FXUS62 KFFC 031849 AAA AFDFFC AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PEACHTREE CITY GA 149 PM EST SAT JAN 3 2015 ...SEVERE STORMS POSSIBLE NW GEORGIA AFTER MIDNIGHT... .UPDATE... NEAR TERM FCST APPEARS ON TRACK. MAIN CONCERN IS POTENTIAL FOR SVR STORMS AND HVY RAIN. 12Z SYNOPTIC MODELS AND HIRES GUIDANCE INDICATING LINE OF CONVECTION SHOULD MOVE INTO NW CORNER AROUND OR AFTER 06Z. NAM AND GFS 0-1KM BULK SHEAR /35-45KTS/ AND MLCAPE /100-250 J/KG/ FAVORABLE FOR QLCS STORMS WITH ISOLD WIND DMG AND EVEN BRIEF TORNADO POSSIBLE IN THE NW 1/3RD OF GA BETWEEN 06Z AND 12Z...MAINLY NORTH OF I-85. LATEST QPF GUIDANCE INDICATING 1 TO 2 INCHES THRU 00Z MON WITH ONLY NE GA AREA EXPECTING AMOUNTS OF 1.5 INCHES. 3HR FFG IS QUITE LOW /2-2.5 INCHES/ IN NORTH GA DUE TO ANTECEDENT RAINFALL THE LAST 36 HRS. WILL BE COLLABORATING AND LOOKING AT A LITTLE MORE DATA BEFORE DECIDING BUT FOR NOW HOLDING OFF ON WATCH. SNELSON && .PREV DISCUSSION... /ISSUED 649 AM EST SAT JAN 3 2015/ SHORT TERM /TODAY THROUGH SUNDAY/... INITIAL BAND OF MODERATE RAIN THAT DEVELOPED AS 3K TO 5K WENT SW UP AND OVER COLD WEDGE IN PLACE HAS SINCE DEPARTED NE OF THE AREA. WE ARE LARGELY POP FREE IN ITS WAKE BUT RADAR TRENDS DO INDICATE INCREASING AREAL COVERAGE OF DRIZZLE ACROSS CENTRAL PORTIONS OF THE FORECAST AREA AND WILL INCLUDE IN THE INITIALIZED GRIDS. ALSO NOTED IS AN INCREASE IN THE FOG BUT THUS FAR ONLY ISOLATED REPORTS OF DENSE FOG. WILL MONITOR TRENDS CLOSELY THROUGH DAYBREAK FOR POSSIBLE DENSE FOG ADVISORY. FOR THE REMAINDER OF THE MORNING...RAIN CHANCES WILL BE MOSTLY DEPENDENT UPON HOW MUCH OF THE DRIZZLE CAN ACTUALLY MEASURE AS DONT EXPECT TO SEE ANY LARGE SCALE LIGHT RAIN DEVELOPMENT LIKE LAST NIGHT. AS WE GET TO 18Z HOWEVER...WINDS AROUND 5K FT INCREASE TO AROUND 40 KTS AND SHOULD ONCE AGAIN SEE GOOD ISENTROPIC ASCENT RESULTING IN ANOTHER BATCH OF LIGHT TO MODERATE RAIN DEVELOPING. WILL GO WITH THE HIGHER POPS FOR THE ENTIRE AREA BASED ON SOME OF THE HIRES REFLECTIVITY GUIDANCE BUT FOCUS SHOULD EVENTUALLY SHIFT TO JUST THE NORTH BY THIS EVENING. TIMING ON THE PRE FRONTAL SQUALL LINE HAS NOT CHANGES ALL THAT MUCH WITH THIS RUN WITH CATEGORICAL POPS FOR THE NW CORNER BY 06Z AND THEN MOVING INTO THE REMAINDER OF NORTH GA AFTER 12Z. ALTHOUGH THERE WILL BE SOME NARROWING OF THE LINE AS IT PUSHES ACROSS THE FORECAST AREA...ENOUGH MOISTURE AND LIFT IS PRESENT TO WARRANT CATEGORICAL POPS FOR THE DURATION OF THE EVENT. SEVERE THREAT...MODELS IN GOOD AGREEMENT IN INDICATING 500 TO 700 J/KG MUCAPE BUT SURFACE CAPE LOOKS MUCH HARDER TO COME BY...MORE LIKELY 200 TO MAYBE 400 AT THE HIGHEST. OF NOTE IS THE FACT THAT WE ARE ALMOST CERTAIN TO REMAIN OVERCAST FOR THE ENTIRE EVENT WITH POTENTIAL OF BECOMING MORE UNSTABLE THAN MODEL PROJECTIONS LOOKING LOW AT THIS POINT. WHAT IS NOT IN QUESTION FOR THIS EVENT WILL BE THE WIND SHEAR AND IN PARTICULAR THE LOW LEVEL WIND SPEEDS. 850 JET ON THE NAM12 APPROACHES 70KT OVER THE NW CORNER WHILE 925MB WINDS REMAIN A HEALTHY 45KTS. EXPECT RECENT RAINS ALONG WITH WINDS MIXING DOWN IN JUST SHOWERS COULD POSE SOME PROBLEMS FOR THOSE WEST SOUTHWEST ORIENTED HIGHER ELEVATION LOCATIONS OF NW GA. EXPECTATIONS ARE AT THIS POINT FOR SCATTERED STRONG STORMS WITH ISOLATED SEVERE IN THE FORM OF MAINLY STRAIGHTLINE WINDS. GIVEN HELICITY HOWEVER AND LATEST SHERB PROJECTIONS...CANNOT RULE OUT AN ISOLATED TORNADO AS WELL. DEESE LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... WELL...AFTER A VERY EVENTFUL SHORT-TERM...THE EXTENDED IS PRETTY QUIET. SOME LINGERING SHOWERS REMAIN IN SOUTHEAST ZONES EARLY SUNDAY NIGHT BUT ARE GONE BY MONDAY MORNING...WITH DEEP TROUGHING DOMINATING THE EASTERN HALF OF THE COUNTRY. COLD SURFACE HIGH DIPPING INTO THE PLAINS FROM CANADA WILL SLIDE EAST ACROSS THE OHIO VALLEY AND GREAT LAKES MONDAY...WITH A SHORTWAVE DIGGING DOWN THE BACK EDGE OF THE UPPER TROUGH. THIS SHORTWAVE WILL PUSH A REINFORCING DRY FRONT THROUGH THE SOUTHEAST ON TUESDAY. MIGHT SEE A BRIEF INCREASE IN CLOUDS ACROSS NORTH GEORGIA BUT NO PRECIPITATION EXPECTED. THE BIG STORY FOR THE EXTENDED IS THE EXTREMELY COLD /AND DRY/ AIRMASS PLUNGING INTO THE COUNTRY BEHIND THE SECONDARY FRONT. TEMPERATURES BEGIN DROPPING BEHIND THE FRONT TUESDAY EVENING WITH THE REALLY STRONG CAA DEVELOPING WEDNESDAY INTO THURSDAY. HIGHS WEDNESDAY MIGHT STRUGGLE TO REACH THE LOWER 40S ACROSS THE METRO AREA...AND EVEN COLDER THURSDAY. THE 00Z ECMWF IS DEFINITELY ON THE COLD SIDE OF THINGS BUT HAS A LOW OF 13 FOR ATL WEDNESDAY NIGHT AND A HIGH OF 29 ON THURSDAY. 00Z GFS/MEX GUIDANCE IS 18 AND 34 RESPECTIVELY. GOING FORECAST IS CLOSER TO THE MEX NUMBERS BUT WE VERY WELL MAY HAVE TO TREND TOWARD THE COLDER ECMWF. SOME MODERATION EXPECTED LATE IN THE WORK WEEK AS YET ANOTHER TROUGH AXIS PUSHES THROUGH ON FRIDAY WITH VERY WEAK FLOW...AND EVEN HINTING AT RIDGING...BUILDING IN ALOFT. NO POPS THROUGH THE END OF THE PERIOD. STAY WARM! TDP HYDROLOGY... LATEST PROJECTIONS REMAIN IN THE 1.5 TO MAYBE 2 INCH RANGE FOR FAR NORTH GEORGIA. THIS WOULD PRODUCE ONLY VERY MINOR FLOODING IF ANY AT ALL SHOULD THE BALANCE OF TODAY REMAIN RELATIVELY BENIGN. WILL LET DAY SHIFT SEE HOW TODAY UNFOLDS FOR SURE BEFORE HOISTING A FLOOD WATCH. DEESE && .AVIATION... 18Z UPDATE... LIFR/IFR CONDITIONS WILL PERSIST THRU ABOUT 14Z SUN AFTER LINE OF HVY SHRA MOVES THRU. VFR CONDITIONS LIKELY AFTER 17Z. EAST COMPONENT SFC WINDS WILL ALSO VEER TO SW AFTER LINE OF SHRA MOVES THRU. COULD SEE ISOLD TSRA BUT WITH LOW INSTABILITY...LIKELIHOOD TOO SMALL TO MENTION IN FCST. //ATL CONFIDENCE...18Z UPDATE... HIGH CONFIDENCE ON ALL ELEMENTS. SNELSON && .PRELIMINARY POINT TEMPS/POPS... ATHENS 54 54 61 36 / 70 70 100 10 ATLANTA 56 56 62 34 / 60 70 100 10 BLAIRSVILLE 51 51 59 29 / 70 90 100 10 CARTERSVILLE 54 54 61 31 / 60 90 100 10 COLUMBUS 71 62 66 37 / 40 60 100 10 GAINESVILLE 52 52 60 34 / 70 70 100 10 MACON 61 61 66 37 / 50 40 100 20 ROME 56 56 61 31 / 60 100 100 10 PEACHTREE CITY 58 58 63 34 / 60 70 100 10 VIDALIA 72 63 70 44 / 50 30 80 20 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...SNELSON LONG TERM....NLISTEMAA AVIATION...SNELSON daculaweather
Posted on: Sat, 03 Jan 2015 18:49:51 +0000