528 FXUS61 KRLX 211415 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 1015 AM EDT FRI SEP 21 2012 .SYNOPSIS... UPPER LEVEL LOW APPROACHES FROM NORTHWEST TODAY...WITH SURFACE LOW SLIDING IN FROM THE WEST. COLD FRONT PASSES SATURDAY. COOLER SUNDAY AND MONDAY. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... SENT A QUICK UPDATE FOR SKY COVER...HOURLY DEWPOINTS AND TEMPERATURES. REST OF FORECAST CONTINUES REPRESENTATIVE OF EXPECTED CONDITIONS. PREVIOUS DISCUSSION BELOW... 630 AM UPDATE...CLOUDS FROM OVERNIGHT BEGINNING TO MOVE NORTH AND CLEAR THE AREA...BUT IT WILL NOT BE TOO LONG BEFORE NEXT DISTURBANCE BEGINS INCREASING CLOUDS AGAIN FROM THE WEST. CONVECTIVE COMPLEX IN SOUTHERN MO ASSOCIATED WITH VORT MAX THAT IS EXPECTED TO TURN NORTHEAST AND CROSS CENTRAL OHIO THIS AFTERNOON...IF IT DOES NOT START TURNING SOON...IT MAY PASS CLOSER TO/OVER CWA WHICH WOULD REQUIRE AN INCREASE IN POPS. FOR NOW JUST UPDATED GRIDS BASED ON CURRENT OBS AND TRENDS...BUT NO SIGNIFICANT CHANGES MADE. PREVIOUS DISCUSSION...UPPER LEVEL LOW WILL BE DROPPING INTO WESTERN GREAT LAKES TODAY AND TONIGHT...AS A SURFACE LOW MOVES TOWARDS THE OHIO RIVER VALLEY FROM THE WEST. A WARM FRONT WILL BE IN THE AREA THIS AFTERNOON...WITH INCREASING POPS ALONG THE OHIO RIVER TOWARDS 00Z AS FRONT/500MB RIPPLES MEANDER THROUGH. LOW PRESSURE SYSTEM WILL MOVE ACROSS SOUTHERN OHIO OVERNIGHT...WITH COLD FRONT JUST REACHING NW CWA BORDER AT END OF NEAR TERM PERIOD. THIS IS A BIT SLOWER THAN PREVIOUS FORECAST...SO SLOWED ENTIRE SYSTEM A FEW HOURS. COOLED HIGHS FOR THIS AFTERNOON ONE TO TWO DEGREES WITH CLOUDS THICKENING UP. WENT WITH SEMI NON-DIURNAL LOWS OVERNIGHT...WITH DROPPING TEMPS THROUGH ABOUT 2AM...AND THEN NEAR STEADY FOR THE REST OF THE EARLY MORNING. EXPECTING TIGHTENING PRESSURE GRADIENT AHEAD OF THE COLD FRONT...SO WINDS SHOULD NOT DECOUPLE EXCEPT FOR POSSIBLY IN THE MOST SHELTERED VALLEYS. && .SHORT TERM /7 PM THIS EVENING THROUGH MONDAY/... AS DYNAMICS IN THE MID/UPPER LEVELS LIFT QUICKLY NORTH SATURDAY MORNING INTO ONTARIO...LEAVING THE FRONT/WIND SHIFT TO CROSS OUR CWA DURING THE DAY WITH LIMITED MOISTURE AND NOT MUCH SUPPORT ALOFT. WILL LEAVE POPS MOSTLY 30 SOUTH TO 40/50 NORTH WITH AMOUNTS MOSTLY A TENTH OF AN INCH OR LESS IF IT DOES OCCUR. A SECONDARY 500 MB VORT MAXIMUM SWINGS THROUGH THE NORTHERN HALF OF OHIO BY 00Z SUNDAY. DID INCREASE POPS BACK INTO THE 20 TO 30 RANGE FOR THE POSSIBILITY OF A FEW LIGHT SHOWERS REACHING AS FAR SOUTH AS EASTERN OHIO INTO NORTHERN WEST VIRGINIA SATURDAY EVENING. 850 MB THERMAL TROF OF PLUS 1C TO PLUS 3C PASSES AROUND 12Z MONDAY...ALONG WITH ANOTHER MID LEVEL DISTURBANCE. SO PATCHES OF STRATOCUMULUS CLOUDS MAY STILL BE AN ISSUE OVERNIGHT SUNDAY NIGHT INTO MONDAY MORNING...LIMITING THE FROST POTENTIAL IN THE MOUNTAINS. WILL LEAVE THE MENTION OF THAT IN THE HAZARDOUS WEATHER POTENTIAL...AND WILL ADD THAT SAME FROST POTENTIAL FOR MONDAY NIGHT/DAWN TUESDAY...WHEN CLOUDS SHOULD BE LESS AN ISSUE. FIGURING THE LOWEST DAYTIME MAX TEMPERATURES WILL BE SUNDAY...EVEN HOLDING SNOWSHOE IN THE 40S. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... GENERALLY FOLLOWED HPC THINKING IN THE EXTENDED. THIS WILL UPR TROF LIFTING OUT EARLY NEXT WEEK WITH SOME SHOWERS POSSIBLE MID WEEK FROM AN APPROACHING FRONT. MODERATING TEMPS WILL BE FEATURED...WITH READINGS CLIMBING TO SEASONABLE LEVELS. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... CLOUDS BEGINNING TO PULL NORTH...WITH CLEARING TAKING PLACE ACROSS SOUTHERN CWA. CLOUDS HAVE REDUCED CHANCES FOR FOG AT MOST LOCATIONS...WHERE T/TD SPREADS ARE STILL 5 DEGREES PLUS AT ALL TAF SITES EXCEPT KEKN...WHERE DENSE FOG HAS BEEN IN AND OUT ALL NIGHT. ALL THE FOG THAT IS LEFT WILL DISSIPATE 12-13Z WITH VFR CONDITIONS EXPECTED FOR THE REST OF THE DAY. LOW PRESSURE APPROACHES LATER TODAY...INCREASING CHANCE OF SHOWERS FROM LATE AFTERNOON INTO TONIGHT...ESPECIALLY ACROSS THE NORTH. WILL SEE PRESSURE GRADIENT STARTING TO TIGHTEN...RESULTING IN A S/SW FLOW PERSISTING TODAY AND TONIGHT. COMBINED WITH CLOUDS...THIS SHOULD LIMIT FOG CHANCES OVERNIGHT. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z SATURDAY... FORECAST CONFIDENCE: HIGH. ALTERNATE SCENARIOS: SMALL CHANCE OF MVFR IN SHOWERS OVERNIGHT. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. UTC 1HRLY 14 15 16 17 18 19 20 21 22 23 00 01 EDT 1HRLY 10 11 12 13 14 15 16 17 18 19 20 21 CRW CONSISTENCY H H H H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY H H H H H H H H H H H H EKN CONSISTENCY H H H H H H H H H H H H PKB CONSISTENCY H H H H H H H H H H H H CKB CONSISTENCY H H H H H H H H H H H H AFTER 12Z SATURDAY... NO WIDESPREAD IFR CONDITIONS EXPECTED. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...KTB/MZ NEAR TERM...ARJ/MZ SHORT TERM...KTB LONG TERM...30 AVIATION...MZ