Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 200607 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 207 AM EDT MON APR 20 2015 .SYNOPSIS... SOUTHEAST FLOW BREAKS DOWN OVERNIGHT...ALLOWING MORE HUMID/UNSTABLE AIR TO CREEP FURTHER EAST. COLD FRONT MONDAY WITH SHOWERS AND STORMS...FOLLOWED BY AN EXTENDED PERIOD OF COOLER AND DRIER WEATHER. && .NEAR TERM /THROUGH TODAY/... 200 AM UPDATE... FCST ON TRACK WITH A BRIEF BREAK IN THE PRECIPITATION ONCE SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A NEGATIVELY TILTED UPPER LEVEL S/W TROUGH AXIS LIFT NEWD OUT OF THE AREA. WHATEVER IS LEFT OF CONVECTIVE COMPLEX UPSTREAM ARRIVES NEAR DAWN. 1000 PM UPDATE...TWEAKED POPS TO BETTER MATCH N-S ORIENTATION OF LINE OF GUSTY SHOWERS AND STORMS APPROACHING FROM THE WEST. ALSO INCREASED POPS WITH THE LINE. STILL THINK IT WILL WEAKEN AS IT MOVES INTO FORECAST AREA. AREA WHERE THE STRONGEST STORMS ARE...WESTERN TN...HAD SOME LATE AFTERNOON SUNSHINE...WHILE WE REALLY DID NOT. PREVIOUS DISCUSSION... LIGHT RAIN CONTINUES ACROSS THE AREA. HAVE BEEN WRESTLING WITH THE POTENTIAL FOR HEAVY RAIN THROUGH THE TONIGHT PERIOD GIVEN THE FAST FLOWS THROUGH THE LOW LEVELS AND THE HIGH PRECIPITATION EFFICIENCY. HOWEVER...CONVECTION ONGOING ACROSS THE DEEP SOUTH CONTINUES TO THROW HIGH LEVEL CLOUDS INTO THE AREA WITH AFOREMENTIONED LIGHT RAIN. SO...THERMODYNAMICALLY SPEAKING...NOT GETTING THE DEEPER CONVECTION THAT MIGHT OTHERWISE BE POSSIBLE. ALSO ASSISTING IN THE SUPPRESSION IS THE STRONG SOUTHEASTERLY FLOW...PROVIDING SOME LOW LEVEL DRYING THAT HAS LARGELY CUT OFF THE INSTABILITY ACROSS THE CWA. THE EASTERN SLOPES STILL HAVE THE CHANCE FOR THE HIGHER PRECIPITATION AMOUNTS...BUT WILL KEEP ANY FLOOD WATCHES OUT OF THE FORECAST FOR NOW. RAINFALL RATES JUST ARE NOT THERE...BUT THIS WILL NEED TO BE MONITORED. OVER TOWARDS THE WESTERN CWA/TRI STATE AREA...THIS IS WHERE SOME CONVECTION WOULD BE POSSIBLE THROUGH TONIGHT...AS THIS AREA LIES ON THE WESTERN FRINGE OF THE CIRRUS COMING UP FROM THE SOUTHERN CONVECTION. THERE IS SOME CLEARING RIGHT NOW OVER CENTRAL KENTUCKY AND TENNESSEE WHICH WOULD ALLOW FOR SOME STORMS TO ORGANIZE...AND WITH THE 0-6KM BULK SHEAR SOUTHWESTERLY...THIS WOULD STEER IT TOWARDS THIS PARTICULAR AREA. VISIBLE SATELLITE IMAGE IS SHOWING SOME ENHANCEMENT HERE...AND SPC HAS RECENTLY ISSUED A MESOSCALE DISCUSSION FOR THIS AREA. INTO LATE TONIGHT AND MONDAY...THE COLD FRONT SWINGS THROUGH AFTER 09Z. HEATING WILL HELP WITH THE CONVECTION WITH THE FRONT...AND HAVE HIGHER POPS AND HIGHER CHANCES FOR THUNDER BASED ON SURFACE INSTABILITY AFTER 12Z AND IN THE EASTERN CWA. SPC HAS A SLIGHT CHANCE RISK FOR SEVERE IN THE NORTHEASTERN THIRD OF THE CWA. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY/... EASTERN CANADIAN UPPER LOW WILL BE THE CONTROLLING FEATURE THIS PERIOD. SHOWERS WILL END EARLY MONDAY NIGHT AS THE COLD FRONT EXITS TO THE EAST. WEAK UPPER DISTURBANCES ROTATING AROUND THIS UPPER LOW WILL BRING REINFORCING SHOTS OF COOLER AIR TUESDAY NIGHT AND WEDNESDAY...SO A SHOWER IS POSSIBLE TUESDAY NIGHT AND WEDNESDAY. BELOW NORMAL TEMPERATURES WILL BE THE RULE. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... THANKFULLY...THE DRIER AND COOLER PATTERN APPEARS TO CONTINUE. WITH TROFS OFF NORTHWEST COAST AND OVER NEW ENGLAND AND NORTHEAST COAST. THE LACK OF DEEPER MOISTURE IS CERTAINLY WELCOMED. STILL FAST MOVING MID LEVEL DISTURBANCES IN THE WNW STEERING FLOW THAT CAUSES PROBLEMS HERE WITH DETERMINISTIC POPS HERE. WAS DRIER FOR THE START OF THIS LONG TERM...THINKING WEDNESDAY`S WEAK SYSTEM WILL BE EXITING WEDNESDAY EVENING. MEDIUM RANGE GUIDANCE FROM WPC INTRODUCED LKLY POPS SATURDAY...BUT WILL HAVE JUST CHANCE POPS WORKING NORTH SATURDAY. CONFIDENCE IN TIMING SOUTHERN MOISTURE MOVING NORTH IS LOW. STRATOCUMULUS CLOUD IN THE COOLER FLOW AND WIND LIKELY TO MESS WITH OUR FORECAST LOW TEMPERATURES...BUT HAVE 30S AND LOWER 40S FOR SEVERAL NIGHTS...FOR DAWN FRIDAY...SATURDAY...AND SUNDAY. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... GUSTY SE WINDS SWITCH TO S TO SW OVERNIGHT...AS A SFC WARM FRONT AND UPPER LEVEL TROUGH AXIS MOVES THROUGH. THIS SHIFT WAS ALREADY THROUGH HTS AND CRW AND NEAR BKW AT THE START OF THE FCST PERIOD...AND WILL GO THROUGH PKB...CKB AND EKN 08-09Z. THIS BRINGS AN END TO THE SHOWERS BUT AN ONSET OF MVFR STRATOCU THAT WILL LAST UNTIL MIXING OUT AFTER DAYBREAK. BKW MAY SEE IFR STRATOCU. A COMPLEX APPROACHING FROM CENTRAL KY AND CENTRAL TN WILL REACH THE MIDDLE OHIO VALLEY AND CENTRAL APPALACHIANS BY DAWN...BUT THERE MAY NOT BE MUCH LEFT OF IT. A COLD FRONT CROSSING THE AREA MON AFTERNOON WILL BRING ONE MORE ROUND OF SHOWERS AND THUNDERSTORMS. STRONG WIND GUSTS AND BRIEF IFR CONDITIONS ARE POSSIBLE WITH THE THUNDERSTORMS. THE PRECIPITATION WILL MOVE OUT OF THE AREA BY MON NT...BUT MVFR STRATOCU IS POSSIBLE IN THE MOUNTAINS. STRONG SW WINDS WILL GUST TO AROUND 30 KTS AT TIMES MON AND PERSIST INTO MON NT...ONLY DIMINISHING SLIGHTLY. MODERATE SW FLOW ALOFT THROUGH MON WILL BECOME LIGHT TO MODERATE W MON NT. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z TUESDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: BRIEF IFR POSSIBLE IN HEAVY RAIN...BUT SHOULD NOT LAST LONG. TIMING OF PRECIPITATION BEGINNING/END MAY VARY. 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. DATE MON 04/20/15 UTC 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17 EDT 1HRLY 02 03 04 05 06 07 08 09 10 11 12 13 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 M M M M M M H H H H EKN CONSISTENCY M M 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 06Z TUESDAY... IFR POSSIBLE MONDAY IN SHOWERS AND THUNDERSTORMS. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...KTB/JMV/26 NEAR TERM...TRM/MZ/26 SHORT TERM...JMV LONG TERM...KTB AVIATION...TRM

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