THIS AFTERNOON WHERE SREF PROBABILITIES OF NEGATIVE LI VALUES AND CAPES OF 500-1000 J/KG ARE BETTER THAN 50%... AND WHERE A POOL OF 100-150 M MID LEVEL HEIGHT FALLS WILL MOVE IN LATE IN THE DAY. AFTER COLD FRONTAL PASSAGE BETWEEN 2 AND 8 PM... THE LOW LEVEL COLD AIR WILL SLOWLY FILTER INTO THE CWA WITH THE TERRAIN TEMPORARILY HOLDING OFF THE HIGH BUILDING IN FROM THE WEST. THERE IS SOME CONCERN ABOUT A POSSIBLE END AS A BRIEF PERIOD OF WINTRY PRECIP TONIGHT. THE EXTENT AND SPEED OF THE COLDER AIR PUSHING IN AND THE POTENTIAL RAPID DEEPENING OF A SURFACE LOW OVER OR JUST OFF THE NE NC COAST... AS THE DEEPENING MID LEVEL LOW SHIFTS OVER THE AREA... BOTH POSE SOME CONCERN. AT THIS TIME IT LOOKS LIKE THE COLD AIR WILL LARGELY BE CHASING THE BEST MOISTURE... AND FORECAST BUFR SOUNDINGS FROM BOTH THE NAM AND GFS INDICATE WANING MOISTURE IN THE CRYSTAL GROWTH AREA ALOFT. BUT GIVEN ENOUGH DYNAMIC LIFT PRODUCED BY THE MID LEVEL LOW... THERE IS SOME POTENTIAL FOR SATURATION IN THIS AREA. BASED ON THIS... AND ON THE OVERALL VIGOROUS AND HIGHLY ANOMALOUS NATURE OF THIS SYSTEM... WILL INCLUDE A SHORT PERIOD OF INCONSEQUENTIAL RAIN/SNOW MIX IN THE NORTH BEFORE PRECIP ENDS OVERNIGHT. LOWS 28-37 ACROSS THE CWA. -GIH && .SHORT TERM /THURSDAY THROUGH FRIDAY/... AS OF 250 AM WEDNESDAY... A CHILLY NORTH-SOUTH ORIENTED SURFACE HIGH BUILDS QUICKLY INTO AND OVER NC THURSDAY. IN THE WAKE OF THE DEPARTING MID LEVEL TROUGH... SHORTWAVE RIDGING AND STRONG SUBSIDENCE WITH A VERY DRY COLUMN WILL EQUATE TO CONSIDERABLE SUNSHINE. THE LOW LEVEL THERMAL PROFILE SUPPORTS HIGHS CLOSE TO NORMAL THURSDAY... 52-58. AS THE SURFACE HIGH SHIFTS OFFSHORE LATE THURSDAY AND RETURN FLOW COMMENCES... LOW LEVEL THICKNESSES BOUNCE UP AROUND 10-15 M ABOVE NORMAL... SUPPORTING HIGHS AROUND 61-66 WITH INCREASING HIGH CLOUDS THROUGH THE DAY. -GIH && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... AS OF 330 AM WEDNESDAY... OUR NEXT SIGNIFICANT STORM SYSTEM... NOW PUSHING THROUGH THE PACIFIC NW... DROPS INTO THE DESERT SOUTHWEST AND DEEPENS FRIDAY NIGHT. MEANWHILE... A NORTHERN STREAM COLD FRONT WILL DROP THROUGH THE AREA FRIDAY NIGHT. BUT WITH A PRECEDING DRY AND STABLE AIR MASS WITH DOWNSLOPE 850 MB FLOW... ALONG WITH A LACK OF SIGNIFICANT ISENTROPIC UPGLIDE OR OTHER LARGE SCALE FORCING MECHANISM... THIS FRONT SHOULD COME THROUGH LARGELY DRY BUT WITH CONSIDERABLE CLOUDINESS FRIDAY NIGHT. LOWS 34-40. LOW LEVEL THICKNESSES DROP BACK BELOW NORMAL BEHIND THE FRONT AND TEMPERATURES SHOULD FOLLOW SUIT... ONLY RISING TO 48-56 AS A POLAR SOURCE HIGH BUILDS IN FROM THE NORTH. EXPECT SKIES TO REMAIN MOSTLY CLOUDY FOR MUCH OF SATURDAY... PRIMARILY OVER SOUTHERN SECTIONS CLOSER TO THE FRONT... AS MID LEVEL MOISTURE ADVECTS ENE FROM THE SOUTHWEST LOW. THE GFS AND ECMWF CONTINUE TO PART WAYS WITH THE SPEED OF THIS STORM SYSTEM AS IT EJECTS THROUGH TX INTO THE OH VALLEY AND INTERIOR NE... ONLY NOW IT`S THE ECMWF THAT IS A TAD FASTER. BUT THEY DO SEEM TO BE CONVERGING ON A COMMON SOLUTION. THE CLOSED MID LEVEL LOW IS LIKELY TO RIDE NORTHEAST AND DAMPEN INTO A SHORTWAVE PASSING JUST TO OUR NW SUNDAY/SUNDAY NIGHT... AS THE LARGE SCALE PATTERN TRANSITIONS TO DEEP TROUGHING OVER ALL OF EASTERN NOAM. THE SURFACE HIGH CENTERED TO OUR NE IS EXPECTED TO NOSE BACK INTO THE PIEDMONT IN A DAMMING FASHION... AND AS RAIN CHANCES INCREASE SUNDAY WITH IMPROVING OVERRUNNING... A DAMMING REGIME IS LIKELY TO ENSUE. SURFACE CYCLOGENESIS IS LIKELY SOMEWHERE OVER THE WEST GULF COAST EARLY SUNDAY... AND WHILE THIS LOW IS LIKELY TO TRACK ALONG OR JUST EITHER SIDE OF THE APPALACHIANS ALONG A COLD FRONT... WHETHER IT ENDS UP AS A MILLER TYPE-A OR TYPE-B CYCLOGENESIS PATTERN IS STILL UP IN THE AIR. WILL HAVE INCREASING POPS FROM CHANCE SUNDAY TO LOW END LIKELY SUNDAY NIGHT INTO MONDAY. EXPECT BLUSTERY NW LOW LEVEL FLOW BEHIND THIS SYSTEM LATE MONDAY INTO TUESDAY WITH THE LARGE SCALE TROUGH AXIS PUSHING THROUGH... AND TEMPERATURES SHOULD BE WELL BELOW NORMAL. -GIH && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 200 AM WEDNESDAY... SHARP CONTRAST IN TEMPERATURES ACROSS THE CWA DUE IMPART TO HIGH PRESSURE WEDGED OVER THE WESTERN PORTION OF THE CWA...COOLER AIR AND WARM/STATIONARY FRONT THROUGH THE EASTERN PORTION... WARMER AIR. AS A RESULT OF THIS WEATHER PATTERN... INT AND GSO WILL HAVE LIFR CONDITIONS THROUGH THE MORNING. WITH TEMPERATURES HOVERING AROUND FREEZING THERE IS A POSSIBILITY OF SOME FREEZING RAIN. RDU WILL SERVE AS THE TRANSITION ZONE WITH LIFR TO IFR CONDITIONS... WHILE FAY AND RWI... WHO WILL BE ALONG AND EAST OF THE FRONT WILL EXPERIENCE MVFR TO IFR CONDITIONS. THE SOUTHERLY FLOW ON THE EAST SIDE OF THE FRONT WILL ENHANCE THE CHANCE FOR RAIN OVER THE CENTRAL AND EASTERN PORTIONS OF THE CWA THROUGH THE MORNING. AS THE COLD FRONT THROUGH EASTERN TENNESSEE MOVES SLOWLY EAST... THE WEDGE SHOULD WEAKEN DURING THE LATE MORNING AS THE BOUNDARY THROUGH THE CENTRAL PORTION OF THE CWA MOVES WEST... SQUEEZING OUT THE WEDGE. AS THE COLD FRONT MOVES THROUGH THE CWA MAINLY DURING THE AFTERNOON... RAIN WILL OVERSPREAD THE AREA... BRINGING THE POSSIBILITY OF MVFR TO IFR CONDITIONS SHOWERS AND ISOLATED THUNDERSTORMS. CONDITIONS WILL IMPROVE TONIGHT AS HIGH PRESSURE BUILDS OVER THE AREA FROM THE WEST... HOWEVER SOME RESIDUAL LOW LEVEL MOISTURE COULD LEAD TO SOME CLOUD BASES BETWEEN 25 HUNDRED AND 5 THOUSAND FEET THROUGH EARLY THURSDAY MORNING... OTHERWISE VFR CONDITIONS WILL PREVAIL THURSDAY THROUGH EARLY FRIDAY MORNING. HIGH PRESSURE OVER THE AREA WILL MOVE EAST AND SOUTHEAST OFFSHORE FRIDAY AFTERNOON AS A LOW OVER THE NORTHEAST UNITED STATES DRIFTS EAST AND SOUTHEAST. AS MOISTURE INCREASES OVER THE AREA WITH THE PASSAGE OF THE BOUNDARY THROUGH THE AREA... MVFR CEILINGS WILL BE POSSIBLE SATURDAY NIGHT. WIDESPREAD RAIN IS POSSIBLE SUNDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...HARTFIELD LONG TERM...HARTFIELD AVIATION...RHJ