Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 201356 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 956 AM EDT MON OCT 20 2014 .UPDATE... ISSUED AT 958 AM EDT MON OCT 20 2014 UPDATED THE FORECAST TO UP THE PROBABILITY OF PRECIPITATION FOR TODAY BASED UPON THE CURRENT RADAR AND THE HIGH RESOLUTION RAPID REFRESH MODEL. THE REST OF THE FORECAST IS ON TRACK. UPDATE ISSUED AT 724 AM EDT MON OCT 20 2014 THE LINE OF SHOWERS MOVING INTO KY IS STILL SHOWING SIGNS OF STRENGTHENING...WITH FAIRLY GOOD COVERAGE ACROSS THE NORTH CENTRAL PORTION OF THE STATE. AFTER SENDING OUT THE PREVIOUS UPDATE...DECIDED TO GO BACK AND RE-EVALUATE OUR ONGOING POP FORECAST TO MAKE SURE IT WAS LINING UP WITH THE RECENT RAINFALL TRENDS. ENDED UP USING A BLEND OF RADAR TRENDS AND LATEST MODEL GUIDANCE TO COME UP WITH A FORECAST THAT SHOULD BETTER SUIT THE PROGRESSION OF THE LINE OF SHOWERS INTO EASTERN KY DURING THE DAY TODAY. UPDATE ISSUED AT 635 AM EDT MON OCT 20 2014 FORECAST SEEMS TO BE ON TRACK SO FAR THIS MORNING FOR THE MOST PART. THE LINE OF RAIN SHOWERS IS SHOWING SOME SIGNS OF STRENGTHENING AND BETTER ORGANIZATION AS WE CONTINUE TO TRACK IT/S MOVEMENT ACROSS THE OHIO RIVER INTO KY. HOWEVER...LATEST OBSERVATIONS ARE STILL ONLY INDICATING LIGHT RAIN WITH VERY LITTLE VISIBILITY RESTRICTION. MAIN UPDATE WAS TO TWEAK TEMPERATURES IN THE NEAR TERM. LOADING IN THE OBSERVATIONAL DATA TO THE ONGOING TEMPERATURE FORECAST PROVED TO DROP CURRENTLY FORECASTED TEMPERATURES DOWN SEVERAL DEGREES IN SOME LOCATIONS. BLENDED THIS OUT FOR SEVERAL HOURS...WITH TEMPERATURES EXPECTED TO START HEATING FROM THIS POINT FORWARD AS THE SUN BEGINS TO RISE. && .SHORT TERM...(TODAY THROUGH TUESDAY) ISSUED AT 359 AM EDT MON OCT 20 2014 THE REX BLOCK PATTERN CONTINUES OVER THE CONUS THIS MORNING...WITH MUCH OF THE EASTERN CONUS BEING INFLUENCED BY A STRONG TROUGHING PATTERN. THIS TROUGH WILL CONTINUE TO BE OUR MAIN WEATHER DRIVER FOR THE SHORT TERM TODAY THROUGH TUESDAY. DURING THE DAY TODAY...A SHORTWAVE EMBEDDED IN THE LONGWAVE PATTERN WILL CONTINUE TO STRENGTHEN AS IT MOVES FROM THE UPPER GREAT LAKES THIS MORNING TO THE LOWER GREAT LAKES BY LATE THIS AFTERNOON AND EVENING. BY TOMORROW NIGHT IT WILL STRENGTHEN INTO A CLOSED LOW...THEN DIVE SOUTHWARD DURING THE DAY TUESDAY...REACHING THE VIRGINIA/S BY TUESDAY EVENING. HERE IT WILL STALL OUT BEFORE SLOWLY MOVING UP THE NEW ENGLAND SEA BOARD DURING THE EXTENDED PERIOD. FOR TODAY...AS THE SHORTWAVE STRENGTHENS...IT WILL DRIVE A SURFACE LOW PRESSURE SYSTEM FROM THE UPPER GREAT LAKES TO THE LOWER GREAT LAKES. FROM THIS SURFACE SYSTEM WILL EXTEND A COLD FRONT. AS THE LOW MOVES...THE COLD FRONT WILL SWEEP FROM NW TO THE SE...AND EVENTUALLY TRAVERSE EASTERN KY LATE TONIGHT AND INTO TUESDAY MORNING. AS SUCH...UPPER LEVEL CLOUDS HAVE ALREADY PROTRUDED INTO THE REGION THIS MORNING IN ADVANCE OF THIS SYSTEM. A WEAK SCATTERED LINE OF RAIN SHOWERS IS NOT FAR BEHIND...CURRENTLY MOVING ACROSS MUCH OF NORTHERN OH...IN...AND WESTERN KY. SO FAR THESE SHOWERS ARE SHOWING UP ON THE RADAR AS VERY LIGHT...WITH LITTLE IMPACTS EXPECTED. UNFORTUNATELY...LATEST MODELS ARE HAVING A HARD TIME COMING TO A CONCLUSION ABOUT THE PRECIP AS IT REACHES EASTERN KY AND CONTINUES AHEAD OF THE FRONT TODAY AND TONIGHT. THE EXACT LOCATION OF WHERE THE BEST QPF AND POPS WILL BE LOCATED CONTINUES TO DIFFER FROM MODEL TO MODEL. THERE IS A SLIGHT LACK IN CONSISTENCY BETWEEN OFFICES FOR POPS OVER THE NEXT 24 HOURS. TRIED TO MATCH UP AS BEST AS POSSIBLE. REGARDLESS...THIS IS A MOISTURE DEPRIVED SYSTEM...SO ANY RAIN THAT DOES OCCUR IS NOT EXPECTED TO CAUSE MUCH IN THE WAY OF IMPACTS AND SHOULD BE MOVING THROUGH THE AREA FAIRLY FAST. ONCE THE FRONTAL BOUNDARY MOVES THROUGH US BY TOMORROW MORNING...EXPECT THE RETURN OF A MORE NORTHERLY FLOW PATTERN AND COOLER TEMPERATURES. AFTERNOON TEMPS WILL ONLY TOP OFF IN THE UPPER 50S TO AROUND 60 ONCE MORE. ALTHOUGH THE FRONTAL BOUNDARY WILL HAVE EXITED...THE UPPER LEVEL LOW WILL BE ON ITS TRANSITION SOUTHWARD TOWARDS THE VIRGINIA/S...PULLING THE SURFACE LOW PRESSURE SYSTEM WITH IT. STRONG NORTHERLY FLOW WILL ALLOW FOR WRAP AROUND MOISTURE TO CONTINUE TO FLOW INTO EASTERN KY OFF THE BACKSIDE OF THE LOW. THIS MOISTURE WILL BE VERY WEAK...BUT UPSLOPE FLOW IN THE FAR EAST COULD BE ENOUGH TO PRODUCE LIGHT SHOWERS IN THIS AREA BOTH TONIGHT AND THROUGH THE DAY TOMORROW. EXPECT LITTLE IMPACT FROM THIS...WITH ONLY VERY LIGHT ACCUMULATIONS EXPECTED. .LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY) ISSUED AT 501 AM EDT MON OCT 20 2014 AN UPPER TROUGH AXIS IS FORECAST TO BE OVER THE APPALACHIANS AT THE START OF THE PERIOD...IN THE PROCESS OF FORMING A LARGE CLOSED LOW AT ITS BASE AS IT SLOWLY SHIFTS EASTWARD. AT THE SURFACE...A LARGE LOW PRESSURE SYSTEM IS EXPECTED TO BE MEANDERING NEAR THE MID ATLANTIC COAST. IT WILL PUT OUR LOCAL AREA IN A REGION OF COLD AIR ADVECTION AND UPSLOPE FLOW...FAVORING LOW LEVEL INSTABILITY WITH CLOUDS AND POSSIBLY SHOWERS. AS THE ENTIRE SET-UP SLOWLY SHIFTS EASTWARD...IT SHOULD TAKE ANY SHOWERS WITH IT BY WEDNESDAY. A SURFACE RIDGE WILL THEN BE OUR DOMINANT FEATURE INTO FRIDAY. BY FRIDAY EVENING BOTH THE GFS AND ECMWF INDICATE A SHORTWAVE TROUGH NEARING FROM THE NORTHWEST. THE 00Z ECMWF HAS SOME LIGHT PRECIP WITH THIS ON FRIDAY NIGHT...BUT THIS WAS NOT THE CASE IN THE PREVIOUS RUN...AND THE GFS IS STILL BASICALLY DRY. WILL STICK WITH POPS BELOW THE 20 PERCENT THRESHOLD AT THIS POINT...KEEPING THE FORECAST DRY. A COOL AIR MASS AND SUFFICIENT RADIATING AT NIGHT WILL PRESENT A POSSIBILITY OF FROST FOR THE FIRST FEW NIGHTS...MAINLY IN VALLEYS. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING) ISSUED AT 646 AM EDT MON OCT 20 2014 A LINE OF SHOWERS IS CURRENTLY MOVING ACROSS THE OHIO RIVER INTO KY AHEAD OF AN APPROACHING COLD FRONT. EXPECT THESE SHOWERS TO BE LIGHT AND SCATTERED IN NATURE...AFFECTING MUCH OF EASTERN KY THROUGH THE DAY AND INTO THE OVERNIGHT. WENT AHEAD AND INCLUDED VCSH AT THIS TIME...GIVEN THE UNCERTAINTY OF WHERE AND WHEN EXACTLY THESE SHOWERS WILL AFFECT A GIVEN TAF SITE. LATEST MODELS ARE STILL SHOWING CIGS LIKELY LOWERING THROUGHOUT THE AFTERNOON AND INTO THE OVERNIGHT HOURS AS WELL. EXPECT VFR CONDITIONS TO GENERALLY STAY INTACT UNTIL THE OVERNIGHT TONIGHT...WHEN SOME MVFR CIGS ARE POSSIBLE. DESPITE A FRONTAL PASSAGE...WINDS SHOULD GENERALLY REMAIN UNDER 10KTS BOTH TODAY AND TONIGHT...SWITCHING FROM SW DURING THE DAY TODAY...TO MORE WRLY LATE TONIGHT AFTER THE FRONTAL PASSAGE. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JJ SHORT TERM...JMW LONG TERM...HAL AVIATION...JMW

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