Flash Flood Warning 7, NWS New York, NY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE UPTON NY
236 PM EDT FRI OCT 19 2007

.SYNOPSIS...
A STRONG FRONTAL SYSTEM WILL APPROACH THE AREA THIS AFTERNOON...
AND RESULT IN SHOWERS AND THUNDERSTORMS ACROSS THE REGION THROUGH
LATE TONIGHT. THE COLD FRONT WILL MOVE THROUGH AROUND MIDNIGHT
FOR NEW YORK CITY AND DURING THE EARLY MORNING HOURS ACROSS
EASTERN LONG ISLAND AND SOUTHEAST CONNECTICUT. HIGH PRESSURE IS
THEN EXPECTED TO BUILD TO OUR SOUTH FOR THE WEEKEND. THE HIGH WILL
CONTROL AREA WEATHER THROUGH MONDAY BEFORE ANOTHER STORM SYSTEM
APPROACHES TUESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
BASED ON LATEST RADAR TRENDS...WITH SHOWERS AND EMBEDDED
THUNDERSTORMS EXPANDING TO THE SOUTH AND EAST OF NYC...HAVE
BROUGHT IN CATEGORICAL POPS FROM NYC AND POINTS EAST FOR EARLY
THIS AFTERNOON. THE CURRENT ACTIVITY APPEARS TO BE DRIVEN BY
LOW-LEVEL CONVERGENCE DUE TO A STRENGTHENING LOW-LEVEL JET. IN
FACT...ACTIVITY WILL LIKELY BE ENHANCED ALONG THE COASTAL PLAIN
DUE TO FRICTIONAL EFFECTS. TO THE WEST...LOOKING AT LIKELY POPS
FOR THE REST OF THE AFTERNOON....WHICH IS A SLIGHT DOWNWARD
ADJUSTMENT.

MODELS HAVE BEEN ADVERTISING THIS SYSTEM FOR QUITE SOMETIME NOW.
WARM AND HUMID AIRMASS IN PLACE...AND STRENGTHENING VERTICAL WIND
PROFILE WILL OCCUR AS SHORTWAVE TROUGH APPROACHES FROM THE WEST.
MODELS STILL INCREASE PRECIPITABLE WATER TO AROUND 2 INCHES RIGHT
AHEAD OF THE SFC COLD FRONT. SFC BASED INSTABILITY WILL BE LIMITED
DUE TO CLOUD COVER. SOME INSTABILITY ALOFT THOUGH ALONG WITH LOW
LEVEL THETA E/TEMP ADVECTION TO RESULT IN HEAVY SHOWER/TSTM
DEVELOPMENT THIS AFTERNOON AND EVENING. WIND PROFILES CONDUCIVE
FOR SUPERCELL DEVELOPMENT IF CELLS SUSTAIN THEMSELVES THIS FAR
EAST...AND DAMAGING WIND GUSTS IN TSTMS POSSIBLE. PORTION OF CWA
IN SLIGHT RISK FROM SPC FOR SEVERE TSTMS. THE OTHER OBVIOUS
CONCERN WILL BE URBAN/POOR DRAINAGE FLOODING. SOUTHERLY FLOW
PARALLEL TO FRONT WOULD RESULT IN TRAINING OF CELLS...AND THUS
FLOODING CONCERNS. OVERALL...GENERALLY 1/2 TO 1 1/2 INCHES OF
BASIN WIDE RAINFALL EXPECTED...BUT OF COURSE LOCALLY HEAVIER 2
INCH AMOUNTS LIKELY.

THE FRONT STILL ON TARGET TO PASS ACROSS THE REGION THIS EVENING AND
OVERNIGHT...FROM WEST TO EAST. DRIER AIR MOVES ON IN BEHIND THE
SFC FRONT/INITIAL SHORTWAVE...WITH UPPER TROUGH AXIS LAGGING. SO
WIDESPREAD RAINFALL GIVES WAY TO SCT LEFTOVER SHOWERS LATE
TONIGHT.

AS FOR TEMPS...ANOTHER WARM DAY ON TAP...WITH AREA GETTING OFF TO
A WARM START. HOWEVER...CLOUD COVER WILL LIMIT AMOUNT OF
HEATING...AND GENERALLY EXPECT MIDDLE TO UPPER 70S NYC
METRO...WITH 70 TO 75 ELSEWHERE. RECORDS MAY BE IN JEOPARDY ONCE
AGAIN TODAY...WITH LGA...JFK...ISP THE MOST SUSCEPTIBLE. RECORDS
FOR EWR...BDR...AND NYC IN THE 80S SHOULD REMAIN INTACT. SEE
DETAILS IN THE CLIMATE SECTION.

TEMPS TONIGHT WILL NOT DROP TOO MUCH AS FRONT PASSES THROUGH LATE...AND
WEAK CAA EXPECTED BEHIND THIS SYSTEM. WILL ACCEPT A MODEL BLEND HERE.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
UPPER TROUGH AXIS MOVES ACROSS THE AREA SATURDAY...BUT WITH MUCH
DRIER AIR ALREADY IN PLACE...DO NOT FORESEE ANY SHRA DEVELOPMENT.
HIGH PRESSURE BUILDS TO OUR SOUTH THROUGH THE WEEKEND AS UPPER
RIDGING QUICKLY MOVES IN BEHIND DEPARTING TROUGH.

THE MAIN CHANGE IN AIRMASS WILL BE WITH THE MOISTURE CONTENT RATHER
THAN THE TEMPERATURE. SO...EXPECT ABOVE NORMAL TEMPERATURES TO
CONTINUE ON SATURDAY..WITH HIGHS IN THE LOWER 70S...BUT THIS WILL BE
ACCOMPANIED BY DEW POINTS IN THE 40S RATHER THAN THE 60S. SUNDAY
LOOKS A DEGREE OR TWO WARMER IN WARM AIR ADVECTION UP THE COLUMN.
WENT CLOSE TO OR SLIGHTLY ABOVE MAV/MEX SUNDAY. AS FOR
SATURDAY...WENT BETWEEN WARMER MET AND COOLER MAV NUMBERS...WHICH IS
CLOSER TO FWC OUTPUT.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
IT IS STARTING TO LOOK LIKE NEXT UPSTREAM UPPER TROUGH CLOSES OFF
ACROSS MID PORTION OF THE COUNTRY AS NORTHERN SHORTWAVE IN SPLIT
FLOW QUICKLY RACES ACROSS SE CANADA BY WEDNESDAY AND DIGS ACROSS
NRN NEW ENGLAND. THIS COULD MEAN SLOWER MOVING SFC COLD FRONT
SAGGING SOUTH TOWARD AREA...BUT NOT ABLE TO MAKE MUCH SOUTHWARD
PROGRESS IN SW PARALLEL MID AND UPPER STEERING FLOW. WE WILL SEE
WHAT LATER MODEL SOLUTIONS PREDICT AS EVENT GETS CLOSER...BUT
LOOKS UNSETTLED BY MID WEEK.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
A SIGNIFICANT CHANGE FROM THE 12Z TAF PACKAGE...WITH IFR CEILINGS
NOW FORECAST THROUGH THIS EVENING WITH A STRENGTHENING ONSHORE
FLOW. BUFKIT SOUNDINGS WEAKLY INVERTED WHICH DOES LEAVE SOME
UNCERTAINTY FOR A HIGHER CEILING FORECAST. HOWEVER...WITH HIGH DEW
POINTS TRAVERSING THE NEAR SHORE WATERS...CONFIDENCE IS HIGHER FOR
THE LOWER END OF THINGS...ESPECIALLY FOR THE COASTAL TERMINALS.
CURRENT ROUND OF SHOWERS MOVING THROUGH THE AREA WILL RESULT IN
MVFR VSBYS WITH LOCALIZED IFR VSBYS. HAVE ALSO INCLUDED A WIND
SHEAR GROUP WITH THE LOW-LEVEL JET STRENGTHENING TO AROUND 50 KT BY
20Z...PERSISTING THROUGH ABOUT 02Z.

A SECOND..MORE ORGANIZED AREA OF CONVECTION IS EXPECTED BETWEEN
00Z AND 07Z ALONG AND AHEAD OF THE SFC COLD FRONT. LIMITING FACTOR
IS INSTABILITY...WHICH IS MARGINAL...BUT STRONG WIND SHEAR SHOULD
COMPENSATE AND ALLOW FOR A LINE OF SHOWERS AND EMBEDDED
THUNDERSTORMS. DUE THE STRONG WINDS IN THE LOW-LEVELS...SHOWERS
MAY MIX DOWN GUSTS UP TO 30 KT...POSSIBLY EVEN STRONGER WITH ANY
THUNDERSTORMS.

COLD FRONT MOVES THROUGH KSWF AROUND 05Z...KLGA 06Z..KISP 07Z AND
KGON 08Z. WINDS WILL VEER AROUND TO THE W AT THIS TIME WITH
PRONOUNCED DRYING. VFR CEILINGS MAY HANG ON UNTIL AROUND 12Z.

OUTLOOK FOR 18Z SAT THROUGH TUESDAY...
A GUSTY WEST WIND WITH GUSTS UP TO 25 KT IS POSSIBLE IN THE WAKE
OF THIS FRONT LATE SAT THROUGH EARLY SUNDAY AS HIGH PRES BUILDS
TOWARD THE AREA. THIS HIGH WILL MOVE OFF THE COAST ON MONDAY AND
AN INCREASING SOUTHERLY FLOW WILL DEVELOP. WEATHER CONDITIONS
DETERIORATE ON TUESDAY AS THE NEXT SYSTEM APPROACHES THE
TERMINALS.

&&

.MARINE...
SOUTHERLY FLOW BEGINS TO GRADUALLY INCREASE OUT OF THE SOUTH THIS
MORNING AS THE PRESSURE GRADIENT BEGINS TO TIGHTEN. DESPITE THE
INCREASED WINDS...WE SHOULD STAY BELOW SCA LEVELS UNTIL THIS
AFTERNOON...WHEN SEAS ACROSS THE SOUTHERN PORTION OF THE COASTAL
OCEAN ZONES INCREASE TO 5 FT...AND GUSTS COULD REACH 25 KT. THE
PRESSURE GRADIENT AND STRENGTH OF LOW LEVEL SOUTHERLY JET INCREASES
FRIDAY NIGHT...TO WARRANT A SCA OVER ALL THE AREA WATERS FOR
TONIGHT.

WINDS SHIFT TO WESTERLY BEHIND FRONT SAT AND WILL CONTINUE TO BE
GUSTY (POTENTIALLY TO SCA LEVELS) THROUGH SATURDAY NIGHT. THIS COULD
RESULT IN LOW WATER ISSUES OVER THE WESTERN SOUND/NY HARBOR/SOUTH
BAYS OF LI/PECONIC BAY.

WINDS AND SEAS SHOULD SUBSIDE TO SUB SCA LEVELS OVER ALL WATERS BY
SUNDAY AND REMAIN SO INTO EARLY NEXT WEEK. AS HIGH PRESSURE BUILDS
IN FROM THE S OVER THE WEEKEND AND THEN MOVES OFFSHORE EARLY NEXT
WEEK.

&&

.HYDROLOGY...
HEAVY RAINFALL IS EXPECTED LATER THIS AFTERNOON INTO TONIGHT WITH
AMOUNTS OF BETWEEN 1/2 AND 1 1/2 INCHES...WITH LOCALLY HIGHER AMOUNTS
UPWARDS OF TWO INCHES. THERE WILL BE PERIODS OF HEAVY RAIN DUE TO
CONVECTION AND THE POSSIBILITY OF TRAINING OF CONVECTIVE CELLS.
AS IT STANDS NOW...URBAN/POOR DRAINAGE FLOODING IS LIKELY...AND
FLOODING OF SMALLER FLASHIER STREAMS IS POSSIBLE LATE THIS AFTERNOON
AND EARLY TONIGHT. THE BIGGEST PROBLEM WILL LIKELY BE THE
CLOGGING AND BLOCKING OF SEWERS AND STORM DRAINS FROM FALLEN LEAVES.
EVEN A PERIOD OF MODERATE RAIN WOULD RESULT IN URBAN FLOODING
PROBLEMS.

&&

.CLIMATE...
HERE ARE RECORD HIGH AND FORECASTED HIGH TEMPERATURES FOR TODAY.

     RECORD HIGH | FORECASTED HIGH

EWR 82/1945      | 78
BDR 81/1963      | 74
NYC 83/1963      | 76
LGA 79/1963      | 77
JFK 75/1965      | 74
ISP 74/1998      | 73

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EDT
     SATURDAY FOR ANZ330-335-338-340-345.
     SMALL CRAFT ADVISORY UNTIL 6 PM EDT SATURDAY FOR ANZ350-353-
     355.

&&

AVIATION...DW

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE UPTON NY
418 AM EDT FRI OCT 19 2007

CTZ005-006-009-010-NJZ002>006-011-NYZ067>078-080-200900-
NORTHERN FAIRFIELD-NORTHERN NEW HAVEN-SOUTHERN FAIRFIELD-
SOUTHERN NEW HAVEN-WESTERN PASSAIC-BERGEN-EASTERN PASSAIC-ESSEX-
HUDSON-UNION-ORANGE-PUTNAM-ROCKLAND-NORTHERN WESTCHESTER-
SOUTHERN WESTCHESTER-NEW YORK (MANHATTAN)-BRONX-
RICHMOND (STATEN ISLAND)-KINGS (BROOKLYN)-QUEENS-NASSAU-
NORTHWESTERN SUFFOLK-SOUTHWESTERN SUFFOLK-
418 AM EDT FRI OCT 19 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHERN
CONNECTICUT...NORTHEAST NEW JERSEY AND SOUTHEAST NEW YORK.

.DAY ONE...TODAY AND TONIGHT
NATIONAL WEATHER SERVICE STORM PREDICTION CENTER HAS PLACED THE
REGION IN A SLIGHT RISK FOR SEVERE WEATHER TODAY. SHOWERS AND
THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND EVENING. SOME OF
THESE STORMS WILL BE CAPABLE OF PRODUCING DAMAGING WIND
GUSTS...AND HEAVY RAINFALL. THE HEAVY RAINFALL WILL LIKELY PRODUCE
URBAN AND POOR DRAINAGE FLOODING...WHILE FLASH FLOODING OF
SMALLER STREAMS WILL ALSO BE POSSIBLE. THE COMBINATION OF
SOUTHERLY WINDS INCREASING TO 10 TO 20 MPH...WITH HIGHER GUSTS AND
PERIODS OF MODERATE TO HEAVY RAIN WILL RESULT IN AN ABUNDANCE OF
DOWNED LEAVES. THESE LEAVES WILL CLOG AND BLOCK STORM DRAINS AND
SEWERS...LIKELY RESULTING IN URBAN FLOODING FROM LATE THIS
AFTERNOON THROUGH THIS EVENING AS THE AREA RECEIVES BETWEEN ONE
HALF AND ONE AND A HALF INCHES...ALONG WITH LOCAL AMOUNTS NEAR TWO
INCHES.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TODAY AND TONIGHT.

ANZ330-335-338-340-345-350-353-355-200900-
LONG ISLAND SOUND EAST OF NEW HAVEN CT/PORT JEFFERSON NY-
LONG ISLAND SOUND WEST OF NEW HAVEN CT/PORT JEFFERSON NY-
NEW YORK HARBOR-PECONIC AND GARDINERS BAYS-
SOUTH SHORE BAYS FROM JONES INLET THROUGH SHINNECOCK BAY-
MORICHES INLET NY TO MONTAUK POINT NY OUT 20 NM-
FIRE ISLAND INLET NY TO MORICHES INLET NY OUT 20 NM-
SANDY HOOK NJ TO FIRE ISLAND INLET NY OUT 20 NM-
418 AM EDT FRI OCT 19 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR ATLANTIC COASTAL WATERS.

.DAY ONE...TODAY AND TONIGHT

SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING WILL PRODUCE
HEAVY RAIN...REDUCING VISIBILITIES. IN ADDITION...SOME OF THE
THUNDERSTORMS MAY PRODUCE WIND GUSTS IN EXCESS OF 35 KT.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

CTZ007-008-011-012-NYZ079-081-200900-
NORTHERN MIDDLESEX-NORTHERN NEW LONDON-SOUTHERN MIDDLESEX-
SOUTHERN NEW LONDON-NORTHEASTERN SUFFOLK-SOUTHEASTERN SUFFOLK-
418 AM EDT FRI OCT 19 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHERN CONNECTICUT AND
SOUTHEAST NEW YORK.

.DAY ONE...TODAY AND TONIGHT
SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND
EVENING. THESE SHOWERS AND THUNDERSTORMS WILL BE CAPABLE OF PRODUCING
HEAVY RAINFALL. THE HEAVY RAINFALL WILL LIKELY PRODUCE URBAN AND
POOR DRAINAGE FLOODING...WHILE FLASH FLOODING OF SMALLER STREAMS
WILL ALSO BE POSSIBLE. THE COMBINATION OF SOUTHERLY WINDS
INCREASING TO 10 TO 20 MPH...WITH HIGHER GUSTS AND PERIODS OF
MODERATE TO HEAVY RAIN WILL RESULT IN AN ABUNDANCE OF DOWNED
LEAVES. THESE LEAVES WILL CLOG AND BLOCK STORM DRAINS AND
SEWERS...LIKELY RESULTING IN URBAN FLOODING FROM LATE THIS
AFTERNOON THROUGH THIS EVENING AS THE AREA RECEIVES BETWEEN ONE
HALF AND ONE AND A HALF INCHES...ALONG WITH LOCAL AMOUNTS NEAR TWO
INCHES.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED.

PW