364
FXUS61 KOKX 090626
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE UPTON NY
226 AM EDT WED JUL 9 2008
SYNOPSIS
A SUBTROPICAL HIGH OVER THE WESTERN ATLANTIC WILL GIVE WAY TO AN
APPROACHING UPPER TROUGH AND SURFACE COLD FRONT CURRENTLY OVER THE
GREAT LAKES. THIS WILL MEAN ONE MORE DAY OF VERY WARM AND MUGGY
WEATHER. SHOWERS AND THUNDERSTORMS WILL PRECEDE THE COLD FRONT WED
AFT AND NIGHT WITH ITS PASSAGE EARLY THU MORNING. BEHIND THE FRONT...
CONSIDERABLY DRIER AND MORE SEASONABLE WEATHER WILL RETURN FOR
THE END OF THE WEEK.
NEAR TERM /UNTIL 6 AM THIS MORNING/
ANOTHER WARM...MUGGY NIGHT IS ON TAP WITH OVERNIGHT LOWS
GENERALLY IN THE 70S AND SIMILAR DEW POINTS. MOSTLY CLEAR SKIES
ANTICIPATED. A LOW-LEVEL SW FLOW AT 5 TO 10 KT SHOULD LIMIT ANY
FOG DEVELOPMENT OVERNIGHT TO PATCHY. IN ADDITION...WARM SEASON
CLIMATOLOGY DOES NOT SUPPORT FOG.
SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/
ANOTHER VERY WARM...HUMID DAY IS ON TAP ON WED WITH A COLD FRONT
APPROACHING FROM THE LOWER GREAT LAKES IN THE MORNING. A SW FLOW
WILL ALLOW MUCH OF THE AREA TO HEAT UP INTO THE MID AND UPPER 80S
WITH A FEW READINGS TOPPING OUT IN THE LOWER 90S. THIS WILL PRIME
THE AIRMASS FOR LATE DAY CONVECTION WITH MODERATE INSTABILITY AND
MLU CAPES OF 1000-1500 J/KG. DEEP-LAYERED SHEAR LOOKS TO BE WEAK
AND NOT SUPPORTIVE OF ORGANIZED STRONG/SEVERE CONVECTION.
HOWEVER...A PRE-FRONTAL TROUGH IN THE AFTERNOON FOLLOWED BY A
COLD FRONT AT NIGHT SHOULD BE SUFFICIENT TRIGGERS FOR WIDESPREAD
SHOWERS AND THUNDERSTORMS. PULSE SEVERE STORMS CAN NOT BE RULED IN
A HIGH CAPE...WEAK SHEAR ENVIRONMENT.
COLD FRONTAL PASSAGE IS FORECAST BETWEEN 04Z AND 10Z THU. 12Z GFS
IS ABOUT 6 HOURS SLOWER AS IT IS THE LONE MODEL THAT FORMS A WAVE
OF LOW PRESSURE ALONG THE FRONT OVER SW PA WED NIGHT...THEN TRACKS
IT EAST AND OFF THE NJ COAST AROUND 12Z THU. THIS SCENARIO WOULD
RESULT IN CONVECTION THROUGH MUCH OF THE MORNING HOURS ON THU.
MODEL CONSENSUS AS WELL AS ENSEMBLES DO NOT SUPPORT THIS SOLUTION
WHICH APPEARS TO BE DERIVED FROM GRID SCALE FEEDBACK PROBLEMS
(LOWERING SFC PRESSURES TOO MUCH FROM FORECAST CONVECTION).
BEHIND THE FRONT...DRIER..SEASONABLE WEATHER RETURNS FOR THE END OF
THE WEEK.
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
HIGH PRESSURE OVER THE TRI-STATE AREA WILL MOVE OFFSHORE LATE FRIDAY
NIGHT INTO SATURDAY MORNING PROVIDING A SOUTHERLY FLOW. THIS FLOW
WILL PROVIDE WARM AND HUMID WEATHER BOTH SATURDAY AND SUNDAY. HIGH
TEMPERATURES BOTH DAYS WILL CLIMB INTO THE MIDDLE AND UPPER
80S...WHICH IS SLIGHTLY ABOVE NORMAL FOR THIS TIME OF YEAR.
A COLD FRONT WILL APPROACH THE CWA SUNDAY AFTERNOON AND MOVE ACROSS
THE AREA DURING THE DAY ON MONDAY. AS A RESULT...EXPECT SHOWERS AND
THUNDERSTORMS TO DEVELOP SUNDAY AFTERNOON OUT AHEAD OF THE
FRONT...AND THEN ADDITIONAL SHOWERS AND THUNDERSTORMS CAN BE
EXPECTED WITH THE FRONTAL PASSAGE ON MONDAY. ON TUESDAY...THE COLD
FRONT WILL PUSH EAST OF THE CWA...WITH HIGH PRESSURE BUILDING BACK
INTO THE AREA. AS A RESULT...EXPECT DRIER AND MORE SEASONABLE
CONDITIONS. TEMPERATURES ON MONDAY AND TUESDAY WILL FEATURE HIGHS IN
THE LOWER AND MIDDLE 80S.
AVIATION /06Z WEDNESDAY THROUGH SUNDAY/
VFR CIGS WITH AREAS OF MVFR TO LOCALLY IFR VSBY IN FOG/HZ THROUGH
14Z OR SO OUTSIDE OF NYC TERMINALS. SW FLOW BETWEEN 5 AND 10 KT
SHOULD KEEP CONDITIONS VFR HERE. OTHERWISE...MID AND HIGH
CONVECTIVE DEBRIS CLOUDS OVER CENTRAL AND EASTERN PA WILL ENTER
THE AREA BETWEEN 12Z AND 14Z. SYNOPTIC FLOW LOOKS TOO STRONG FOR
TRUE SEABREEZE DEVELOPMENT TODAY AND EXPECT SW WINDS GENERALLY
BETWEEN 10 AND 15 KT WITH GUSTS 20 TO 25 KT DEVELOPING THIS
AFTERNOON.
PREFRONTAL TROUGH EXPECTED TO DEVELOP THIS AFTN...BUT DYNAMICAL
FORCING DOESN'T ARRIVE UNTIL LATE AFTN WITH THE UPPER TROUGH/SFC
COLD FRONT...SO HAVE PUSHED OFF CB DEVELOPMENT A FEW HOURS AND
INCLUDED A TEMPO GROUP FOR TSTMS AT ALL TERMINALS EXCEPT KGON.
EXPECT MVFR TO IFR CONDITIONS IN TSTMS.
MVFR CONDITIONS EXPECTED UNTIL THE PASSAGE OF COLD FRONT TONIGHT.
CHANCE OF SHOWERS AND TSTMS CONTINUES UNTIL FROPA AS WELL...BUT
WILL LIKELY WEAKEN AND BECOME MORE ISOLATED WITH THE LOSS OF
DAYTIME HEATING.
OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY...VFR CONDITIONS SHOULD RETURN
FROM WEST TO EAST AFTER 06Z WITH DRYER AIR FILTERING IN. KGON MAY
HOLD ON TO SUB-VFR CONDITIONS THROUGH THU MORNING...BUT DEPENDS ON
HOW FAST THE FRONT MOVES THROUGH. VFR CONTINUES FRI AND SAT WITH
RIDGE IN PLACE. SUB VFR POSSIBLE IN LATE DAY CONVECTION SUN.
MARINE
SW FLOW CONTINUES THROUGH WED INCREASING THIS EVE WITH GUSTS
REACHING MARGINAL SCA LEVELS ON THE OCEAN. SEAS WILL BUILD ON THE
OCEAN AS WELL...REACHING 5 TO 7 FT OVERNIGHT.
SCA RUNS THROUGH THU MORNING WITH THE PASSAGE OF THE COLD FRONT.
NO FLAGS EXPECTED ON REMAINING WATERS.
WITH HIGH PRESSURE OVER THE AREA WATERS...WINDS AND SEAS ARE
EXPECTED TO REMAIN BELOW SCA LEVELS THROUGH SATURDAY. THE NEXT
CHANCE FOR SCA CONDITIONS COULD BE SUNDAY AFTERNOON AND MONDAY AS A
COLD FRONT APPROACHES AND MOVES ACROSS THE AREA WATERS.
HYDROLOGY
DRY TONIGHT...THEN CONVECTION BECOMES MUCH MORE LIKELY ON WEDNESDAY
AFTN AS A COLD FRONT APPROACHES. CONVECTION COULD TRAIN FROM
SOUTHWEST TO NORTHEAST AND WITH HIGH PRECIPITABLE MOISTURE VALUES
SOME FLOODING SEEMS POSSIBLE. STORM MOTION OF 20 KNOTS SHOULD
PREVENT WIDESPREAD FLOODING...SO NO WATCH ANTICIPATED.
DRY WX THURSDAY INTO WEEKEND.
OKX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ350-353-
355.
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