AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 322 PM EDT FRI JUL 29 2011 ...HOT AND HUMID WEATHER TO RETURN THIS WEEKEND WITH HEAT INDICES APPROACHING 110 DEGREES... .SYNOPSIS...19 UTC SURFACE ANALYSIS SHOWS A HIGH PRESSURE AREA CENTERED ABOUT NEAR DOTHAN ALABAMA. THIS HIGH PRESSURE AREA IS ALSO EVIDENT QUITE WELL IN THE VISIBLE SATELLITE IMAGERY THIS AFTERNOON. THE SEA BREEZE IS SLOWLY MOVING INLAND ACROSS THE FLORIDA BIG BEND AND PANHANDLE. SHOWER AND THUNDERSTORM ACTIVITY HAS BEEN ISOLATED AT BEST...IN PART DUE TO THE DRIER MID LEVEL AIR THAT IS OVERSPREADING THE REGION AS A RIDGE BUILDS OVERHEAD. && .SHORT TERM...(TONIGHT THROUGH SUNDAY NIGHT). NOT MUCH OVERALL CHANGE TO THE FORECAST THINKING THIS CYCLE...THOUGH SOME DIFFERENCES IN THE SHORT TERM FORECAST COMPLICATE MATTERS A LITTLE. THE LARGE RIDGE BUILDING OVER THE REGION TODAY IS EXPECTED TO SHIFT WESTWARD QUICKLY OVER THE WEEKEND AS A TROF DEVELOPS ACROSS THE EAST COAST BY MONDAY IN RESPONSE TO A STRONG SHORTWAVE MOVING THROUGH ONTARIO. AS THE RIDGE RECEDES TO THE WEST AND IS REPLACED BY THIS TROF...RAIN CHANCES WILL BEGIN TO INCREASE LATE IN THE PERIOD. THE NOTICEABLE DIFFERENCE THIS CYCLE IS WITH RESPECT TO THE SPEED AT WHICH THE NAM WEAKENS THIS RIDGE. THE NAM ESSENTIALLY ERODES THE RIDGE OVER THE SOUTHEAST BY 00Z SUNDAY...WHEREAS THE GFS HOLDS ON TO THE RIDGE THROUGH AT LEAST 18Z SUNDAY. IT SEEMS A LITTLE ODD THAT THE RIDGE WOULD ERODE AS QUICKLY AS THE NAM IS INDICATING GIVEN HOW STRONG IT IS NOW. AS A RESULT...WILL PUT MORE WEIGHT ON THE GFS SOLUTION OF THE FORECAST THROUGHOUT THE SHORT TERM PERIOD. THIS COMPROMISE SOLUTION...WEIGHTED TOWARD THE GFS...DOES FIND SOME SUPPORT AFTER A QUICK LOOK AT THE 29/12Z GFS. SATURDAY...IT`S GOING TO BE QUITE HOT. WITH THE HIGH PRESSURE RIDGE BUILDING OVER THE REGION AND SHIFTING SLIGHTLY OFF TO THE WEST BY THE END OF THE DAY...EXPECT TEMPERATURES TO WARM INTO THE UPPER 90S AT MOST LOCATIONS. A FEW 100 DEGREES READINGS ARE ALSO EXPECTED. GIVEN THE CONTINUED UNFAVORABLE THERMODYNAMIC ENVIRONMENT EXPECT GENERALLY ISOLATED THUNDERSTORM COVERAGE AT BEST. THE LATEST MODEL RUNS DO SHOW A SLIGHT ENHANCEMENT TO THE FLOW OVER NE FLA AND INTO THE EASTERN FLA BIG BEND SO WILL INCLUDE A 30 POP THERE AS CONVERGENCE ALONG THE SEA BREEZE FRONT WILL BE ENHANCED THERE. CONSIDERED POSTING A HEAT ADVISORY FOR SATURDAY AFTERNOON FOR A GOOD PORTION OF THE REGION...BUT LATEST FORECAST HEAT INDICES TOP OUT AT ABOUT 108 DEGREES JUST IN A FEW AREAS...SO WITH VALUES COMING IN JUST SHY OF CRITERIA...WILL DELAY ANY ADVISORY DECISION TO THE MID SHIFT. SUNDAY...AS THE RIDGE BEGINS ITS RETREAT WEST...THUNDERSTORM ACTIVITY WILL BEGIN TO INCREASE...INITIALLY IN THE EASTERN AREAS WHERE LESS SUPPRESSION WILL BE IN PLACE. POPS WILL INCREASE TO NEAR CLIMATOLOGICAL NORMS...AROUND 40 PERCENT IN THE EAST TAPERING DOWN TO SLIGHTLY BELOW NORMAL VALUES (30 PERCENT) IN THE WEST. TEMPERATURES WILL CONTINUE TO BE HOT...BUT SHOULD STAY AWAY FROM THE 100 DEGREE MARK. .LONG TERM...(MONDAY THROUGH FRIDAY). THE LARGE SCALE LONGWAVE PATTERN COMMENCES WITH EXPANSIVE RIDGE FROM WEST COAST EWD. IN NRN STREAM RIDGE EXTENDS TO ERN STATES BUT IN SRN STREAM SUB-TROPICAL RIDGE EXTENDS WELL INTO WRN ATLC. GUIDANCE SHOWS A STRONG SHORTWAVE DROPPING SOUTH DOWN EAST COAST AND ACROSS LOCAL ARE INTO MONDAY. AT SURFACE...LOW OFF NEW ENGLAND COAST WITH TRAILING FRONT SSW TO WEAK LOW OVER COASTAL CAROLINA THEN WEAK STATIONARY FRONT ACROSS CWA. BERMUDA HIGH PRESSURE FROM WRN ATLC CROSS CNTRL PENINSULA. THIS PLACES LOCAL AREA IN ONSHORE FLOW BETWEEN BOTH SYSTEMS WITH SURFACE BOUNDARY AIDED BY SHORTWAVE PROVIDING FOCUS FOR CONVECTION INTO THE WORK WEEK. MODELS ARE IN AGREEMENT THAT BEGINNING ON MONDAY THE UPPER LEVEL HIGH RETREATS BACK TO SRN/CNTRL PLAINS AND PERSISTS THERE. AT SURFACE...AREA FRONT DISSIPATES AS UPSTREAM HIGH PUSHES SEWD...AND BERMUDA HIGH SAGS SWD TO SRN FLORIDA PENINSULA BY MIDWEEK. AT SAME TIME...A STRONG CANADIAN TROUGH MOVES ACROSS THE NRN TIER STATES GRADUALLY AMPLIFYING REACHING THE NERN STATES WED. IN RESPONSE... UPPER TROUGH DEEPENS ALONG AND JUST OFF NE/MID-ATLC SEABOARD AND DIGS DOWN THE EXTREME WRN ATLC. SO LOCAL AREA IN DIVERGENT FLOW BETWEEN RETREATING HIGH TO WEST AND AMPLIFIED TROUGH TO EAST. ASSOCD WEAK VORT MAXES MAY ROTATE WWD FROM TROUGH THRU PERIOD AND PROVIDE BRIEF LIFT OF CONVECTION MOST DAYS. BY FRI LOW CUTS OFF FROM BASE OF TROUGH OFF SE FL WITH CYCLONIC FLOW INCHING TOWARDS LOCAL AREA. WITH SHORTWAVES SLATED TO REMAIN WELL TO OUR WEST...PRECIPITATION WILL BE FOCUSED ALONG SEA BREEZE THROUGH THE ENTIRE PERIOD. WITH MID AND SOME UPPER LEVEL MOISTURE REMAINING HIGH ESPECIALLY END OF PERIOD...THE SEA-BREEZE WILL BE SOMEWHAT ENHANCED. WILL GO WITH LOW-MID SCT POPS SUN NIGHT THRU TUES (HIGHEST MON AFTN) AND WDLY SCT-LOW SCT POPS REST OF DAYTIME PERIODS. GENERALLY WDLY SCT OR BELOW AT NIGHT. MIN AND TEMPS WILL REMAIN 3 TO 5 DEGREES ABOVE CLIMO THRU THE PERIOD. (AVG INLAND MAX/MIN TEMPS ARE 71/92 DEGREES). THE COMBINATION OF TEMPS IN THE MID 90S AND HIGH HUMIDITIES WILL ALLOW MAXIMUM HEAT INDICES WILL RISE TO 105 TO 110 DEGREES MOST AFTERNOONS. && .AVIATION...WITH HIGH PRESSURE IN CONTROL...VFR CONDITIONS WILL PREVAIL THROUGH THE OVERNIGHT HOURS...WITH JUST SOME PATCHY MVFR CIGS AT KDHN AND KVLD. && .MARINE...LOOKS LIKE ANY SWELL FROM DON IS JUST ABOUT DONE AS BUOYS ARE RETURNING TO 2 TO 3 FEET OVER OUR PART OF THE GULF. EXPECT THIS DOWNWARD TREND TO CONTINUE. AS THE SUBTROPICAL RIDGE BECOMES REESTABLISHED ACROSS THE REGION WILL SEE TYPICAL SUMMERTIME CONDITIONS WITH LOW WINDS AND SEAS BY SUNDAY. && .FIRE WEATHER...DESPITE THE LOW RAIN CHANCES AND HOT TEMPERATURE...HUMIDITY VALUES ARE EXPECTED TO REMAIN ABOVE CRITICAL VALUES THROUGH THE WEEKEND. && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 75 98 77 97 76 / 10 20 10 30 20 PANAMA CITY 76 94 78 93 78 / 10 20 10 30 20 DOTHAN 74 98 75 97 76 / 10 20 10 30 20 ALBANY 74 100 75 99 77 / 10 20 10 30 20 VALDOSTA 75 100 75 99 76 / 10 30 10 40 20 CROSS CITY 74 96 77 95 75 / 10 30 10 40 20 APALACHICOLA 77 94 78 92 79 / 10 20 10 30 20 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...NONE. GM...NONE. && $$