January 14, 2013 Forecast Discussion

000
FXUS61 KALY 150019
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
720 PM EST MON JAN 14 2013

.SYNOPSIS…
HIGH PRESSURE WILL BUILD INTO THE REGION TONIGHT AND TUESDAY…WHILE
A DISTURBANCE PASSES BY TO OUR SOUTH. THIS HIGH PRESSURE SYSTEM WILL
MOVE OFFSHORE TUESDAY NIGHT. ANOTHER DISTURBANCE WILL PASS BY TO OUR
SOUTH LATE TUESDAY NIGHT AND WEDNESDAY…AND THIS ONE WILL BE CLOSE
ENOUGH TO BRING SOME SNOW TO THE REGION.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/…
AS OF 700 PM…PREVIOUS GRIDDED FORECAST IN GOOD SHAPE. THE ONLY
CHANGES MADE WERE TO UPDATE THE HOURLY TEMP GRIDS TO REFLECT CURRENT
CONDITIONS…AND TO UPDATE THE HOURLY SKY GRIDS TO REFLECT SOMEWHAT
THICKER HIGH CLOUD COVER SPREADING ACROSS THE SOUTHERN PART OF THE
FORECAST AREA.

.PREVIOUS DISCUSSION…
AS OF 345 PM…DRY WEATHER ACROSS THE ENTIRE REGION. STILL DEALING
WITH SOME LAKE EFFECT CLOUDS…MAINLY CONFINED TO WEST OF A
JOHNSTOWN/GLOVERSVILLE LINE. TO THE SOUTH…HIGH CIRRUS CLOUDS WERE
FOUND SOUTH OF ALBANY…WELL TO THE NORTH OF A FRONT THAT WAS IN THE
PROCESS OF STALLING ACROSS THE MID ATLANTIC REGION. A WAVE WILL
PROPAGATE ALONG THIS FRONT WITH ITS PRECIPITATION SHIELD VERY
LIKELY REMAIN SOUTH OF OUR REGION.

RADARS INDICATED NO RETURNS AT ALL COMING FROM THE CLOUDS…TOO THIN
TO SUPPORT PRECIPITATION.

IT WILL REMAIN DRY THROUGH TONIGHT AS WEAK BUBBLE OF HIGH PRESSURE
BUILDS INTO THE REGION. THIS IS NOT AN ARCTIC HIGH BUT WILL BRING A
RETURN TO MORE SEASONABLY CHILLY TEMPERATURES TONIGHT…STILL ABOUT
10 DEGREES ABOVE THE NORMAL MID JANUARY READINGS. HOWEVER…EVERYONE
WILL DIP WELL BELOW FREEZING TONIGHT…GENERALLY IN THE 20S (TEENS
ACROSS THE ADIRONDACKS).

AS FAR AS THE CLOUDS ARE CONCERNED…THE LAKE EFFECT CLOUDS TO OUR
WEST SHOULD DISSIPATE DURING THE EVENING AS THE FLOW OFF LAKE
ONTARIO WEAKENS. WE WILL BE LEFT WITH A CLEAR TO PARTLY CLOUDY SKY
EXCEPT TO THE SOUTH WHERE MORE IN THE WAY OF HIGHS CLOUDS WILL TAKE
PLACE FROM TIME TO TIME.

A GUSTY WIND HAS BEEN USHERING THE COOLER AIR. THIS WIND TOO WILL
DIMINISH SLOWLY THROUGHOUT THE EVENING…DOWN TO AROUND 5 MPH
OVERNIGHT FROM THE NORTH OR NORTHWESTERLY DIRECTION.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/…RIDGING WILL
CONTINUE TO BUILD IN ON TUESDAY…WITH THE FRONTAL BOUNDARY
STALLED TO OUR SOUTH ACROSS THE MID ATLANTIC REGION. TEMPERATURES
WILL BE CLOSER TO SEASONABLE LEVELS BUT STILL RUN ABOUT 5 TO 10
DEGREES ABOVE NORMAL.

WAVES OF LOW PRESSURE WILL MOVE ALONG THE STALLED FRONTAL BOUNDARY.
MODEL GUIDANCE INDICATES THE NORTHERN FRINGE OF THE PRECIPITATION
MAY REACH THE SOUTHERN MOST PORTION OF THE FORECAST AREA WEDNESDAY
MORNING. THE FIRST ONE LOOKS TO STAY WELL SOUTH OF OUR REGION.

HOWEVER…A SECOND ONE…CURRENTLY OVER SOUTHERN TEXAS…NOW LOOKS
TO BE A LITTLE STRONGER. ALL THE 12Z MODELS HAVE TRENDED
CONSIDERABLY FURTHER NORTH WITH THIS WAVE…COMPARED TO THE
OVERNIGHT RUNS. THE 12Z/18Z NAM IS THE FURTHEST SOUTH…BUT EVEN
THIS MODEL BRINGS TO QPF RIGHT TO ABOUT THE INTERSTATE 90 CORRIDOR.

MEANWHILE…THE 12Z GGEM/ECMWF/AND GFS BRING PRECIPITATION WELL
NORTH OF EVEN ALBANY. A DECENT AREA OF LOW PRESSURE LOOKS TO DEVELOP
ON THE STALLED OUT FRONTAL BOUNDARY…STILL DRAPED ACROSS THE MID
ATLANTIC REGION. A DECENT SHOT OF ISENTROPIC LIFT COURTESY OF A
PRETTY POTENT LOW LEVEL SSW JET AND THE REGION BEING IN THE RIGHT
ENTRANCE REGION OF THE UPPER LEVEL JET. SYNOPTICALLY…A
LONG-FETCHED POSITIVELY TILTED TROUGH ACROSS THE SW CORNERS WILL
HELP PROPEL THIS DISTURBANCE QUICKLY EASTWARD.

HAVE INCREASED POPS TO LIKELY AS FAR NORTH AS ALBANY…CHANCES UP TO
GLENS FALLS LATE TUESDAY NIGHT INTO EARLY WEDNESDAY. THE THERMAL
PROFILES OFF THE NAM SUGGEST ALL SNOW (ALTHOUGH AGAIN THE
PRECIPITATION STAYS MAINLY SOUTH OF ALBANY). THE 12Z GFS MODEL
SOUNDINGS WERE A LITTLE WARMER…BUT THEY TOO MOSTLY IMPLY
MOSTLY…IF NOT ALL SNOW FOR OUR REGION.

FOR NOW…FOLLOWED THIS TREND AND THE NERFC QPF GRIDS VERY CLOSELY.
USED LIQUID TO SNOW RATIOS OF 12:1 LATE TUESDAY NIGHT…THEN 10:1
DURING THE MORNING WEDNESDAY. AGAIN…ALL MODELS INDICATED THAT THE
PRECIPITATION WILL QUICKLY EXIT OUR REGION DURING THE
AFTERNOON.

THE POTENTIAL IS THERE FOR A LIGHT TO PERHAPS A MODERATE SNOWFALL
ACCUMULATION FROM THE CAPITAL DISTRICT SOUTHWARD. AT THIS
TIME…SINCE MOST OF THE NUMBERS FALL BELOW ADVISORY CRITERIA…WILL
NOT EVEN MENTION THE HWO AT THIS TIME. LATER SHIFTS WILL MONITOR
TRENDS TO SEE IF WE HAVE TO RAMP UP POTENTIAL SNOWFALL ACCUMULATIONS
EVEN MORE.

IN THE WAKE OF THIS SYSTEM…AN ARCTIC BOUNDARY WILL APPROACH FROM
THE NORTHWEST LATE WEDNESDAY NIGHT INTO EARLY THURSDAY. THIS
BOUNDARY WILL USHER A COLDER…. AIRMASS IN FOR LATE IN THE WEEK
ALTHOUGH THE MAIN SURGE OF THIS AIR MASS LOOKS TO STAY MAINLY NORTH
OF ALBANY. MOISTURE WITH THIS FRONT LOOKS VERY LIMIT AND CONTINUE TO
MENTION ONLY CHANCE POPS FOR SNOW SHOWERS ACROSS OUR NORTHWESTERN
AREAS.

TEMPERATURES ON TUESDAY LOOK TO BE CLOSE TO 40 IN THE HUDSON
VALLEY…30S HIGHER TERRAIN SO STILL ABOVE NORMAL. OVERNIGHT LOWS
TUESDAY NIGHT WILL BE IN THE 20S (EXCEPT TEENS ADIRONDACKS). LOWERED
TEMPERATURES A CATEGORY WEDNESDAY AS THE ANTICIPATED CLOUDS/SNOW
SHOULD KEEP THEM IN THE LOWER TO MID 30S.

WEDNESDAY NIGHT WILL SEE TEMPERATURES DIP AGAIN MAINLY INTO THE 20S
FROM ALBANY SOUTHWARD…TEENS AND EVEN SOME SINGLE NUMBERS WELL
NORTH OF ALBANY (WHERE A MORE EXTENSIVE SNOW PACK COULD BE IN
PLACE). THESE OVERNIGHT LOWS ASSUME SOME CLOUDINESS. IF WE WERE TO
CLEAR AND RECEIVE MORE SNOW THAN WE ARE CURRENTLY THINKING…THESE
NUMBERS MIGHT NOT BE LOW ENOUGH.

THURSDAY…WITH THE ARCTIC BOUNDARY…TEMPERATURES LOOK TO STAY AT
OR BELOW FREEZING FROM ALBANY NORTHWARD…MID TO UPPER 30S FURTHER
SOUTH. THIS ASSUMES THIS FRONT WILL ARRIVE DURING THE DAY
(LATER…NOT EARLIER). IF IT WERE TO ARRIVE EARLIER…AGAIN NUMBERS
WOULD HAVE TO BE LOWERED A LITTLE BIT.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/…
MEDIUM RANGE MODELS NOW SHOWING THAT THE INITIAL SURGE OF COLD AIR
EARLY IN THE EXTENDED PERIOD WILL NOT BE THAT COLD (GENERALLY TEMPS
DROPPING TO NEAR AVERAGE FOR MID JANUARY). THEN A BRIEF WARMUP
DURING THE WEEKEND AHEAD OF WHAT APPEARS TO BE THE FIRST OF ARCTIC
AIR INTO THE REGION LATE SUNDAY INTO EARLY NEXT WEEK. PCPN WISE THE
WEATHER WILL BE FAIRLY TRANQUIL WITH NOTHING MORE THAN 20 TO 30
PERCENT POPS FORECAST DURING THE PERIOD AS VARIOUS FRONTAL
BOUNDARIES MOVE THROUGH.

LOWS THURSDAY NIGHT WILL RANGE FROM JUST BELOW ZERO IN THE
ADIRONDACKS TO THE TEENS OVER THE SOUTHERN HALF OF THE FORECAST
AREA. HIGHS FRIDAY IN THE UPPER TEENS TO LOWER 30S. LOWS FRIDAY
NIGHT IN THE UPPER SINGLE NUMBERS TO LOWER 20S. AS A DEEPENING
SURFACE LOW MOVES EAST ACROSS THE NORTHERN GREAT LAKES AND THEN DOWN
THE SAINT LAWRENCE RIVER VALLEY…THE FORECAST AREA WILL BE IN THE
WARM SECTOR OF THIS SYSTEM WITH LITTLE MORE THAN SCT PCPN AND MILDER
TEMPS. HIGHS SATURDAY WILL BE IN THE UPPER 20S AND 30S. LOWS
SATURDAY NIGHT IN THE MID TEENS TO MID 20S. HIGHS SUNDAY WILL BE IN
THE MID 20S TO THE 30S…BUT THIS COULD CHANGE SIGNIFICANTLY BASED
ON THE TIMING OF THE ARCTIC COLD FRONT THAT WILL BE CROSSING THE
REGION THAT DAY. TEMPS WILL DROP SHARPLY LATE SUNDAY AND SUNDAY
NIGHT WITH LOWS REACHING ZERO TO 5 BELOW ZERO OVER THE ADIRONDACKS
TO NEAR 20 OVER THE EXTREME SOUTH WITH A STRONG NORTHWEST WIND.
HIGHS MONDAY WILL BE IN THE TEENS AND 20S. A LOOK AT THE MODELS
FURTHER AHEAD INTO NEXT WEEK SHOWS EVEN COLDER AIR ARRIVING AND
LINGERING MUCH OF THE WORKWEEK.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/…
HIGH PRESSURE WILL BUILD INTO THE REGION TONIGHT AND TUESDAY WITH
VFR CONDIIONS EXPECTED AT THE KGFL/KALB/KPOU/KPSF TAF SITES THROUGH
THE TAF PERIOD ENDING AT 00Z WEDNESDAY. SURFACE LOW PRESSURE PASSING
BY TO THE SOUTH OF THE REGION WILL KEEP HIGH CLOUDS OVER THE REGION
MUCH OF THE NIGHT…AND AT KPOU TAF SITE THROUGH THE DAY TUESDAY.

NORTHWEST SURFACE WINDS THIS EVENING AT 5 TO 15 KTS WILL DIMINISH TO
AROUND 5 KTS OR LESS AT ALL THE TAF SITES BY MIDNIGHT…AND CONTINUE
LIGHT THROUGH TUESDAY.

OUTLOOK…
TUE NIGHT/WED…VFR…BCMG SUB-VFR CIG. -SN LKLY KALB SOUTH/CHC -SN
KGFL).
WED NT-SAT…VFR…NO SIG WX.

&&

.HYDROLOGY…
A COLDER AND MORE SEASONABLE AIRMASS HAS RESULTED IN THE SLOWDOWN OF
RUNOFF LATER TODAY AND ESPECIALLY TONIGHT WHEN TEMPERATURES FALL
WELL FREEZING REGION WIDE. THIS WILL END THE THREAT OF INCREASING
RISES ON RIVERS AND STREAMS.

IT NOW APPEARS LIKELY THAT ANOTHER SURGE OF PRECIPITATION WILL
SPREAD NORTHWARD TO AT LEAST THE CAPITAL DISTRICT TUESDAY NIGHT INTO
EARLY WEDNESDAY. HOWEVER…THIS LOOKS TO BE MOSTLY IN THE FORM OF
SNOW…WITH THE POTENTIAL FOR LIGHT ACCUMULATIONS. THEREFORE…NO
IMPACTS ARE EXPECTED ON THE WATERSHEDS.

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/HWJIV
NEAR TERM…GJM/HWJIV
SHORT TERM…HWJIV
LONG TERM…GJM
AVIATION…GJM
HYDROLOGY…HWJIV

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