830 FXUS62 KFFC 181137 AAA AFDFFC AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PEACHTREE CITY GA 637 AM EST MON FEB 18 2013 .PREV DISCUSSION... /ISSUED 359 AM EST MON FEB 18 2013/ SHORT TERM /TODAY THROUGH TUESDAY/... VERY QUIET DAY EXPECTED FOR TODAY...WITH WEAK RIDGING ALOFT AND SURFACE HIGH PRESSURE MOVING EAST OFF THE CAROLINAS INTO THE WESTERN ATLANTIC. TROUGH PUSHING OFF THE ROCKIES AND ATTENDANT SURFACE LOW IN THE CENTRAL PLAINS WILL BE THE MAIN WEATHER MAKER FOR THE SHORT TERM...BRINGING A QUICK SHOT OF SHOWERS TO THE AREA ON TUESDAY. AS THE TROUGH DEEPENS IN THE PLAINS TODAY...THE WAVETRAIN AMPLITUDE WILL INCREASE...INCREASING THE DIFFLUENCE ALOFT AND STRENGTHENING THE SURFACE FRONT AS IT APPROACHES. HOWEVER...BY 12Z TUESDAY THE FRONT WILL BEGIN TO OCCLUDE WITH BEST DYNAMICS REMAINING WELL TO THE NORTH ASSOCIATED WITH THE SURFACE AND UPPER LOWS...SO THE FRONT WILL BEGIN TO WEAKEN AS IT MOVES THROUGH. OVERALL THERE IS GENERAL AGREEMENT BETWEEN THE MODELS FOR THE SHORT-TERM ESPECIALLY WITH MASS FIELDS. IF A PREFERENCE HAD TO BE DEFINED...IT WOULD BE WEAKLY GFS BASED ON MORE CONSISTENT TRENDS BUT FOR MOST PART STARTED WITH A GENERIC BLEND FOR ELEMENTS THROUGHOUT THE SHORT TERM. HAVE POPS MOVING INTO NORTHWEST GEORGIA BY AROUND 06Z TUESDAY...WITH LIKELY TO CATEGORICAL SPREADING ACROSS NORTH GEORGIA THROUGH 12Z BUT DIMINISHING INTO CENTRAL GEORGIA BY 18Z. POPS PRETTY MUCH CLEAR OUT BY 00Z WEDNESDAY. OVERALL QPF VALUES NOT PARTICULARLY IMPRESSIVE WITH STORM TOTAL /AT LEAST FOR THIS EVENT/ OF BETWEEN 0.25 TO 0.5 INCHES. MAIN WEATHER TYPE WILL BE SHOWERS...BUT CONCERN IS THE POSSIBILITY OF THUNDER SOUTH AND WINTRY PRECIP IN THE MOUNTAINS. FOR THE THUNDER...SPC DOES HAVE JUST A SLIVER OF WEST CENTRAL GEORGIA IN GENERAL THUNDER FOR DAY1...AND EXTREME SOUTHERN PORTIONS OF THE AREA IN GENERAL THUNDER FOR DAY2...BUT LOOKING AT MUCAPE VALUES JUST DO NOT SEE ENOUGH TO SUPPORT THUNDER AT THIS TIME. DAY SHIFT CAN REEVALUATE BASED ON 12Z GUIDANCE BUT FOR NOW HAVE CONTINUED TREND OF LEAVING IT OUT. FOR WINTRY PRECIP IN THE MOUNTAINS...00Z GUIDANCE IS COMING IN COLDER AND MORE MOIST THAN PREVIOUS RUNS. GFS IS THE COLDEST AND NAM THE WARMEST...WITH NEW 00Z ECMWF BETWEEN THE TWO BUT SLIGHTLY CLOSER TO THE NAM. THERE WILL BE A CRITICAL WINDOW AHEAD OF THE FRONT WHEN PRECIP MOVES IN BUT TEMPERATURES WILL BE COLD ENOUGH TO SUPPORT SOME FREEZING OR FROZEN PRECIPITATION IN THE MOUNTAINS. OVERALL LOW TEMPS WILL DEPEND ON EXTENT OF CLOUD COVER AHEAD OF THE SYSTEM BUT THINK THAT WE SHOULD GET SOME RADIATIONAL COOLING BEFORE THE PRECIP MOVES IN. HAVE LOW TEMPS IN THE MOUNTAINS AT OR JUST SLIGHTLY BELOW FREEZING. THE DIFFICULTY LIES IN THE SOUNDING DETAILS...ESPECIALLY CONSIDERING THE WAA AHEAD OF THE SYSTEM AT 850MB...LEADING TO A WARM NOSE. GFS BUFR SOUNDINGS FOR BRASSTOWN BALD INDICATE ALL SNOW /WARM NOSE DOES NOT GET ABOVE FREEZING/...BUT NAM BUFR SOUNDINGS INDICATE ALL LIQUID REACHING THE SURFACE LAYER DUE TO THE STRENGTH OF THE WARM NOSE...WITH FINAL P-TYPE DEPENDENT ON SURFACE TEMPS. CONFIDENCE NOT PARTICULARLY HIGH GIVEN THESE DIFFERENCES BUT FEEL IT IS LIKELY THAT AT LEAST SOME SORT OF WINTRY PRECIP WILL MAKE IT TO THE GROUND...SO TOOK A BLEND OF BOTH...STUCK THE TEMPS AND POPS IN THE BLENDER WITH THE TOP-DOWN METHODOLOGY...AND RESULTANT WEATHER GRIDS GIVE MAINLY A RAIN/SLEET MIX ACROSS THE MOUNTAINS WITH A LITTLE SNOW EARLY ON BEFORE THE 850MB TEMPS BEGIN WARMING...AND PERHAPS SOME FREEZING RAIN MIXED IN HERE AND THERE. SINCE THE PERIOD OF TIME WITH AT OR BELOW FREEZING TEMPS IS ONLY FOR A COUPLE OF HOURS AT BEST AROUND 12Z TUESDAY...AND THEN TEMPS BEGIN TO WARM AGAIN...EXPECT VERY LITTLE IF ANY ACCUMULATION OF WHATEVER ENDS UP OCCURRING. IF ANYTHING DOES BEGIN TO ACCUMULATE...IT SHOULD MELT QUICKLY WITH THE WARMING TEMPS AND CHANGEOVER TO LIQUID PRECIP AFTER 12Z. SO...LONG STORY SHORT...EXPECT A BRIEF SHOT OF JUST ABOUT EVERY P-TYPE OUT THERE ACROSS THE NORTHEAST MOUNTAINS...PRIMARILY BETWEEN 09-13Z BUT NO ACCUMULATIONS. NO WINTER WEATHER PRODUCTS PLANNED AT THIS TIME... BUT WILL MENTION THE POSSIBILITY IN THE HWO. OTHER CONCERN IS STRONG WINDS AHEAD OF THE FRONT WITH 925-850MB LLJ OF 40-50KT MOVING IN ACROSS NORTH GEORGIA...BUT FOR RIGHT NOW WINDS REMAIN JUST BELOW ADVISORY CRITERIA. OBVIOUSLY THIS LEAVES A LOT FOR LATER SHIFTS TO REEVALUATE WITH 12Z GUIDANCE. TDP LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... LONG RANGE ECMWF AND GFS MODELS CONTINUE TO SHOW GOOD AGREEMENT... AT LEAST INITIALLY THROUGH FRIDAY... WITH HIGH PRESSURE DOMINATING TUESDAY NIGHT THROUGH EARLY THURSDAY... THEN WEAKENING ITS GRIP IN RESPONSE TO A LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT PUSHING EAST OF THE PLAINS ON THURSDAY. MODELS AGREE WITH SHOWERS AND POSSIBLY A FEW EMBEDDED THUNDERSTORMS SPREADING INTO NORTH GEORGIA THURSDAY NIGHT... THEN INTO CENTRAL GEORGIA ON FRIDAY ALONG AND AHEAD OF A COLD FRONT. BOTH MODELS SHOW 200-400 CAPE NOSING INTO PARTS OF CENTRAL GEORGIA ON FRIDAY DURING DAYTIME HEATING. THIS LOCATION AND TIMING WILL LIKELY BE THE GREATER CHANCE FOR THUNDER. THE NOTED MARGINAL INSTABILITIES AND UPPER SUPPORT DOES SUGGEST ANY STORM DEVELOPMENT WILL LIKELY REMAIN UNDER SEVERE LIMITS. HOWEVER... THIS COULD CHANGE AND ALL INTERESTS ARE ENCOURAGED TO MONITOR CLOSELY LATER FORECASTS. AS FOR THE WEEKEND... THE MODELS DIVERGE... WITH THE FASTER GFS PUSHING THE COLD FRONT EAST BY SATURDAY MORNING WITH DRY HIGH PRESSURE DOMINATING SATURDAY AND SUNDAY. THE SLOWER/WETTER ECMWF STALLS THE FRONT ACROSS CENTRAL GEORGIA ON SATURDAY AND HOLDS OFF CLEARING IT AND THE ASSOCIATED SHOWERS EAST UNTIL SUNDAY MORNING. TOOK A BLEND WITH A SLIGHT LEAN TOWARD THE DRIER/CLEANER GFS... AND HELD ONTO A SLIGHT CHANCE OF RAIN ACROSS PARTS OF CENTRAL GEORGIA FOR SATURDAY AND SUNDAY. 39 FIRE WEATHER... FUEL MOISTURES DROPPED TO NEAR 8 PERCENT YESTERDAY ACROSS A LARGE PORTION OF THE AREA...HOWEVER NEW GUIDANCE COMING IN IS SPEEDING UP THE MOISTURE RETURN TODAY LEAVING JUST MARGINAL FIRE DANGER CONDITIONS. SINCE FIRE DANGER STATEMENT IS ALREADY OUT HAVE REISSUED AND ADJUSTED WORDING. ANY FIRE WEATHER ISSUES AFTER TODAY WILL BE DEPENDENT ON FUEL MOISTURES. TDP && .AVIATION... 12Z UPDATE... VFR THROUGH ABOUT 10Z TUESDAY MORNING...THOUGH LOW VFR CLOUDS SHOULD START TO INCREASE BETWEEN 06-08Z /LATER SOUTH AND EAST/. -SHRA MOVES IN BETWEEN 08-10Z WITH MVFR CIGS BY 10Z AS WELL. SHOULD SEE AT LEAST A BRIEF PERIOD OF IFR CONDITIONS...CURRENT TIMING FOR THE METRO AREA IS 13-16Z BUT WILL HAVE TO BE REFINED. IMPROVEMENT BACK TO MVFR BEFORE THE END OF THE ATL PERIOD. LIGHT SSE WINDS THIS MORNING INCREASE TO AROUND 10KT THIS AFTERNOON... SHIFTING TO SSW 12-13Z TUESDAY. //ATL CONFIDENCE...12Z UPDATE... MEDIUM ON TIMING OF ELEMENTS /LOWERING CIGS...WIND SHIFTS/ MEDIUM ON CIG HEIGHTS TUESDAY MORNING HIGH ON WIND SPEEDS...WX...AND VSBY TDP && .PRELIMINARY POINT TEMPS/POPS... ATHENS 58 38 57 28 / 0 60 80 5 ATLANTA 57 41 55 30 / 0 70 80 5 BLAIRSVILLE 52 32 49 22 / 0 80 80 5 CARTERSVILLE 58 39 55 27 / 0 80 80 5 COLUMBUS 61 45 62 32 / 0 50 80 5 GAINESVILLE 54 37 52 29 / 0 70 80 5 MACON 60 41 62 30 / 0 40 80 10 ROME 59 39 55 26 / 0 80 80 5 PEACHTREE CITY 59 39 58 26 / 0 70 80 5 VIDALIA 60 43 66 36 / 0 30 50 20 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$