February 13, 2013 Forecast Discussion

000
FXUS61 KALY 131806
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
105 PM EST WED FEB 13 2013

.SYNOPSIS…
WEAK HIGH PRESSURE WILL BUILD INTO THE REGION TODAY. AN AREA OF LOW
PRESSURE WILL MOVE OFF THE VIRGINIA COAST THIS EVENING…PASSING
WELL SOUTH OF LONG ISLAND OVERNIGHT. THE PRECIPITATION ASSOCIATED
WITH THIS LOW WILL REACH THE MID HUDSON VALLEY AND NORTHWESTERN
CONNECTICUT. ANOTHER WEAK HIGH PRESSURE SYSTEM WILL BUILD INTO THE
REGION FOR THURSDAY WITH DRY CONDITIONS AND MILD TEMPERATURES. A LOW
PRESSURE SYSTEM WILL MOVE ACROSS THE GREAT LAKES REGION THURSDAY
NIGHT AND INTO EASTERN CANADA FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/…
AS OF 1245 PM EST…THE CLOUDS FINALLY BEGINNING TO BREAK FROM SOUTH
TO NORTH. HAVE RE-TOOLED THE SKY GRIDS JUST A LITTLE TO REFLECT THE
CURRENT TRENDS.

RADAR INDICATE SOME SNOW SHOWERS STILL WORKING INTO NORTHERN
HERKIMER AND EVEN NORTHWESTER HERKIMER COUNTIES. REALLY MORE LIKE
FLURRIES. HAVE AN ISOLATED POP (20) FOR THESE THROUGH MID
AFTERNOON…THEN AS HIGH PRESSURE BUILDS RIGHT ON TOP OF
THEM…SHOULD BE GONE LATER ON AND SHOULD PRODUCE NO ADDITIONAL
SNOWFALL ACCUMULATIONS.

TWEAKED A FEW TEMPERATURES UPWARD BASED ON SUNSHINE AND THE
OPPORTUNITIES FOR A FEW MORE POINTS ON THE THERMOMETER.

TEMPERATURES WILL BE SLIGHTLY ABOVE SEASONAL LEVELS TODAY…MAINLY
IN THE 30S…AROUND 40 IN THE CAPITAL DISTRICT…WITH MID 40S IN THE
MID HUDSON VALLEY. TEMPERATURES TONIGHT ARE EXPECTED TO RUN 5 TO 10
DEGREES ABOVE NORMAL.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/…
INITIALLY MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THE GFS ENSEMBLES
WELL CLUSTERED BRINGING A NORTHERN STREAM SHORT WAVE AND SURFACE LOW
ACROSS THE GREAT LAKES REGION THURSDAY AND THURSDAY NIGHT. THIS LOW
IS THEN EXPECTED TO MOVE NORTHEASTWARD INTO EASTERN CANADA FRIDAY.
THE SPREAD IN THE GUIDANCE INCREASES AS THERE ARE TIMING DIFFERENCES
WITH ADDITIONAL SHORT WAVE ENERGY MOVING THROUGH THE DEEPENING
LONGWAVE TROUGH OVER THE EASTERN UNITED STATES. AT THIS TIME…THERE
ARE INDICATIONS A LOW MAY TRY TO DEVELOP OVER NEW ENGLAND FRIDAY
NIGHT.

EXPECTING A DRY DAY THURSDAY WITH INCREASING CHANCES FOR SHOWERS
THURSDAY NIGHT AS THE SHORT WAVE AND LOW APPROACH ESPECIALLY ACROSS
THE NORTHWESTERN PORTION OF THE FORECAST AREA. ON FRIDAY…CHANCES
FOR SHOWERS WILL SPREAD SOUTHEASTWARD. DUE TO UNCERTAINTY IN THE
FORECAST HAVE BROAD BRUSHED FORECAST AREA WITH CHANCE POPS FOR
FRIDAY NIGHT.

AS FOR TEMPERATURES ABOVE NORMAL ESPECIALLY ON FRIDAY BY ABOUT 10
DEGREES.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/…
THE LONG TERM FORECAST OPENS UP A BIT UNSETTLED WITH A QUITE A BIT
OF UNCERTAINTY IN THE MEDIUM RANGE GUIDANCE…AND THE ENSEMBLES.
THIS FORECAST WILL REFLECT MORE OF AN HPC/ECMWF BLEND FOR THE
STRETCH…AS A LONGWAVE TROUGH IMPACTS THE ERN HALF OF THE LOWER 48
MOVING INTO THE WEEKEND.

THE LONGWAVE TROUGH WILL HAVE MULTIPLE DISTURBANCES MOVING THROUGH
IT. SOME OF THE SHORT-WAVES ARE CONNECTED WITH THE NRN
STREAM…WHILE SOME MORE PROGRESSIVE DISTURBANCES EJECT OUT OF THE
BASE OF THE TROUGH CONNECTED TO THE SRN STREAM/SUBTROPICAL UPPER
JET. THE CANADIAN GGEM IS SIMILAR TO THE ECMWF/GFS/HPC THIS RUN
BRINGING A DISTURBANCE IN THE SOUTHWEST FLOW ALOFT WITH A WAVE OF
LOW PRESSURE ON SAT. THIS DISTURBANCE MAY PRODUCE A CHANCE OF SNOW
SHOWERS OR LIGHT SNOW.

HOWEVER…ON SUNDAY ANOTHER PIECE OF ENERGY PHASES WITH THE INITIAL
WAVE SOUTHEAST OF LONG ISLAND AND CAPE COD ACCORDING TO THE CANADIAN
GGEM. THIS WOULD YIELD A PROLONGED PERIOD OF SNOW…ESPECIALLY FROM
CAPITAL REGION SOUTH AND EAST TO CLOSE THE WEEKEND. THE ECMWF AND
GFS KEEP THIS SECOND STORM /OCEANIC CYCLONE/ OFF THE COAST WITH
LITTLE IF ANY IMPACT TO CLOSE THE WEEKEND. THE LATEST 00Z GEFS
PLUMES FOR ALY SHOW LESS SPREAD ON THE WEEKEND WITH MAINLY A LIGHT
SNOW EVENT. HOWEVER…3-4 MEMBERS IMPLY A MODERATE TO HEAVY SNOW
EVENT WITH 4 TENTHS OF AN INCH TO AN INCH POSSIBLE. POPS WERE
LOWERED TO SLIGHT CHC VALUES FROM THE HUDSON VALLEY EAST ON
SUNDAY…WITH CHC VALUES TO THE WEST ASSOCIATED WITH ANY LAKE EFFECT
SNOW. THE LOW WILL DEEPEN AND INTENSIFY IN THE CANADIAN MARITIMES
WITH SOME CHILLY AIR MOVING INTO THE REGION TO CLOSE THE WEEKEND.
H850 TEMPS CRASH TO -17C TO -22C FROM THE LATEST OPERATIONAL GFS.
EXPECT HIGHS ON SATURDAY IN THE U20S TO M30S IN THE VALLEYS…AND
20S TO L30S OVER THE HILLS AND MTNS. SAT NIGHT…THE ARCTIC AIR
SPILLS IN WITH LOWS IN THE SINGLE DIGITS TO BELOW ZERO ACROSS THE
SRN DACKS…AND LAKE GEORGE REGION…WITH TEENS ELSEWHERE.
SUNDAY…HIGHS WILL BE ABOUT 10-15 DEGREES BELOW NORMAL WITH HIGHS
IN THE UPPER TEENS TO M20S IN THE VALLEYS…AND SINGLE DIGITS TO
TEES OVER THE HIGHER PEAKS.

SUNDAY NIGHT INTO MONDAY NIGHT…QUIETER STRETCH OF THE LONG TERM
WITH HIGH PRESSURE BUILDING IN FROM THE SOUTH. TEMPS WILL GRADUALLY
MODERATE CLOSER TO NORMAL TO OPEN THE WEEK WITH LOW TO MID LEVEL
WARM ADVECTION. THE H500 TROUGH BREAKS DOWN WITH SOME WEAK RIDGING
MOVING IN OVERHEAD. MEANWHILE…A CLIPPER WILL BE APPROACHING FROM
THE NRN PLAINS WITH THE POLAR JET STREAM….AND LOW PRESSURE WILL BR
MOVING INTO THE LOWER MS RIVER VALLEY MON NIGHT ASSOCIATED WITH THE
SRN STREAM.

TUESDAY…LOTS OF SPREAD AND DIFFERENCES IN THE TRACK AND EVOLUTION
WITH THE POTENTIAL COMPLEX STORM SYSTEM APPROACHING FROM THE GREAT
LAKES AND MID ATLANTIC REGIONS. THIS LOOKS LIKE A DOUBLE BARREL
SYSTEM THAT COULD PRODUCE SOME SNOW…BEFORE MIXING BRIEFLY…AND
CHANGING BACK TO SNOW ONCE A DECENT SECONDARY OR COASTAL LOW FORMS
NEAR NEW ENGLAND. FOR NOW…WE HAVE GONE WITH A CHANCE OF SNOW TUE
INTO TUE NIGHT…AND WILL CONTINUE TO MONITOR TRENDS WITH THIS
SYSTEM OVER THE NEXT SEVERAL DAYS.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/…
LOW PRESSURE MOVING OUT TO SEA WELL SOUTH OF THE REGION MAY BRING
SOME LIGHT SNOW TO THE KPOU TAF SITES LATE TONIGHT…OTHERWSIE
EXPECT DRY WEATHER AND VFR CONDITIONS AT THE KGFL/KALB/KPSF/KPOU
TAF SITES THROUGH THE TAF PERIOD ENDING AT 18Z THURSDAY.

CLOUD DECK CURRENTLY OVER KALB/KPSF/KGFL GENERALLY IN THE VFR
RANGE…BUT KPSF HAS BEEN OSCILATING BETWEEN VFR AND MVFR. EXPECT
THE CLOUD DECK TO CLEAR OUT AT KPSF/KALB BY 20Z AND AROUND 00Z AT
KGFL. AFTER THAT…MAINLY MID/HI CLOUDS ASSOCIATED WITH THE LOW
MOVING OFFSHORE WILL AFFECT THE KPSF/KGFL/KALB TAF SITES THROUGH
TONIGHT. AT KPOU LOWS CLOUDS AND POSSIBLE MVFR CIGS/VSBY POSSIBLE
TONIGHT AS THE NORTHERN EDGE OF THE SNOW ASSOCIATED WITH THE LOW GET
CLOSE TO THE SITE. AFTER 12Z THURSDAY…VFR CONDITIONS EXPECTED.

THE WINDS WILL BE LIGHT AND VARIABLE AT THE TAF SITES FOR MOST OF
THE TAF PERIOD. KPSF WILL HAVE A LIGHT WEST WIND TODAY AT LESS THAN
8 KTS…AND A LIGHT NORTHWEST WINS AT 5 KTS OR LESS POSSIBLE AT THE
TAF SITES ON THURSDAY.

OUTLOOK…
THU NT…MAINLY VFR. CHC OR SCHC -SHSN.
FRI…MAINLY VFR. SLIGHT CHC -SHSN/-SHRA.
FRI NIGHT-SAT…MAINLY VFR. CHC -SHSN.
SUN…MAINLY VFR. SLIGHT CHC -SHSN.

&&

.HYDROLOGY…
NO HYDROLOGIC PROBLEMS ARE ANTICIPATED OVER THE NEXT FEW DAYS. SNOW
MELT WILL BE GRADUAL AND DIURNAL WITH ABOVE FREEZING TEMPERATURES
DURING THE DAY WITH BELOW FREEZING EACH NIGHT.

SOME LIGHT PRECIPITATION IS EXPECTED ACROSS THE MID HUDSON VALLEY
AND NORTHWESTERN CONNECTICUT TONIGHT IN THE FORM OF SNOW. MORE LIGHT
PRECIPITATION IS EXPECTED THURSDAY NIGHT AND FRIDAY IN THE FORM OF
RAIN AND SNOW SHOWERS AS A LOW PRESSURE SYSTEM PASSES TO OUR WEST
AND NORTH.

AS FOR THE WEEKEND…IT APPEARS A POTENTIAL STORM SYSTEM WILL TRACK
WELL TO OUR SOUTH…ALTHOUGH THE PROBABILITY THAT THE STORM WILL
IMPACT OUR REGION IS LOW …IT IS NOT ZERO. REFER TO THE LONG TERM
SECTION OF THIS DISCUSSION FOR DETAILS.

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…IAA
NEAR TERM…IAA/HWJIV
SHORT TERM…IAA
LONG TERM…WASULA
AVIATION…WASULA
HYDROLOGY…IAA

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