834
FXUS61 KALY 230147
AFDALY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
845 PM EST SUN NOV 22 2009
SYNOPSIS
HIGH PRESSURE OVER THE CANADIAN MARITIMES THIS EVENING
WILL CONTINUE TO DRIFT NORTHEAST TONIGHT...AS A LOW PRESSURE SYSTEM
ALONG THE CAROLINA COAST STARTS TO MOVE NORTHEASTWARD. THIS LOW
PRESSURE SYSTEM WILL PASS FAR EAST OF CAPE COD ON TUESDAY...
RESULTING IN MAINLY LIGHT PRECIPITATION ACROSS MUCH OF OUR REGION
MONDAY NIGHT INTO TUESDAY. A SERIES OF MUCH STRONGER STORMS WILL
IMPACT OUR REGION LATER IN THE WEEK...RESULTING IN UNSETTLED WEATHER
FROM THANKSGIVING THROUGH MUCH OF THE HOLIDAY WEEKEND.
NEAR TERM /UNTIL 6 AM MONDAY MORNING/
SKIES WERE CLEAR ACROSS THE REGION AND WINDS WERE CALM OR NEARLY
SO...IDEAL CONDITIONS FOR RADIATIONAL COOLING. TEMPERATURES WERE
DROPPING AND IN MANY LOCATIONS WERE WITHIN TWO OR THREE DEGREES
OF THE DEWPOINT. HAVE ADJUSTED GRIDS PER LATEST OBS AND TRENDS.
HAVE INCREASED THE AREAL EXTENT OF THE VALLEY FOG. GLENS FALLS
ALREADY DROPPED BELOW THE IFR THRESHOLD SHORTLY AFTER 8PM ALTHOUGH
IT HAD IMPROVED TO MVFR. WE EXPECT THIS IMPROVEMENT WILL BE
TEMPORARY. LOWERED TEMPS AND OVERNIGHT LOWS ACROSS THE EASTERN
MOHAWK VALLEY AND CAPITAL DISTRICT BASED ON MOST RECENT OBS.
THE 00Z ALY SOUNDING SHOWED A RATHER STRONG INVERSION JUST BELOW
THE 850 HPA LEVEL WITH A TEMPERATURE OF PLUS 1 AT 880 HPA AND
PLUS 6 AT 860. THERE WAS AN ABRUPT DRYING ABOVE THAT LEVEL AS
WELL. OVERNIGHT LOWS ARE FORECAST TO RANGE FROM THE LOW 20S IN
THE ADIRONDACKS TO THE LOW 30S IN THE HUDSON VALLEY. SKIES WILL
BE CLEAR FOR MOST OF THE NIGHT...BUT EXPECT SOME LOW STRATUS
MAY FORM IN THE INVERSION OVER THE RIVER VALLEYS AS WELL AS
VALLEY FOG. MORE GENERAL CLOUDINESS...WHICH COVERED SOUTHEASTERN
NEW ENGLAND...IS EXPECTED TO MOVE IN FROM THE EAST AROUND
DAYBREAK.
SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/
FA WILL BE BRUSHED BY COASTAL LOW MAINLY LATE MONDAY INTO TUESDAY
WHICH WILL BE FOLLOWED BY HIGH PRESSURE TUESDAY NIGHT INTO
WEDNESDAY.
FOR MONDAY EXPECT THAT MID AND HIGH CLOUDS WILL START TO INCREASE
QUICKLY MONDAY MORNING FROM SOUTHEAST TO NORTHWEST WITH LOW LEVEL
CLOUDS QUICKLY OVERSPREADING SOUTHEAST PORTION OF FA BEFORE 18Z AS
GOOD MOISTURE CONVERGENCE H10-H8. FOR MONDAY AFTERNOON WILL BRING
CHANCE POPS MAINLY UP TO 190. HIGHS ON MONDAY WILL BE LIMITED BY
CLOUDS AND SLOW RECOVERY FROM OVERNIGHT LOWS. EXPECT HIGHS ON
MONDAY ONLY IN THE 40S ACROSS THE FA.
FOR MONDAY NIGHT INTO TUESDAY THE UNCERTAINTY EXISTS WITH HOW FAR
NORTH AND WEST PRECIPITATION SHIELD WILL EXTEND WITH SURFACE LOW
PASSING WELL EAST OF CAPE COD ON TUESDAY. FOR NOW WILL GO WITH
JUST CHANCE POPS MOST AREAS MONDAY NIGHT INTO TUESDAY...ALTHOUGH
WILL INCLUDE LIKELY POPS MONDAY NIGHT ACROSS FAR SOUTHEAST PORTION
OF FA. H10-H8 FRONTOGENESIS BARELY REACHES SOUTHEAST PORTION OF FA
MONDAY EVENING AND THEN AXIS SLIDES WELL EAST ACROSS FAR SOUTHEAST
NEW ENGLAND AND OFF CAPE COD. THIS EVENT LOOKS TO HAVE VERY
LITTLE QPF TO WORK WITH ACROSS FA AND ONLY HAVE QPF AMOUNTS MONDAY
NIGHT THROUGH TUESDAY FROM LESS THAN A TENTH OF AN INCH FAR NW
PORTION OF FA TO JUST OVER A THIRD OF AN INCH FAR SOUTHEAST
PORTION. ON MONDAY NIGHT WOULD EXPECT THAT ANY PCPN ACRS WRN
ADIRONDACKS WOULD BE IN THE FORM OF SNOW...BUT NOT SURE MOISTURE
WILL MAKE IT THAT FAR NORTH AND WEST. FOR NOW HAVE JUST PLACED A
FEW TENTHS OF AN INCH OF SNOW ACCUMULATION IN THE GRIDS.
EXPECT LOWS MONDAY NIGHT IN THE UPPER 20S TO LOWER 4S0 WITH HIGHS
ON TUESDAY IN THE UPPER 40S TO LOWER 50S.
FOR TUESDAY NIGHT HIGH PRESSURE EXPECTED TO BUILD ACROSS FA WITH
LOWS IN THE UPPER 20S TO MID 30S AND THIS WILL QUICKLY BE FOLLOWED
BY INCREASING CLOUDS ON WEDNESDAY AHEAD OF NEXT SYSTEM LIFTING
INTO THE UPPER GREAT LAKES LATE IN THE DAY. FOR NOW WILL ONLY
INCLUDE SLIGHT CHANCE POPS ACROSS FAR WESTERN ZONES WEDNESDAY
AFTERNOON. HIGHS ON WEDNESDAY EXPECTED TO BE IN THE UPPER 40S TO
LOWER 50S.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
MUCH OF THE EXTENDED PERIOD WILL BE DOMINATED BY A DEVELOPING TROUGH
ACROSS THE EASTERN CONUS AND THE POSSIBILITY OF A PHASED STORM
SYSTEM AFFECTING THE NORTHEAST.
ON THANKSGIVING EVE INTO THANKSGIVING...A SLOW MOVING CUTOFF TROUGH
WILL BE MOVING ACROSS THE GREAT LAKES. AT THE SAME TIME...SFC LOW
PRESSURE WILL BE DEVELOPING IN THE SOUTHERN STREAM IN THE VICINITY
OF FLORIDA. AHEAD OF THE APPROACHING CUTOFF TROUGH...SOUTHERLY FLOW
WILL ALLOW FOR WEAK ISENTROPIC LIFT ACROSS OUR AREA...WHICH MAY
ALLOW FOR SOME SHOWERS. WITH 850 HPA TEMPS REMAINING ABOUT 1-5
DEGREES C...THIS SHOULD BE IN THE FORM OF RAIN SHOWERS. THE ACTIVITY
WILL BE RATHER SCT DUE TO THE WEAK FORCING...SO WILL KEEP POPS IN
THE CHC RANGE.
BY THURSDAY NIGHT...HOWEVER...THE FORECAST GETS A BIT MORE
INTERESTING...HOWEVER...STILL MUDDLED DUE TO SOME MODEL
INCONSISTENCIES. THE LARGE UPPER TROUGH OVER THE GREAT LAKES BEGINS
TO SHIFT EASTWARD TOWARDS THE UPPER OHIO VALLEY AND TAKES ON A MORE
NEGATIVE TILT AT 500 HPA. MEANWHILE...SFC PRESSURE BEGIN TO RAPIDLY
DEEPEN OFF THE COAST OF NJ...WITH SURPRISINGLY GOOD AGREEMENT
BETWEEN THE 12 UTC GFS/ECMWF AND MANY MEMBERS OF THE 12 UTC GEFS AS
WELL.
WITH THIS SFC/UPPER LEVEL SETUP...A STEADY PERIOD OF PRECIPITATION
IS LIKELY ACROSS THE REGION FOR SOMETIME THURSDAY NIGHT INTO FRIDAY.
WITH THE AIRMASS STARTING OUT NOT AWFULLY COLD AT ALL...PRECIP TYPE
WILL LARGELY BE ELEVATION DEPENDENT FOR THIS PORTION OF THE STORM.
SOME COLDER AIR WILL BE DRAWN INTO THE SYSTEM THROUGH THE DAY ON
FRIDAY...BUT AT THIS POINT...MUCH OF THE PRECIP IN THE VALLEYS LOOKS
TO BE A COLD RAIN...WITH A RAIN/SNOW MIX ACROSS THE HIGHER
ELEVATIONS...AS SFC TEMPS WILL REMAIN IN THE LOWER 30S ACROSS THE
HIGHER TERRAIN TO THE LOW 40S IN THE VALLEYS.
BY LATE FRIDAY...THE LOW PRESSURE WILL LIKELY BE SOMEWHERE NEAR THE
COAST OF MAINE OR EVEN SLIGHTLY INLAND ACROSS NORTHERN NEW ENGLAND.
HOWEVER...COLDER AIR WILL BE RUSHING IN ON THE WESTERN SIDE OF THE
SYSTEM...AND 850 HPA TEMPS WILL PLUNGE TO 0 TO -4 DEGREES C. THIS
MAY ALLOW FOR SOME LINGERING SNOW SHOWERS DUE TO THE UPPER TROUGH
OVERHEAD...EVEN ACROSS THE VALLEYS. SOME STEADY SNOW MAY CONTINUE
ACROSS THE DACKS DUE TO A DEFORMATION BAND...ALTHOUGH THIS WILL
ULTIMATELY DEPEND OF THE EXACT TRACK OF BOTH THE 500 HPA LOW AND SFC
SYSTEM. IN ADDITION...THE STRONG PRESSURE GRADIENT WILL ALLOW FOR
GUSTY NORTHWESTERLY WINDS...ESP ACROSS THE HIGHER TERRAIN AND
CHANNELED VALLEY LOCATIONS.
BY SATURDAY...LINGERING RAIN OR SNOW SHOWERS ARE POSSIBLE DUE TO THE
CYCLONIC FLOW AROUND THE LARGE UPPER TROUGH ACROSS THE NORTHEAST.
PRECIP TYPE WILL LARGELY BE ELEVATION AND DIURNAL
DEPENDENT...ALTHOUGH MAX TEMPS WILL BE LUCKY TO HIT THE 40 DEGREE
MARK...EVEN IN THE VALLEYS.
IT/S IMPORTANT TO NOTE THAT DESPITE SOME SIMILARITIES IN THE
MODELS...THERE IS STILL A GREAT DEAL OF UNCERTAINTY WITH THIS
SYSTEM. THE 12 UTC GGEM SHOWS NO PHASING...AS WELL AS A FEW GEFS
MEMBERS AS WELL. CONFIDENCE WILL BE INCREASED...HOWEVER...IF
SUBSEQUENT MODEL RUNS CONTINUE TO SHOW A SIMILAR SETUP TO TODAY/S
MODEL SUITE.
AVIATION /00Z MONDAY THROUGH FRIDAY/
SKIES HAVE CLEARED ACROSS THE HUDSON VALLEY TERMINALS THIS EVE
ALLOWING FOR TEMPS TO DROP RAPIDLY. WITH T/TD SPREADS LOW AT
KALB/KGFL...AND WITH LIGHT TO CALM WINDS FORECASTED FOR MUCH OF THE
NIGHT...WOULD EXPECT A PERIOD OF RADIATIONAL FOG AT BOTH TERMINALS.
BASED ON WHAT OCCURRED LAST NIGHT...WOULD EXPECT IFR FOG AT KGFL AS
EARLY AS 03Z...AND DEF FROM 06Z UNTIL SUNRISE. KALB IS A BIT
TRICKIER...AS WOULD EXPECT MVFR FOG THERE AS EARLY AS 05Z...AND DEF
AFTER 07Z...BUT AM NOT CONFIDENT THAT IFR FOG WILL DEVELOP AT ALL.
IF IT DOES OCCUR...IT WOULD PROBABLY BE JUST AN HOUR OR TWO BEFORE
SUNRISE...AND THE 06Z TAF ISSUANCE SHOULD HAVE A BETTER HANDLE ON
THIS AT THAT POINT. MEANWHILE...KPOU EXPERIENCED LOW CLOUDS THROUGH
THE LATE AFTN...SO T/TD SPREAD NOT QUITE AS LARGE THERE. IN
ADDITION...SOME LOW CLOUDS MAY DEVELOP THERE LATE TONIGHT DUE TO AN
UPPER LOW OVER NJ...SO WILL ONLY EXPECT MVFR FOG AT WORST THERE FOR
A BRIEF PERIOD BEFORE SUNRISE.
ON MONDAY...THE MAIN AVIATION CONCERNS WILL BE AT KPOU...WHERE LOW
STRATUS WILL CONTINUE TO DEVELOP THROUGH THE MORNING HOURS...AS THE
UPPER LEVEL LOW REMAINS NEARBY THE REGION. THIS WILL LIKELY LEAD TO
MVFR CIGS THERE. THIS STRATUS WILL ATTEMPT TO MOVE UP THE HUDSON
VALLEY...WHICH COULD EVEN LEAD TO MVFR CIGS AT KALB FOR THE MON AFTN
HOURS. KGFL SHOULD BE FAR ENOUGH NORTH TO REMAIN VFR ALL DAY. IN
ADDITION...SOME RAIN SHOWERS MAY BEGIN TO AFFECT KPOU BY THE MID
AFTN...WHICH COULD POTENTIALLY DROP VSBYS TO MVFR LEVELS THERE AS
WELL.
WINDS WILL BE NEARLY CALM OVERNIGHT. ON MONDAY...A LIGHT EAST TO
NORTHEAST SFC WIND OCCUR AT ALL TERMINALS...AT SPEEDS GENERALLY 5
KTS OR LESS.
OUTLOOK...
MON NIGHT-TUE...VFR-MVFR...CHC OF RAIN, MAINLY KPOU.
WED...VFR...CHC OF SHOWERS.
THU-FRI...MVFR/IFR...RAIN POSSIBLE LATE THU THROUGH FRI.
HYDROLOGY
WITH DRY CONDITIONS EXPECTED TO LAST AT LEAST INTO MONDAY RIVERS
WILL CONTINUE RECEDE THROUGH MONDAY. THE NEXT THREAT OF
PRECIPITATION WILL BE LATE MONDAY INTO TUESDAY. EXPECT TOTAL QPF
AMOUNTS TO BE FAIRLY LIGHT WITH LESS THAN A TENTH OF AN INCH OF
QPF ACROSS NW ZONES TO A LITTLE OVER A THIRD OF AN INCH FAR
SOUTHEAST ZONES. THIS EVENT SHOULD HAVE VERY LITTLE IMPACT ON
RIVERS AND STREAMS. FURTHER OUT AN UNSETTLED PERIOD OF WEATHER
THURSDAY INTO THE WEEKEND COULD RESULT IN SIGNIFICANT
PRECIPITATION AMOUNTS.
FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING
OBSERVED AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE
VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON
OUR WEBSITE.
ALY WATCHES/WARNINGS/ADVISORIES
CT...NONE.
NY...NONE.
MA...NONE.
VT...NONE.
SYNOPSIS...11
NEAR TERM...RCK
SHORT TERM...11
LONG TERM...FRUGIS
AVIATION...FRUGIS
HYDROLOGY...11
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