FXUS61 KALY 021118
AFDALY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
618 AM EST WED DEC 2 2009
.SYNOPSIS...
A RIDGE OF HIGH PRESSURE WILL MOVE OFF THE EAST COAST
TODAY...PROVIDING DRY AND RELATIVELY MILD WEATHER. A STRONG LOW
PRESSURE SYSTEM WILL TRACK FROM THE GULF COAST INTO THE EASTERN
GREAT LAKES TONIGHT AND THURSDAY...BRINGING A SOAKING RAIN TO THE
REGION...FOLLOWED BY COLDER AIR FOR THE END OF THE WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 4 AM EST...PATCHY CLOUDS ARE PERSISTING ACROSS NW AREAS...AS
MOISTURE REMAINS TRAPPED BENEATH RAPIDLY LOWERING INVERSION. THESE
CLOUDS SHOULD GRADUALLY ERODE FROM SW TO NE AROUND
DAYBREAK...ALTHOUGH MAY PERSIST A BIT LONGER ACROSS PORTIONS OF
SOUTHERN VT...AND PERHAPS THE SOUTHERN DACKS.
WE EXPECT A BRIEF PERIOD OF SUNSHINE THIS MORNING...BEFORE HIGH
CLOUDS FROM THE SOUTHWEST INCREASE BY MID TO LATE MORNING...AND
THICKEN DURING THE AFTERNOON. GIVEN THE EXPECTATION FOR LIMITED
SUNSHINE...ALONG WITH SHALLOW MIXING TO ONLY 950-975 MB...WE HAVE
INDICATED MAXES CLOSER TO...OR EVEN A BIT BELOW TO COOLER MET
MOS...WITH MAINLY 45-50 EXPECTED IN THE VALLEYS...AND LOWER/MID 40S
ACROSS HIGHER ELEVATIONS. AS A SE WIND DEVELOPS LATER
TODAY...LOCALLY HIGHER MAX TEMPS ARE POSSIBLE FOR AREAS IMMEDIATELY
W OF THE SOUTHERN GREENS...BERKS AND TACONICS DUE TO
DOWNSLOPING...PERHAPS REACHING THE LOWER 50S.
SOME LIGHT RAIN COULD REACH EXTREME S/W AREAS AROUND OR SHORTLY
AFTER SUNSET...THUS WE HAVE INDICATED SLIGHT CHC POPS FOR THESE
AREAS TOWARD EVENING.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
TONIGHT...POTENT STORM SYSTEM WILL APPROACH FROM THE SW. RAPIDLY
STRENGTHENING LOW LEVEL JET WILL TRANSPORT ABUNDANT MOISTURE
NORTHWARD...RESULTING IN WIDESPREAD RAINFALL...DEVELOPING FROM SSW
TO NNE THIS EVENING...AND PERSISTING OVERNIGHT. GIVEN PWAT/S
APPROACHING OR EVEN SURPASSING 1 INCH...AND STRONG UPPER LEVEL
FORCING...A FEW PERIODS OF HEAVY RAIN ARE LIKELY. IN ADDITION...AS
850 LI'S DIP INTO INTO SLIGHTLY NEGATIVE TERRITORY...SOME EMBEDDED
ELEVATED TSTMS ARE POSSIBLE TOWARD DAYBREAK. WINDS WILL ALSO
INCREASE FROM THE SE TO S...WITH SOME GUSTS POSSIBLY REACHING 40-45
MPH ACROSS HIGHER ELEVATIONS AND CHANNELED N/S ORIENTED VALLEYS
WITHIN THE SOUTHERN GREENS/WESTERN BERKS/TACONICS. THESE WINDS
FORECAST TO BE JUST BELOW ADVISORY LEVELS...BUT WILL MENTION IN
HWOALY...AS SOME POTENTIAL STILL EXISTS FOR WIND GUSTS TO REACH THE
ADVISORY LEVELS IN THESE REGIONS.
THU...LOW PRESSURE SHOULD TRACK ACROSS...OR JUST N/W OF THE FORECAST
REGION DURING THE MORNING. STEADY RAIN SHOULD BECOME SHOWERY FROM SW
TO NE SHORTLY AFTER DAYBREAK. HOWEVER...STRONG DYNAMICS...COMBINED
WITH POTENTIAL DRYING OF MID LEVELS COULD ALLOW FOR A PERIOD OF
SFC-BASED INSTABILITY...POTENTIALLY RESULTING IN A NARROW...LOW
TOPPED LINE OF CONVECTION...ESP N AND W OF ALBANY DURING THE MID TO
LATE MORNING HOURS. SHOULD THIS OCCUR...THERE IS ALSO THE
POSSIBILITY OF DRAGGING STRONGER WINDS FROM ALOFT TO THE SFC. WE
WILL NEED TO WATCH THIS SITUATION...AS ISOLATED DAMAGING WIND GUSTS
FROM CONVECTION COULD OCCUR WITH PASSAGE OF THE MAIN SHORTWAVE AND
ATTENDANT WIND SHIFT LINE. THEREAFTER...SKIES SHOULD BECOME PARTLY
TO MOSTLY SUNNY...BEFORE LOWER CLOUDS INCREASE ONCE AGAIN ACROSS
CENTRAL AND WESTERN AREAS AS COLD ADVECTION INTENSIFIES. SOME RAIN
SHOWERS MAY ALSO REDEVELOP ACROSS PORTIONS OF THE SW ADIRONDACKS BY
LATE AFTERNOON GIVEN INCREASING OVER WATER TRAJECTORY OF W WINDS
OVER LAKE ONTARIO. AS FOR SYNOPTIC WINDS...BEST ISALLOBARIC RISES
APPEAR TO OCCUR OVER WESTERN AREAS. HOWEVER...GIVEN THE EXPECTED
TRACK OF THE LOW TOWARD THE NE...ISALLOBARIC WIND COMPONENT WOULD
FAVOR A MORE WSW FLOW...POSSIBLY REDUCING CHANNELING POTENTIAL DOWN
THE MOHAWK RIVER VALLEY IN THE WAKE OF THE LOW. THUS...WE HAVE
INDICATED SUB ADVISORY GUSTS OF AROUND 40 MPH FOR THU AFTERNOON.
AGAIN...WILL MENTION IN HWOALY...AS LATER MODEL TRENDS COULD
INDICATE STRONGER WIND POTENTIAL. AS FOR TEMPS...WE HAVE LEANED
CLOSER TO THE WARMER MET MOS...GIVEN POTENTIAL DEEP MIXING...AND A
SW/W DOWNSLOPING WIND. MAXES SHOULD BE A BIT COOLER ACROSS NORTHERN
AREAS...WHERE LOW LEVEL RAIN COOLED AIR AND LOW CLOUDS MAY BE MORE
DIFFICULT TO SCOUR OUT INITIALLY.
THU NT-FRI...FORECAST SOUNDING HINT AT RAPIDLY LOWERING INVERSION
HEIGHTS ONCE AGAIN...WHICH SHOULD TRAP LOW LEVEL MOISTURE AND RESULT
IN CLOUDS ACROSS CENTRAL AND NORTHERN AREAS MUCH OF THU
NT...POSSIBLY LINGERING INTO FRI AM. AS FOR LAKE EFFECT
POTENTIAL...ALTHOUGH SOME SNOW SHOWERS ARE EXPECTED...THE LOWERING
INVERSION HEIGHTS...COMBINED WITH RELATIVELY WARM CLOUD TOP TEMPS
GENERALLY WARMER THAN -10C...SHOULD PREVENT SIGNIFICANT ACCUMS FROM
OCCURRING. ANY LAKE BANDS THAT DEVELOP SHOULD INITIALLY MIGRATE
SOUTH...INTO THE WESTERN MOHAWK VALLEY THU NT...THEN SHOULD LIFT
NORTHWARD INTO NORTHERN HERKIMER/HAMILTON COS DURING FRI GIVEN
BACKING LOW LEVEL WINDS. ELSEWHERE...EXPECT PARTLY TO MOSTLY SUNNY
SKIES ON FRI...WITH MAX TEMPS GENERALLY RANGING FROM THE LOWER/MID
40S WITHIN THE VALLEYS...AND MID/UPPER 30S ACROSS HIGHER ELEVATIONS.
FOR THU NT/FRI AM MINS...EXPECT HAVE INDICATED MINS CLOSER TO THE
WARMER MET MOS ACROSS NORTHERN AREAS...WHERE CLOUDS AND SOME WIND
ARE EXPECTED...AND COLDER TO THE S WHERE SKIES SHOULD BECOME MOSTLY
CLEAR...AND WINDS LIGHT TO CALM.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
MODEL CONSENSUS FAVORS THE FURTHER OFFSHORE TRACK WITH NEXT EAST
COAST CYCLOGENESIS AS NEXT SHORT WAVE ROUNDS THE BASE OF THE UPPER
LOW OVER THE GREAT LAKES REGION. MOISTURE IN THE FORM OF CLOUDINESS
WILL BE THE MOST EVIDENT FRIDAY NIGHT WITH A WINDOW OF OPPORTUNITY
FOR A LITTLE SNOW TO EVOLVE ACROSS THE SOUTHERN REACHES OF THE MID
HUDSON VALLEY AND PORTIONS OF NW CT INTO SATURDAY. THE SURFACE AND
UPPER WAVE EXIT EAST OF THE REGION SATURDAY NIGHT WITH A BROAD
CYCLONIC FLOW REMAINING OVER THE REGION. IT SEEMS...AT THIS
TIME...SUBSIDENCE WILL BE RATHER PRONOUNCED OVER THE DACKS TO
PRECLUDE MUCH IN THE WAY OF LAKE EFFECT ACTIVITY FRIDAY NIGHT
THROUGH EARLY SATURDAY. THIS IS EXPECTED TO CHANGE THROUGH THE DAY
SATURDAY AND INTO SUNDAY WITH INCREASING STEEP LOW LEVEL LAPSE RATES
AS DELTA T/S INCREASE TOWARD 20C. LOW LEVEL FLOW TRAJECTORY IS
BETWEEN 270-290 DEGREES WITH A BIT MORE NORTHWEST FLOW TRAJECTORY
EXPECTED LATER IN THE WEEKEND. WE WILL CONTINUE TO WATCH THIS
CLOSELY AS THIS COULD BE THE FIRST EVENT OF THIS TYPE FOR THE DACKS
AND WESTERN MOHAWK VALLEY.
A LITTLE MORE TRANQUILITY EXPECTED FOR THE START OF NEXT WEEK AS
NARROW REGION OF HIGHER SURFACE PRESSURES SLIDES ACROSS THE REGION.
FROM THIS POINT...MODELS DIVERGE SIGNIFICANTLY AS A STRONG SHORT
WAVE DIVES SOUTH ACROSS THE PACIFIC COAST. A VERY COMPLEX AND
TIMING INTERACTION OF ADDITIONAL SHORT WAVES DOWNSTREAM WILL MAKE
FOR AN INTERESTING MID WEEK FORECAST. THE ECMWF WOULD INDICATE
THE POTENTIAL FOR THE SEASONS FIRST WIDESPREAD SNOW EVENT /SOME RAIN
IN THE VALLEY LOCATIONS/ WHILE THE GFS IS SOMEWHAT RESEMBLES THE
SYSTEM ABOUT TO IMPACT THE AREA TONIGHT. ENSEMBLES DO NOT OFFER
MUCH INSIGHT WITH HIGH STANDARD DEVIATIONS AT THE SURFACE AND 500MB
THIS MORNING SO WILL CONTINUE WITH LOW CHANCE POPS AND A MIXTURE OF
RAIN/SNOW.
TEMPERATURES THROUGH THE PERIOD WILL AVERAGE NEAR TO SLIGHTLY BELOW
NORMAL AND PRECIPITATION NEAR TO SLIGHTLY BELOW NORMAL.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
STRATUS DECK REAPPEARED AGAIN AND WILL SLIDE NORTH OF THE CAPITAL
REGION AND KGFL THIS EARLY WEDNESDAY MORNING. THE THREAT OF FOG
SEEMS TO HAVE ABATED BUT WILL LEAVE A TEMPO MVFR GROUP FOR KPOU
WHERE DEWPOINT DEPRESSIONS ARE LOW AT THE PRESENT TIME.
WE WILL HAVE A GOOD PERIOD OF VFR CONDITIONS THROUGH THE DAY BUT
THIS TOO WILL QUICKLY CHANGE TOWARD SUNSET FROM SOUTH TO NORTH.
CONDITIONS WILL DETERIORATE QUICKLY THIS EVENING FROM VFR CONDITIONS
DOWN TO IFR WITHIN A COUPLE OF HOURS IN BOTH CIG/VIS. SURFACE WIND
FORECAST WILL BE A CHALLENGE...BUT ALOFT WILL BE AN INCREASING
SOUTHEAST WIND TOWARD 50KTS. HENCE...HAVE INCLUDED A LLWS FOR ALL
TAF LOCATIONS OVERNIGHT. IN ADDITION...TRENDS IN THE LATEST
GUIDANCE AND UPSTREAM OBSERVATIONS SUGGEST THE POTENTIAL FOR
CONVECTION AND HAVE INCLUDED A CB GROUP OVERNIGHT AS WELL. WE WILL
CONTINUE TO MONITOR TRENDS.
OUTLOOK...
THU AM...MVFR-IFR IN RAIN/FOG. POSS LLWS.
THU PM-FRI...VFR...NO SIG WX. WINDY.
FRI NT-SAT NT...VFR...CHC MVFR -SN SOUTH OF KGFL.
SUN...VFR...NO SIG WX.
&&
.HYDROLOGY...
NO HYDRO PROBLEMS ARE EXPECTED THROUGH TODAY.
A SYSTEM APPROACHING FROM THE OHIO VALLEY IS FORECAST TO BRING A
WIDESPREAD RAINFALL...WITH TOTAL RAINFALL OF ONE TO ONE AND A HALF
INCHES LIKELY...TONIGHT AND EARLY THURSDAY. THIS RAINFALL WILL CAUSE
SIGNIFICANT RISES ON THE RIVERS...BUT THEY WILL LIKELY STOP SHORT OF
FLOOD STAGE.
MODELS INDICATE THAT MOST OF THE RAIN WILL OCCUR IN THE MIDDLE OF
THE NIGHT...BETWEEN MIDNIGHT WEDNESDAY AND AROUND 7AM THURSDAY. THIS
HIGH INTENSITY RAINFALL MAY CAUSE SOME SMALL STREAMS TO FLOOD EARLY
THURSDAY...AND WITH FALLEN LEAVES STILL AROUND MAY ALSO RESULT IN
SOME DRAINAGE PROBLEMS ON ROADS AND PARKING AREAS. AN EMBEDDED
THUNDERSTORM OR TWO IS POSSIBLE.
SOME LAKE EFFECT SNOW MAY OCCUR THURSDAY NIGHT AND FRIDAY IN THE
WAKE OF THE STORM AS COLDER AIR MOVES BACK IN...BUT OTHERWISE IT
WILL BE DRY. MAINLY DRY WEATHER IS EXPECTED THE REMAINDER OF THE
PERIOD INTO THE WEEKEND.
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...KL
NEAR TERM...KL
SHORT TERM...KL
LONG TERM...BGM
AVIATION...BGM
HYDROLOGY...RCK/KL
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