122
FXUS61 KBTV 241829
AFDBTV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BURLINGTON VT
229 PM EDT THU JUL 24 2008
SYNOPSIS
THE POTENTIAL FOR HEAVY RAIN AND FLOODING WILL CONTINUE THROUGH
MUCH OF THE DAY ACROSS A GOOD DEAL OF THE NORTH COUNTRY. THIS
WILL BE IN RESPONSE TO A SLOW MOVING UPPER LEVEL TROUGH OF LOW
PRESSURE OVER THE OHIO VALLEY INTERACTING WITH TROPICAL MOISTURE
FLOWING NORTHWARD INTO NEW ENGLAND. THE POTENTIAL FOR MORE HEAVY
RAIN WILL CONTINUE THROUGH EARLY THIS EVENING.
NEAR TERM /UNTIL 6 PM THIS EVENING/
AS OF 1100 AM EDT THURSDAY...WIDESPREAD 1 TO 3 INCH RAIN TOTALS
LAST NIGHT IN VERMONT...A BIT LESS IN NORTHERN NY. MUCH OF THE
AREA SAW A LULL IN THE PCPN EARLIER THIS MORNING...BUT RAIN HAS
RETURNED TO MUCH OF THE REGION AS OF LATE THIS MORNING...AS
ADVERTISED IN DISCUSSION BELOW. EXPECT THE RAIN TO CONTINUE
THROUGH FIRST PART OF THE AFTERNOON...AFTER WHICH TIME SOME BREAKS
IN COVERAGE EXPECTED AS LATEST RADAR INDICATING A BIT OF A DRY
SLOT LIFTING MOVING INTO SRN VT. BUT MORE CONVECTIVE TYPE PCPN
EVIDENT FURTHER SOUTH AND WEST...SO OVERALL THE FCST OF RAIN FOR
THIS PM LOOKS GOOD...AND THE RAIN MAY BE MODERATE TO PSBLY HEAVY
AT TIMES. CAN'T RULE OUT AN EMBEDDED THUNDERSTORM OR TWO AS WELL.
RAINFALL RATES IN PCPN THIS MORNING ARE GENERALLY A TENTH TO A
QUARTER INCH AN HOUR...WITH LOCALLY HIR AMOUNTS. EXPECT THIS TO
REMAIN THE CASE THIS PM...WITH AXIS OF HEAVIER RAIN SLOWLY
SHIFTING TO THE EAST IN RESPONSE TO APRCH OF DEEP UPPER LEVEL
TROUGH AND ASSOCD SFC BOUNDARY. NO CHANGE TO CURRENT FLOOD WATCH
THAT IS IN EFFECT.
PREVIOUS DISCUSSION...
MODERATE TO HEAVY RAINFALL HAS MOVED OUT OF THE AREA EARLY THIS
MORNING AND THERE WILL BE A SHORT BREAK IN THE PERSISTENT
PRECIPITATION...THEN MORE RAIN LATER THIS MORNING AND THROUGH THE
DAY. DEEP SOUTHERLY FETCH WITH TROPICAL ORIGINS FLOWING UP AHEAD
OF A PRONOUNCED UPPER TROUGH OVER THE OHIO VALLEY WILL CONTINUE TO
BE MAIN FORCING FEATURE FOR AXIS OF HEAVIEST RAINFALL WHICH WILL
SET UP ALONG CHAMPLAIN VALLEY BEFORE SLIDING EAST LATER TODAY AS
UPPER LEVEL TROF AND SURFACE BOUNDARY ALSO PUSH EAST. SYNOPTIC
SCALE PATTERN CONTINUES TO BE CONDUCIVE TO HEAVY PRECIPITATION AND
THUS FLOOD WATCH WILL CONTINUE THROUGH TONIGHT AS UPPER TROUGH
MOVES EAST AND DEEP MOISTURE FLOWS NORTHWARD. SHOULD SEE SMALLER
STREAMS AND CREEKS RISING RAPIDLY...PONDING ON ROADWAYS...THEN A
TREND TOWARD RAPID RISES ON LARGER MAINSTEM RIVERS LATER TODAY.
CAN SEE A LOT OF 1 TO 3 INCH RAIN AMOUNTS FROM THIS EVENT WITH AN
AXIS OF 2 TO 4 INCHES ACROSS PARTS OF WESTERN VERMONT WITH SOME
ISOLATED 5 INCH READINGS.
SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/
AS OF 500 AM EDT THURSDAY...RAIN WILL SLOWLY EXIT TO THE EAST
TONIGHT AND DRIER AIR WILL BEGIN TO WRAP AROUND THE SOUTHEAST
SIDE OF THE LOW PRESSURE SYSTEM. GFS CONTINUES TO SHOW THE PRECIP
ENDING ABOUT 6 HOURS SOONER THAN THE NAM. RAINFALL TOTALS WITH
THE EVENT STILL EXPECT TO AVERAGE 2 TO 4 INCHES IN THE WATCH
AREA...WITH LOCALIZED AMOUNTS OF 5+ INCHES. LINGERING SHWRS
FRIDAY...MAINLY IN THE MORNING...THEN MAINLY DRY FOR LATER
FRI/FRI NIGHT AS WEAK AND TEMPORARY RIDGING DEVELOP OVER THE
AREA. BY SATURDAY NEXT LOW PRESSURE SYSTEM ON DECK TO AFFECT THE
AREA WILL BE TAKING SHAPE OVER CANADA...BECOMING VERY VERTICALLY
STACKED.
LONG TERM /SUNDAY THROUGH THURSDAY/
AS OF 229 PM EDT THURSDAY...FRNTL BOUNDARY ACROSS THE CENTRAL
PORTION OF THE CWA BY SUNDAY MORNING...AND EAST OF THE AREA BY
THE EVENING HRS. FRNT DOES HOLD TOGETHER AS IT PUSHES THRU THE
FA...SO WILL BE KEEPING LIKELY POPS FOR VT. WILL CONTINUE MENTION
OF SOME TRW FOR THE AFTNOON HRS...ALTHOUGH POTENTIAL WILL BE
LIMITED DO TO CLD COVER...BUT DAYTIME HEATING ALONG BOUNDARY MAY
TRIGGER A FEW ISO TRW. UPPER LOW REMAINS OVER QUEBEC INTO MONDAY.
THIS WILL ALLOW A WEAK SHORTWAVE TO PINWHEEL SE OVER THE AREA. ITS
POSITIONING WILL ALLOW BEST CHANCES IN NORTHERN AREAS...SO WILL
HIGHLIGHT THERE. THIS SHORTWAVE CLRS THE AREA BY NIGHTFALL WITH
HIGH PRESSURE BUILDING IN FROM THE WEST. SOME RESIDUAL CLDS WILL
REMAIN OVERNGT IN NE VT...SO WILL KEEP SL CHANCE IN FOR THAT AREA.
TUES/WED CONTINUE TO LOOK LIKE GD DAYS FOR REPRIEVE OF RAINY WX AS
SFC HIGH SITS OVER THE REGION. BY THURSDAY...RIDGE SHIFTS OFFSHORE
ALLOWING WAA ON SSW FLOW TO WORK INTO THE AREA. THIS MINOR INCR IN
INSTAB AHEAD OF NEXT SYSTEM FOR FRIDAY...MAY TRIGGER A FEW
RW/TRW...ESPECIALLY IN THE AFTNOON SO WILL PUT IN SL CHANCE.
AVIATION /19Z THURSDAY THROUGH TUESDAY/
THROUGH 18Z FRIDAY...MAINLY MVFR/IFR RAINFALL THRU 00Z FRIDAY AS
SYSTEM WORKS THRU THE REGION. VSBY DOWN TO 2-3SM AT TIMES...WITH
CEILINGS OVC015-030. AFT 00Z FRI...MAINLY MVFR FG W/ OCNL IFR FG
ESPECIALLY AT SLK/MPV WHERE VSBY COULD LWR DOWN TO 1SM AT TIMES.
AFT 12Z-13Z VFR COND AT ALL SITESWITH SCT LOW CLDS 020-040.
SOUTHERLY WINDS AROUND 10-15KTS WILL GO LGT/VAR AT TIMES AFT 00Z
FRI...BECM WSW 5-10KTS AFT 12Z-13Z FRI. HIR TRRN OBSCD AT TIMES.
18Z FRIDAY THROUGH MONDAY...UPPER LOW LIFTS OUT OF REGION DURING
DAY FRIDAY...WITH SURFACE HIGH PRESSURE MOVING ACROSS TAF SITES.
FRIDAY IS ABOUT THE ONLY DRY DAY FORECAST DURING THIS TIME
PERIOD...WITH VFR CIGS/VIS. MORE RAIN EXPECTED FOR SATURDAY AND
SUNDAY ESPECIALLY IN THE AFTERNOON...THEN DEEPENING LOW PRESSURE
MONDAY INCREASES RAIN CHANCES. VFR CONDITIONS WITH OCCASIONAL MVFR
IN SHOWERS AND THUNDERSTORMS SATURDAY AND SUNDAY...THEN MVFR IN
RAIN AND CIGS MONDAY.
HYDROLOGY
AFTER A LULL IN THE PCPN EARLIER THIS MORNING...RAIN HAS RETURNED
TO MUCH OF THE FORECAST AREAS AS OF LATE THIS MORNING. DYNAMIC
FORCING ASSOCIATED WITH A VERY SLOW MOVING UPPER TROUGH OVER THE
EASTERN GREAT LAKES MOVES INTO THE AREA TODAY. THIS IS A FAVORABLE
SYNOPTIC PATTERN FOR HEAVY RAIN AND GIVEN THE ALREADY SATURATED
ENVIRONMENT...IT WILL NOT TAKE MUCH TO CAUSE ADDITIONAL FLOODING.
LOOK FOR TOTAL RAINFALL AMOUNTS ACROSS EASTERN NEW YORK AND
VERMONT IN THE 2 TO 4 INCH RANGE WITH LOCALIZED AMOUNTS TO 5
INCHES. GIVEN TROPICAL CONNECTION TO THIS EVENT...FAVORABLE
SYNOPTIC SCALE PATTERN...ALREADY WET CONDITIONS...AND LOW FLASH
FLOOD GUIDANCE VALUES IT WILL NOT TAKE MUCH TO HAVE POTENTIALLY
SERIOUS FLOOD CONCERNS. THUS THIS SITUATION WILL CONTINUE TO BE
CLOSELY MONITORED. FLOOD WATCH HAS BEEN EXTENDED TO NOW END ON
FRIDAY MORNING ALLOWING FOR SOME OF THE SLOWER RESPONDING RIVERS
AND CREEKS TO HAVE A LULL BEHIND END OF PRECIP.
BTV WATCHES/WARNINGS/ADVISORIES
VT...FLOOD WATCH THROUGH FRIDAY MORNING FOR VTZ001>012-016>019.
NY...FLOOD WATCH THROUGH FRIDAY MORNING FOR NYZ028-030-031-034-035.
SYNOPSIS...JAN
NEAR TERM...RJS/JAN
SHORT TERM...JAN
LONG TERM...JN
AVIATION...JN/HANSON
HYDROLOGY...
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