FXUS61 KCLE 242055
AFDCLE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CLEVELAND OH
355 PM 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 AM FRIDAY MORNING/...
MODELS ARE SIMILAR AS FAR AS TIMING THE ONSET OF PRECIPITATION LATER
TONIGHT. EVENING PRECIPITATION MOVING NORTH ACROSS INDIANA MAY JUST
BRUSH THE I-75 CORRIDOR BUT I HAVE A FEELING THAT PRECIP WILL NOT
REACH THE GROUND AS THE LOW LEVELS ARE DRY WITH THE EAST WIND. WITH
THE SLOW ADVANCE OF THE PRECIPITATION SHIELD FROM THE WEST... W2E
WILL ESSENTIALLY HAVE TO WAIT UNTIL EXTRA MOISTURE AND UPWARD MOTION
MOVES IN FROM THE SOUTH AND SOUTHWEST. IT WILL TAKE UNTIL THE EARLY
MORNING HOURS TO MAKE IT EVEN TO THE WESTERN COUNTIES. THE LACK OF
CLOUDS WILL ENABLE SOME RADIATIONAL COOLING TO OCCUR ACROSS EXTREME
NE OH/NW PA ALTHOUGH THE EAST WIND WILL KEEP THINGS MIXED SO TEMPS
WILL NOT TANK. COUNTING ON TEMPS SNEAKING UP ANOTHER DEGREE OR TWO
BEFORE THE MAIN PRECIPITATION STARTS ACROSS THE TOLEDO AREA BUT
CANNOT RULE OUT SOME PATCHY FREEZING RAIN. EVEN IF THE AIR
TEMPERATURE IS 33F OR 34F ODOT TELLS US THAT THE SURFACE TEMPERATURE
MAY REMAIN AT 32F OR COLDER FOR A WHILE. ELSEWHERE... AFTER A DROP
IN THE EVENING...TEMPS WILL TREND SLOWLY UPWARD OVERNIGHT AS WIND
AND CLOUDS INCREASE.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
THE NAM/WRF IS STILL SLOWER MOVING THE PRECIPITATION EASTWARD ON
SATURDAY MORNING. NOT REAL CONFIDENT ON THE START TIME WITH THE DRY
EAST DOWNSLOPE FLOW IN PLACE AND THE MAIN LOW PRESSURE SYSTEM SO FAR
WEST. TYPICALLY THE MODELS ARE A LITTLE QUICK IN THIS SITUATION AND
OFTEN HAVE TOO MUCH QPF...ESPECIALLY ACROSS NE OH/NW PA. I WILL USE
AN AVERAGE OF THE MODELS FOR THE ONSET OF PRECIPITATION. IF
PRECIPITATION ARRIVES AT INLAND NORTHWEST PENNSYLVANIA BEFORE
MIDDAY... THERE WILL LIKELY BE AREAS OF FREEZING RAIN. SHOULD NOT
BE A BIG EVENT BUT IT DOES NOT TAKE MUCH TO MAKE UNTREATED
SURFACES SLIPPERY AND WILL ISSUE A FREEZING RAIN ADVISORY FOR
MORNING AND EARLY AFTERNOON FOR INLAND ERIE AND CRAWFORD COUNTY
PA. TEMPS SHOULD SNEAK JUST ENOUGH ABOVE FREEZING ACROSS THE
REMAINDER OF NORTHERN OHIO TO MINIMIZE THE RISK OF ICE AND THE
SOUTHEAST FLOW DURING THE DAY FRIDAY SHOULD STEADILY WARM THINGS
UP ALTHOUGH THE GUSTY WIND WILL NOT MAKE IT FEEL ALL THAT WARM.
WIND IS A CONCERN ON SATURDAY FOR ERIE AND THE EAST LAKESHORE. NICE
SOUTH TO SOUTHEAST LOW LEVEL JET PROGGED TO DEVELOP. 12Z GFS NOW UP
TO 70 KNOTS AT 850 MB WITH THE OTHER MODELS SLIGHTLY LESS. WHILE
THIS DOWNSLOPE WIND CERTAINLY POSES A THREAT...SOME OF THE OTHER
HIGH WIND FACTORS DO NOT LINE UP AS WELL. RAIN WILL OCCUR ROUGHLY AT
THE SAME TIME OF MAX WIND WHICH WILL STABILIZE THE ATMOSPHERE. THE
MIXING LAYER IS PROGGED TO REMAIN QUITE LOW DUE TO THE RAIN. BUFKIT
MOMENTUM TRANSFER INDICATES A STABLE CONDITION WITH A PEAK GUST WITH
25 TO 30 KNOTS. THERE IS A WINDOW OF OPPORTUNITY DURING THE
AFTERNOON AND EARLY EVENING DURING THE MAXIMUM LOW LEVEL JET AND I
THINK THE INVERSION CAN POTENTIALLY BE OVERCOME AS IT DRIES OUT
ALOFT DURING THE LATE AFTERNOON AND MIXING INCREASES. THERE COULD BE
A FEW HOURS OF GUSTS BETWEEN 40 AND 45 KNOTS WHICH MAY REQUIRE A
WIND ADVISORY. WITH THE UNCERTAINTY AND THE TIMING LATER ON FRIDAY
MAY NOT NEED AN ADVISORY AND WILL NOT ISSUE AN ADVISORY AT THIS
TIME.
THE COLD AIR RETURNS GRADUALLY...THE STORM SYSTEM IS PROGGED TO STAY
WELL TO THE WEST. I HAVE SEEN THESE TYPE OF SYSTEMS SPIN FOR A LONG
TIME BEFORE PRECIPITATION OF ANY SIGNIFICANCE RETURNS ESPECIALLY
WITH A SOUTHWEST FLOW KEEPING THE LAKE EFFECT/LAKE ENHANCEMENT OFF
SHORE. WILL CALL IT FLURRIES ON SATURDAY.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
MODELS IN GOOD AGREEMENT WITH WEAKENING LOW PRESSURE MOVING OVER
NORTHERN GREAT LAKES SUNDAY WHILE CLOSED UPPER LOW SWINGS OVER
NORTHERN OHIO THROUGH SUNDAY NIGHT. WITH THE APPROACHING UPPER LOW
WENT WITH LIKELY POPS ACROSS WESTERN AREAS FOR SNOW SHOWERS DURING
THE DAY AND THEN LIKELY POPS SHIFTING TO EASTERN AREAS FOR SUNDAY
NIGHT. FOR MONDAY CONTINUED LIKELY POPS ACROSS NORTHEAST OH AND NW
PA WITH THE REMAINDER OF THE AREA DROPPING BACK TO CHANCE POPS AS
SNOW SHOWERS BECOME MORE LAKE EFFECT. BOTH GFS AND ECMWF SHOWING
SURFACE TROUGH DROPPING SOUTH OVER LAKE ERIE LATE MONDAY AND MONDAY
NIGHT WHICH WOULD ALLOW FOR GOOD POTENTIAL OF ADDITIONAL LAKE EFFECT
SNOW SHOWERS. SNOW SHOWERS EXPECTED TO LINGER THROUGH MUCH OF
TUESDAY ACROSS NE OH AND NW PA. MEANWHILE...SURFACE HIGH PRESSURE
AND RIDGING ALOFT WILL BE BUILDING IN FROM THE WEST ALLOWING FOR AN
END TO PRECIP ACROSS AT LEAST THE WESTERN HALF OF THE FORECAST AREA.
MODELS SHOWING HIGH PRESSURE BUILDING OVERHEAD TUESDAY NIGHT
ALLOWING FOR DRY CONDITIONS ACROSS THE ENTIRE AREA. HIGH PRESSURE
WILL CONTINUE THROUGH WEDNESDAY...BUT THEN INTRODUCED POPS AT THE
END OF THE PERIOD WITH A WEAK LOW PRESSURE AND COLD FRONT
APPROACHING FROM THE UPPER MIDWEST FOR THE END OF THE PERIOD.
WITH UPPER LOW MOVING OVER THE AREA...CLOUDS AND SNOW SHOWERS
TRENDED A BIT COOLER THAN GUIDANCE SUNDAY AND SUNDAY NIGHT. CONTINUE
TO LEAN ON COLDER SIDE OF GUIDANCE ON MONDAY...THEN BEGIN A GRADUAL
RECOVERY ON TUESDAY AND WEDNESDAY. NIGHTTIME LOWS WILL BE TRICKY
ESPECIALLY LATER IN THE PERIOD WHEN HIGH PRESSURE BUILDS OVER THE
AREA. WITH THAT LEANED ON COLDER SIDE OF GUIDANCE FOR MINS TO
ACCOUNT FOR POSSIBLE RADIATING CONDITIONS AND ADDITIONAL SNOW COVER.
&&
.AVIATION /21Z THURSDAY THROUGH TUESDAY/...
HIGH PRESSURE RIDGING GIVING WAY THROUGH THIS AFTERNOON...BUT
CONDITIONS WILL REMAIN VFR THROUGH AT LEAST THE FIRST HALF OF THE
PERIOD. MODELS CONTINUING TO BE EVEN SLOWER IN BRINGING PRECIP
INTO SITES THROUGH TONIGHT SO TRENDED BACK A FEW HOURS FROM
PREVIOUS FORECAST. THINKING THAT TOL WOULD BE MOST LIKELY SITE FOR
ANY CHANCES OF FZRA AT ONSET OF PRECIP OVERNIGHT WITH SURFACE
TEMPS NEAR FREEZING. NOT EXPECTING THE FZRA TO LAST FOR MORE THAN
AN HOUR OR TWO WITH WARMER AIR QUICKLY BUILDING OVER THE AREA.
PRECIP WILL GRADUALLY INCREASE FROM SW TO NE THROUGH 12Z INTO NE
OH AND THEN BY MID MORNING AT ERI. CONDITIONS ARE EXPECTED TO
GRADUALLY DROP TO MVFR AFTER THE RAIN BEGINS AND THEN CONTINUE
MVFR INTO THE AFTERNOON. GUIDANCE TRYING TO INDICATE IFR
CONDITIONS INCREASING INTO THE AREA LATER TOMORROW BUT NOT YET
CONFIDENT IN PREDOMINATE IFR DURING THE LAST FEW HOURS OF TAFS.
WILL HAVE TO MONITOR LATER FORECASTS FOR THIS POSSIBLE TREND.
OTHER ITEMS OF CONCERN THROUGH THE PERIOD WILL BE STRONGER SE
WINDS DEVELOPING LATER TONIGHT AND THROUGH FRIDAY. GUSTS OF 30KT
ARE POSSIBLE ACROSS THE ENTIRE AREA. ANOTHER ITEM OF CONCERN ARE
WINDS ALOFT LATER TONIGHT AND FRIDAY MORNING. THERE IS THE
POSSIBILITY OF SOME LOW LEVEL WIND SHEAR DEVELOPING...BUT WINDS AT
THE SURFACE WILL ALSO BE INCREASING DURING THE SAME TIME.
.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...
EAST WINDS CONTINUE ON THE LAKE THIS EVENING. WINDS ALREADY 15 TO
20 KNOTS OVER THE WESTERN BASIN AND WINDS BEGINNING TO PICK UP IN
THE EAST. I WILL KEEP SCA FOR ALL AREAS TONIGHT AND FRIDAY. WINDS
WILL GRADUALLY BECOME MORE SE OVERNIGHT AND CONTINUE IN THE 15 TO 25
KNOT RANGE. WINDS WILL BECOME MORE SOUTHERLY ON SAT AND SUN. THE
GRADIENT WILL DECREASE AND WIND SPEEDS WILL SUBSIDE.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
PA...FREEZING RAIN ADVISORY FROM 6 AM FRIDAY TO 2 PM EST SATURDAY
FOR PAZ002-003.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST SATURDAY FOR LEZ142>149.
&&
$$
SYNOPSIS...KOSARIK
NEAR TERM...KOSARIK
SHORT TERM...KOSARIK
LONG TERM...ABE
AVIATION...ABE
MARINE...GARNET
