February 6, 2013 Forecast Discussion

000
FXUS61 KALY 070229
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
929 PM EST WED MAR 6 2013

.SYNOPSIS…
A LOW PRESSURE SYSTEM OFF THE MID ATLANTIC COAST WILL CONTINUE TO
MOVE EAST TONIGHT AND THURSDAY. IT WILL BRING SOME LIGHT SNOW OR
RAIN TO SOUTHERN PORTIONS OF THE AREA TONIGHT AND EARLY THURSDAY.
THE COMBINATION OF MOISTURE FROM THE COASTAL STORM…AND UPPER LEVEL
ENERGY APPROACHING FROM THE GREAT LAKES REGION…WILL BRING A MORE
WIDESPREAD LIGHT TO MODERATE SNOWFALL TO THE AREA FOR LATE THURSDAY
AFTERNOON AND NIGHT.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/…
BASED ON CURRENT RADAR TRENDS AND OBSERVATIONS…HAVE BACKED OFF
LIKELY POPS ACROSS SOUTHERN ZONES UNTIL THURSDAY MORNING AS
DEWPOINT DEPRESSIONS ARE STILL AROUND 10F IN THESE AREAS AND RADAR
RETURNS ARE NOT LIKELY REACHING THE SURFACE AT THIS TIME. STEADIER
PRECIPITATION WILL CONTINUE TO BE SLOW TO EVOLVE AS COASTAL STORM
CONTINUES TO SLOWLY TRACK EAST NORTHEAST OFF THE MID ATLANTIC
COAST. HAVE UPDATED SKY COVER AND TEMPERATURES AS WELL TO REFLECT
WESTWARD PROGRESSION OF OVERRUNNING CLOUD COVER.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/…
THE WEATHER FOR MOST OF THURSDAY WILL BE RELATIVELY TRANQUIL AS THE
MOISTURE ASSOCIATED WITH THE COASTAL LOW MOVES OUT IN THE MORNING
AND NOTHING MORE THAN SPOTTY LIGHT PCPN EXPECTED DUE TO THE EASTERLY
FLOW. HOWEVER…AS THE SECONDARY UPPER LOW DROPS SOUTHEAST ACROSS
THE GREAT LAKES AND REACHES WESTERN NY BY THURSDAY EVENING…IT WILL
BEGIN TO PULL MOISTURE ASSOCIATED WITH THE OFFSHORE STORM WESTWARD
INTO THE ALBANY FORECAST AREA. IT WILL LIKELY TAKE UNTIL LATE IN THE
DAY ON THURSDAY BEFORE THIS UPPER LOW BEGINS TO PRODUCE ANY
WIDESPREAD PCPN ACROSS THE REGION…WITH THE PCPN STARTING OVER
SOUTHERN AND EASTERN AREAS FIRST. WITH WIDESPREAD PCPN HOLDING OFF
UNTIL LATER IN THE DAY…TEMPS SHOULD BE ABLE TO RISE TO HIGHS IN
THE 30S TO AROUND 40. AS A RESULT…WHEN PCPN FIRST STARTS…IT WILL
LIKELY BE WARM ENOUGH FOR RAIN OR RAIN/SNOW MIXED ACROSS LOWER
TERRAIN AREAS…AND WARM ENOUGH TO KEEP SNOW FROM ACCUMULATING VERY
MUCH ACROSS HIGHER TERRAIN AREAS. SO ONCE AGAIN…NO MORE THAN UP TO
AROUND AN INCH OF ACCUMULATION HAS BEEN FORECAST.

AS THE UPPER LEVEL LOW SLIDES OFF THE MID ATLANTIC COAST BY LATE
THURSDAY NIGHT…IT WILL PRODUCE ENOUGH VERTICAL MOTION ACROSS THE
REGION FOR A LIGHT TO MODERATE SNOWFALL. THIS SCENARIO HAS GENERALLY
BEEN ACCEPTED…BUT THE AMOUNT OF PCPN FORECAST APPEARS TO BE ON THE
HIGH SIDE. THE ONE TO TWO INCH LIQUID AMOUNTS OF THE NAM HAS BEEN
DISCOUNTED…BUT EVEN THE HALF TO ONE INCH AMOUNTS OF THE
GFS/CANADIAN AND ECMWF APPEAR TO BE ON THE HIGH SIDE BECAUSE THE
STRONGEST DYNAMICS REMAIN WELL OUT AT SEA NEAR THE SURFACE LOW. WITH
MANY DOUBTS ABOUT THE MODEL LIQUID PCPN AMOUNTS AND ALSO ABOUT HOW
COLD IT WILL BE INITIALLY WHEN PCPN BEGINS…HAVE DECIDED TO HOLD
OFF ON ANY ADVISORIES AT THIS TIME SINCE THE MAIN PCPN EVENT
(SNOWFALL POTENTIAL) IS IN THE THIRD PERIOD OF THE FORECAST
(THURSDAY NIGHT). SNOWFALL AMOUNTS OF 2 TO 6 INCHES HAVE BEEN
FORECAST FOR THIS EVENT…WITH THE HIGHEST AMOUNTS ACROSS WESTERN
NEW ENGLAND AND THE CATSKILLS. THERE IS STILL PLENTY OF TIME TO
ISSUE ADVISORIES IF AND WHEN IT APPEARS THAT SNOWFALL AMOUNTS WILL
BE CLOSER TO THE UPPER END OF THE 2 TO 6 INCH SNOWFALL RANGE. LOWS
THURSDAY NIGHT WILL BE IN THE 20S.

SOME LIGHT SNOW MAY LINGER INTO EARLY FRIDAY MORNING…BUT ONLY UP
TO AN INCH ADDITIONAL ACCUMULATION HAS BEEN FORECAST. OTHERWISE
EXPECT SLOW CLEARING TO OCCUR FRIDAY WITH MAINLY CLEAR SKIES FRIDAY
NIGHT. HIGHS FRIDAY WILL BE IN THE MID 30S TO LOWER 40S. LOWS FRIDAY
NIGHT IN THE UPPER TEENS TO MID 20S.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/…
THE LONG TERM PERIOD WILL BE CHARACTERIZED BY A WARM UP IN
TEMPERATURES AND THE ARRIVAL OF ANOTHER STORM SYSTEM EARLY NEXT WEEK.

SATURDAY THROUGH SUNDAY…THE WEEKEND WILL BE DOMINATED BY HIGH
PRESSURE SPRAWLING ACROSS THE FORECAST AREA AND DRY CONDITIONS.
MEDIUM RANGE MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A PERIOD OF
DRIER AIR USHERING IN MOSTLY CLEAR SKIES…ACCOMPANIED BY A
SOUTHWESTERLY RETURN FLOW…WHICH COUPLED WITH THE INCREASING MARCH
SUN ANGLE…WILL ALLOW TEMPERATURES TO RISE INTO THE LOW 50S IN
VALLEY REGIONS WITH MID TO UPPER 40S ELSEWHERE. THIS HIGH PRESSURE
WILL BEGIN TO SLIDE OFFSHORE SUNDAY AS ANOTHER STORM SYSTEM
APPROACHES FROM THE MIDWEST.

MONDAY THROUGH WEDNESDAY…MODEL GUIDANCE BEGINS TO DIVERGE DURING
THIS TIME PERIOD AS ANOTHER STORM SYSTEM WILL DEVELOP ACROSS THE
CENTRAL PLAINS AND MOVE OUT ACROSS THE MIDWEST MONDAY. ONCE AGAIN
THE UPPER-LEVEL FLOW TRIES TO CUTOFF FROM THE BROADER FLOW
REGIME…WITH THE ECMWF CONTINUING TO BE THE MORE PROGRESSIVE
SOLUTION OVER THE GFS/CANADIAN. HAVE INTRODUCED SLIGHT CHANCE POPS
ACROSS THE FORECAST AREA BEGINNING SUNDAY NIGHT TO ACCOUNT FOR ANY
MODEL TIMING DIFFERENCES.

REGARDLESS OF THE INITIAL TIMING OF PRECIPITATION…THE LONG RANGE
MODEL SUITE CONTINUES TO FAVOR A TRACK OF THE STORM SYSTEM WEST OF
THE FORECAST AREA…WHICH GIVEN WARM BOUNDARY LAYER TEMPERATURES
ACROSS MOST OF THE REGION…WILL FAVOR MAINLY A RAIN EVENT WITH SOME
HIGHER ELEVATION LOCATIONS EXPERIENCING A WINTRY MIX. HAVE INCLUDED
HIGH CHANCE POPS LATE MONDAY THROUGH TUESDAY AS A FRONTAL BOUNDARY
APPROACHES THE AREA.

OF INTERESTING NOTE HOWEVER IS THE JET ORIENTATION ASSOCIATED WITH
THIS STORM SYSTEM…AS GUIDANCE CONTINUES TO SUGGEST COUPLING OF THE
NORTHERN AND SOUTHERN STREAMS. THIS WOULD PLACE MUCH OF THE FORECAST
AREA UNDER BOTH THE RIGHT ENTRANCE REGION OF THE NORTHERN STREAM AND
LEFT EXIT REGION OF THE SOUTHERN STREAM…ALLOWING FOR RAPID
MOISTURE TRANSPORT INTO THE AREA WITHIN A REGION OF FAVORABLE
DYNAMIC ASCENT. GIVEN ANTECEDENT WARM CONDITIONS AND CURRENT
SNOWPACK ESPECIALLY ACROSS THE ADIRONDACKS…LATEST HYDROLOGICAL
ENSEMBLE FORECASTS SHOW BANK RISES APPROACHING ACTION STAGE…SO
WILL NEED TO CONTINUE TO MONITOR THE LATEST GUIDANCE. THE SYSTEM IS
FORECAST TO MOVE OUT OF THE AREA BY WEDNESDAY…WITH A FEW LINGERING
RAIN/SNOW SHOWERS ACROSS THE ADIRONDACKS AS THE REGION REMAINS
INFLUENCED BY CYCLONIC FLOW ALOFT.

TEMPERATURES WILL BE ABOVE NORMAL FOR MUCH OF THE LONG TERM
PERIOD…WITH HIGHS REACHING INTO THE LOWER 50S IN VALLEY LOCATIONS
AND MID TO UPPER 40S ELSEWHERE. LOWS WILL GENERALLY BE IN THE UPPER
20S ACROSS THE ADIRONDACKS TO MID 30S IN VALLEY LOCATIONS. AS THE
STORM SYSTEM EXITS THE REGION BY MIDWEEK…TEMPERATURES LOOK TO
LOWER TO NEAR NORMAL.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/…
THIS EVENING…HAVE PUT VCSH TO COVER THE SPRINKLES AND FLURRIES
OVER THE REGION. HAVE ADDEDSOME LIGHT SNOW TO KPOU WHERE THE VERY
NORTHERN EDGE OF A PRECIPITATION SHIELD COULD BUILD NORTH AFTER
MIDNIGHT. CONDITIONS EXPECTED TO BE GENERALLY MVFR. DESPITE
SIMILAR REGIME…THERE SHOULD BE SOME SLIGHT IMPROVEMENT AFTER
SUNRISE WITH SLIGHTLY HIGHER CIGS/VSBYS AND MVFR OR EVEN SOME VFR
CONDITIONS POSSIBLE. KEEPING VCSH IN THE TAFS THROUGH TOMORROW
MORNING WITH THE PROXIMITY OF THE POTENTIAL PRECIPITATION
SHIELD. ANY STEADIER PRECIPITATION WOULD BE IN THE
AFTERNOON…WITH MVFR VISIBILITIES AND CEILINGS.

WINDS WILL BE NORTH TO NORTHEAST TONIGHT…WITH SPEEDS NOT VARYING
MUCH THROUGH THE 24 HOUR TAF PERIOD DUE TO THE RELATIVELY STAGNANT
PRESSURE PATTERN IN PLACE OVER THE REGION. WIND SPEEDS WILL
CONTINUE TO BE AROUND 10-12 KT WITH GUSTS OF 20-25 KT…WITH THE
GUSTIEST WINDS AT KPSF AND KPOU.

OUTLOOK…
THU AFTN…MVFR/IFR. -SN LIKELY KPOU/KPSF/KALB AND CHC -SN AT KGFL.
BREEZY.
THU NT…MAINLY IFR. -SN/SN LIKELY.
FRI MRNG…MVFR/IFR. -SN LIKELY AT KPOU/KPSF AND CHC -SN AT
KGFL/KALB.
FRI AFTN-MON…VFR. NO SIG WX.

&&

.HYDROLOGY…
NO HYDRO PROBLEMS ARE EXPECTED THE NEXT FEW DAYS. A STORM SYSTEM
EXPECTED TO PASS SOUTH OF LONG ISLAND TONIGHT. MOISTURE FROM THIS
LOW…AND THE APPROACH OF A STRONG UPPER LEVEL DISTURBANCE WILL
PRODUCE PRECIPITATION ACROSS THE REGION LATE THURSDAY INTO EARLY
FRIDAY. AT THIS TIME…STORM TOTAL QPF AMOUNTS THROUGH FRIDAY
MORNING ARE EXPECTED TO RANGE FROM ABOUT A QUARTER TO AROUND A HALF
AN INCH…WHICH SHOULD FALL MAINLY AS SNOW.

LOOKING OUT FURTHER IN TIME…HIGH PRESSURE IS EXPECTED TO BUILD
INTO THE REGION FOR THE WEEKEND. TEMPERATURES ARE EXPECTED TO
MODERATE TO ABOVE NORMAL…WITH TEMPERATURES FALLING BELOW FREEZING
AT NIGHT…SO THERE WILL BE DIURNAL SNOWMELT.

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…GJM/NAS
NEAR TERM…IRL/GJM/NAS
SHORT TERM…GJM
LONG TERM…IRL
AVIATION…NAS
HYDROLOGY…IAA/KL

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