FXUS61 KCLE 241450
AFDCLE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CLEVELAND OH
950 AM EST THU DEC 24 2009
.SYNOPSIS...
A STRONG LOW PRESSURE SYSTEM WILL AFFECT MUCH OF THE COUNTRY ON
CHRISTMAS EVE AND CHRISTMAS DAY. THE LOW WILL TRACK FROM
LOUISIANA TO IOWA BR FRIDAY AND THEN SLOW DOWN AND DRIFT SLOWLY
EAST TO THE GREAT LAKES OVER THE WEEKEND. WE WILL SEE AN
INCREASING EAST TO SOUTHEAST WIND WHICH WILL BRING WARMER AIR TO
THE AREA AND SOME SHOWERS FOR CHRISTMAS.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
STRATUS FORMED UNDER THE STRONG INVERSION ACROSS PARTS OF EXTREME
NORTHEAST OHIO AND NORTHWEST PENNSYLVANIA. AS THE EAST WIND
INCREASES TODAY AND WE GET SOME MIXING WE SHOULD SEE THE STRATUS
DISSIPATE ALTHOUGH HIGH CLOUDS WILL BE THICKENING. DESPITE THE
LOW SUN ANGLE WE WILL CALL IT "PARTLY SUNNY". EVEN WITH THE
INCREASED WIND AND MIXING AND WEAK SUNSHINE IT IS DIFFICULT TO
IMAGINE THAT TEMPERATURES WILL GET INTO THE 40S AS ADVERTISED BY
SOME OF THE GUIDANCE. MID/UPPER 30S IS A BETTER BET AND WILL
ADJUST HIGH TEMPERATURE FORECASTS FOR SOME AREAS. FIRST WAVE OF
PRECIPITATION SHOULD SLIDE JUST WEST OF THE AREA TODAY BUT WILL
KEEP AN EYE ON IT TO SEE IF IT MIGHT BRUSH AREAS ALONG AND WEST OF
I-75.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
MODELS HAVE THEIR DIFFERENCES WITH THE NAM MODEL SHOWING A MUCH
SLOWER SOLUTION THAN THE GFS SOLUTION. MY CONCERN THIS MORNING IS
THAT IF WE BACK OFF ON THE TIMING OF THE PRECIPITATION UNTIL FRIDAY
MORNING...WE WILL WIND UP WITH EXTENSIVE PRECIPITATION OVER THE AREA
TONIGHT. THE MODELS HAVE BEEN HAVING TROUBLE WITH THIS SITUATION IN
SOME PREVIOUS EVENTS BY KEEPING THE DRY AIR FIRMLY ENTRENCHED.
HOWEVER...THE STRONG STORM SYSTEMS TEND TO OVERCOME THE DRY AIR
FAIRLY QUICKLY AND SPREAD PRECIPITATION OVER THE REGION RAPIDLY AND
MUCH EARLIER THAN EXPECTED. SO...WILL STAY CLOSE TO CONTINUITY AND
STICK WITH CURRENT EARLIER TIMING OF PRECIPITATION TONIGHT.
COLD EAST FLOW WILL ALLOW TEMPERATURES TO DROP TO CRITICAL LEVELS
THIS EVENING AND THE ONSET OF PRECIPITATION WILL LIKELY CAUSE SOME
OF THE PRECIPITATION TO START OUT IN THE FORM OF RAIN AND OR
FREEZING RAIN. I AM USING NON-DIURNAL TEMPERATURES THROUGH THE
NIGHT WITH MINIMUMS OCCURRING SHORTLY AFTER SUNSET AND THEN SLOWLY
RISING THROUGH THE NIGHT INTO FRIDAY.
I EXPECT THAT BY THE TIME THE PRECIPITATION PUSHES EAST OVER THE
EASTERN TWO THIRDS OF THE AREA DURING THE NIGHT...THE WARM AIR
ADVECTION SHOULD BE ONGOING ENOUGH TO KEEP THE PRECIPITATION IN THE
FORM OF ALL RAIN. THE EXTREME EAST MAY BE THE EXCEPTION WHERE THEY
MAY SEE SOME FREEZING RAIN AT THE BEGINNING LATE TONIGHT. THE EAST
WILL HAVE TO BE MONITORED CLOSELY TONIGHT IN THE EVENT TEMPERATURES
DO NOT WARM UP VERY FAST AND PRECIPITATION ARRIVES SOONER THAN
EXPECTED. THERE IS THE POTENTIAL FOR SOME LIGHT GLAZING TO OCCUR BY
MORNING IN NORTHWEST PENNSYLVANIA AWAY FROM THE LAKE AND ADVISORIES
MAY BE NEEDED.
THE STORM SYSTEM TAKES ITS GOOD OLD TIME LIFTING NORTHEAST OF THE
AREA EARLY NEXT WEEK AS IT REMAINS STACKED UNDER THE DEEP UPPER
LEVEL LOW PRESSURE SYSTEM. THE FORECAST AREA WILL SEE SOME DRY
SLOTTING OCCURRING FRIDAY INTO SATURDAY THAT WILL REDUCE CHANCES OF
PRECIPITATION DOWN TO A CHANCE. AN UPPER LEVEL AND SURFACE TROUGH
ROTATE EAST ACROSS THE AREA SATURDAY NIGHT INTO SUNDAY AND WILL
BRING A RETURN SHOT OF MOISTURE AND EXTENSIVE CLOUD COVER ONCE
AGAIN.
THE COMBINATION OF SYNOPTIC MOISTURE OVER THE AREA AND FLOW SHIFTING
TO A FAVORABLE LAKE EFFECT SNOW TRAJECTORY WILL CAUSE THE LAKE SNOW
MACHINE TO FIRE UP ONCE AGAIN. THE WHOLE AREA WILL LIKELY SEE SOME
SNOW SHOWERS FROM THE SYNOPTIC SYSTEM BUT A BETTER CHANCE OF SNOW
WILL BE CONFINED TO THE NORTHEAST SNOW BELT REGION SUNDAY NIGHT INTO
MONDAY NIGHT. REINFORCING SHOTS OF COLD AIR WILL HIT THE AREA BY
THE END OF THE WEEKEND AND THIS WILL LIKELY CAUSE THE LAKE EFFECT TO
PRODUCE SOME SIGNIFICANT SNOW ACCUMULATIONS IN THE NORTHEAST IN SOME
LOCATIONS. WE WILL BE MONITORING THIS OVER THE NEXT SEVERAL DAYS.
TEMPERATURES THROUGH THIS PERIOD WILL SEE COLD AIR ADVECTION
PLUNGING TEMPERATURES BACK DOWN BELOW FREEZING AGAIN AND NO RECOVERY
IS EXPECTED THROUGH MONDAY NIGHT. REINFORCING ARCTIC AIR WILL KEEP
HIGHS BARELY TOUCHING FREEZING SUNDAY.
&&
.LONG TERM /MONDAY THROUGH WEDNESDAY/...
MODELS ARE SIMILAR AT THE BEGINNING OF THE LONG TERM FORECAST FOR
NEXT WEEK. TROUGH REMAINS BACK ACROSS THE GREAT LAKES REGION ON
MONDAY WITH A COLD WEST TO NORTHWEST FLOW OFF LAKE ERIE. THE ENTIRE
AREA WILL SEE SOME SNOW SHOWERS...WITH ENHANCED LAKE EFFECT SNOW
SHOWERS FOR NE OHIO AND NW PENNSYLVANIA. BOTH GFS AND ECMWF SHOW A
COLD FRONT DROPPING SOUTH ACROSS THE AREA MONDAY NIGHT. THIS COULD
CREATE SOME LIGHT SYNOPTIC TYPE SNOW WHICH WOULD TRANSITION BACK
INTO SOME LAKE EFFECT SNOW SHOWERS ON TUESDAY AND TUESDAY NIGHT.
ECMWF CONTINUES TO BRING THE HIGH PRESSURE OVER THE AREA FASTER THAN
THE GFS. FOR NOW WILL FOLLOW CLOSER TO THE ECMWF WHICH IS CLOSER TO
WHAT THE PREVIOUS FORECAST FOLLOWED. THIS WOULD BRING THE HIGH OVER
THE AREA ON WEDNESDAY BRINGING AN END TO AND SNOW SHOWERS.
&&
.AVIATION /15Z THURSDAY THROUGH MONDAY/...
HIGH PRESSURE RIDGE NW TO SE ACROSS THE EASTERN PORTION OF THE
FORECAST AREA WILL MOVE SLOWLY EAST THROUGH THE TAF PERIOD. MAINLY
VFR CONDITIONS THROUGH THIS EVENING. A NORTHEAST FLOW IS CAUSING SOME
STRATOCUMULUS OVER NORTHWEST PENNSYLVANIA AND EXTREME NORTHEAST
OHIO. AS THE LOW LEVELS WINDS BECOME SOUTHEAST THIS MORNING THESE
CLOUDS SHOULD LIFT OUT BY 18Z. ELSEWHERE SOME WARM ADVECTION
PRECIPITATION AHEAD OF A SOUTHERN PLAINS LOW WILL STAY WEST OF
THE FORECAST AREA THROUGH 00Z FRIDAY. LIGHT RAIN SHOULD BEGIN
ARRIVING IN THE FAR WEST BETWEEN 00Z-06Z...SPREADING EAST ACROSS
MOST OF THE AREA BY 12Z. GFS AND ECMWF WERE CLOSE ON THEIR TIMING
OF THE PRECIP BUT NAM HELD IT OFF TO NEAR 12Z FRIDAY IN THE FAR
WEST. STARTED TO LOWER CIGS AND VSBYS TO MVFR IN THE RAIN WESTERN
AREAS AFTER 06Z. THERE IS A RISK THAT THE PRECIP COULD BEGIN AS A
BRIEF PERIOD OF FREEZING RAIN...BUT DIDN'T MENTION IN MOST OF THE
TAFS SINCE THE PROBABILITY IS LOW SINCE THE SE WINDS TONIGHT SHOULD
WARM TEMPERATURES UP ABOVE FREEZING BY THE TIME PRECIP ARRIVE. WINDS
MAY BEGIN TO GUST TO AROUND 30KT AFTER 06Z.
.OUTLOOK...NON-VFR CONDITIONS...MAINLY MVFR CEILINGS...ALONG WITH
GUSTY WINDS...WILL CONTINUE MUCH OF FRIDAY. NON- VFR CONDITIONS
WILL CONTINUE THROUGH MONDAY MUCH OF THE TIME ESPECIALLY ON SUNDAY
AND MONDAY WITH SNOW SHOWERS.
&&
.MARINE...
WINDS WILL BE INCREASING OUT OF THE EAST TODAY. WESTERN AREAS SHOULD
SEE SMALL CRAFT CRITERIA MET BY BOTH WIND AND WAVES. WAVE
FORECAST THERE IS UNCERTAIN BECAUSE OF SOME ICE ON THE WEST END.
WINDS AND WAVES ON THE EAST END WILL NOT LIKELY REACH SCA UNTIL
TONIGHT THOUGH OFF SHORE IT WILL BE QUITE CHOPPY. SCA THEN LIKELY
LASTING INTO AT LEAST FRIDAY NIGHT AS WINDS GRADUALLY VEER TO THE
SOUTHEAST LATER TONIGHT AND FRIDAY...AND FINALLY TO THE SOUTHWEST
FRIDAY NIGHT. WINDS FRIDAY AFTERNOON INTO EARLY FRIDAY NIGHT SHOULD
BE NEAR 30KT AND POSSIBLY QUITE GUSTY...IT IS POSSIBLE THAT WINDS
COULD BE LITTLE STRONGER REACHING GALE FORCE. LOW PRESSURE TO THE
WEST WEAKENS SATURDAY. WINDS PICK UP AGAIN LATE MONDAY INTO EARLY
TUESDAY AS A COLD FRONT DROPS SOUTH THROUGH THE AREA. IT IS POSSIBLE
THAN WINDS COULD REACH GALE FORCE.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
PA...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 4 AM EST
SATURDAY FOR LEZ145>149.
SMALL CRAFT ADVISORY UNTIL 4 AM EST SATURDAY FOR LEZ142>144.
&&
$$
SYNOPSIS...KOSARIK
NEAR TERM...KOSARIK
SHORT TERM...LOMBARDY
LONG TERM...RANDEL
AVIATION...RANDEL
MARINE...RANDEL
