FXUS63 KLMK 272317
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
617 PM EST FRI NOV 27 2009
...UPDATED AVIATION DISCUSSION...
.SHORT TERM (TONIGHT AND SATURDAY)...
RIDGING AT THE SURFACE AND ALOFT WILL KEEP OUR SKIES CLEAR...OTHER
THAN SOME OCCASIONAL HIGH THIN CIRRUS...TONIGHT AND TOMORROW. WINDS
WILL BE LIGHT TONIGHT AND THEN INCREASE OUT OF THE SOUTHWEST
SATURDAY AROUND 10 MPH WITH HIGH PRESSURE TO OUR SOUTH AND LOW
PRESSURE REACHING FROM THE GREAT LAKES TO THE DESERT SOUTHWEST.
EXPECT LOW TEMPERATURES TONIGHT AROUND THE FREEZING MARK AND HIGHS
SATURDAY NEAR 60.
.LONG TERM (SATURDAY NIGHT - FRIDAY)...
SATURDAY NIGHT THROUGH MONDAY NIGHT...
SHORT-MED RANGE MODEL SOLUTIONS CONTINUE TO BE IN VERY GOOD
AGREEMENT AND HAVE GOOD CONTINUITY. MID-LEVEL RIDGING WILL CONTINUE
TO BE IN PLACE SATURDAY NIGHT RESULTING IN MOSTLY CLEAR SKIES WITH
TEMPERATURES FALLING INTO THE LOWER 40S AS LIGHT SOUTHWEST PBL FLOW
WILL RETARD ANY RADIATIONAL COOLING EFFECTS. 27/12Z EURO AND GFS
SOLUTIONS CONTINUE TO ADVERTISE A SPLIT FLOW PATTERN ACROSS NORTH
AMERICA AS WE START OFF THE LAST WEEK OF NOVEMBER AND FIRST WEEK OF
DECEMBER. BOTH THE MODELS ARE MORE PROGRESSIVE WITH THE NORTHERN
BRANCH OF THE JET WHICH WILL SEND A MID-LEVEL WAVE THROUGH THE
REGION DURING THE DAY ON MONDAY. SFC COLD FRONT ASSOCIATED WITH
THIS WAVE WILL BRING A VERY GOOD SHOT OF RAIN SHOWERS TO THE SYSTEM
BEGINNING SUNDAY NIGHT FOLLOWED BY A RAPID DRYING TREND DURING THE
DAY ON MONDAY. PRECIPITATION IS EXPECTED TO BE WELL EAST OF THE
REGION BY MONDAY NIGHT. GIVEN THE GOOD MODEL AGREEMENT AND
CONTINUITY...HAVE INCREASED POPS TO AROUND 90 PERCENT FOR SUNDAY
NIGHT WITH A RAPID NW TO SE DRY PROGRESSION WORKING ACROSS THE
REGION ON MONDAY.
AS FOR TEMPERATURES...SUNDAYS TEMPS ARE A BIT CHALLENGING AS THEY
WILL DEPEND ON THE AMOUNT OF CLOUD COVER MOVING IN FROM THE WEST
AHEAD OF THE NEXT SYSTEM. FOR NOW HAVE TRENDED TEMPS SIMILAR TO THE
ONGOING FCST WITH HIGHS IN THE UPPER 50S IN THE EAST AND SOUTHEAST
AND MID-UPPER 50S IN THE NORTHWESTERN HALF. TEMPERATURES WILL
SLOWLY FALL BEHIND THE FRONT LATE SUNDAY NIGHT WITH MONDAY MORNING
READINGS BOTTOMING OUT IN THE UPPER 30S IN THE WEST TO AROUND 40 IN
THE EAST. HAVE GENERALLY TRENDED TEMPS ON MONDAY CLOSE TO THE
EUROPEAN 2M RAW TEMPS WITH HIGHS IN THE LOWER 40S IN THE NORTH AND
LOWER-MID 40S ACROSS THE SOUTH. WITH CLEARING EXPECTED TO TAKE
PLACE MONDAY NIGHT...LOWS SHOULD DROP DOWN INTO THE UPPER 20S TO
AROUND 30 IN MOST LOCATIONS.
TUESDAY THROUGH FRIDAY...
FAIRLY ACTIVE WEATHER PATTERN SETTING UP FOR THIS TIME FRAME WITH
THE POTENTIAL FOR A SIGNIFICANT LOW PRESSURE SYSTEM TO MOVE UP THE
WEST SIDE OF THE APPALACHIANS. IN THE UPPER LEVELS THE MODELS ARE
ADVERTISING A FAIRLY FAST NORTHERN BRANCH ACROSS THE NORTHERN CONUS
WITH A CUT OFF LOW DOWN IN THE SOUTHERN STREAM. BY EARLY WEDNESDAY
THE NORTHERN BRANCH QUICKLY DEEPENS AS SHARP HEIGHT RISES OCCUR OVER
THE WESTERN COAST OF CANADA. BY LATE WEDNESDAY THE POTENTIAL IS
THERE FOR THE BRANCHES TO PHASE WITH EACH OTHER AND LEAD TO A STRONG
LOW PRESSURE SYSTEM TO DEVELOP OVER THE SOUTHEAST STATES AND MOVE UP
ALONG THE WEST SIDE OF THE APPALACHIANS.
THE 12Z GFS AND EURO RUNS HANDLE THIS PHASING VERY DIFFERENTLY AS
THE GFS IS FAR MORE PROGRESSIVE AND RESULTS A LOW THAT MOVES ACROSS
THE SOUTHEAST AND THEN OFF THE COAST...A VERY COMMON BIAS OF THE GFS
MODEL. ON THE OTHER HAND...THE 12Z EURO HAS BEEN VERY CONSISTENT
OVER THE LAST FEW RUNS WITH THE PHASING COMING TOGETHER NEAR THE MS
RIVER. WE HAVE TRENDED THE FORECAST CLEARLY ON THE SIDE OF THE EURO
HERE TO MAINTAIN FORECAST CONSISTENCY AND TRENDS.
THE CRUX OF THIS FORECAST WILL HINGE ON THE TIMING AND LOCATION OF
WHERE THE UPPER LEVEL PHASING OCCURS. RIGHT NOW THE 12Z EURO HAS
THE PHASING OCCURRING EAST OF THE MISSISSIPPI RIVER WHICH RESULTS IN
A LOW GOING UP THE WESTERN SIDE OF THE APPALACHIANS. THERMAL
PROFILES STAY WARM THROUGH MUCH OF THE EVENT WITH RAIN AS THE MAIN
PRECIPITATION TYPE. HOWEVER...MUCH COLDER AIR LOOKS TO RUSH IN
BEHIND THE SYSTEM RESULTING IN A CHANGEOVER TO SNOW. THE LOW THEN
BOMBS OUT ACROSS WESTERN NY STATE BY THU MORNING. IT SHOULD BE
NOTED THAT IF THE PHASING IS DELAYED AND OCCURS A BIT MORE SOUTH IT
WOULD RESULT IN A SFC TRACK A BIT MORE EAST WITH A BETTER CHANCE OF
THE COLD AIR GETTING IN HERE MORE QUICKLY RESULTING IN A QUICKER
CHANGEOVER TO SNOW. OBVIOUSLY SOMETHING TO WATCH IN THE COMING
DAYS. AFTER THIS SYSTEM PASSES...THE EURO IS STILL ON BOARD WITH A
DECENT COLD SHOT BUILDING INTO THE REGION.
AGAIN...GENERALLY TRENDED TEMPS CLOSE TO THE 2M RAW TEMPS FROM THE
GFS AND EURO SOLUTIONS. HIGHS TUESDAY LOOK TO WARM INTO THE
MID-UPPER 40S WITH LOWS TUE NIGHT IN THE LOWER 30S. AS THE ABOVE
MENTIONED SYSTEM MOVES TOWARD THE REGION HIGH TEMPS ON WED WILL WARM
INTO THE UPPER 40S TO THE LOWER 50S. TEMPERATURES FOR THU MORNING
WILL DEPEND ON THE EXACT TRACK OF THE LOW...SO HAVE GONE WITH BIT OF
A COMPROMISE OF THE 27/00Z AND 27/12Z EURO 2M TEMPS HERE WITH LOWS
IN THE LOWER 30S. CURRENTLY HAVE LOWER 40S IN FOR THU FOR
CONSISTENCY SAKE...BUT IF THE EURO IS RIGHT...WE'LL NEED TO KNOCK
THESE DOWN SIGNIFICANTLY IN LATER FORECASTS. LOWS THU NIGHT LOOK TO
DROP INTO THE UPPER 20S WITH HIGHS ON FRIDAY IN THE MID 30S.
&&
.AVIATION (00Z TAF ISSUANCE)...
SUBSIDENCE AND A DRY AIRMASS WILL ALLOW CLEAR SKIES TO CONTINUE
OVERNIGHT AND SATURDAY. VFR FLYING EXPECTED THROUGH THE TAF PERIOD.
EXPECT LIGHT SOUTH WINDS OVERNIGHT UP TO 5 MPH. WINDS WILL INCREASE
TO SOUTHWEST 8 TO 12 MPH BY EARLY AFTERNOON SATURDAY.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
SHORT TERM........JSD
LONG TERM.........MJ
AVIATION..........JSD
