361
FXUS61 KOKX 041120
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
720 AM EDT SAT JUL 4 2009
SYNOPSIS
AN ALBERTA CLIPPER SYSTEM WILL PASS NORTH OF THE REGION TODAY.
ANOTHER LOW WILL PASS TO THE SOUTH SUNDAY INTO SUNDAY NIGHT.
AN UPPER LEVEL TROUGH WILL APPROACH ON MONDAY...AND AFFECT THE
REGION THROUGH MID WEEK. HIGH PRESSURE MAY RETURN FOR THE END OF
THE WEEK.
NEAR TERM /UNTIL 6 PM THIS EVENING/
A STRONG SHORTWAVE AND CLIPPER LOW OVER CENTRAL ONTARIO THIS
MORNING DIVES INTO CENTRAL/NORTHERN NEW ENGLAND TODAY. DEEP NW
FLOW AND BEST COLD POOL INSTABILITY TO THE NORTH WILL KEEP THE
REGION DRY...WITH JUST SOME AFTERNOON CU DEVELOPMENT WITH
ASSOCIATED COLD FRONT PASSAGE THIS AFTERNOON.
STRONG OFFSHORE FLOW SHOULD INHIBIT SEABREEZE DEVELOPMENT.
MOSTLY SUNNY SKIES AND DOWNSLOPE FLOW WILL HAVE HIGHS IN THE UPPER
70S TO LOWER 80S AREAWIDE...WARMEST NY/NJ METRO AND COAST.
SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/
GENERALLY ZONAL FLOW TONIGHT IN WAKE OF CLIPPER TYPE SYSTEM...WITH
WEAK HIGH PRESSURE BUILDING OVER THE REGION. THIS WILL HAVE MOSTLY
CLEAR SKIES...WITH JUST SOME HIGH AND MID CLOUDS ACROSS SOUTHERN
ZONES LATE FROM DEVELOPING LOW PRES OVER THE TN VALLEY. CANADIAN
AIRMASS ADVECTS IN THE WAKE OF THE CLOD FRONT THIS EVENING. THEN
WITH GOOD RADIATIONAL COOLING CONDS OVERNIGHT...TEMPS WILL RUN
SEVERAL DEGREES BELOW NORMAL ACROSS OUTLYING AREAS...FALLING INTO
THE 50S. PERHAPS SOME UPPER 40S IN THE PINE BARRENS AND NORTHERN
VALLEYS.
NEXT PIECE OF NORTHERN STREAM ENERGY WILL HAVE AN UPPER LOW
DEVELOPING OVER ONTARIO ON SUNDAY AND DIGGING TOWARDS THE EASTERN
GREAT LAKES SUN NIGHT. AT THE SAME TIME A WEAK SOUTHERN STREAM
SHORTWAVE WILL TRACK E ACROSS THE TENNESSEE VALLEY AND THEN
OFFSHORE SUN NIGHT. MODELS ARE NOT INDICATING ANY PHASING OF THESE
TWO IMPULSES...BUT WILL BE A CLOSE CALL. WITHOUT PHASING...WEAK
LOW PRESSURE TRACKING THROUGH THE TENNESSEE VALLEY ON SUN WILL
PASS WELL SOUTH OF NYC/LONG ISLAND LATE SUN/SUN NIGHT. IF THE
NORTHERN AND SOUTHERN STREAM ENERGY WERE TO PHASE THIS WOULD DIG
THE NORTHERN STREAM TROUGH FURTHER SOUTH...BRINGING THE LOW
FURTHER NORTH WITH MORE WIDESPREAD SHOWER ACTIVITY SUN NIGHT. BUT
CONFIDENCE IS NOT HIGH ON THAT OCCURRING. WILL CONTINUE WITH
SLIGHT CHANCE POPS FOR SOUTHERN PORTIONS OF THE CWA FOR SUN
EVE/SUN NIGHT BASED ON THIS UNCERTAINTY AND CLOSEST APPROACH.
OTHERWISE...SHOULD BE MAINLY DRY DAY ON SUN WITH PARTY CLOUDY
CONDITIONS WITH MAINLY HIGH AND MID DECK CLOUDS. BACKING FLOW ON
SUN WILL ALLOW FOR AFTERNOON SEA BREEZE DEVELOPMENT. HIGHS IN THE
LOWER 80S INTERIOR...MID TO UPPER 70S ALONG THE COAST.
UPPER LOW CONTINUES TO DIG TOWARDS THE NORTHEAST ON MON. UNCERTAINTY
ON HOW FAR S AND E THIS FEATURE DIGS...WHICH WILL DETERMINE AMOUNT
OF INSTABILITY SHRA/TSRA DEVELOPMENT. WILL CONTINUE AFTERNOON SLIGHT
CHANCE POPS FOR NW 1/2 OF CWA. TEMPS RUNNING NEAR SEASONABLE.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
UPPER LOW SLOWLY MOVES THROUGH THE NORTHEAST...BRINGING US LOWER-END
POPS THROUGH WEDNESDAY. HIGHEST OVERALL CHANCES OF CONVECTIVE
ACTIVITY LOOK TO BE DIURNAL ON TUESDAY AND WEDNESDAY. RIDGING ALOFT
AND AT THE SURFACE MOVES IN BEHIND THE UPPER LOW. DRY WEATHER
THEREFORE FOR THE REST OF THE LONG TERM. HIGH TEMPERATURES AT OR
SLIGHTLY BELOW NORMAL TO START...THEN WARMING ABOVE NORMAL LATE IN
THE PERIOD WITH THE RIDGING ALOFT.
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
VFR...WITH W-NW FLOW GUSTING TO 20-25 KT AT TIMES THIS AFTERNOON...
UNCOMMON FOR EARLY JULY. COASTAL TERMINALS COULD BRIEFLY EXPERIENCE
SOME VARIABILITY IN DIRECTION BETWEEN SW-W THIS MORNING...AND
EVENTUALLY SETTLE IN WITH A LITTLE MORE WESTERLY COMPONENT THAN
INLAND TERMINALS ONCE DAYTIME HEATING TRANSPORTS STRONGER WINDS DOWN
FROM ALOFT. HAVE ADJUSTED FOR TYPICAL MOS LOW EARLY EVENING SPEED
BIAS IN THIS TYPE OF POST-FRONTAL COOL AIR ADVECTION SITUATION...AND
HELD ONTO STRONGER WINDS THROUGH ABOUT 01Z-02Z...THEN SETTLED THINGS
DOWN TO UNDER 10 KT LATE THIS EVENING AND OVERNIGHT.
OUTLOOK FOR 12Z SUNDAY THROUGH WEDNESDAY...
LOOK FOR A SLIGHT CHANCE OF BRIEF SUB-VFR CONDITIONS ON MON...THEN A
SOMEWHAT BETTER CHANCE TUE-WED...VIA DIURNAL AFTERNOON/EARLY EVENING
CONVECTION...AS YET ANOTHER UPPER LOW AND ASSOCIATED SFC TROUGH
APPROACH.
MARINE
GUSTY W-NW FLOW WILL TAKE HOLD THIS AFTERNOON AND EARLY EVENING...
15-20 KT WITH AN OCCASIONAL GUST UP TO 25 KT POSSIBLE NEAR SHORE
JUST DOWNWIND OF BETTER VERTICAL MIXING OVER THE NYC URBAN HEAT
ISLAND. GIVEN NUMBER OF RECREATIONAL BOATERS WHO WILL BE OUT ON THE
WATERS THIS INDEPENDENCE DAY HOLIDAY...ISSUED MARINE WX STATEMENT TO
HIGHLIGHT THE SITUATION. ISSUING SCA WOULD BE OVERKILL GIVEN BRIEF
EXPECTED COVERAGE/DURATION OF ANY 25-KT GUSTS.
QUIET CONDITIONS WILL OTHERWISE BE THE RULE THROUGH THE REST OF THE
FORECAST PERIOD...WITH A LACK OF SIGNIFICANT SURFACE FEATURES IN
THE REGION.
HYDROLOGY
GENERALLY DRY CONDITIONS THROUGH THE WEEKEND. MORE CONVECTIVE PRECIP
POSSIBLE EARLY NEXT WEEK.
OKX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...NONE.
SYNOPSIS/NEAR TERM/SHORT TERM/HYDROLOGY...NV
LONG TERM...JC
AVIATION/MARINE...BG
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