192
FXUS61 KALY 241132
AFDALY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
633 AM EST TUE NOV 24 2009
SYNOPSIS
WEAK HIGH PRESSURE WILL BUILD IN FROM EASTERN CANADA
TODAY...POSSIBLY BRINGING SOME BREAKS OF SUNSHINE FOR THE AFTERNOON.
THIS HIGH PRESSURE WILL HOLD INTO WEDNESDAY BEFORE DRIFTING OFFSHORE
BY THANKSGIVING. A FEW DISTURBANCES WILL SPREAD SOME CLOUDS OUR WAY
WITH ONLY MINIMAL CHANCES OF RAIN SHOWERS.
NEAR TERM /THROUGH TODAY/
AS OF 330 AM...RADARS STILL INDICATED SCATTERED LIGHT
SHOWERS...MAINLY EAST OF THE HUDSON VALLEY. MORE THAN
LIKELY...PATCHY DRIZZLE OUT THERE WHICH IS HARD TO DETECT ON RADAR.
THE MAIN DISTURBANCE STAYED WELL TO OUR SOUTH AND EAST BUT A PRETTY
GOOD ONSHORE FLOW SATURATED THE LOWER LEVELS OF THE COLUMN.
NOW...THE CHALLENGE IS TO FORECAST WHEN ANY AND ALL PRECIPITATION
ENDS AND IF THE CLOUDS WILL BREAK UP.
THE LATTER IS NO EASY TASK SINCE ONCE AGAIN...ANY MIXING WILL BE
MITIGATED BY THE MERE FACT THAT WE ARE DEALING WITH NO MORE THAN A
23 DEGREE SUN ANGLE. ALSO...MODEL SOUNDINGS INDICATE A PRETTY
IMPRESSIVE SHALLOW INVERSION THAT WOULD HAVE BE WORKED OUT BEFORE
MIXING WOULD SCOUR THE CLOUDS.
WE FELL ANY SHOWER/DRIZZLE ACTIVITY SHOULD BE OVER BY AFTERNOON IN
ALL AREAS.
WE WILL FOLLOW THE CANADIAN ASTRONOMICAL FORECAST AND FORECAST SOME
"BREAKS" BY AFTERNOON (CLOUD COVER INTO THE HIGH END OF THE
SCATTERED RANGE). THE CANADIAN ASTRONOMICAL FORECAST ACTUALLY LOOKS
SLIGHTLY OPTIMISTIC TO US BUT IT HAS HAD A PRETTY GOOD TRACK RECORD
IN OUR OPINION. BREAKS OR NOT...MODEL SOUNDINGS FROM BOTH THE NAM
AND GFS INDICATE THAT OUR HIGH TEMPERATURES WILL LIKELY FALL A
LITTLE SHORT OF BOTH THE NAM AND MAV MOS NUMBERS...DESPITE STARTING
OUT ON THE MILD SIDE. WE FIGURE HIGH TEMPERATURES WILL TOP OUT
WITHIN A FEW DEGREES OF 50S REGION WIDE...PERHAPS MID 50S IN THE MID
HUDSON VALLEY.
SHORT TERM /TONIGHT THROUGH THURSDAY/
OUR CLOUD CHALLENGE HARDLY ENDS AFTER TODAY. TONIGHT...THE BIG
QUESTION WILL BE WHETHER CLOUDS REFORM UNDERNEATH MOISTURE TRAPPED
UNDERNEATH THE INVERSION OR NOT. AT THE SURFACE...WEAK HIGH PRESSURE
WILL BUILD DOWN FROM CANADA. THE KEY IS THAT THE HIGH IS INDEED
WEAK...AND DEVELOPS UNDERNEATH A RIDGE ALOFT. THIS SETUP FAVORS A
PRETTY GOOD INVERSION WHICH WOULD FAVOR THE REFORMATION OF STRATUS
CLOUDS...AT LEAST IN VALLEY AREAS. IF THE SKY WERE TO REMAIN
CLEAR...FOG WOULD LIKELY FORM.
SIGNALS ARE CROSSED WHETHER THE FOG OR STRATUS CLOUDS WOULD
DOMINATE. SINCE THE JURY IS STILL OUT...WE WILL PLAY IT IN THE
MIDDLE...GOING WITH PARTLY CLOUD CONDITIONS...EXCEPT MORE CLOUDS IN
THE ESPECIALLY THE HUDSON VALLEY. WILL MENTION PATCHY DENSE FOG FOR
NOW. DEWPOINTS UPSTREAM ARE NOT ALL THAT LOW (IN THE 30S) SO WE DO
NOT LOOK FOR TEMPERATURES TO FALL BELOW NORMAL...BUT CERTAINLY
COOLER THAN THIS OVERNIGHT WAS. LOOK FOR LOW TEMPS GENERALLY IN THE
30S...EXCEPT UPPER 20S IN SOME SHELTERED MOUNTAIN VALLEYS IN THE
DACKS.
WEDNESDAY...THE BIG TRAVEL DAY BEFORE THANKSGIVING...STILL LOOKS
MAINLY DRY ACROSS OUR REGION. AFTER STARTING OUT WITH SOME PATCHY
DENSE FOG AND/OR LOW CLOUDS...SOME FILTERED SUNSHINE IS POSSIBLE
BEFORE MORE HIGH CLOUDS MOVE IN FROM THE WEST. THERE IS A SHORT WAVE
FORECAST TO LIFT SOUTHWEST TO NORTHEAST ACROSS OUR REGION.
HOWEVER...INTEGRATED MOISTURE IN THE COLUMN WILL BE LIMITED (ONCE
YOU GET MUCH OFF THE DECK) WITH VERY LITTLE IF ANY ISENTROPIC LIFT.
WE WILL CONTINUE THE SLIGHT CHANCE OF SHOWERS WEST OF THE HUDSON
VALLEY OVER THE ELEVATED TERRAIN...BUT ANY ISOLATED SHOWERS IN THESE
AREAS WOULD BE LIGHT AND SHOULD HAVE ALMOST NO IMPACT ON TRAVEL.
MIXING LOOKS SLIGHTLY BETTER ON WEDNESDAY...BUT STILL LIMITED...AND
NO WHERE NEAR THE TYPICAL H850...OR EVEN H925MB FOR THAT MATTER.
THIS WOULD TRANSLATE TO SURFACE TEMPERATURES A COUPLE POINTS HIGHER
THAN TODAY...GENERALLY IN THE 50-55 RANGE...EXCEPT 45-50 RANGE
ACROSS THE HIGHER TERRAINS. NEVERTHELESS...THESE VALUES ARE A GOOD
5-7 DEGREES OVER NORMAL HIGHS.
"QUITE" WEATHER WILL CONTINUE WEDNESDAY NIGHT ALTHOUGH BY THIS
TIME...A SURFACE RIDGE OVER THE NORTHEAST WILL BEGIN TO BREAK
DOWN. CLOUDS...FROM AN EVOLVING UPPER AIR LOW WELL UPSTREAM...WILL
TEND TO INCREASE. TEMPERATURES OVERNIGHT WILL LIKELY BE ABOUT 5 DEGS
MILDER THAN TUESDAY NIGHT...GENERALLY IN THE 35-40 RANGE...WITH SOME
COLDER READINGS IN OUTLYING REGIONS.
THANKSGIVING WILL SEE THE AFOREMENTIONED UPPER AIR LOW/TROUGH
BEGINNING TO MOVE TOWARDS US FROM THE OHIO VALLEY...BUT AT A SNAILS
PACE. ALL THE GUIDANCE WE HAVE PERUSED WOULD INDICATE NOTHING MORE
THAN A FEW SCATTERED LIGHT SHOWERS OR POCKETS OF DRIZZLE WITH AN
OTHERWISE DRY DAY. THERE COULD EVEN BE A FEW BREAKS OF MIDDAY
SUNSHINE BUT CLOUDS LOOK TO INCREASE DURING THE AFTERNOON. EVEN
SO...HIGH TEMPERATURES LOOKS VERY SIMILAR TO WEDNESDAY. MORE ABOUT
THE EVOLVING UPPER AIR LOW WILL FOLLOW IN THE EXTENDED.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
..CONSIDERABLE UNCERTAINTY REMAINS WITH DEVELOPING NOR-EASTER
UNLIKE THIS TIME YESTERDAY...THE GFS AND ASSOCIATED INTERNATIONAL
GLOBAL MODELS HAVE DIVERGED ONCE AGAIN. THE GFS AND RELATED
ENSEMBLE DATA ARE IN A CLOSE CLUSTER WITH LOW STANDARD DEVIATIONS
ALOFT AND AT THE SURFACE WHICH FAVORS AN IMPRESSIVE NOR-EASTER FOR
THE REGION. HOWEVER...THE GGEM/ECMWF AND EVEN THE 18Z/23 DGEX POINT
TOWARD A FURTHER OFFSHORE SURFACE CYCLONE WITH THE MAIN IMPACT FOR
THE REGION FROM THE UPPER LOW. BASED ON CLOSE COLLABORATION WITH
NEIGHBORING OFFICES AND HPC...WE WILL FAVOR THE 00Z ECMWF AT THE
SURFACE AND BLEND THE 500MB FIELDS WHICH POINTS US TOWARD ANOTHER
SCENARIO. BASED ON CSTAR RESEARCH OF COOL SEASON CUTOFF UPPER
LOWS...WE WILL HAVE TO MONITOR THE HIGHER TERRAIN AS THESE SYSTEMS
CAN PRODUCE A BIT MORE QPF WHICH SEEMS TO MAXIMIZE DURING THIS
MONTH.
WITH THE FURTHER OFFSHORE SURFACE WAVE...UPPER LOW SHOULD BECOME THE
MORE DOMINANT PLAYER HEADING INTO FRIDAY AND HAVE ADJUST POPS
DOWNWARD INTO THE LIKELY RANGE TO AVOID A LARGE SWING FROM THE
PREVIOUS FORECAST. BASED ON THE AFOREMENTIONED CSTAR
RESEARCH...WILL GO TOWARD THE HIGHER END OF LIKELY WITH REGARD TO
POPS AND RAISE THE QPF ROUGHLY A TENTH OF AN INCH PER 1K FEET. THE
QUESTION NEXT BECOMES THE THERMAL PROFILE AS COLD ADVECTION IS
EXPECTED TO PURSUE THROUGH THE DAY. THIS IS EXPECTED TO BE AN
ELEVATION DEPENDENT RAIN/SNOW LINE AS WE HAVE ATTEMPTED TO REFLECT
THIS NOTION IN THE GRIDS/FORECAST THROUGH FRIDAY. EVENTUALLY...THE
COLDER AIR WILL PENETRATE THE ENTIRE COLUMN FRIDAY NIGHT WITH MOST
PRECIP IN THE FROZEN VARIETY. WE WILL CONTINUE TO MONITOR THE
POTENTIAL FOR A DEFORMATION AXIS AS THE UPPER LOW SLOWLY LIFTS
NORTHEAST OVERNIGHT.
THE NEXT CONCERN WILL BE WINDS FRIDAY NIGHT INTO SATURDAY AS 30-50KT
WINDS AT 925MB AND 850MB RESPECTFULLY ARE EXPECTED WITH TIGHT
SURFACE PRESSURE GRADIENT AS DEEP SURFACE LOW OVER THE CANADIAN
MARITIMES. COINCIDING WITH THE COLD ADVECTION THIS MAY JUSTIFY THE
POTENTIAL FOR ADDITIONAL HEADLINES WITH RESPECT TO THE WIND.
THESE HAZARDS WILL BE ADDRESSED IN THE HWO THIS MORNING.
QUIETER WEATHER EXPECTED FOR THE SECOND HALF OF THE WEEKEND AS
SUBSIDENCE UNFOLDS WITH ASSOCIATED HEIGHT AND SURFACE PRESSURE
RISES. A LIGHT OVERRUNNING EVENT...PER THE ECMWF...MAY BRING A
LIGHT WINTRY MIX TO THE REGION OVERNIGHT SUNDAY INTO MONDAY.
CONFIDENCE IN THIS SCENARIO IS QUITE LOW AND WILL ONLY PLACE 20 POPS
AT THIS TIME.
TEMPERATURES THROUGH THE PERIOD WERE A BLEND OF HPC AND ECMWF.
AVIATION /08Z TUESDAY THROUGH SATURDAY/
CLOUD DECK HANGING TOUGH...BUT THE TREND HAS BEEN FOR THEM TO RISE
INTO THE VFR THRESHOLD...AT LEAST AT KALB AND KPOU. HIGH CLOUDS
MOVING OVER THE LOWER ONES MIGHT ACTUALLY HAVE HELP TRANSPORT HEAT
FLUX DOWNWARD AND RAISE THE CONDENSATION POINT. HOWEVER...THE HIGHER
CLOUDS ARE IN THE PROCESS OF LIFTING NORTHWARD SO THE CIGS MIGHT
ACTUALLY SLIP BACK TO MVFR FOR AWHILE LATER THIS MORNING...EXCEPT
REMAINING AT MVFR AT KPOU.
LATER...BY AFTERNOON...SOME DRIER AIR WILL LIKELY ATTEMPT TO SCOUR
THE CIGS AWAY...BUT NOT COMPLETELY. EITHER WAY...VFR CONDITIONS
SHOULD PREVAIL THIS AFTERNOON THROUGH A LITTLE AFTER SUNDOWN. THE
WIND AT ALL THREE TERMINALS WILL BE LIGHT OUT OF THE NORTH OR
NORTHEAST.
BY TONIGHT...IT APPEARS THAT SOME FOG/AND OR AREAS OF LOW CLOUDS
COULD FORM ONCE AGAIN AS MOISTURE "POOLS" BELOW THE INVERSION. FOR
NOW...WE CALLED IT IFR AT ALL STATIONS BEGINNING AT 03Z-06Z. THE
WIND WILL BE LIGHT OR NIL.
OUTLOOK...
WED...VFR/MVFR...CIGS. NO SIGN WX EXPECTED AT THIS TIME. WED
NT...MVFR...CHC IFR FOR FOG/DZ.
THANKSGIVING DAY...VFR/MVFR...CIG...NO SIG WX EXPECTED AT THIS TIME.
THU NGT-FRI...VFR TO MVFR/IFR...RAIN LIKELY. CHC LLWS.
FRI NGT-SAT...MVFR/IFR...CHC -RA CHANGING TO -RASN. CHC LLWS.
HYDROLOGY
NO HYDRO PROBLEMS THROUGH THANKSGIVING DAY.
VERY LITTLE RAIN FELL WITH THE LAST SYSTEM AND HAD NO AFFECT ON
RIVERS AND STREAMS. MAINLY DRY WEATHER EXPECTED THROUGH
THANKSGIVING...WITH ANY LIGHT SHOWERS BRINGING WELL UNDER A TENTH OF
AN INCH AND HAVING NO BEARING ON WATERSHEDS THROUGH THE HYDROLOGICAL
SERVICE AREA.
THE NEXT CHANCE OF WIDESPREAD PRECIPITATION WILL BE FROM LATE
THURSDAY NIGHT INTO THE WEEKEND...AS A POTENTIALLY STRONG STORM MAY
IMPACT THE REGION. SIGNIFICANT PRECIPITATION IS POSSIBLE BUT PRECIP
AMOUNTS AND TYPE CONTINUE TO BE HIGHLY UNCERTAIN AT THIS TIME.
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...HWJIV
NEAR TERM...HWJIV
SHORT TERM...HWJIV
LONG TERM...BGM
AVIATION...BGM
HYDROLOGY...HWJIV
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