000 FXUS62 KMFL 161127 AFDMFL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIAMI FL 627 AM EST MON FEB 16 2009 .AVIATION... INTERMITTENT LOW CLOUDS/FOG WILL CONTINUE AT EAST COAST TERMINALS THROUGH JUST AFTER SUNRISE UNTIL MIXING CAN OCCUR AND SCATTER THINGS OUT. DO NOT ANTICIPATE DENSE FOG BUT VERY LOW CIGS BLO 500FT ARE POSSIBLE. SEA FOG AND LOW CLOUDS SHOULD GRADUALLY BURN OFF AT KAPF. NW WINDS INCREASE BEHIND COLD FRONT THIS MORNING. GUIDANCE SHIFTS WINDS NE AT E CST TERMINALS THIS AFTERNOON...AND SHOULD BE COLD ENOUGH FOR LAND BREEZE WITH SHIFT TO NW MOST OF THESE SITES TONIGHT. /STRASSBERG && .PREV DISCUSSION... /ISSUED 418 AM EST MON FEB 16 2009/ DISCUSSION... NOCTURNAL VISIBLE SATELLITE IMAGERY NOW SHOWING A FAIR AMOUNT OF MID AND HIGH LEVEL CLOUD COVER SPREADING ACROSS THE FORECAST AREA IN SOUTHWEST FLOW ALOFT. THIS HAS LIMITED FORMATION OF FOG ACROSS THE MAINLAND...BUT WILL MAINTAIN DENSE FOG ADVISORY FOR THE LOCAL GULF WATERS AND ADJACENT COASTAL ZONES THROUGH 10Z...AS PHONE CALLS STILL INDICATE A SUBSTANTIAL AMOUNT OF LINGERING FOG IN THIS REGION. MEANWHILE...A WEAK COLD FRONT IS MOVING SLOWLY SOUTHWARD ACROSS CENTRAL FLORIDA...WITH A FEW SHOWERS ALONG BOUNDARY OVER THE MAINLAND...BUT MOST OF THE SHOWER ACTIVITY OCCURRING OVER THE GULF/ATLANTIC WATERS. SHORT TERM MODELS STILL SUGGEST THAT THE SPEED OF THIS FRONT WILL INCREASE LATER THIS MORNING...AS MID- LEVEL VORT MAX CURRENTLY MOVING OFF THE COAST OF THE CAROLINAS INDUCES STRONGER SURFACE CYCLOGENESIS OVER THE ADJACENT GULF STREAM WATERS. EXPECT COLD FRONT TO PRESS STEADILY SOUTHWARD ACROSS THE AREA BETWEEN 10-16Z...WITH A FEW SHOWERS POSSIBLE ALONG FRONT...ESPECIALLY AFTER SUNRISE. INFLUENCE OF CANADIAN SURFACE HIGH WILL DOMINATE THIS AFTERNOON...WITH CLEARING SKIES...INCREASING NORTH WINDS AND MODERATE COLD ADVECTION RESULTING IN A VERY PLEASANT PRESIDENTS DAY FOR SOUTH FLORIDA. LOW TEMPERATURES MAY APPROACH 40F ACROSS GLADES/HENDRY COUNTIES TONIGHT...WITH FLOW OVER THE ATLANTIC COAST EXPECTED TO GRADUALLY SHIFT TO NORTH-NORTHEAST THROUGH THE NIGHT RESULTING IN LOWS ONLY FALLING INTO THE MID/UPPER 50S. THE FORECAST AREA WILL REMAIN ON NORTHERN PERIPHERY OF UPPER-LEVEL RIDGE ANCHORED ACROSS CENTRAL AMERICA THROUGH TUESDAY...BUT THIS RIDGE IS FORECAST TO EXPAND NORTHWARD TUESDAY NIGHT INTO WEDNESDAY...DOWNSTREAM FROM A PROGRESSIVE MID-LEVEL SHORTWAVE TROUGH...WHICH WILL PIVOT AROUND UPPER LOW OFF THE CALIFORNIA COAST AND ACROSS THE CENTRAL ROCKIES/PLAINS. THIS WILL LEAD TO DRY CONDITIONS PREVAILING THROUGH WEDNESDAY...DESPITE A DEEPENING SURFACE CYCLONE OVER THE CENTRAL PLAINS ASSOCIATED WITH THIS SYSTEM COMBINING WITH SURFACE RIDGE AXIS MOVING OFF COAST OF THE MID- ATLANTIC...TO BRING A RETURN TO EASTERLY FLOW ACROSS SOUTH FLORIDA. THE PREVIOUSLY MENTIONED MID-LEVEL TROUGH IS EXPECTED TO SLOWLY PHASE WITH A DEEPER UPPER LOW OVER ONTARIO/MANITOBA ON TUESDAY NIGHT...WITH THIS FEATURE TRACKING ACROSS THE GREAT LAKES REGION ON WEDNESDAY...AND MAINTAINING STEADY SURFACE CYCLOGENESIS...RESULTING IN A MUCH COLDER ARCTIC AIRMASS MOVING SOUTHEASTWARD ACROSS THE GREAT PLAINS. THE LEADING EDGE OF THIS COLDER AIRMASS IS CURRENTLY EXPECTED TO SPREAD ACROSS SOUTH FLORIDA FROM THURSDAY EVENING INTO FRIDAY MORNING...WITH A SLIGHT TO LOW CHANCE OF SHOWERS ASSOCIATED WITH FRONTAL PASSAGE. SURFACE RIDGE AXIS IS PROGGED BY GLOBAL MODELS TO SHIFT EASTWARD OVER THE NORTHERN GULF COAST ON FRIDAY...RESULTING IN A COOL AND BLUSTERY DAY FOR SOUTH FLORIDA. BASED ON MEX GUIDANCE FOR KPGD AND EXPECTATIONS OF GOOD RADIATIONAL COOLING ON SATURDAY MORNING...TEMPERATURES WILL LIKELY DIP INTO AT LEAST THE UPPER 30S OVER GLADES/HENDRY COUNTIES...BUT WILL MAINTAIN TEMPS IN THIS CATEGORY UNTIL THERE IS CONCLUSIVE EVIDENCE TO SUPPORT LOWERING TEMPERATURES EVEN FURTHER. BOTH THE GFS/ECMWF INDICATE ANOTHER STRONG UPPER LOW OR CLIPPER-TYPE SYSTEM DROPPING SOUTHWARD INTO THE NORTHERN PLAINS ON FRIDAY...AND USHERING A REINFORCING SURGE OF COLD/DRY AIR INTO THE U.S. BEST GUESS ON TIMING OF SECONDARY FRONTAL PASSAGE IN SOUTH FLORIDA IS SUNDAY...AND THE SECOND AIRMASS MAY VERY WELL BE COLDER THAN THE FIRST...BUT WILL MAKE NO MAJOR CHANGES TO EXTENDED MOS AT THIS TIME...AS THERE IS STILL TOO MUCH UNCERTAINTY. MARINE... DENSE SEA FOG PERSISTS ACROSS THE LOCAL GULF WATERS THIS MORNING...AND WILL MAINTAIN DENSE FOG ADVISORY THROUGH 10Z. OTHERWISE...COLD FRONT WILL MOVE ACROSS THE LOCAL WATERS LATER THIS MORNING...USHERING A MUCH COOLER/DRIER AIRMASS INTO THE REGION AND ENDING THREAT FOR FOG. SCA WILL BE ISSUED FOR ATLANTIC AND OFFSHORE GULF WATERS THROUGH 15Z TUESDAY IN ANTICIPATION OF NORTHERLY FLOW IN THE 20-25 KNOT RANGE...WITH SCEC HEADLINE FOR REMAINDER OF WATERS. ALTHOUGH SEAS WILL BE SLOW TO DECLINE FROM PEAK OF 8-9 FEET IN THE GULF STREAM...CONDITIONS WILL IMPROVE BY LATE TUESDAY AS GRADIENT WEAKENS AND WIND DIRECTION VEERS TO EAST. MARGINAL SCA CONDITIONS MAY DEVELOP ONCE AGAIN FROM WEDNESDAY INTO THURSDAY...AS STRONG SOUTH WINDS OCCUR IN ADVANCE OF NEXT COLD FRONT...SCHEDULED TO PASS ACROSS THE AREA ON THURSDAY NIGHT. WINDS MAY NOT BE QUITE AS HIGH WITH THIS FRONT...BUT PROLONGED PERIOD OF NORTHERLY FLOW OVER GULF STREAM WATERS THIS WEEKEND WILL LIKELY RESULT IN HAZARDOUS MARINE CONDITIONS ONCE AGAIN. FIRE WEATHER... MINIMUM AFTERNOON RH VALUES MAY FALL INTO THE 35-40 PERCENT RANGE OVER THE NORTHWEST INTERIOR THIS AFTERNOON...WITH A MORE SIGNIFICANT PROBLEM TOMORROW...AND FIRE WEATHER WATCH FOR WESTERN HALF OF THE FORECAST AREA MAY BE REQUIRED LATER TODAY. MOISTURE RETURN WILL LIMIT FIRE WEATHER THREAT ON WEDNESDAY/THURSDAY...WITH CONDITIONS DETERIORATING ONCE AGAIN AT THE END OF THE WEEK FOLLOWING PASSAGE OF A STRONGER COLD FRONT. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 75 54 71 58 / 10 - - - FORT LAUDERDALE 76 58 73 61 / 10 - - - MIAMI 77 59 73 60 / 10 - - - NAPLES 75 50 75 54 / 10 - - - && .MFL WATCHES/WARNINGS/ADVISORIES... FL...DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR FLZ063-FLZ066- FLZ067-FLZ069-FLZ070-FLZ075. AM...SMALL CRAFT ADVISORY UNTIL 10 AM EST TUESDAY FOR AMZ650-AMZ651- AMZ670-AMZ671. GM...SMALL CRAFT ADVISORY UNTIL 10 AM EST TUESDAY FOR GMZ676. && $$ LONG TERM...15/JR SHORT TERM/AVIATION...65/GS