FXUS63 KJKL 011146 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 600 AM EST SAT MAR 1 2003 BIGGEST FORECAST CHALLENGES ARE TEMPERATURES TODAY AND RAIN CHANCES TONIGHT. SPLIT FLOW PATTERN STILL EVIDENT...WITH RIDGE OVER THE PACIFIC...SHORTWAVE TROUGH IN THE WEST...AND MEAN LONGWAVE TROUGH INFLUENCING MUCH OF THE COUNTRY. MODELS ARE INITIALIZING TERRIBLY OVER THE CENTRAL PLAINS REGARDING HEIGHTS AND HAVE LITTLE GRASP ON SMALL SCALE PERTURBATIONS. LOW CONFIDENCE WITH ESPECIALLY THE PRECIPITATION FORECAST IN THE NEAR TERM. I HAVE ELECTED TO TRY NOT TO VEER TOO MUCH FROM THE PREVIOUS FORECAST BECAUSE OF THIS. MODELS ARE MUCH BETTER AT TEMPERATURES AND OVERALL JET PATTERN. BRIEF WARM AIR ADVECTION SEEMS TO BE HELPING TEMPERATURES OUT TODAY WITH BROAD SHORTWAVE RIDGING IN THE SOUTHEAST CONUS. WARMER 850 TEMPS ARE ADVECTING IN...WITH SURFACE TEMPS SLOWLY CLIMBING DURING THE LATE OVERNIGHT. NORTHERN COUNTIES ARE NOT SEEING THE SAME BENEFIT AND HAVE HELD STEADY OR LOWERED OVER THE LAST SEVERAL HOURS. MESOETA SEEMS TO HAVE A GOOD GRASP ON THE LOW LEVEL WIND FIELD AND INDICATES THAT THE NORTHERN COUNTIES WILL PROBABLY REMAIN SIGNIFICANTLY COOLER THAN THE REST OF THE CWA AS WEAK WWA WILL BE FOCUSED FROM JKL AND SOUTH. THE INVERTED SURFACE TROUGH CURRENTLY OVER THE AREA WILL EVENTUALLY GIVE WAY TO A DEVELOPING SURFACE LOW ALONG THE CAROLINA COAST AND CONTINUE FOLLOWING NORTH ALONG THE COASTLINE. WITH THE RIDGE OVER THE PACIFIC BECOMING MORE NARROW AND POSITIVELY TILTED...MORE ENERGY WILL BREAK OFF INTO THE NORTHERN STREAM...NORTH OF THE QUASI-STATIONARY LOW OVER THE WEST CONUS. AS THE NORTHERN STREAM DIVES SOUTH BY SUNDAY NIGHT...THIS WILL WORK IN CONCERT WITH A LOBE OF THE POLAR VORTEX OVER THE HUDSON BAY TO HELP ALLOW SOME OF THE VERY COLD AIR OVER THE EASTERN NORTHWEST TERRITORIES AND NORTHERN MANITOBA TO MAKE ITS WAY SOUTH ON SUNDAY NIGHT AND MONDAY. THIS WILL ALSO HELP CUT OFF THE LOW WHICH IS IN THE WESTERN CONUS AND CAUSE IT AND THE PACIFIC RIDGE TO RETROGRADE WEST...BUT CONTINUING TO LEAVE THE CONUS IN A MEAN LONGWAVE TROUGH. THICKNESS VALUES INDICATE THAT THIS WAVE OF COLD AIR SHOULD BRING THE COLDEST AIR SUNDAY NIGHT...WITH TUESDAY SHOWING PROMISE OF A BRIEF WARMUP. I THINK THAT CURRENT FORECAST WITH HIGHS IN THE 50S WEDNESDAY WILL SURELY NEED TO BE DRASTICALLY LOWERED AS THE ROSBY WAVE PATTERN AND PROGRESSION WOULD INDICATE. ALSO POPS ON TUESDAY NIGHT WILL PROBABLY HAVE TO BE RAISED TO LIKELY AS A STRONG COLD FRONT SEEMS TO BE A GOOD BET...WITH A DECENT AMOUNT OF LIFT AND MOISTURE TO UTILIZE IN ADVANCE OF THE FRONT. GOING WITH TEMPS NEAR NGM AND AVN MOS FOR CENTRAL AND SOUTH...BUT A BIT LOWER IN THE NORTH...AS WARMER AIR WILL HAVE A MORE DIFFICULT TIME WORKING NORTH OF JKL. WENT CLOSER TO HIGHER ETA MOS GUIDANCE FOR POPS AS CONFIDENCE IN THE NEW MODEL RUNS IS LOW IN THIS CATEGORY AND SEE NO REASON TO BREAK FROM PREVIOUS FORECAST POPS. WENT SIGNIFICANTLY COOLER FOR LOWS SUNDAY NIGHT/MONDAY MORNING AS IT APPEARS THAT THERE IS A GENERAL SLUGGISHNESS IN BRINING THE COLD AIR IN BY MOS MODEL OUTPUT. ALSO DID NOT DWELL TOO MUCH ON SNOW CHANCE SUNDAY NIGHT AS I EXPECT QUICK DRYING TAKES PLACE WITH STRONG SURFACE HIGH MOVING IN SUNDAY NIGHT. MAY BE ENOUGH LOW LEVEL MOISTURE TO PRODUCE SOME SNOW SHOWERS IN HIGH TERRAIN...BUT DO NOT EXPECT EVEN THIS TO LAST VERY LONG. .JKL...NONE. HEINLEIN -------------------------------------------------------------------- 920 PM EST FRI FEB 28 2003 01Z SFC ANALYSIS SHOWS WEAK LOW PRESSURE SOUTHWEST OF THE APPALACHIANS MAINTAINING AN INVERTED TROUGH LOOK JUST EAST OF JKL. PLENTY OF MOISTURE REMAINS STUCK UNDER A DEEP INVERSION THAT IS HELPING TO LOWER CEILINGS AND VISBY STARTING OVER OUR NORTHERN COUNTIES AND ON THE RIDGES LIKE HERE AT JKL. THIS INVERSION WILL ONLY STRENGTHEN AS THE NIGHT WEARS ON ACCORDING TO THE 18Z MESOETA. EXPECT DRIZZLE TO KICK IN PRETTY SOON AS WELL. AS A RESULT...WILL ISSUE A DENSE FOG ADVISORY FOR THE CWA WITH SOUTHERN AND VALLEY LOCATIONS EXPECTED TO PARTICIPATE IN THE FOG LATER TONIGHT. THE REST OF THE FORECAST IS SOUND AND THE ONLY UPDATES NECESSARY WILL BE TO BEEF UP FOG WORDING...ADD A HEADLINE AND FIX THE GRAPHICS. UPDATE TO THE GRIDS/GRAPHICS AND TEXT PRODUCTS ISSUED SHORTLY. WILL ALSO UPDATE THE HWO TO FURTHER EMPHASIZE DENSE FOG CONCERNS. .JKL...NPW FOR DENSE FOG FOR MOST OF EAST KENTUCKY THROUGH 10 AM. GREIF PREVIOUS FORECAST DISCUSSIONS FOLLOW: --------------------------------------------------------------------- 415 PM EST FRI FEB 28 2003 FORECAST CHALLENGES: MAX TEMPS IN THE NEAR TERM AND CHANCE OF DRIZZLE TONIGHT AS WELL AS POPS SAT NIGHT AND SUN. LATEST SFC ANALYSIS SHOWS HIGH PRESSURE OVER THE GREAT LAKES WITH AN INVERTED TROUGH UP ALONG THE APPALACHIANS. LOW PRESSURE WAS OFF THE NEW ENGLAND COAST WITH A COLD FRONT TRAILING SW INTO SOUTH FLORIDA. PERSISTENT LOW LEVEL MOISTURE REMAINS TRAPPED UNDER AN INVERSION AND DO NOT EXPECT IT TO BREAK UNTIL TOMORROW MORNING. OVERNIGHT...THE INVERSION SHOULD STRENGTHEN A BIT BASED ON META FORECAST SOUNDINGS. THIS WILL LEAD TO CONTINUED OVERCAST LOW CLOUDS AND SOME AREAS OF FOG AGAIN. WITH LOW CLOUDS AND LIGHT WINDS...TEMPS WON'T FALL TOO FAR. WITH LOW TEMPS IN THE MID 30S...PRECIPITATION WILL STAY AS LIQUID. WITH DRIZZLE ALREADY FALLING IN SOME SPOTS AND ANOTHER VORT LOBE TO PASS THROUGH THE OH VALLEY THIS EVENING...WILL CONTINUE AREAS OF DRIZZLE OVERNIGHT. TOMORROW...SOME DISPARITY IN GUIDANCE TEMPS. MET IS WAY OUT TO LUNCH AND WITH LOW CLOUDS...MAV APPEARS TOO HIGH AS WELL. WARM ADVECTION WILL BE TAKING PLACE ALOFT WITH ISENTROPIC LIFT BY LATE IN THE DAY AHEAD OF THE NEXT SW/V BRINGING A CHANCE/SLIGHT CHANCE OF RAIN VERY LATE IN THE DAY. THE NEXT BEST CHANCE FOR PRECIP WILL COME DURING TOMORROW NIGHT AS A 500 MB TROF CROSSES THE OH AND TN VALLEY REGION AND HELPS GEN UP A NICE STORM ALONG THE EAST COAST. FOR THE LOCAL AREA...IT LOOKS LIKE A HIGH CHANCE (LIKELY POPS) FOR RATHER LIGHT PRECIP (TOTAL QPF UNDER 0.25"). THE REAL COLD AIR DOESN'T MAKE ITS WAY INTO THE REGION UNTIL LATE SUNDAY FOLLOWING AN ARCTIC FRONTAL PASSAGE. THE MODELS HAVE GENERALLY BEEN SPEEDING UP THE TIMING OF THIS SYSTEM. WITH LIMITED MOISTURE...THIS SYSTEM AND ITS ASSOCIATED UPPER TROUGH WILL ONLY BRING A CHANCE OF RAIN INITIALLY...WITH THE POSSIBILITY FOR ENOUGH COLD AIR TO WORK IN BY SUN NIGHT TO TURN ANY LEFTOVER PRECIP TO LIGHT SNOW. SUN NIGHT WILL ALSO BE MUCH COOLER THAN RECENT NIGHTS...WITH LOWS IN THE LOWER 20S. HIGH PRESSURE WILL BUILD INTO THE OH VALLEY ON MONDAY...HOPEFULLY BRINGING SOME LONG AWAITED SUNSHINE. HOWEVER...THE AIRMASS WILL BE COLD AND EVEN WITH MARCH SUN...THE TEMPERATURES SHOULD STRUGGLE TO REACH 35 DEGREES (15 OR MORE DEGREES BELOW NORMAL). ...EXTENDED... MODELS IN GENERALLY GOOD AGREEMENT IN THE EXTENDED. IN GENERAL THE UPPER LEVEL PATTERN CHANGES VERY LITTLE OVER THE EASTERN US DURING THE PERIOD WITH GENERALLY WAVY FLOW GOING TO MORE OF A SOUTHWEST FLOW LATER ON AS HIGH AMPLITUDE BLOCKING PATTERN TAKES SHAPE OVER THE NORTH ATLANTIC. AS TO THE DETAILS TO THE FORECAST...BASICALLY IN AGREEMENT WITH SURROUNDING OFFICES IN KEEPING THINGS DRY FOR TUESDAY AS WEAK HIGH PRESSURE MOVES OFF TO OUR EAST. NEXT WEATHER MAKER MOVES IN FOR WED AND THURSDAY. MODELS IN A LITTLE BIT OF DISAGREEMENT WITH THE OVERALL SPEED OF THIS STORM SYSTEM. HOWEVER...LOOKS LIKE WE'LL SEE ANOTHER SHOT OF RAIN WEDNESDAY AND TAPERING OFF DURING THE DAY ON THURSDAY. NEXT STORM SYSTEM THEN POISED TO HIT NEAR THE END OF THE EXTENDED PERIOD (PROBABLY SATURDAY). FOR NOW...WILL KEEP FRIDAY DRY AND WARM AS SOUTHWEST FLOW WILL BE ABUNDANT. AS FOR TEMPERATURES...OPERATIONAL 00Z GFS NUMBERS ARE JUST WAY TOO WARM. HAVE SCALED TEMPS BACK SIGNIFICANTLY AND HAVE GONE CLOSER TO THE 00Z GFS ENSEMBLE MEANS. SHORT TERM: PELTON LONG TERM: JARVIS --------------------------------------------------------------------- 1045 AM EST FRI FEB 28 2003 UPDATED ZONES FOR PRECIP TYPE AND TEMPERATURE TRENDS. SHORTWAVES CONTINUE TO MOVE THROUGH THE FLOW AND INTERACT WITH SATURATED LOW LEVEL MOIST LAYER. ONE SW/V IN PARTICULAR IS EXITING THE CWA ATTM. ONCE THIS SW/V PASSES...EXPECT SOME DRYING OF THE MOIST LAYER...ENDING THE DRIZZLE AND ALLOWING CEILINGS TO IMPROVE. LATEST RADAR TRENDS INDICATE THAT THE DRIZZLE HAS ENDED OVER THE SW...SO JUST CLOUDY SKIES IN THOSE ZONES. AS FOR TEMPS...UPPED THEM A COUPLE OF DEGREES IN MOST ZONES BASED ON CURRENT OBS...BUT NO DRASTIC CHANGES. UPDATED ZONES ARE ALREADY OUT...WITH UPDATED GRIDS MOMENTARILY. PELTON $$