January 29, 2012 Forecast Discussion

000
FXUS61 KALY 292348
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
648 PM EST SUN JAN 29 2012

.SYNOPSIS…
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A FAST MOVING COLD FRONT WILL BRING SNOW SHOWERS AND
SQUALLS TONIGHT…MAINLY FOR WESTERN AND NORTHERN PARTS OF THE
REGION. A WEAK RIDGE OF HIGH PRESSURE WILL BUILD INTO THE REGION ON
MONDAY BEFORE BEING FOLLOWED BY A WARM FRONT…WHICH WILL BRING
ANOTHER ROUND OF SNOW TO THE AREA FOR MONDAY NIGHT INTO TUESDAY
MORNING.
- End Changed Discussion —

&&

.NEAR TERM /THROUGH MONDAY/…
— Changed Discussion —
AS OF 648 PM EST…HAVE UPDATED T/TD TO ACCOUNT FOR LATEST
OBSERVATIONS AND TRENDS. CURRENT FORECAST MIN TEMPS APPEAR ON
TRACK WITH 20S FOR MOST AREAS /SOME TEENS ACROSS THE SRN ADKS/.

LATEST RADAR RETURNS SHOW SOME MODERATE SNOWFALL DUE TO SOME LAKE
MOISTURE UPSLOPING THE HIGH TERRAIN AFFECTING THE WESTERN
ADKS…MAINLY TO THE NORTH OF OLD FORGE AND INLET. THIS LOOKS TO
CONTINUE OVER THE NEXT SEVERAL HOURS…WITH A FEW INCHES POSSIBLE. THIS
ACTIVITY WILL WANE SOMEWHAT AS THE FLOW SHIFTS AHEAD OF AN
APPROACHING SHORTWAVE AND ASSOCIATED SURFACE BOUNDARY.

THE 20Z 3KM HRRR GUIDANCE STILL DEPICTS A FAST MOVING LINE OF SNOW
SHOWERS/SQUALLS ASSOCIATED WITH THE AFOREMENTIONED COLD FRONTAL
BOUNDARY HEADING TOWARDS OUR AREA AROUND MIDNIGHT. MODEL GUIDANCE
SUGGESTS THAT THIS ACTIVITY WON/T BE QUITE AS STRONG AS IT WILL BE
EARLIER IN THE EVENING ACROSS WESTERN NY/WESTERN AND CENTRAL
PA…BUT IT SHOULD STILL BE ENOUGH TO BRING ADDITIONAL ACCUMULATION
AND PROVIDE LOW VISIBILITY WITHIN GUSTY WINDS. THE 18Z NAM STILL
DEPICTS SHOWALTER VALUES NEAR OR JUST BELOW ZERO FOR WESTERN PARTS
OF THE AREA. LTG DETECTION HAS ALREADY NOTED SOME LTG ACROSS
WESTERN PA AND WESTERN NY…SO CANNOT TOTALLY RULE OUT SOME LTG
WITHIN THE HEAVIEST SQUALLS. HOWEVER…DO NOT FEEL CONFIDENT THIS
WILL BE WIDESPREAD ENOUGH TO INCLUDE IN THE GRIDS…BUT IT
CERTAINLY COULD OCCUR IN A FEW ISOLD SPOTS. THE BEST CHANCE OF
SEEING THE SNOW SQUALLS WILL BE ACROSS THE MOHAWK VALLEY/SRN
ADIRONDACKS AND EVENTUALLY THE LAKE GEORGE SARATOGA REGION…WHERE
WE CURRENTLY HAVE THE HIGHEST POPS /LIKELY TO CATEGORICAL/. THE
ACTIVITY LOOKS TO WEAKEN ENOUGH FOR SNOW SHOWERS TO BE RATHER SCT
ONCE ACTIVITY GETS TOWARDS THE CAPITAL REGION BY AROUND 06Z TO
07Z. WHILE A COATING OF SNOWFALL IS POSSIBLE…THE LINE LOOKS TO
BREAK ENOUGH FOR IT TO BE HIT OR MISS ACROSS FOR THE CAPITAL REGION.
FURTHER SOUTH…DOWNLOPING OFF THE CATSKILLS SHOULD KEEP ANY
ACTIVITY FAIRLY ISOLD FOR THE MID HUDSON VALLEY AND NW
CT…ALTHOUGH UPSLOPE FLOW COULD ALLOW FOR A LITTLE BETTER
COVERAGE ACROSS THE TACONICS/BERKSHIRES/SOUTHERN GREENS…WHERE A
LIGHT ACCUMULATION IS POSSIBLE.

PREVIOUS FORECAST DISCUSSION IS BELOW…

AS OF 4 PM EST…FIRST BATCH OF SNOW MOVING THROUGH THE
ADIRONDACKS WITH THE FIRST BOUNDARY WITH THE MAIN EVENT YET TO
FOLLOW AS THE LEADING EDGE OF SNOW AHEAD OF THE CLIPPER SYSTEM
MOVING INTO WESTERN NEW YORK. THE WINTER WEATHER ADVISORY
CONTINUES FOR THE WESTERN ADIRONDACKS AND WESTERN MOHAWK VALLEY
UNTIL 10 AM MONDAY MORNING. EXPECT SNOWFALL AMOUNTS RANGING FROM 3
TO 8 INCHES IN THE ADVISORY AREA ALONG WITH BLOWING SNOW AS WEST
TO NORTHWEST WINDS OF 10 TO 20 MPH WITH GUSTS UP TO 25 MPH WILL BE
COMMON WITH HIGHER GUSTS POSSIBLE WITH SOME SNOW SQUALLS LATER
THIS EVENING. THIS CLIPPER TYPE SYSTEM HAS SOME FAIRLY GOOD
DYNAMICS WITH IT INCLUDING A STRONG VORT AXIS AND LATEST IR SAT
PICS ARE INDICATING COOLING CLOUD TOPS. THERE ALSO COULD BE SOME
EMBEDDED SNOW SQUALLS THIS EVENING AND EVEN AN ISOLATED CHC OF
SOME THUNDER SNOW ESPECIALLY CLOSER TO LAKE ONTARIO AS THE
SHOWALTER INDICES BRIEFLY GET BELOW ZERO. BOTH THE HIRESWRF MODEL
COMPOSITE REFLECTIVITY AND THE HRRR COL MAX REFLECTIVITY HAVE
REFLECTIVITY VALUES INDICATIVE OF SNOW SQUALLS DURING THE LATE
EVENING TO AROUND MIDNIGHT TIME FRAME. IF THESE SNOW SQUALLS
BECOME MORE CERTAIN SPS WILL LIKELY BE ISSUED. LOWS TONIGHT ARE
EXPECTED TO RANGE FROM THE MID TO UPPER TEENS NORTHWEST TO UPPER
20S SOUTHEAST.

LATE TONIGHT AND MONDAY…IN THE WAKE OF THE CLIPPER TYPE SYSTEM
A LAKE EFFECT BAND WILL SET UP WHICH WILL INITIALLY BE ORIENTED
TOWARD THE WESTERN ADIRONDACKS AND THEN SLIDE SOUTHEASTWARD INTO
THE MOHAWK VALLEY. AS THIS BAND WILL BE SHORT LIVED WITH A RIDGE
OF HIGH PRESSURE BUILDING QUICKLY INTO THE REGION BY
LATE MORNING…EXPECT THE GREATEST ACCUMULATIONS WILL BE ACROSS
SOUTHERN PORTIONS WESTERN ADIRONDACKS AND THE WESTERN MOHAWK
VALLEY. THIS ADDITIONAL SNOW IN THE WESTERN MOHAWK VALLEY SHOULD
BE ENOUGH TO RESULT IN THE AREA AVERAGING OVER 4 INCHES OF SNOW
WHEN COUPLED WITH THE SNOW FROM THE CLIPPER TYPE SYSTEM. BY MONDAY
AFTERNOON THE RIDGE OF HIGH PRESSURE IS ALREADY CRESTING ACROSS
THE FA AND THEN SLIDING EAST OF THE FA BY EVENING. EXPECT HIGHS ON
MONDAY TO RANGE FROM THE LOW TO MID 20S NORTHWEST TO MID TO UPPER
30S SOUTHEAST.
— End Changed Discussion —

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/…
MONDAY NIGHT INTO TUESDAY MORNING THE FA IS EXPECTED TO BE
IMPACTED BY A WARM FRONT LIFTING NE FROM THE OHIO VALLEY. LIGHT
SNOW IS EXPECTED TO OVERSPREAD MUCH OF THE FA FROM SOUTHWEST TO
NORTHEAST MONDAY EVENING WITH THE HIGHEST QPF FROM THE MOHAWK
VALLEY NORTH IN NEW YORK AND ACROSS SOUTHERN VERMONT. THIS EVENT
GENERALLY LOOKS LIKE 2 TO 4 INCHES TOTAL ACROSS NORTHWEST PORTIONS
OF THE FA WITH MOST OTHER AREAS HAVING AROUND AN INCH OF
SNOW…ALTHOUGH THE MOUNTAINS EITHER SIDE OF THE GREATER CAPITAL
DISTRICT MAY PICK UP A COUPLE OF INCHES. EXPECT LOWS MONDAY NIGHT
TO BE IN THE MID TEENS TO MID 20S.

TUESDAY AFTERNOON INTO TUESDAY NIGHT EXPECT THE WARM FRONT TO BE
NORTH OF THE BULK OF THE FA BY TUESDAY EVENING WITH THE FA LEFT IN
THE WARM SECTOR. THERE WILL STILL BE A CHANCE OF PCPN TUESDAY
AFTERNOON INTO TUESDAY NIGHT MAINLY ACROSS THE NORTHERN HALF OF
THE FA UNTIL THE COLD FRONT ARRIVES ON WEDNESDAY. EXPECT HIGHS ON
TUESDAY TO RANGE FROM THE MID 30S NORTHWEST TO UPPER 40S TO AROUND
50 SOUTHEAST WITH LOWS TUESDAY NIGHT RANGING FROM THE UPPER 20S TO
LOWER 30S NORTH TO MID 30S SOUTH.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/…
THE EXTENDED FORECAST STARTS OUT VERY MILD MID WEEK…AND THEN
BECOMES VERY UNSETTLED WITH CONTINUED MEDIUM RANGE DETERMINISTIC AND
ENSEMBLE MODEL UNCERTAINTY…WITH A LOW CONFIDENCE FORECAST FROM
THURSDAY INTO WEEKEND. WE WENT CLOSE TO THE HPC GUIDANCE…HOWEVER
THE LATEST 12Z ECMWF WOULD INDICATE THAT TWO SEPARATE SYSTEMS IN THE
W/SW FLOW COULD IMPACT THE NORTHEAST THU NIGHT THROUGH FRIDAY…AND
ANOTHER SYSTEM LATER ON THE WEEKEND WITH SOME SNOW. THE CANADIAN
GGEM IS ALSO HINTING AT ANOTHER SYSTEM DEVELOPING SATURDAY NEXT
WEEKEND OVER THE CNTRL MS RIVER VALLEY THAT COULD IMPACT THE
NORTHEAST FOR SUNDAY TOO. MEANWHILE…THE GFS IS COLD AND DRY LATE
IN THE WEEK WITH A SHORT-WAVE TROUGH IN THE NW FLOW THAT COULD
PRODUCE SOME SOME SNOW SHOWERS LATER NEXT WEEKEND.

WED-WED NIGHT…HIGH PRESSURE RETREATS OFF THE MID ATLANTIC
COAST…AS A WAVE OF LOW PRESSURE MOVES ACROSS SRN QUEBEC. MOST OF
THE FCST AREA GETS INTO A WARM SECTOR WITH H850 TEMPS JUMPING UP TO
+1 TO +5C. MAX TEMPS COULD BE 10 TO 20 DEGREES ABOVE NORMAL WITH
HIGHS IN THE M40S TO L50S IN THE VALLEYS…AND LOWER TO M40S OVER
THE HILLS AND MTNS. THE COLD FRONT QUICKLY APPROACHES LATE IN THE
DAY INTO THE EVENING WITH A GOOD CHANCE OF SHOWERS…TRANSITIONING
TO SNOW SHOWERS WITH THE COLD AIR ADVECTION. WE KEPT THE TREND OF
LIKELY POPS NORTH OF THE CAPITAL REGION CLOSER TO THE BETTER
CONVERGENCE AND LIFT WITH THE WAVE AND FRONT. LOWS WILL RANGE FROM
THE LOWER TO M20S OVER THE MTNS…AND U20S TO L30S IN THE VALLEYS.

THU-THU NIGHT…THE GFS HAS HIGH PRESSURE BUILDING IN FROM SRN
QUEBEC WITH A BROAD LONGWAVE TROUGH OVER THE NRN TIER. THE ECMWF
HAS A SHORT-WAVE IN THE SRN STREAM PHASING INTO THE NRN STREAM NEAR
THE CNTRL MS RIVER VALLEY…AND MOVES IT INTO THE OHIO VALLEY BY
THURSDAY MORNING. THIS SYSTEM MOVES ALONG THE BAROCLINIC ZONE FROM
THE FRONTAL PASSAGE ON WED NIGHT. THE SFC WAVE MOVES NORTHEAST INTO
PA AND UPSTATE NY BY LATE IN THE DAY ON THU VIA THE ECMWF. THE HPC
GUIDANCE…AND GFS HAVE A SECONDARY COLD FRONT SLIP SOUTH OF THE
REGION DURING THE DAY…AND THE WAVE IS MUCH FLATTER PASSING SOUTH
OF THE REGION. WE KEPT MUCH OF THE DAY DRY ON THU WITH HIGH
PRESSURE IN CONTROL. WE DID ADD A SLIGHT CHC OF SNOW THU NIGHT
OVER MOST OF THE REGION IN THE GRIDDED FCST JUST IN CASE THE ECMWF
IS CORRECT HERE. LATER RUNS OF THE GFS COULD TREND FURTHER NORTHWARD
WITH THE ACTIVE W/SW FLOW ALOFT.

FRI-FRI NIGHT…THIS IS WHERE THE MEDIUM RANGE GUIDANCE CONTINUES TO
DIVERGE. THE HPC GUIDANCE AND GFS HAVE A COLD FRONT MOVING SOUTH
WITH HIGH PRESSURE RIDGING BACK IN WITH A NRN STREAM DISTURBANCE
DIGGING S/SE FROM THE UPPER MIDWEST. THE SUBTROPICAL JET/SRN STREAM
DISTURBANCE IS EJECTING OUT OF TX. WE KEPT SOME SLIGHT OR LOW CHC
POPS IN FOR SNOW SHOWERS OR LIGHT SNOW DURING THIS TIME FRAME WITH
THE FIRST WAVE MOVING INTO GULF OF MAINE AND THE CANADIAN
MARITIMES. THE ECMWF/CANADIAN GGEM/SOME GLOBAL ENSEMBLES MEMBERS
HAVE A AN IMPRESSIVE SYSTEM FORMING OVER THE SRN PLAINS/LOWER MS
RIVER VALLEY FRI NIGHT WITH A POSITIVELY TILTED LONGWAVE TROUGH
BEING CARVED OUT OVER THE CNTRL PLAINS.

SAT-SUN…VERY LOW CONFIDENCE FORECAST CONTINUES. CAN GGEM AND
ECMWF CONTINUES TO HAVE COASTAL WAVE MOVING NORTHEAST INTO MID
ATLANTIC REGION…AND SOUTH OF LONG ISLAND BY SUNDAY. THE 18Z HPC
GUIDANCE IS TRENDING FURTHER NORTH LATE SAT INTO SUNDAY WITH THE
WAVE. WE KEPT SLIGHT TO LOW CHC POPS IN FOR THE WEEKEND WITH SNOW
AS THE MAIN PTYPE /AS SUFFICIENTLY COLD ENOUGH AIR IS IMPLIED/. THE
TIMING AND EVOLUTION OF THE LATE WEEK INTO THE WEEKEND SYSTEMS IS
VERY UNCERTAIN. IT COULD BE VERY ACTIVE. TEMPS LOOK TO AVERAGE
NEAR NORMAL FOR FEBRUARY DURING THIS STRETCH.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/…
MAINLY VFR CONDITIONS ARE EXPECTED AT THE KGFL/KALB/KPOU TAF SITES
THROUGH THE TAF PERIOD ENDING AT 00Z TUESDAY. HOWEVER…AS ANOTHER
FRONTAL BOUNDARY CROSSES THE REGION DURING THE NITE…THERE IS THE
POTENTIAL FOR MVFR/IFR CONDITIONS IN SNOW SHOWERS BEFORE/DURING AND
AFTER FORNTAL PASSAGE. THE CHANCES ARE BEST AT KGFL WHERE A PERIOD
OF MVFR CONDITIONS HAVE BEEN FORECAST BETWEEN 05Z AND 10Z…WITH A
TEMPO GROUP FOR IFR VSBYS IN SNOW SHOWERS BETWEEN 05Z AND 08Z. MUCH
LESS THREAT FOR MVFR/IFR CONDITIONS AT KALB…SO ONLY VCSH HAS BEEN
INCLUDED IN THE FORECAST. AT KPOU NO PCPN IS EXPECTED DURING THE TAF
PERIOD. AFTER ABOUT 10Z…VFR CONDITIONS WILL PREVAIL AT ALL THREE
TAF SITES AS GUSTY WESTERLY WINDS BRING COLDER AIR TO THE REGION AND
GNERALLY SCT/BKN CU/SC.

SURFACE WINDS WILL BE 10 KTS OR LESS FROM THE SOUTH OR SOUTHWEST
THIS EVENING AHEAD OF THE FRONTAL BOUNDARY. WINDS WILL SHOFT BETWEEN
05Z AND 07Z AT THE TAF SITES AND BECOME WESTERLY AT 10 TO 15 KTS
WITH GUSTS OF 15 TO 25 KTS BEHIND THE FRONT AND THROUGH MOST OF
MONDAY. BY LATE IN THE DAY ON MONDAY THE WINDS WILL DECREASE TO LESS
THAN 10 KTS.

CLOUDS WILL ALSO BEGIN TO INCREASE AGAIN LATE IN THE DAY AHEAD OF A
WARM FRONT.

OUTLOOK…
MON NIGHT…VFR/MVFR WITH -SN LIKELY.
TUE…VFR/MVFR AT KGFL WITH -SN LIKELY ESP IN THE MORNING. KALB
SOUTH TO KPOU VFR.
TUE NIGHT-WED…VFR/MVFR. CHC -SHRA/-SHSN.
THU…VFR…SLIGHT CHC -SHRA AT KPOU.
FRI…VFR…SLIGHT CHC -SHRA/-SNSHS.

&&

.HYDROLOGY…
RIVER FLOWS CONTINUE TO RECEDE…ALTHOUGH SOME GAGE SITES REMAIN
IMPACTED BY ICE INCLUDING MCKN6. NO MAJOR PROBLEMS ARE EXPECTED ON
THE RIVERS THROUGH THE MID WEEK PERIOD…OTHER THAN THOSE AREAS
SUCH AS MCKN6 WHERE ICE JAMS ARE STILL A POSSIBILITY. THE
PRECIPITATION THROUGH THE MID WEEK PERIOD IS EXPECTED TO BE MAINLY
IN THE FORM OF SNOW WITH QPF AMOUNTS RANGING FROM A FEW HUNDREDTHS
OF AN INCH TO A QUARTER TO A THIRD OF AN INCH ACROSS NORTHWEST
PORTIONS OF THE HSA.

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…WINTER WEATHER ADVISORY UNTIL 10 AM EST MONDAY FOR NYZ032-033-
038.
MA…NONE.
VT…NONE.

&&

$$
SYNOPSIS…FRUGIS/11
NEAR TERM…FRUGIS/11
SHORT TERM…11
LONG TERM…WASULA
AVIATION…GJM
HYDROLOGY…11

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