November 25, 2013 Forecast Discussion

000
FXUS61 KALY 252353
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
653 PM EST MON NOV 25 2013

.SYNOPSIS…
LOW PRESSURE DEVELOPING IN THE GULF STATES…LOOKS TO TRACK UP THE
EASTERN SEABOARD LATE TUESDAY THROUGH EARLY THANKSGIVING DAY…
RIGHT THROUGH THE HUDSON VALLEY. THIS TRACK WILL LIKELY BRING MOST
AREAS MORE RAIN THAN SNOW…BUT SIGNIFICANT AMOUNTS OF WINTRY
PRECIPITATION ARE POSSIBLE OVER THE ADIRONDACKS.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/…
…BURST OF SNOW POSSIBLE FOR THE MORNING RUSH HOUR TUESDAY…

AS OF 650 PM EST…HAVE MADE SOME MAJOR CHANGES TO THE GRIDDED
DATABASE FOR LATE TONIGHT INTO TUESDAY MORNING. LATEST RUC13/HRRR
AND 21Z/SREF SUITE INDICATE A BURST OF WARM ADVECTION
PRECIPITATION…DEVELOPING AFTER 08Z TONIGHT…AND LINGERING UNTIL
13Z-15Z/TUESDAY. RECENT SATELLITE IMAGERY INDICATES ABUNDANT MID
AND HIGH LEVEL MOISTURE APPROACHING FROM THE SOUTHWEST…IN
ADVANCE OF THE INCOMING CLIPPER-TYPE SYSTEM ACROSS THE GREAT
LAKES. AS STRONG DYNAMICAL LIFT INTERACTS WITH THE INCOMING MID
LEVEL MOISTURE…PRECIPITATION IS EXPECTED TO DEVELOP BEFORE
DAYBREAK…AND LINGER INTO MID MORNING TUESDAY. THE ONLY QUESTION
IS…HOW QUICKLY WITH THE LOW LEVELS SATURATE TO ALLOW PRECIP TO
REACH THE GROUND. AT THIS TIME…BASED HEAVILY ON RUC/HRRR
OUTPUT…HAVE ADDED LIKELY POPS TO MUCH OF THE CAPITAL
REGION/MOHAWK RIVER VALLEY/BERKSHIRES/EASTERN CATSKILL
REGIONS…WITH CHC POPS ELSEWHERE. SNOWFALL ACCUMS WILL GENERALLY
BE A DUSTING TO AN INCH…ALTHOUGH THERE MAY BE LOCALLY HIGHER
AMTS JUST N OF THE MOHAWK RIVER…ESP ACROSS PORTIONS OF SARATOGA
CO…WHERE AROUND AN INCH IS EXPECTED…AND ALSO ACROSS PORTIONS OF THE
CENTRAL TACONICS AND NORTHERN BERKSHIRES…WHERE 1-3 INCHES COULD
OCCUR.

TEMPERATURES SHOULD HOLD STEADY..AND PERHAPS RISE A DEGREE OR TWO
TOWARD SUNRISE AS WARM ADVECTION BEGINS TO INCREASE.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/…
…WINTER STORM WATCH REMAINS IN EFFECT FOR THE SOUTHERN
ADIRONDACKS…

AS MENTIONED IN THE PREVIOUS SECTION…EXPECT A BURST OF SNOW
SHOWERS IN THE MORNING HOURS…WITH MINOR ACCUMS LIKELY. A BREAK
IN THE PRECIPITATION IS THEN EXPECTED FROM MID MORNING THROUGH AT
LEAST EARLY AFTERNOON.

THEN…THE MAIN STORM SYSTEM STILL EXPECTED TO AFFECT THE REGION
LATE TOMORROW AFTERNOON THROUGH WEDNESDAY NIGHT. BASED ON THE
SOUTHERN STREAM DOMINANCE OF THE SYSTEM…THE ASSOCIATED
CONVECTION AND DOWNSTREAM UPPER RIDGING…SIDING WITH MORE WESTERN
TRACK OF THE SURFACE FEATURE AND WARMER GUIDANCE IN TERMS OF
TEMPERATURES ALOFT. THIS WOULD SUGGEST SOME PERIODS OF LIGHT SNOW
TO DEVELOP ONCE AGAIN LATE TOMORROW AFTERNOON ALONG THE FORWARD
SURGE OF THE MID LEVEL JET…MOISTURE AND ISENTROPIC LIFT WITH
TEMPERATURES REACHING THE 30S IN THE AFTERNOON…PERHAPS AROUND 40
HUDSON VALLEY TOWARD AND AFTER SUNSET ONCE THE WARM ADVECTION
INCREASES RAPIDLY. SNOW SHOULD CHANGE TO A MIX AND RAIN IN VALLEY
AREAS AND SOUTHERN AREAS AROUND OR JUST AFTER SUNSET. ANY SNOW
ACCUMULATIONS AFTER THE INTIAL MORNING BURST SHOULD BE LITTLE IF
ANYTHING.

LOW LEVEL JET ENERGY SURGES NORTH TUESDAY NIGHT WITH VERY HIGH
PWAT…FORCING AND UPPER DYNAMICS. BASED ON THE LOW LEVEL RIDGING
BEING OFFSHORE THE MID ATLANTIC COAST…AGEOSTROPHIC WINDS NOT
SUGGESTING ANY COLD ADVECTION TO ANCHOR COLD AIR AT LOW LEVELS…
SO WARM AIR SHOULD BE ABLE TO SPREAD NORTH THROUGH THE NIGHT.
STILL…AREAS OF THE WESTERN MOHAWK VALLEY…LAKE GEORGE SARATOGA
REGION AND SOUTHERN ADIRONDACKS WILL BE THE SLOWEST TO WARM WHERE
ACCUMULATING SNOW…FREEZING RAIN AND SLEET WILL OCCUR.
TEMPERATURES MAY FALL A DEGREE OR TWO TOMORROW EVENING BUT THEN
RISE AFTER MIDNIGHT AND THROUGH SUNRISE…AGAIN…WITH THE MOST
WARMING OUTSIDE OF NORTHERN AND NORTHWESTERN AREAS.

THE COMBINATION OF SNOW…FREEZING RAIN AND SLEET COULD BE ENOUGH
FOR WINTER STORM WARNINGS…BUT JUST KEEPING THE WATCHES UP UNTIL
THE ACTUAL STORM TRACK PRECIPITATION TRANSITION ZONE IS MORE
CLEAR. AREAS THAT SEE MOSTLY RAIN WILL SEE RAIN HEAVY AT TIMES…
WHICH WILL CONTINUE THROUGH WEDNESDAY MORNING. ENSEMBLE
PROBABILITIES FOR 2 OR MORE INCHES OF RAIN EXIST OVER SOUTHERN NY
AND WESTERN NEW ENGLAND WHERE FLOOD WATCHES MAY BE CONSIDERED
AFTER THE NEXT SET OF GUIDANCE IS CONSULTED TONIGHT. HIGHS
WEDNESDAY WITH THE WARM ADVECTION IN THE 40S…AROUND 40
SOUTHERN ADIRONDACKS…AND SOME 50S MID HUDSON VALLEY AND NW CT.

SYSTEM EXITS LATER WEDNESDAY AND WEDNESDAY NIGHT…WITH
INDICATIONS OF A DRY SLOT AND VERY LITTLE IN THE WAY OF UPPER
DEFORMATION…SUGGESTING ONLY SCATTERED SNOW SHOWER OR SNOW FLURRY
ACTIVITY AS THE PRECIPITATION EXITS. LAKE EFFECT SNOW SHOWER
ACTIVITY SHOULD QUICKLY EVOLVE TO NORTHWEST/SOUTHEAST ORIENTED
MULTI BANDS AS NORTHWEST LOW LEVEL FLOW SETS UP AND COLD ADVECTION
DEEPENS. HIGHS THURSDAY IN THE MID 20S TO LOWER 30S…SOME UPPER
TEENS SOUTHERN ADIRONDACKS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/…
THU NT-FRI NT…AS THE STORM SYSTEM CONTINUES TO DEPART TO OUR NORTH
AND NORTHEAST…HIGH PRESSURE BUILDS IN FROM THE SOUTHWEST THU NT
AND EARLY FRI…WITH REINFORCING HIGH PRESSURE BUILDING ACROSS SOUTH
CENTRAL CANADA. A WEAK SFC TROUGH WILL SEPARATE THESE TWO
HIGHS…AND WILL SLOWLY PASS SOUTHWARD ACROSS OUR REGION ON FRIDAY.
AT THIS TIME…HAVE KEPT CONDITIONS DRY…BUT WILL HAVE TO WATCH FOR
THE POSSIBILITY OF SOME LIGHT SNOW SHOWERS OR FLURRIES ACCOMPANYING
THIS BOUNDARY…ESPECIALLY FOR CENTRAL AND SOUTHERN PORTIONS OF THE
REGION. TEMPS SHOULD REMAIN BELOW SEASONAL LEVELS…WITH DAYTIME
MAXES MAINLY IN THE 20S TO LOWER 30S…AND OVERNIGHT MINS FALLING
INTO THE SINGLE DIGITS AND TEENS FOR MOST AREAS…EXCEPT FOR 15-20
ACROSS PORTIONS OF THE MID HUDSON VALLEY.

SAT-SUN NT…HIGH PRESSURE INITIALLY BUILDS ACROSS FROM SOUTHEAST
CANADA…WITH MAINLY FAIR CONDITIONS…AND CHILLY TEMPS FOR SAT.
HOWEVER…AS THE HIGH MOVES FURTHER EAST…A VEERING LIGHT EAST TO
SOUTHEAST FLOW ABOVE THE BOUNDARY LAYER MAY ALLOW FOR SOME LOW LEVEL
MOISTURE TO BUILD NORTHWARD…WHICH THE 12Z/25 SHOWS MOST
AGGRESSIVELY. AT THIS TIME…WILL ONLY ADD SOME SLIGHT CHC POPS FOR
SUNDAY…AND LOW CHC POPS FOR SUN NT…MAINLY FOR LIGHT SNOW
SHOWERS…GIVEN COLD THERMAL PROFILES. FOR TEMPS…EXPECT SAT MAXES
TO REACH MID 20S TO LOWER 30S …ALTHOUGH PERHAPS SOME UPPER
TEENS/LOWER 20S ACROSS SOME HIGHER ELEVATIONS. ON SUNDAY…EXPECT
MAX TEMPS TO REACH THE MID 30S TO NEAR 40 IN VALLEY AREAS…AND
GENERALLY 20S TO LOWER 30S ACROSS HIGHER ELEVATIONS. SAT NT/SUN AM
MINS SHOULD FALL INTO THE TEENS TO LOWER 20S IN MOST AREAS…WHILE
SUN NT/MON AM MINS SHOULD FALL INTO THE 20S.

MONDAY…UNCERTAINTY INCREASES AMONG SOURCES OF
GUIDANCE…ESPECIALLY WITH REGARD TO THE HANDLING OF A PV MAX
OFF THE CALIFORNIA COAST…AND THE POSSIBLE INTERACTION WITH A
NORTHERN STREAM PV MAX. THE 12Z/25 ECMWF HINTS AT A STRONGER PIECE
OF THE SOUTHWEST PV EJECTING OUT AND ALLOWS FOR GREATER INTERACTION
WITH THE NORTHERN STREAM ENERGY…AND SUBSEQUENT STRONGER SFC
DEVELOPMENT CLOSER TO THE EAST COAST EARLY NEXT WEEK. AT THIS
TIME…DUE TO OVERALL LOW CONFIDENCE…HAVE INDICATED CHC POPS…FOR
RAIN/SNOW SHOWERS…WITH SNOW SHOWERS DOMINANT DURING NIGHTTIME

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/…
SURFACE HIGH PRESSURE CONTINUES TO MOVE OFF THE MID ATLANTIC COAST
THIS AFTERNOON INTO TONIGHT. LOW PRESSURE WILL BE ORGANIZING OVER
THE DEEP SOUTHEAST TOMORROW MORNING…AS AN UPPER LEVEL
DISTURBANCE PRODUCES SNOW SHOWERS TOWARD AND JUST AFTER DAYBREAK.

SO…VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 06Z/TUE.
THEN…SNOW SHOWERS WILL LIKELY DEVELOP/EXPAND ACROSS THE
REGION…WITH THE GREATEST POTENTIAL TO IMPACT KGFL/KALB/KPSF
BETWEEN ROUGHLY 08Z-15Z/TUE. MVFR VSBYS/CIGS ARE LIKELY WITH
THIS…AND SOME IFR VSBYS COULD ALSO OCCUR.

ONCE THE INTIAL BURST OF SNOW SHOWERS TAPERS OFF TUE
MORNING…EXPECT MAINLY VFR CIGS…UNTIL AFTER 21Z-22Z…WHEN MVFR
TO IFR CONDITIONS OVERSPREAD THE REGION ONCE AGAIN…ALONG WITH
SNOW AND/OR A MIX OF SNOW AND SLEET.

THE WINDS WILL BE FROM THE SOUTH TO SOUTHWEST AT LESS THAN 10 KTS
THROUGH TUESDAY MORNING…THEN SHOULD GRADUALLY BACK INTO THE S TO
SE AT 5-10 KT LATE TUE AFTERNOON.

OUTLOOK…
TUE NT AND WED: HIGH OPERATIONAL IMPACT. DEFINITE RA.
WED NT: MODERATE OPERATIONAL IMPACT. BREEZY LIKELY SHSN…SN.
THU: LOW OPERATIONAL IMPACT.BREEZY SLIGHT CHANCE OF SHSN.
THU NT THROUGH SAT: NO OPERATIONAL IMPACT. NO SIG WX.

&&

.HYDROLOGY…
A POTENT COASTAL STORM WILL IMPACT THE REGION WITH MODERATE TO
POTENTIALLY SIGNIFICANT AMOUNTS OF WATER EQUIVALENT.

IT WILL BE MAINLY DRY THROUGH EARLY TUESDAY.

THE TIME FRAME WILL BE FROM LATE TUESDAY AFTERNOON INTO WEDNESDAY
EVENING AS A COASTAL STORM COULD BRING 1.5 TO 3+ INCHES OF LIQUID
EQUIVALENT PRECIPITATION TO THE REGION /LOCALLY HIGHER AMOUNTS ARE
POSSIBLE/. IT WILL BEGIN AS SNOW AND COULD LINGER AS SNOW AND
SLEET IN THE NORTHERN MOUNTAINS. HOWEVER IN MUCH OF THE REGION IT
IS EXPECTED TO CHANGE TO RAIN…RESULTING IN SIGNIFICANT WITHIN
BANK RISES. IN THIS STORMS WAKE IT WILL TURN SHARPLY COLDER AGAIN
WEDNESDAY NIGHT…WITH ICE FORMATION LIKELY TO BEGIN ANEW.

RAIN…POSSIBLY HEAVY AT TIMES…COULD CAUSE SOME PONDING OF SOME
ROADWAYS WHERE LEFTOVER LEAVES COULD CLOG STORM DRAINS. A FLOOD
WATCH MAY BE NEEDED FOR PARTS OF THE REGION IF THE POTENTIAL FOR
MINOR FLOODING INCREASES.

THE GOOD NEWS IS THAT FLOW WERE RUNNING A BIT BELOW NORMAL DUE TO
PERSISTENT DRY WEATHER OF LATE. HOWEVER…ONE TO TWO PLUS INCHES
OF RAINFALL IN LESS THAN 12 HRS COULD CAUSE SOME PROBLEMS.

AFTER THE STORM BLASTS THROUGH ANOTHER MAINLY DRY SPELL IS EXPECTED
WITH CONTINUED BELOW NORMAL TEMPERATURES.

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 STORM WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
EVENING FOR NYZ032-033-038-042-082.
MA…NONE.
VT…NONE.

&&

$$
SYNOPSIS…NAS
NEAR TERM…KL/NAS
SHORT TERM…NAS
LONG TERM…KL
AVIATION…KL/WASULA
HYDROLOGY…NAS

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