December 22, 2014 Forecast Discussion

000
FXUS61 KALY 222117
AFDALY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
417 PM EST MON DEC 22 2014

.SYNOPSIS…
AN APPROACHING WARM FRONT TO THE WEST WILL ALLOW FOR A WINTRY MIX
CHANGING TO RAIN FOR TONIGHT INTO TOMORROW. ON WEDNESDAY…A STORM
WILL ORGANIZE IN THE TENNESSEE VALLEY AND INTENSIFY RAPIDLY AS IT
MOVES NORTH TO THE OTTAWA VALLEY. IT WILL BRING A PERIOD OF
LOCALLY HEAVY RAIN AND STRONG WINDS WEDNESDAY INTO WEDNESDAY
NIGHT…BEFORE TAPERING TO SHOWERS FOR CHRISTMAS DAY WITH
TEMPERATURES FALLING DURING THE AFTERNOON.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/…
FOR TONIGHT…PRECIPITATION TYPES LOOK TRICKY. THEY WILL BE HIGHLY
DEPENDENT ON HOW MUCH WARM AIR ADVECTION ALOFT WORKS TO THE
SURFACE. MODEL SOUNDINGS AND PARTIAL THICKNESS VALUES SUPPORT A
QUICK TRANSITION FROM SNOW…SLEET AND A FEW POCKETS OF FREEZING
RAIN SOUTH THIS EVENING TO MAINLY RAIN OVERNIGHT. THUS THE HUDSON
VALLEY FROM THE CAPITAL DISTRICT THROUGH THE MID HUDSON VALLEY AND
INTO PARTS OF NW CT HAVE THE BEST CHANCE TO BE AT OR JUST ABOVE
FREEZING WHEN THE STEADIER PRECIPITATION ARRIVES AROUND AND AFTER
MIDNIGHT. AREAS ACROSS THE NORTH WILL LIKELY NOT RISE ABOVE
FREEZING BEFORE MORNING. HAVE ISSUED A WINTER WEATHER ADVISORY AT
THIS TIME FOR THE SOUTHERN ADIRONDACKS AND LAKE GEORGE REGION TO
RUN FROM MIDNIGHT THROUGH 9 AM TUESDAY.

LOWS OVERNIGHT ARE EXPECTED TO RANGE FROM THE UPPER 20S IN THE
SOUTHERN ADIRONDACKS TO THE MID 30S SOUTHEAST. TEMPS ARE EXPECTED
TO RISE OVERNIGHT.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/…
ON TUESDAY…FAIRLY STRONG WARM AIR ADVECTION IS EXPECTED TO
CHANGE ANY MIX TO JUST A COLD RAIN FAIRLY EARLY WITH HIGHS IN THE
UPPER 30S TO MID 40S. ON TUESDAY NIGHT…TEMPS WILL DROP A FEW
DEGREES TUESDAY EVENING BUT STAY ABOVE FREEZING ALONG WITH MORE
PERIODS OF RAIN AND LOWS IN THE MID 30S TO LOWER 40S. FOR
WEDNESDAY…IT WILL BE A LITTLE WARMER WITH STILL MORE PERIODS OF
RAIN AND HIGHS IN THE 40S TO MID 50S…EXCEPT SOME UPPER 30S
ACROSS THE ADIRONDACKS. AT THIS TIME DO NOT EXPECT STRONG WINDS
ABOVE THE BOUNDARY LAYER TO MIX TO THE SURFACE EXCEPT ACROSS THE
HIGHER TERRAIN. THE TIMING OF THE PASSAGE OF THE COLD FRONT IS IN
QUESTION…BUT THE TEMPERATURES STILL LOOK TO BE WELL ABOVE
FREEZING FOR WEDNESDAY NIGHT WITH TEMPS NOT FALLING AT ALL OR EVEN
SLOWLY RISING IN SOME AREAS WEDNESDAY NIGHT. LOWS ARE EXPECTED TO
BE IN THE UPPER 30S NORTH TO LOW TO MID 50S SOUTH/.

FOR CHRISTMAS MORNING…A COLD FRONT ATTACHED TO A DEEPENING LOW
PRESSURE SYSTEM WILL BE RACING EASTWARD ACROSS OUR REGION. THERE
IS GOOD MODEL CONSENSUS THAT THE LOW WILL TRACK WELL TO OUR NORTH
AND WEST…DEEPENING TO NEAR 975 MB NEAR JAMES BAY BY AFTERNOON.
AFTER AN EARLY MORNING HIGH IN MOST AREAS TEMPS WILL BE FALLING
THROUGH THE DAY. EXPECT MORNING HIGHS IN THE UPPER 30S NORTHWEST
TO MID 50S SOUTHEAST WITH TEMPS BY LATE IN THE DAY RANGING FROM
THE MID 30S NORTHWEST TO MID 40S SOUTHEAST.

THERE WILL BE STRONG GUSTY WINDS ON CHRISTMAS DAY MAINLY FROM THE
WEST TO NORTHWEST IN THE WAKE OF THE COLD FRONT. 0-30 MB AGL WINDS
SUGGEST GUSTS OF OVER 50 MPH ARE NOT OUT OF THE QUESTION ESPECIALLY
ACROSS THE HIGHER TERRAIN. WHILE IT IS TOO FAR OUT TO ISSUE ANY
WIND HEADLINES WILL KEEP THIS MENTIONED IN THE HOW FOR NOW. THE
PRECIPITATION WILL GRADUALLY DECREASE DURING THE DAY EXCEPT
ACROSS NORTHWEST PORTIONS OF THE FA WHERE SOME LAKE EFFECT SNOW
WILL BE POSSIBLE.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/…
THE EXTENDED FORECAST BEGINS WITH HIGH PRESSURE ATTEMPTING TO RIDGE
IN FROM THE MID ATLANTIC REGION…AND SOUTHEASTERN STATES CHRISTMAS
NIGHT. DEEP LOW PRESSURE…AROUND 965 HPA…WILL STILL BE CHURNING
OVER N-CNTRL QUEBEC. IT WILL REMAIN WINDY XMAS NIGHT DUE TO THE
STRONG SFC PRESSURE GRADIENT BETWEEN THE SFC CYCLONE AND THE
ANTICYCLONE. SOME WESTERLY UPSLOPE SNOW SHOWERS WILL PERSIST NEAR
THE WRN DACKS. ALSO A FEW LAKE EFFECT SNOW SHOWERS WILL LINGER NEAR
THE W-CNTRL MOHAWK VALLEY AND NRN CATSKILLS. LOWS WILL BE IN THE
M20S TO L30S WITH WESTERLY WINDS OF 15 TO 25 MPH WITH SOME GUSTS
STILL IN THE 30-40 MPH RANGE.

FRIDAY INTO FRIDAY NIGHT…TRANQUIL WX WITH HIGH PRESSURE RIDGING IN
FROM THE SOUTH. H850 TEMPS INCREASE +2C TO +6C WITH THE WARM
ADVECTION PATTERN. HIGHS WILL BE IN THE MID TO U30S OVER THE
MTNS…AND LOWER TO MID 40S IN THE VALLEY LOCATIONS. THE SFC HIGH
DRIFTS OFF THE COAST FRI NIGHT WITH A CLIPPER TYPE LOW APPROACHING
FROM THE UPPER GREAT LAKES REGION AND SRN ONTARIO. SOME HIGH CLOUDS
MAY INCREASE LATE. LOWS WILL RANGE FROM THE U20S TO L30S OVER THE
FCST AREA.

SATURDAY TO SATURDAY NIGHT….CLIPPER TYPE CYCLONE LIFT N/NE INTO
QUEBEC WITH A WEAK WARM FRONT AND A COLD FRONT SWINGING ACROSS THE
REGION LATE SATURDAY AFTERNOON INTO SATURDAY NIGHT. THE LOW-LEVEL
CONVERGENCE IS RELATIVELY WEAK WITH THE FRONTAL PASSAGE WITH THE
BEST SYNOPTIC FORCING NORTH AND WEST OF THE GREATER CAPITAL REGION.
SLIGHT AND LOW CHC POPS WERE KEPT IN THESE LOCATIONS PRIOR TO
00Z/SUN FOR RAIN OR SNOW SHOWERS. THE POPS WERE EXPANDED TO SLIGHT
CHC VALUES ACROSS THE REST OF THE FCST AREA SATURDAY NIGHT WITH THE
COLD FRONTAL PASSAGE AND WESTERLY UPSLOPE SNOW SHOWERS IN ITS WAKE.
ANY SNOW ACCUMULATIONS LOOK LIGHT AT THIS TIME. HIGHS ON SATURDAY
WILL BE IN THE LOWER TO M40S FROM THE MOHAWK VALLEY AND I-90
CORRIDOR SOUTH AND M30S TO L40S TO THE NORTH. LOWS WILL RANGE FROM
THE M20S TO L30S.

SUNDAY INTO MONDAY…THERE IS NOT A GOOD CONSENSUS WITH THE MEDIUM
RANGE GUIDANCE LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THE 12Z
GFS…THE GEFS MEAN AND MANY OF ITS ENSEMBLE MEMBERS HAVE HIGH
PRESSURE BUILDING IN FROM THE SOUTH AND WEST. THE ECMWF HAS A SRN
STREAM SFC WAVE FORMING OVER THE TN VALLEY SUNDAY MORNING AND MOVING
NORTHEAST AHEAD OF A PROGRESSIVE UPPER LEVEL TROUGH. AS IT TRACKS
NORTHEAST IT WOULD BRING OVER RUNNING RAIN AND SNOWFALL TO MOST OF
THE REGION. IT WOULD LIKELY BE SNOW FOR THE INTERIOR AND A BRIEF
MIXTURE OF RAIN AND SNOW IN THE HUDSON RIVER VALLEY SOUTH…CHANGING
TO ALL SNOW LATE IN THE DAY INTO THE EVENING. THE ECMWF HAS THE
CYCLONE TRACK JUST EAST OF LONG ISLAND 06Z/MON. THE WPC GUIDANCE
DISREGARDS THE ECMWF SOLUTION FAVORING A FRONTAL PASSAGE. THE ECMWF
TENDS TO DO A DECENT JOB…BUT NOT ALWAYS CORRECT…WITH IDENTIFYING
THESE EAST COAST WAVES IN DAYS 4 TO 7. WE WILL CONTINUE A LOW
CONFIDENCE 30-40 CHANCE OF SNOW/RAIN AND WILL MONITOR IF ANY BETTER
AGREEMENT OCCURS WITH THE MEDIUM RANGE GUIDANCE HERE. HIGH PRESSURE
LOOKS TO RETURN EARLY NEXT WEEK WITH SEASONABLY COLD AND DRY
WEATHER. HIGHS SUNDAY RANGE FROM THE U20S TO THE L30S NORTH AND
WEST OF THE CAPITAL DISTRICT…TO M30S TO AROUND 40F TO THE SOUTH
AND EAST. LOWS MONDAY MORNING WILL BE IN THE TEENS AND 20S…WITH
SEASONABLE LATE DECEMBER HIGH TEMPS FOR MONDAY.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/…
WITH A MOIST SOUTHERLY FLOW ALOFT…PLENTY OF CLOUDS ARE CURRENTLY
IN PLACE…WITH BKN-OVC CIGS. CIG HEIGHTS VARY BETWEEN 1.5 TO 3.5
KFT…SO FLYING CONDITIONS ARE EITHER VFR OR MVFR. CIGS WILL
GENERALLY REMAIN SIMILAR TO CURRENT CONDITIONS THROUGH THE AFTN AND
EARLY EVENING HOURS…WITH VFR/MVFR CONDITIONS AND LIGHT TO CALM SFC
WINDS. NO PRECIPITATION IS EXPECTED THROUGH THE EARLY EVENING
HOURS…AS LIGHT SNOW SHOWERS/FLURRIES HAVE MAINLY ENDED OVER THE
AREA.

WITH A WEAK STORM SYSTEM JUST OFF THE EASTERN SEABOARD…LIGHT
PRECIP IS EXPECTED DURING THE OVERNIGHT FOR ALL TAF SITES. KPOU
LOOKS TO SEE ONLY RAIN…AND KALB/KPSF WILL ONLY SEE A VERY BRIEF
PERIOD OF SLEET MIXING WITH RAIN BEFORE CHANGING TO JUST PLAIN RAIN
BY LATE TONIGHT. MEANWHILE…KGFL WILL SEE SN/PL EVENTUALLY CHANGE
TO PL/FZRA AND CONTINUING THROUGH DAYBREAK. PRECIP THERE WILL
EVENTUALLY CHANGE TO PLAIN RAIN BY MID MORNING. AT ALL SITES…IFR
CONDITIONS ARE EXPECTED FOR BOTH VSBYS/CIGS DURING PRECIP. PRECIP
WILL START TO LIGHTEN UP TOWARDS LATE MORNING TUESDAY…BUT CIGS
WILL REMAIN IFR DUE TO MOIST LOW LEVELS BENEATH A STRONG INVERSION
FOR THROUGH THE ENTIRE DAY ON TUESDAY. LIGHT S-SE SFC WINDS WILL BE
ABOUT 5 KTS OR LESS TONIGHT INTO TUESDAY MORNING.

OUTLOOK…

TUESDAY NIGHT: HIGH OPERATIONAL IMPACT. DEFINITE RA.
WEDNESDAY: HIGH OPERATIONAL IMPACT. DEFINITE RA.
WEDNESDAY NIGHT: HIGH OPERATIONAL IMPACT. DEFINITE RA.
CHRISTMAS DAY: HIGH OPERATIONAL IMPACT.BREEZY LIKELY RA.
THURSDAY NIGHT: LOW OPERATIONAL IMPACT.BREEZY NO SIG WX.
FRIDAY: NO OPERATIONAL IMPACT. NO SIG WX.
FRIDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
SATURDAY: NO OPERATIONAL IMPACT. NO SIG WX.

&&

.HYDROLOGY…
NO HYDROLOGIC ISSUES ARE ANTICIPATED THROUGH TUESDAY NIGHT. A
WIDESPREAD RAINFALL IS EXPECTED WEDNESDAY INTO WEDNESDAY NIGHT AS
A LARGE LOW PRESSURE SYSTEM MOVES ACROSS THE REGION. RAINFALL
AMOUNTS OF 1 TO 2.25 INCHES ARE LIKELY ALONG WITH SIGNIFICANT
SNOWMELT WHICH RAISES THE POTENTIAL FOR MINOR FLOODING AND
SIGNIFICANT WITHIN BANK RISES OF LARGER STEM RIVERS. MMEFS
GUIDANCE SUGGESTS THE BEST CHANCES FOR MINOR FLOODING WOULD BE
FROM THE HUDSON VALLEY THROUGH WESTERN NEW ENGLAND. IT IS TOO
EARLY TO ISSUE ANY FLOOD WATCHES…HOWEVER WILL CONTINUE TO MENTION
IN THE HWO AT THIS TIME.

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 FROM MIDNIGHT TONIGHT TO 9 AM EST
TUESDAY FOR NYZ032-033-042-043-082-083.
MA…NONE.
VT…NONE.

&&

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

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