March 19, 2013 Forecast Discussion

000
FXUS61 KALY 190844
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
444 AM EDT TUE MAR 19 2013

.SYNOPSIS…
A DEVELOPING COASTAL STORM WILL TRACK ALONG THE NORTHEAST CORRIDOR
TODAY REDUCING ITS IMPACTS ACROSS THE REGION AS THE DAY
PROGRESSES. IN THE WAKE OF THIS STORM SYSTEM…WE WILL REMAIN IN
AN UNSETTLED WEATHER PATTERN WITH BRISK WESTERLY WINDS AND THE
CHANCE FOR ADDITIONAL WINTRY PRECIPITATION FOR THE REMAINDER OF
THIS WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/…
COMPLEX STORM WAS UNDERWAY WITH REDEVELOPING OF THE SURFACE LOW
ALONG THE SOUTH SHORE OF LONG ISLAND WITH 3HR PRESSURE FALLS OF
NEAR 6MB/3HR. RADAR IMAGERY SUGGESTS THE PRECIPITATION HAS BECOME
INTERMITTENT AND DUAL POL DATA SUGGESTS MIX OF PRECIP ACROSS THE
SCHOHARIE VALLEY…CATSKILLS…MID HUDSON VALLEY AND NW CT.
BOUNDARY LAYER TEMPS WERE MAINLY INTO THE UPPER 20S SO THE SNOW
RATIO WAS AT OR BELOW 12:1. AS THIS COASTAL STORM
UNFOLDS…INVERTED TROUGH AXIS ALONG WITH THE TROWAL ADVECTING
WESTWARD SHOULD ALLOW FOR THE PRECIP TO REDEVELOP ACROSS MOST OF
THE REGION THIS MORNING AS SUGGESTED BY ALL AVAILABLE GUIDANCE.
THE COMPLICATED FACTOR TO THIS FORECAST WILL BE THE WARMING
BOUNDARY LAYER TEMPS AND THE HIGHER MARCH SUN ANGLE. IT APPEARS
OUR SOUTHERN COUNTIES MAY COME UP SHORT WITH WARNING CRITERIA AS
MOST OF THE ACCUMULATING SNOWFALL HAS ALREADY OCCURRED AND THE
ADDITIONAL PRECIPITATION TODAY WILL BE A WINTRY MIXTURE OR EVEN A
PERIOD OF RAINFALL CLOSE TO NOON HOUR. FURTHER NORTH…SEEMS MOST
OF THE PRECIP WILL FALL AS SNOW BUT ACCUMULATING WILL BECOME
PROBLEMATIC DUE TO THOSE WARMING BOUNDARY LAYER TEMPS AND SOME
POSSIBILITY OF A LITTLE SLEET MIXING IN FROM TIME TO TIME. WE
WILL AWAIT FOR THOSE SNOWFALL REPORTS BEFORE MAKING CHANGES TO THE
HEADLINES. THANKS FOR THE EXCELLENT COORDINATION FROM NEIGHBORING
WFOS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/…
BY SUNSET…THE COAST STORM IS EXPECTED TO BE INTO THE GULF OF
MAINE AS THE H850 LOW CLOSES OFF ACROSS EASTERN NEW ENGLAND. BY
THAT TIME…ACCUMULATIONS WILL BE DIMINISHING ACROSS MOST OF THE
REGION. LAKE EFFECT ACTIVITY WILL BE ON THE INCREASE DURING THE
NIGHT AS DELTA T/S INCREASE AN INVERSION HEIGHTS CLIMBING ABOVE 5K
FEET. QUESTION WILL BE HOW FAR THIS BAND PENETRATES INLAND AS
LOCAL CSTAR RESEARCH SUGGESTS NORTHERN HERKIMER COUNTY COULD
EXPERIENCE ADDITIONAL ACCUMULATING SNOWFALL. THERE IS A POTENTIAL
FOR ADDITIONAL HEADLINES AS LATER SHIFTS CAN ASCERTAIN THIS BETTER
ONCE THE MAIN SYNOPTIC EVENT HAS DIMINISHED.

BRISK WESTERLY WINDS WITHIN A COOL AND MOIST CYCLONIC FLOW WILL
KEEP THE CHANCE FOR PRECIPITATION THROUGH THE REMAINDER OF THE
SHORT TERM FORECAST. THE HIGHER POPS WILL BE RETAIN ACROSS
FAVORABLE UPSLOPE AREAS OF THE CATSKILLS…DACKS WHERE LAKE
CONTRIBUTIONS WILL BE MAXIMIZED. AS H850 TEMPS REMAINS BELOW
-10C…THIS WILL KEEP SURFACE TEMPERATURES BELOW NORMAL.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/…
TEMPERATURES WILL CONTINUE TO RUN BELOW NORMAL THROUGHOUT THE
PERIOD.

A NEGATIVE ARCTIC OSCILLATION (AO)/NEGATIVE NORTH ATLANTIC
OSCILLATION (NAO) WHICH HAS BEEN IN PLACE MOST OF THIS MONTH…LOOKS
TO CONTINUE. THESE BASICALLY INDICATE HIGHER THAN NORMAL PRESSURE AT
HIGHER LATITUDES WHICH ALLOWS ARCTIC AIR TO SLIP FURTHER SOUTH THAN
USUAL. THERE ARE SOME INDICATIONS FROM THE 00Z GFS ENSEMBLES THAT
AFTER PEAKING AT VERY ANOMALOUS LEVELS…BOTH INDICES WILL BEGIN TO
TREND TOWARD NEUTRAL CONDITIONS BUT PROBABLY NOT UNTIL EARLY NEXT
WEEK.

A LARGE UPPER AIR LOW DOMINATING THE CANADIAN MARITIMES…WESTWARD
INTO EASTERN CANADA…WILL UNABLE TO MOVE EAST DUE TO A LARGE
BLOCKING HIGH PARKED NEAR GREENLAND. THIS UPPER AIR LOW WILL
CONTINUE TO BRING CLOUDS AND SCATTERED SNOW SHOWERS…MAINLY TO THE
HIGHER TERRAIN…ESPECIALLY THE ADIRONDACKS INTO THE MOHAWK VALLEY
RIGHT INTO THE BEGINNING OF THE WEEKEND. SPOKES OF VORTICITY WILL
CONTINUE TO ENHANCE PERIODS OF UNSETTLED WEATHER…BUT THESE ARE
ALMOST IMPOSSIBLE TO PERFECTLY PREDICT THIS FAR OUT.

VALLEY AREAS…OUTSIDE THE MOHAWK VALLEY…SHOULD REMAIN MAINLY
DRY…BUT EVEN HERE…FLURRIES CANNOT BE RULED OUT AS THE STRONG
MARCH WILL ATTEMPT TO HEAT THE LOWEST LAYERS OF THE ATMOSPHERE
PRODUCING A STEEP LOW LEVEL LAPSE RATE…AND CUMULUS CLOUDS.

BY SUNDAY…AS THE AFOREMENTIONED UPPER AIR LOW FINALLY MOVES A
LITTLE FURTHER EAST…AND A PIECE OF A HUGE HIGH PRESSURE ANCHORED
OVER HUDSON/S BAY BUILD IN…DRYING SHOULD DIMINISH THE THREAT OF
SNOW SHOWERS…EVEN OVER THE MOUNTAINS. THERE WILL BE A LITTLE MORE
SUNSHINE…BUT IT WILL REMAIN WITH BELOW NORMAL TEMPERATURES.

MONDAY…A STORM LOOKS TO TRACK JUST SOUTH OF OUR REGION. IT WILL
HAVE TO BE WATCHED TO SEE IF WOULD BE ABLE TO PUSH NORTH ENOUGH TO
BRING PRECIPITATION TO PART OR ALL OF OUR REGION. FOR NOW…WE JUST
AVE SLIGHT POPS TO REFLECT THIS OUTSIDE POSSIBILITY. FROM THIS
VANTAGE POINT…IT LOOKS MARGINALLY COLD ENOUGH FOR ANY
PRECIPITATION TO FALL AS SNOW.

HIGH TEMPERATURES THROUGH THIS PERIOD WILL START OUT FROM THE UPPER
20S NORTHWEST TO NEAR 40 IN OUR SOUTHEAST ZONES. TEMPERATURES LOOK
TO MODERATE A LITTLE BIT BY THE WEEKEND…RANGING FROM THE MID 30S
IN OUR NORTHWEST ZONES TO MID 40S SOUTHEASTERN ZONES. OVERNIGHT LOWS
WILL RANGE IN THE TEENS NORTH…TO THE 20S SOUTH.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/…
A SIGNIFICANT LATE WINTER STORM WILL CONTINUE TO IMPACT THE AREA
THROUGH TODAY WITH MAINLY IFR CONDITIONS.

THE INITIAL BURST OF SNOW…ASSOCIATED WITH THE WARM ADVECTION HAS
ALREADY IMPACTED ALL OF THE TERMINALS. A NOTICEABLE "LULL" IN
PRECIPITATION DUE TO A MID LEVEL DRY SLOT HAS REDUCED PRECIPITATION
AT ALL THE TERMINALS.

HOWEVER…WE STILL EXPECT THE SECONDARY STORM…DEVELOPING OFF THE
SOUTHERN NEW JERSEY COAST…WILL COMBINE WITH AN INCOMING SHORT
WAVE…TO RAMP UP PRECIPITATION AS WE HEAD TOWARD THE MORNING PEAK
AND THE STORM TRACKS UP ALONG OR JUST OFF THE EASTERN SEABOARD.
REGIONAL RADARS INDICATED THAT PRECIPITATION WAS ALREADY BEGINNING
TO FILL BACK ACROSS CENTRAL NEW YORK.

AT KPOU…THIS SECOND ROUND OF PRECIPITATION WILL LIKELY FALL AS MIX
OF SLEET/SNOW/FREEZING RAIN AND EVEN SOME PLAIN RAIN WHILE MOSTLY
SNOW…MIXED WITH SLEET…WILL REDEVELOP AT KPSF AND KALB. KGFL
SHOULD BE MOSTLY OR ALL SNOW. WHEN THIS SECOND SURGE OF
PRECIPITATION HAPPENS WE EXPECT ALL THE TERMINALS TO BE
PREDOMINATELY IFR (POSSIBLY EVEN LOW IFR). AT KPOU THE MAJORITY OF
THE RESTRICTION WILL BE DUE TO CIGS…WHILE IT WILL BE A COMBINATION
OF VSBY AND CIGS AT THE OTHER SITES.

BY 22Z…PRECIPITATION WILL BEGIN TO DIMINISH AT EARNEST AT
KPOU…AS WE ASSIGN ONLY A VCSH THERE. STILL HOLD CIGS AT HIGH MVFR
(NO RESTRICTIONS).

IT WILL TAKE A LITTLE WHILE LONGER FOR SNOW TO TAPER OFF AT THE
OTHER TAFS…PROBABLY NOT UNTIL WE ARE DONE WITH THE EVENING PEAK.
AT KALB…THERE IS A CHANCE THAT MOHAWK HUDSON CONVERGENCE COULD
PRODUCE A THIRD FLAREUP OF SNOW (DROPPING CONDITIONS BACK TO IFR
FROM LOW MVFR LATE IN THE AFTERNOON). HOWEVER…DID NOT INCLUDE THAT
POSSIBLE SCENARIO IN THE TAF AT THIS TIME.

BOTTOM LINE IS THAT POOR FLYING CONDITIONS WILL PERSIST THROUGH
TODAY. THERE WILL BE EVEN BE SOME MARGINAL LOW LEVEL WIND SHEAR
ISSUES THROUGH MORNING PEAK…BUT NOT ENOUGH TO INCLUDE IN THE TAFS.
SURFACE WIND WILL GENERALLY BE VARIABLE…BACKING TO THE NORTHEAST
AROUND 5KTS…EXCEPT EASTERLY 10KTS GUSTING TO 20KTS AT KPSF. THE
WIND THERE WILL EVENTUALLY BACK MORE TO A NORTHEASTERLY DIRECTION
LATER TODAY AND WEAKEN A LITTLE.

OUTLOOK…
TUE NIGHT-SAT…MAINLY VFR. CIG. BREEZY. CHC SUB-VFR -SHSN.

&&

.FIRE WEATHER…
NO CRITICAL FIRE WEATHER CONCERNS FOR THE NEXT FIVE DAYS.

A SIGNIFICANT STORM SYSTEM WILL TRACK ACROSS THE REGION TODAY. IN
THE WAKE OF THIS STORM SYSTEM…WE WILL REMAIN IN AN UNSETTLED
WEATHER PATTERN WITH BRISK WESTERLY WINDS AND THE CHANCE FOR
ADDITIONAL WINTRY PRECIPITATION FOR THE REMAINDER OF THE WEEK.

THE GROUND WILL BE SNOW COVERED IN ALL PLACES TODAY. THE SNOW PACK
WILL SLOWLY MELT IN THE VALLEYS THROUGH THE REMAINDER OF THE WEEK
BUT LIKELY REMAIN OVER THE MOUNTAINS.

&&

.HYDROLOGY…
NO HYDROLOGICAL PROBLEMS EXPECTED THROUGH THE WEEK.

A SIGNIFICANT PRECIPITATION WILL BEGIN TO DIMINISH THROUGH THE
DAY. IMPACTS ON AREA STREAMS AND RIVERS WILL BE MINIMAL 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…WINTER STORM WARNING UNTIL 8 PM EDT THIS EVENING FOR CTZ001-
013.
NY…WINTER STORM WARNING UNTIL 8 PM EDT THIS EVENING FOR NYZ032-
033-038>043-047>054-058>061-063>066-082>084.
MA…WINTER STORM WARNING UNTIL 8 PM EDT THIS EVENING FOR MAZ001-
025.
VT…WINTER STORM WARNING UNTIL 8 PM EDT THIS EVENING FOR
VTZ013>015.

&&

$$
SYNOPSIS…BGM
NEAR TERM…BGM
SHORT TERM…BGM
LONG TERM…HWJIV
AVIATION…HWJIV
FIRE WEATHER…HWJIV
HYDROLOGY…GJM/BGM

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