Area Forecast Discussion
Issued by NWS Greer, SC

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KGSP 040838 AFDGSP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 338 AM EST WED MAR 4 2015 .SYNOPSIS... VERY WARM AND MOIST AIR WILL RETURN TO THE AREA TODAY AHEAD OF AN APPROACHING COLD FRONT. THIS FRONT IS FORECAST TO PASS THROUGH THE AREA ON THURSDAY...WITH COOL AND DRY HIGH PRESSURE RETURNING FOR FRIDAY AND INTO THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... DENSE FOG IS SLOWLY BUT SURELY EXPANDING ACROSS THE PIEDMONT THIS MORNING WITHIN WARM/MOIST ADVECTIVE/DECAYING WEDGE REGIME. AS SUCH...THE DENSE FOG ADVISORY APPEARS TO BE VERY WELL PLACED...AND WILL REMAIN IN EFFECT UNTIL 15Z. THE BULK OF SHOWER ACTIVITY CONTINUES TO DEVELOP ACROSS THE GREAT TENN VALLEY AND CUMBERLAND PLATEAU AREAS THIS MORNING...LIFTING PRIMARILY WEST OF THE APPALACHIANS WITHIN DEEP SW FLOW ALOFT. THIS PROBABLY ISN/T GOING TO CHANGE A WHOLE LET OVER THE NEXT 12-18 HOURS...AS THIS IS WHERE THE BETTER FORCING AND MOISTURE PROFILES WILL REMAIN THROUGH THE DAY...UNDER PERSISTENT DEEP SW FLOW. STILL...CHANCE POPS APPEAR WARRANTED ALONG THE TENN BORDER THROUGH THE DAY...WITH 50-60 POPS RESERVED PRIMARILY FOR THE SMOKIES AND SURROUNDING AREAS...WHICH IS SLIGHTLY MORE ALONG THE TRAJECTORY OF THE SHOWER GENERATION AREA...AND STANDS THE BEST CHANCE OF SEEING SHOWERS INITIATE IN RESPONSE TO MECHANICAL LIFT ASSOCIATED WITH THE SW FLOW. THE AIR MASS ABOVE THE DRAINING COOL POOL IS VERY WARM...WITH H8 TEMPS OF +10 TO +13 REPORTED ACROSS THE REGION AT 00Z. ONCE THE FOG AND LOW STRATUS BURN OFF...TEMPS WILL SOAR ACROSS THE AREA...LIKELY REACHING THE 70S ACROSS MUCH OF THE PIEDMONT THIS AFTERNOON . IN FACT...IF THE GRUNGE DISSIPATES EARLIER THAN CURRENTLY ANTICIPATED...EVEN THIS MAY PROVE TO BE TOO COOL...AND WOULD NOT BE SURPRISED TO SEE EXTREME SOUTHERN PIEDMONT AREAS TOP OUT NEAR 80. POPS WILL GRADUALLY RAMP UP ACROSS THE MTNS THIS EVENING...AS COLD/ANAFRONT GRADUALLY BUILDS INTO THE FORECAST AREA. DUE TO THE ANAFRONT NATURE OF THE BOUNDARY...TIMING OF THE WIND SHIFT INTO THE AREA WILL DICTATE HOW SOON LIKELY/CATEGORICAL CHANCES FOR RAIN WILL DEVELOP OVER THE FORECAST AREA...AND THESE THINGS NEVER SEEM TO MOVE AS FAST AS THE MODELS SUGGEST. THEREFORE...THE HIGHEST POPS HAVE BEEN DELAYED UNTIL AFTER MIDNIGHT...CATEGORICAL ACROSS THE MTNS...TAPERING TO HIGH CHANCE/LIKELY ACROSS THE PIEDMONT BY DAYBREAK THU. COLD AIR MAY BEGIN FILTERING INTO THE FAR WESTERN MTN VALLEYS BY DAYBREAK THU...WITH PROFILES EXHIBITING A TREMENDOUS WARM NOSE...AND FREEZING RAIN BEING THE PRIMARY WINTRY P-TYPE. WHILE IT APPEARS THAT FREEZING RAIN WILL BE LIKELY AT SOME POINT DURING THIS EVENT ACROSS THE WESTERN MTN VALLEYS...TIMING OF THE ARRIVAL OF COLD AIR IS STILL HIGHLY UNCERTAIN...AND SUSPECT DAYBREAK THURSDAY IS THE EARLIEST THAT THIS WOULD OCCUR. THEREFORE...NO ADVISORIES WERE ENTERTAINED ON THIS SHIFT. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AT 300 AM EST WEDNESDAY...ON THURSDAY MORNING AN UPPER TROUGH WILL EXTEND FRONT EASTERN CANADA TO THE SOUTHERN PLAINS...WITH A WELL DEFINED SHORTWAVE MOVING THROUGH IT OVER THE UPPER MS RIVE VALLEY AND SOUTHERN PLAINS. THE TROUGH DEAMPLIFIES SOMEWHAT BY FRIDAY...WHILE AN UPPER LOW CLOSES OFF IN NW MEXICO. THE SHORTWAVE MOVING THROUGH BECOMES MORE CHANNELED...APPROACHING THE SOUTHERN APPALACHIANS IN THE MORNING. A SECOND AND MORE ROBUST SHORTWAVE APPROACHES THE MOUNTAINS LATER IN THE DAY...CROSSING THE MOUNTAINS BY FRIDAY EVENING...AND MOVING TO THE SOUTHERN EDGE OF OUR AREA LATE SATURDAY NIGHT. AT THE SURFACE...ON THURSDAY MORNING A STRONG COLD FRONT WILL BE LOCATED JUST SE OF OUR AREA...WITH A SURFACE WAVE MOVING ALONG IT OVER SC. MOISTURE WILL EXTEND WELL BEHIND THE FRONT INTO THE MS RIVER VALLEY...AND POST FRONTAL PRECIPITATION. THE NAM EVEN SHOWS SOME INSTABILITY AND SHEAR BEHIND THE BOUNDARY OVER UPSTATE SC AT MIDDAY. AS THE FRONT MOVES SE DURING THE DAY...COLD ADVECTION WILL SPREAD OVER THE NC MOUNTAINS. MODEL SOUNDINGS ARE INITIALLY TO WARM AT THE TOP OF THE MOIST LAYER TO SUPPORT ICE NUCLEATION...AND FREEZING RAIN IS EXPECTED BY LATE IN THE DAY. DRYING FROM THE TOP DOWN WILL RAPIDLY LESSEN THE CHANCE OF PRECIPITATION IN THE EVENING...BUT RAPID COOLING WILL BRING THE TOP OF THE MOIST LAYER TO THE POINT OF ICE NUCLEATION...SUPPORTING A CHANGEOVER FROM FREEZING RAIN TO SNOW BEFORE PRECIPITATION ENDS LATE THURSDAY NIGHT. FRIDAY AND FRIDAY NIGHT FEATURE DRY AND COOL CONDITIONS. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AT 300 AM EST WEDNESDAY...ON SATURDAY MORNING A WELL AMPLIFIED UPPER TROUGH WILL EXTEND FROM NE CANADA TO THE SOUTHERN APPALACHIANS... WHILE A CLOSED UPPER LOW WILL BE OVER NW MEXICO. THE TROUGH LOSES SOME AMPLITUDE BY SUNDAY...WHILE THE UPPER LOW FILLS AND CROSSES NORTHERN MEXICO. THE REMAINS OF THE UPPER LOW CROSS THE SOUTHERN PLAINS ON MONDAY...RESULTING IN LOW AMPLITUDE RIDGING OVER THE SOUTHERN APPALACHIANS...WHILE NORTHERN STREAM FLOW BECOMES ZONAL. ON TUESDAY THE ECMWF AND GFS DIVERGE...WITH THE FORMER HAVING ZONAL FLOW OVER THE SE...AND THE LATER MAINTAINING A TROUGH IN THE LOWER MS RIVER VALLEY AND A RIDGE TO THE EAST. AT THE SURFACE...ON SATURDAY DRY HIGH PRESSURE WILL EXTEND FROM CHESAPEAKE BAY TO TX...WHILE A STATIONARY FRONT WILL EXTEND FROM S FL TO NEAR THE YUCATAN PENINSULA. MOISTURE AND PRECIPITATION ASSOCIATED WITH THIS FRONT IS EXPECTED TO REMAIN SOUTH OF OUR AREA. A DRY COLD FRONT RAPIDLY CROSSES OUR AREA SATURDAY NIGHT...REACHING THE GA COAST BY SUNDAY MORNING...WHILE THE STATIONARY FRONT REMAIN OVER S FL. ON MONDAY A SURFACE WAVE DEVELOPS ON THE STATIONARY FRONT IN THE WESTERN GULF OF MEXICO. MOISTURE IS EXPECTED TO SPREAD FARTHER NORTH OVER THE FRONT IN FL...PERHAPS SUPPORTING SMALL POPS AS FAR N AS OUR AREA. BY TUESDAY THE SURFACE WAVE REACHES THE SC COAST...WITH PRECIPITATION IN ISENTROPIC UPGLIDE EXTENDING BACK THE THE SOUTHERN APPALACHIANS. && .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/... AT KCLT AND ELSEWHERE (EXCEPT KAVL)...LIFR CONDITIONS AND LIGHT SOUTH WINDS WILL PERSIST THROUGH THE OVERNIGHT AND MUCH OF THE MORNING...WITH PERIODS OF VLIFR BECOMING MORE LIKELY TOWARD DAYBREAK. VERY STRONG WINDS ABOVE ABOUT 3000 FEET WILL RESULT IN LLWS LATER THIS MORNING AT ALL TERMINALS. OTHERWISE...COOL WEDGE IS EXPECTED TO COMPLETELY SCOUR ACROSS THE REGION BY AFTERNOON...WITH VFR CONDITIONS EXPECTED. AS THIS OCCURS...WINDS WILL BECOME MORE SW...AND INCREASE TO 10-15 KTS...WITH GUSTS IN THE LOWER 20S LIKELY DURING THE AFTERNOON. A STRAY SHOWER OR TWO WILL BE POSSIBLE AT JUST ABOUT ANYTIME DURING THE PERIOD...BUT THE PROBABILITY APPEARS TOO LOW FOR A TAF MENTION ATTM. AT KAVL...THE BULK OF THE OVERNIGHT SHOULD SEE CONDITIONS REMAINING NO WORSE THAN MVFR. HOWEVER...DO EXPECT PERIODS OF IFR CIGS TOWARD DAYBREAK IN THE INCREASING MOIST SOUTHERLY FLOW. A STRAY SHOWER OR TWO WILL BE POSSIBLE AT JUST ABOUT ANYTIME OVER THE NEXT 18 HOURS OR SO...BUT THE PROBABILITY APPEARS TOO LOW FOR A TAF MENTION...UNTIL WED EVENING...WHEN CHANCES FOR RAIN AND FLT RESTRICTIONS WILL INCREASE AS A COLD FRONT APPROACHES FROM THE TENN VALLEY. OUTLOOK...A COLD FRONT WILL MOVE SLOWLY THROUGH THE REGION WEDNESDAY NIGHT THROUGH THURSDAY...BRINGING CHANCES FOR HEAVIER RAINFALL AND LOW CIGS/VSBYS TO THE AREA. VFR CONDITIONS ARE EXPECTED TO RETURN FOR FRIDAY THROUGH THE WEEKEND. CONFIDENCE TABLE... 13-19Z 19-01Z 01-07Z 07-12Z KCLT HIGH 95% HIGH 100% HIGH 100% HIGH 100% KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 100% KAVL MED 74% HIGH 100% HIGH 100% HIGH 100% KHKY MED 77% HIGH 100% HIGH 100% HIGH 100% KGMU HIGH 100% HIGH 100% HIGH 100% HIGH 100% KAND HIGH 100% HIGH 100% HIGH 100% HIGH 100% THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE) WWW.WEATHER.GOV/GSP/AVIATION_TABLES && .GSP WATCHES/WARNINGS/ADVISORIES... GA...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR GAZ010-017- 018-026-028-029. NC...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR NCZ035>037- 056-057-068>072-082-502-504-506-508-510. SC...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR SCZ001>014- 019. && $$ SYNOPSIS...WIMBERLEY NEAR TERM...JDL SHORT TERM...JAT LONG TERM...JAT/WIMBERLEY AVIATION...JDL

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.