000 FXUS62 KCHS 100906 AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 406 AM EST FRI FEB 10 2012 ...ARCTIC AIR POISED TO MAKE A RETURN TO THE LOWCOUNTRY AND COASTAL EMPIRE THIS WEEKEND... .SYNOPSIS... A TROUGH OF LOW PRESSURE WILL LINGER OFF THE COAST TODAY. A COLD FRONT WILL PUSH OFFSHORE LATE TONIGHT INTO EARLY SATURDAY AND BE FOLLOWED BY A SECONDARY REINFORCING COLD FRONT SATURDAY NIGHT. COLD HIGH PRESSURE WILL BUILD FROM THE WEST AND PERSIST THROUGH EARLY NEXT WEEK. ANOTHER STORM SYSTEM COULD AFFECT THE AREA BY THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TODAY/... PRESCRIBED BURN ACTIVITIES ARE PRODUCING AREAS OF SMOKE ACROSS PORTIONS OF BERKELEY COUNTY EARLY THIS MORNING. VISIBILITIES HAVE BEEN AS LOW AS 2 MILES AT TIMES AT THE KMKS AWOS...BUT THE COUNTY WARNING POINT INDICATES VISIBILITIES HAVE BEEN LOWER AT TIMES. WILL CONTINUE TO HIGHLIGHT AREAS OF SMOKE IN OUR GRIDDED AND TEXT FORECASTS...BUT CONDITIONS DO NOT SUPPORT DENSE SMOKE ADVISORY CRITERIA ATTM. 10/08Z SURFACE ANALYSIS DEPICTED WEAK RIDGING ACROSS SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA WITH SUBTLE COASTAL TROUGHING SHARPENING UP ALONG THE FLORIDA EAST COAST. THE HEAD OF THE COASTAL TROUGH IS CURRENTLY POSITIONED JUST EAST OF JACKSONVILLE FLORIDA WITH NORTHEAST WINDS NOTED ACROSS THE COASTAL WATERS BETWEEN LONG BAY AND SAINT SIMMONS ISLAND. A PRONOUNCED MID-LEVEL CLOUD DECK IS STEADILY THICKENING AND EXPANDING INLAND IN RESPONSE TO INTENSIFYING 290-295K ISENTROPIC ASSENT ATOP THE INLAND RIDGE AND NEARBY COASTAL TROUGH. CONDENSATION PRESSURE DEFICITS /CPD/ REMAIN FAIRLY HIGH BUT ARE PROGGED TO QUICKLY DROP BELOW 20 NM LATER THIS MORNING PER THE LATEST RUC ISENTROPIC 4-PANELS. WITH SUCH HIGH CPD/S IN PLACE...MOST OF THE ISENTROPIC ASSENT WILL CONTINUE TO CONTRIBUTE TO THICKENING CLOUD COVER VERSUS SHOWER PRODUCTION FOR THE NEXT FEW HOURS...BUT THIS SHOULD CHANGE BY MID-LATE MORNING AS VALUES DROP BELOW 20 NM AND MORE SYNOPTICALLY DRIVEN DYNAMICS SOME INTO PLACE. THE BEST CHANCES FOR MEASURABLE RAINFALL TODAY WILL BE FOUND ROUGHLY ALONG AND EAST OF INTERSTATE 95 AS THIS WILL BE WHERE THE MOST FAVORABLE JUXTAPOSITION OF LOW- LEVEL MOISTURE AND UVV/S WILL OCCUR THROUGH EARLY EVENING. WE CONTINUE TO FAVOR THE DRIER 10/00Z GFS SOLUTION WITH A HEALTHY BLEND FROM THE LATEST NSSL-WRF AS THE 10/00Z NAM STILL APPEARS TOO AGGRESSIVE WITH THE DEVELOPMENT OF THE COASTAL TROUGH/SURFACE LOW WITHIN THE HIGHLY SHEARED H5 VORTICITY PATTERN. PLAN TO INCREASE POPS TO 40-50 PERCENT ALONG AND EAST OF I-95 FOR THIS AFTERNOON WITH POPS NO HIGHER THAN 20-30 PERCENT ACROSS THE FAR WESTERN/INTERIOR ZONES. RAINFALL AMOUNTS WILL RANGE FROM A TRACE WELL INLAND TO POSSIBLY AS HIGH AS 0.10-0.20 INCHES ACROSS CHARLESTON AND EASTERN BERKELEY COUNTIES WHICH WILL DO LITTLE TO IMPROVE THE RAPIDLY EXPANDING AREAS OF EXCEPTIONAL DROUGHT. HIGHS WILL RANGE FROM THE LOWER-MID 60S EXCEPT ACROSS PARTS OF THE FAR SOUTHERN AREA FROM SAVANNAH SOUTH TO DARIEN AND LUDOWICI WHERE MID 60S ARE LIKELY. && .SHORT TERM /TONIGHT THROUGH MONDAY/... TONIGHT...ISOLATED-SCATTERED LIGHT RAIN SHOWERS WILL GRADUALLY END FROM WEST-EAST THIS EVENING AS A COLD FRONT MOVES ACROSS THE REGION. THE FRONT IS EXPECTED TO BE WELL OFFSHORE BY SUNRISE SATURDAY AS LOW PRESSURE RAPIDLY DEEPENS OFF THE MIDDLE ATLANTIC COAST. TEMPERATURES WILL INITIALLY BE HELD UP WITHIN THE WARM SECTOR AND WILL BEGIN TO STEADILY FALL IN ITS WAKE AS COLD AIR ADVECTION ENSUES. LOWS SATURDAY MORNING WILL RANGE FROM THE UPPER 30S/NEAR 40 IN THE MILLEN-SYLVANIA-ALLENDALE CORRIDOR TO THE UPPER 40S ALONG THE COAST. SATURDAY...SURFACE LOW PRESSURE WILL LIFT OFF THE VIRGINIA AND NORTH CAROLINA COASTLINE BY DAYBREAK SATURDAY...WHILE SHORTWAVE ENERGY TRAVERSES THE FORECAST AREA AND PROVIDES THE FINAL PUSH OF THE COLD FRONT OFFSHORE. ANY ASSOCIATED SHOWER ACTIVITY WILL BE QUICKLY SHIFTING INTO THE WATERS SATURDAY MORNING...AS A MUCH DRIER AIR MASS FOLLOWS IN THE WAKE OF THE FRONT. THE FIRST WAVE OF COLD ADVECTION WILL SUPPRESS HIGH TEMPERATURES IN THE UPPER 50S SATURDAY AFTERNOON...WITH BREEZY CONDITIONS UNDER AN INTENSIFYING LOW LEVEL JET AND TIGHTENED PRESSURE GRADIENT. SATURDAY NIGHT...MORE SIGNIFICANT COLD ADVECTION WILL OCCUR OVERNIGHT...AS THE AXIS OF THE BROAD UPPER TROUGH CROSSES THE EAST COAST. A SECONDARY DRY FRONT WILL ALSO PASS THROUGH THE REGION...LEADING AN IMPRESSIVE WAVE OF ARCTIC AIR INTO THE SOUTHEAST STATES. TEMPERATURES WILL RAPIDLY FALL INTO THE 20S FOR MANY LOCATIONS...AS ADVECTION PUSHES CONSIDERABLE COLD AIR TOWARD THE COASTLINE. A 30 TO 40 KT LOW LEVEL JET UNDERNEATH A NEARLY 150 KT UPPER JET WILL MAINTAIN DECENT NORTHWEST FLOW OVERNIGHT...CONTRIBUTING TO WIND CHILL VALUES POSSIBLY IN THE TEENS. RESIDENTS OF SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA WITH SENSITIVE OUTDOOR VEGETATION WILL WANT TO TAKE THE PROPER PRECAUTIONS. SINCE THE FROST/FREEZE PROGRAM HAS YET TO OFFICIALLY BEGIN...FROST ADVISORIES OR FREEZE WATCHES/WARNINGS WILL NOT BE ISSUED FOR THIS EVENT. HOWEVER...WILL CONTINUE TO HIGHLIGHT THE COLD WEATHER IN THE HAZARDOUS WEATHER OUTLOOK AND WILL CONSIDER ISSUING SPECIAL WEATHER STATEMENTS AS THE COLD SPELL APPROACHES. SUNDAY...WITH COLD HIGH PRESSURE IN PLACE...TEMPERATURES ON SUNDAY WILL BE DRAMATICALLY LOWER COMPARED TO PREVIOUS DAYS. EXPECT TEMPERATURES TO BE SUPPRESSED IN THE UPPER 40S TO AROUND 50 DEGREES DESPITE ABUNDANT SUNSHINE. LOW TEMPERATURES ON SUNDAY NIGHT COULD EVEN BE A DEGREE OR TWO COLDER THAN SATURDAY NIGHT...AS RADIATIONAL COOLING WILL BE MORE EFFICIENT UNDER LIGHTER WINDS AND CLEAR SKIES. MONDAY...EXPECT A GRADUAL MODERATION IN TEMPERATURES TO BEGIN ON MONDAY...AS SURFACE HIGH PRESSURE STEADILY TRACKS EAST TOWARD THE COASTLINE AND HEIGHTS ALOFT BEGIN TO SUBTLY INCREASE. LIGHT WINDS COULD ACTUALLY SHIFT AROUND TO THE SOUTH AND EFFECTIVELY SHUT OFF ANY LINGERING COLD ADVECTION. HIGH TEMPERATURES ON MONDAY WILL REACH THE UPPER 50S. LAKE WINDS...STRONG WINDS ARE EXPECTED TO DEVELOP ON LAKE MOULTRIE FOLLOWING THE PASSAGE OF A COLD FRONT SATURDAY AND THEN INCREASE FURTHER BEHIND A REINFORCING COLD FRONT SATURDAY NIGHT. A LAKE WIND ADVISORY WILL LIKELY BE NEEDED SATURDAY AFTERNOON THROUGH SUNDAY MORNING. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... SURFACE HIGH PRESSURE WILL CONTINUE TO TRACK EAST INTO THE ATLANTIC WATERS LATE MONDAY THROUGH TUESDAY. SHORTWAVE ENERGY EMBEDDED WITHIN NEARLY ZONAL FLOW ALOFT WILL SHIFT INTO THE FORECAST AREA BY TUESDAY AFTERNOON...ACCOMPANIED BY A DEVELOPING SURFACE FRONT. THIS SYSTEM APPEARS TO HAVE A DECENT TAP INTO DEEP MOISTURE DURING ITS APPROACH ON TUESDAY...WITH FORECAST MODELS SHOWING EVIDENCE OF STRONG WARM ADVECTION AND SOUTHWEST FLOW LIKELY TAPPING INTO GULF MOISTURE. WILL THUS CONTINUE TO CARRY RAIN CHANCES 30 PERCENT OR LESS LATE MONDAY NIGHT THROUGH TUESDAY NIGHT...ACCOUNTING FOR SOME UNCERTAINTY IN THE TIMING AND TRACK OF THE FRONT. MEDIUM RANGE FORECAST MODELS ARE INDICATING LITTLE TO NO COLD ADVECTION BEHIND THE FRONT...AND TEMPERATURES MID TO LATE WEEK COULD ACTUALLY REMAIN ABOVE SEASONAL NORMALS AS THE WEATHER PATTERN APPEARS MORE UNSETTLED. CONFIDENCE IN FORECAST DETAILS FOLLOWING THE TUESDAY FRONTAL SYSTEM IS QUITE LOW...AND PREFER TO LEAN TOWARD A BLEND OF GUIDANCE AND PERSISTENCE AT THIS TIME. WILL KEEP POPS BELOW 15 PERCENT FOR WEDNESDAY...THEN REINTRODUCE RAIN CHANCES THURSDAY AND FRIDAY AS ANOTHER SURFACE WAVE/FRONTAL SYSTEM COULD IMPACT THE SOUTHEAST STATES LATE WEEK. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... LOW-END VFR CIGS HAVE MOVED INTO THE KCHS-KSAV CORRIDOR ALONG THE LEADING EDGE OF ISENTROPIC ASSENT. EXPECT LOW-END VFR OR HIGH-END MVFR CIGS TO DOMINATE THROUGH SUNRISE WITH INCREASING PROBABILITIES FOR PREVAILING MVFR CIGS THEREAFTER. SHOWER ACTIVITY WILL INCREASE LATER THIS MORNING WITH THE GREATEST COVERAGE OCCURRING EAST OF I-95 THIS AFTERNOON. TIMING AND INTENSITY UNKNOWN SUPPORT KEEPING SHOWERS OUT OF BOTH TAFS SITES ATTM...HOWEVER AT SOME POINT MVFR VSBYS ARE EXPECTED IN SHOWERS... ESPECIALLY AT KCHS. EXTENDED AVIATION OUTLOOK...MVFR CIGS AND/OR VSBYS COULD AFFECT THE TERMINALS THROUGH FRIDAY NIGHT...AS A WAVE OF LOW PRESSURE LIFTS WELL OFF THE COAST OF THE SOUTHEAST UNITED STATES. IN ADDITION...GUSTY WINDS WILL BECOME A CONCERN SATURDAY...WITH LLWS POSSIBLE SATURDAY NIGHT. MVFR CONDITIONS COULD IMPACT THE TERMINALS AGAIN ON TUESDAY...AS ANOTHER STORM SYSTEM MOVES THROUGH THE AREA. && .MARINE... TODAY...THE REGION IS POSITIONED NORTH OF A SHARPENING COASTAL TROUGH ALONG THE FLORIDA EAST COAST THIS MORNING. THIS IS YIELDING A SOLID NORTHEAST WIND REGIME WITH SPEEDS GENERALLY BELOW 15 KT. NORTHEAST WINDS WILL DOMINATE FOR MUCH OF THE DAY BEFORE VEERING MORE SOUTHERLY THIS AFTERNOON AS THE COASTAL TROUGH BREAKS DOWN AND A COLD FRONT APPROACHES FROM THE WEST. BOTH WINDS AND SEAS WILL REMAIN WELL BELOW SMALL CRAFT ADVISORY THRESHOLDS. TONIGHT...THE COLD FRONT WILL MOVE INTO THE COASTAL WATERS THIS EVENING AND WILL EXIT INTO THE GULF STREAM BY SUNRISE SATURDAY. THIS INITIAL BOUT OF POST-FRONTAL COLD AIR ADVECTION LOOKS FAIRLY WEAK...WHICH WILL ONLY YIELD A MODEST INCREASE IN BOTH WINDS AND SEAS FOR MUCH OF THE TONIGHT PERIOD. SPEEDS WILL BE STEADILY RAMPING UP HOWEVER WITH THE GREATEST CHANCES FOR SMALL CRAFT ADVISORY CONDITIONS LIKELY HOLDING OFF UNTIL AFTER SUNRISE. SATURDAY THROUGH TUESDAY...A COLD FRONT WILL PUSH THROUGH THE MARINE AREA SATURDAY MORNING...RAPIDLY FOLLOWED BY A SECONDARY REINFORCING FRONT SATURDAY NIGHT. ALL MARINE ZONES WILL BE SOLIDLY WITHIN SMALL CRAFT ADVISORY CONDITIONS BY LATE SATURDAY...AS COLD ADVECTION INTENSIFIES AND TAPS INTO IMPRESSIVE LOW LEVEL WINDS. FREQUENT GALE FORCE GUSTS ARE ALSO POSSIBLE FOR THE WARMER WATERS MAINLY BEYOND 20 NM...WHERE MIXING WILL BE MAXIMIZED. A GALE WATCH MAY BE NEEDED FOR THE GEORGIA OFFSHORE WATERS LATER TODAY. SLOWLY IMPROVING CONDITIONS ARE EXPECTED ON SUNDAY...AS THE COLD AIR ADVECTION/TIGHT PRESSURE GRADIENT REGIME BEGINS TO WEAKEN. AT THIS TIME...IT APPEARS THAT CONDITIONS WILL DROP BELOW ADVISORY LEVELS ACROSS THE NEARSHORE WATERS AROUND NOON ON SUNDAY...WITH SEAS MOST LIKELY REMAINING AT OR ABOVE CRITERIA ACROSS THE OUTER GEORGIA WATERS THROUGH LATE SUNDAY AFTERNOON OR EARLY SUNDAY EVENING. CONDITIONS WILL CONTINUE TO IMPROVE SUNDAY NIGHT THROUGH MONDAY NIGHT...THEN POSSIBLY GO DOWNHILL AGAIN TUESDAY AS A LOW PRESSURE SYSTEM IMPACTS THE SOUTHEAST STATES. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...NONE. && $$