305 FXUS62 KRAH 200823 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 323 AM EST FRI JAN 20 2012 .SYNOPSIS... A WEAK DRY SURFACE COLD FRONT WILL MOVE INTO CENTRAL NORTH CAROLINA FRIDAY MORNING. THE FRONT WILL STALL ACROSS THE REGION ON FRIDAY AND LIFT BACK NORTHWARD AS A WARM FRONT LATE FRIDAY AFTERNOON INTO THE EVENING. MORE UNSETTLED WEATHER IS EXPECTED BY THE WEEKEND AS AN AREA OF LOW PRESSURE APPROACHES FROM THE SOUTH. && .NEAR TERM /THROUGH SATURDAY NIGHT/... AS OF 305 AM... ZONAL FLOW ALOFT INTO TONIGHT. 850 MILLIBAR WINDS INCREASE TODAY AND SHIFT FROM WEST TOWARD SOUTHWEST AS PRESSURE GRADIENT TIGHTENS AHEAD OF AN 850 MILLIBAR TROUGH. ISENTROPIC LIFT DEVELOPS OVER THE MOUNTAINS AND SOUTHERN FOOTHILLS BY LATE AFTERNOON AND SPREADS ACROSS CENTRAL NORTH CAROLINA INTO TONIGHT. ROUGH AGREEMENT IN UPPER LEVEL DIVERGENCE LATE TONIGHT THOUGH THE WIND FIELD AT JET LEVEL IS RELATIVELY UNIFORM. LOW LEVEL WARM ADVECTION WILL ALSO AID LIFT. MOISTURE IS LIMITED ABOVE 15000 FEET AND THE LOWER AIR MASS STABLE IN SPITE OF THE WARM ADVECTION. EXPECT RAINFALL AMOUNTS TO STAY UNDER TWO TENTHS INCH IN GENERAL ... WITH THE BEST CHANCES FOR THAT AMOUNT IN THE WEST. MIXING HEIGHTS UNDER 3000 FEET TODAY. RAIN DELAYED INTO THE AFTERNOON OR EVENING AND CLOUDS NEAR 7000 FEET WILL HINDER INSOLATION. HIGH TEMPERATURES IN THE LOWER 50S NEAR VIRGINIA RISING TO NEAR 60 SOUTH PARTS. CLOUDS AND POTENTIALLY RAIN TONIGHT WITH NEAR SURFACE INVERSION TRAPPING HEAT ALOFT. THUS THE TWENTY-FIVE METER RISE IN LOW LEVEL THICKNESSES WILL NOT BE FULLY REALIZED AT THE SURFACE. LOW TEMPERATURES IN THE UPPER 30S NEAR VIRGINIA WITH MID 40S COMMON NEAR HIGHWAY 64 AND SOME LOWER 50S SOUTHEAST. LOW TEMPERATURES REACHED BEFORE DAWN WITH SOME LIGHT WARMING TOWARD SUNRISE. NEAR SURFACE WARMING CONTINUES SATURDAY WITH ELONGATED SURFACE LOW TO OUR WEST AT SUNRISE. MODEL CONSENSUS IS A POSITION OF THE LOW COMPLEX FROM CHARLOTTE NORTHEAST TO ALBEMARLE SOUND AT SUNSET. MODEL DETAILS AT THE LOWER LEVELS AND JET LEVEL SHOW LITTLE CONSENSUS. GOING WITH THE BROAD IDEA OF 500 MILLIBAR TROUGH REACHING THE MOUNTAINS NEAR SUNSET WITH BEST DYNAMICS TO ITS EAST AND WARM ADVECTION FINALLY DESTABILIZING THE NEAR SURFACE AIR MASS TO ALLOW FOR SHOWERS INSTEAD OF RAIN. HEAVIEST AMOUNTS SATURDAY IN THE AFTERNOON BUT CONFIDENCE LOW IN PLACING ANY RAINFALL MAXIMA. A BROAD TWO TENTHS WITH LOCAL HEAVIER AMOUNTS SATURDAY. UPPER TROUGH PUSHES THROUGH SATURDAY NIGHT AND TIMING SUGGESTS HEAVIER AMOUNTS HIGHWAY ONE CORRIDOR AND EAST THAN TO THE WEST. ROUGHLY ONE THIRD INCH THERE WITH LESS AMOUNTS EAST. THUNDER RISK FROM LATE AFTERNOON SATURDAY INTO THE EVENING STILL LOOKS TOO SMALL TO MENTION AT THIS TIME. IN SPITE OF THE RAIN... WARM ADVECTION RELIED ON TO PUSH MAXIMUM TEMPERATURES INTO THE SIXTIES SATURDAY. WITH NEAR SURFACE WINDS SHIFTING TO NORTHEAST AND A COLD AIR DAMMING AIR MASS FORECAST SATURDAY NIGHT... HAVE PLACED A FEW UPPER 30S IN THE NORTH RISING TO UPPER 40S EXTREME SOUTH SATURDAY NIGHT. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 305 AM FRIDAY... SUN AND SUN NIGHT: CHILLY...CLOUDY...AND DRIZZLY...IN HYBRID COLD AIR DAMMING. BEHIND THE S/W TROUGH AD SURFACE FRONTAL ZONE FORECAST TO SETTLE OFF THE COAST OF THE CAROLINAS SAT NIGHT...SURFACE HIGH PRESSURE WILL STRENGTHEN TO NEAR 1035 MB AS IT MIGRATES ACROSS NEW ENGLAND AND OFFSHORE -- BENEATH AMPLIFIED BUT PROGRESSIVE RIDGING ALOFT -- SUN AND SUN NIGHT. THE ASSOCIATED CAD SATURATION...IN THIS CASE IN THE LOWEST 6-9 THOUSAND FT AND AT TEMPERATURES THROUGHOUT THE LAYER GENERALLY AOA FREEZING...WILL PROVIDE FAVORABLE CONDITIONS FOR PERIODS OF DRIZZLE OR VERY LIGHT RAIN. HOWEVER...VERY DRY MID LEVELS OWING TO THE RIDGING ALOFT SHOULD RESULT IN MINIMAL RAINFALL AMOUNTS ON THE ORDER OF A FEW HUNDREDTHS AND MOST LIKELY LESS. CHILLY WITH HIGHS ONLY IN THE LOWER 40S IN THE HEART OF THE CAD OVER THE NW PIEDMONT...TO LOWER 50S OVER THE SOUTHERN COASTAL PLAIN. LITTLE DIURNAL VARIATION INTO SUN NIGHT...COOLING 3-5 DEGREES INTO THE UPPER 30S NW TO AROUND 50 SE THROUGH MIDNIGHT...WITH TEMPERATURES LIKELY TO HOLD STEADY OR RISE SLOWLY (PARTICULARLY AT THE EDGES OF THE WEDGE) OVERNIGHT. WHILE FORECAST SOUNDINGS FROM THE 00Z/20TH GFS SUGGEST SUB-FREEZING SURFACE TEMPERATURES AND A RESULTANT THREAT OF FREEZING DRIZZLE OVER THE CLIMATOLOGICALLY- FAVORED NORTHERN AND NW PIEDMONT SUN MORNING... FORECAST PARTIAL THICKNESSES DURING THAT TIME LIE IN THE ALL RAIN CATEGORY...AND THE FORECAST WET BULB-FREEZING LINE NEVER PENETRATES THE RAH CWA. NO FREEZING PRECIPITATION IS ACCORDINGLY EXPECTED AT THIS TIME. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 210 PM THURSDAY... A VERY ACTIVE PERIOD AS PACIFIC WAVETRAIN ROLLS ON WITH A SYSTEM AFFECTING THE AREA EVERY 2.5-3 DAYS. TEMPERATURES BREAK OUT IN THE LOWER TO UPPER 60S ON MONDAY IN THE WARM SECTOR AHEAD OF THE APPROACHING COLD FRONT AS PRIMARY SURFACE LOW TRACKS ACROSS THE GREAT LAKES. COULD SEE A LULL IN PRECIPITATION MONDAY MORNING...BUT RAIN CHANCES SHOULD INCREASE THROUGHOUT THE AFTERNOON WITH MODELS BRINGING THE TRAILING SURFACE COLD FRONT MOVING THROUGH THE AREA BETWEEN MONDAY 18Z TO 06Z. WITH MAIN SHORTWAVE DYNAMICS MOVING WELL OFF TO THE NORTH...THERE IS NO THUNDER OR SEVERE THREAT EXPECTED AT THIS TIME. DRY TUESDAY THROUGH WEDNESDAY AS AS WE WAIT FOR THE NEXT PACIFIC SHORTWAVE TROUGH TO SWEEP EAST AND IMPACT THE REGION. THERE IS A LARGE DEGREE OF UNCERTAINTY WITH THE TIMING OF THIS WAVE...AND WHETHER IT WILL EVOLVE INTO A CLOSED VORTEX OVER THE SW CONUS OR REMAIN AN OPEN WAVE TROUGH BY LATE WEEK. TEMPERATURES WILL REMAIN MILD AND ABOVE NORMAL TUESDAY THROUGH THURSDAY. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... AS OF 320 AM... NOT CONFIDENT IN LAURINBURG OBSERVATION OF LIFT CEILINGS AT THIS TIME. IN GENERAL EXPECT VFR CONDITIONS INTO THE EARLY AFTERNOON BEFORE MVFR CEILINGS BEGIN TO ADVANCE INTO OUR SOUTHWEST PARTS... EAST OF CHARLOTTE. SOME RAIN IN THE SOUTHWEST MID TO LATE AFTERNOON ADVANCING NORTH AND EAST INTO TONIGHT. WIDESPREAD MVFR OR LOWER CEILINGS TOWARD MIDNIGHT AND INTO SATURDAY MORNING. SOUTHWEST WINDS INCREASING TO NEAR 40 MPH BY EARLY EVENING. RAIN CHANGES TO CONVECTION RAIN SHOWERS SATURDAY AFTERNOON AND INTO THE EVENING. SHOWERS EXIT SATURDAY EVENING WITH NORTHEAST SURFACE WINDS DEVELOPING AND A CHANCE FOR LIGHT RAIN OR DRIZZLE SATURDAY NIGHT INTO SUNDAY. A MIDWEST LOW PRESSURE SYSTEM WILL BE CLOSE ENOUGH TO INCREASE RAIN CHANCES AGAIN LATE SUNDAY NIGHT INTO MONDAY. VFR CONDITIONS DEVELOPING LATE MONDAY AND PERSISTING INTO TUESDAY WITH THE EXCEPTION OF PATCHY FOG MONDAY NIGHT. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...MWS LONG TERM...CBL