FXUS61 KALY 121810 AFDALY AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 1257 PM EST FRI MAR 12 2010 .SYNOPSIS... A COMPLEX...SLOW MOVING STORM SYSTEM NEAR THE TENNESSEE VALLEY...AND THE MID ATLANTIC REGION WILL IMPACT EASTERN NEW YORK AND WESTERN NEW ENGLAND TODAY THROUGH THE WEEKEND. ISOLATED TO SCATTERED SHOWERS TODAY WILL TRANSITION TO A STEADIER LIGHT RAIN FROM THE CAPITAL REGION SOUTH TONIGHT...WITH PERHAPS A LIGHT MIXTURE OF RAIN...FREEZING RAIN...AND SLEET NORTH AND EAST. THE MAIN LOW PRESSURE CENTER WILL SHIFT SLOWLY NORTHEAST OF THE DELMARVA REGION SATURDAY INTO SUNDAY WITH RAIN...HEAVY AT TIMES...SOUTH AND EAST OF THE CAPITAL DISTRICT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 400 AM EST...THE LATEST WATER VAPOR LOOP WITH H500 HEIGHTS FROM THE GFS OVERLAYED HAS A STRONG CUTOFF LOW OVER THE CORN BELT OF IA AND NE. SEVERAL SHORT WAVE TROUGHS CONTINUE TO ROTATE AROUND THE CUTOFF. ONE IS OVER THE LOWER MS RIVER VALLEY...WHILE ANOTHER ONE IS MOVING THROUGH THE MID ATLANTIC REGION. AN UPPER LEVEL RIDGE CONTINUES TO REMAIN CENTERED OVER LONG ISLAND...UPSTATE NY AND NEW ENGLAND TILTING NW INTO ONTARIO. A WARM FRONT AT THE SFC IS HUNG UP OVER THE UPPER MID ATLANTIC REGION...AS A BLOCKING ANTICYCLONE REMAINS ANCHORED OVER E-CNTRL QUEBEC. A BATTLE BETWEEN THE COLD DRY AIR BEING FUNNELED SOUTHWARD FROM THE ANTICYCLONE...AND THE MOISTURE WITH THE WARM FRONT WILL CONTINUE TODAY...AND INTO THE WEEKEND. MOST OF THE NWP GUIDANCE SHOWS SOME LIGHT SHOWERY PCPN IMPACTING THE REGION FROM SOUTH TO NORTH WITH THE WEAK ISENTROPIC LIFT ON THE 295K SFC. WE USED ISOLD-SCT WORDING FOR THE SHOWERS...AND WE BELIEVE SOME BREAKS OF SUN ARE POSSIBLE NORTH OF THE CAPITAL REGION. LATE IN THE DAY THE SHOWERS WILL BECOME FROM NUMEROUS WELL SOUTH OF THE CAPITAL REGION. THE CLOUDS WILL BE STUBBORN ACROSS THE REST OF THE REGION. TEMPS WILL BE AT NORMAL TO ABOVE NORMAL MARCH LEVELS WITH MAX TEMPS IN THE MID 40S TO NEAR 50...WITH LOWER 40S OVER THE HIGH PEAKS OF THE SRN GREENS AND ERN CATSKILLS. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... FRIDAY NIGHT...THIS IS THE PERIOD WHERE THE MASSIVE CUTOFF BEGINS TO BE TROUBLESOME WITH ITS INTERACTION WITH THE STRONG SFC HIGH SHIFTING TOWARDS THE GULF OF SAINT LAWRENCE AND NEW BRUNSWICK. CSTAR RESEARCH HAS SHOWN THE PROBLEMS COOL SEASON CUTOFFS CAN YIELD. THE FIRST ISSUE GOING INTO THE WEEKEND IS THE POSSIBILITY OF SOME SPOTTY LIGHT MIXED PCPN. THE NAM/GFS 925 HPA AGEOSTROPHIC WINDS ARE NORTH OR NORTHEAST AT 25-40 KTS. SHALLOW COLD AIR WILL FUNNEL INTO THE REGION IN THE NORTHEASTERN ZONES OF THE CAPITAL REGION /LAKE GEORGE REGION...SRN VT...NRN BERKS...SRN DACKS/. SOME MOISTURE ASSOCIATED WITH THE LEAD SHORT WAVE AND THE ISENTROPIC LIFT WILL BE SLOWLY LIFTING NORTHWARD ACROSS THE REGION AFTER MIDNIGHT. WE ARE LEANING TOWARD A NAM/ECMWF SCENARIO FOR THE NEXT FEW PERIODS...AS THE GFS HAS BECOME TOO AGGRESSIVE WITH THE MOVEMENT OF THE CUTOFF DURING THE WEEKEND. COORDINATION WAS DONE WITH HPC AND NEIGHBORING WFOS. WE FOLLOWED THE NAM THERMAL PROFILES WHICH SHOWS A WEDGE OF -1 TO -3C AIR AT 925 HPA OVER NRN PORTIONS OF THE REGION /GFS WAS ACTUALLY SIMILAR HERE/. THE NAM SOUNDINGS SHOW THE POSSIBILITY OF PERSISTENT VIRGA FOR A PERIOD...BUT THEN IF SATURATION OCCURS SOME SPOTTY -FZRA OR -IP MAY OCCUR NORTH AND EAST OF KALB...ALSO IT IS POSSIBLE OVER THE HIGH PEAKS OF THE ERN CATSKILLS. WE ARE NOT SUPER CONFIDENT DUE TO THE SLOW SATURATION OF THE AIR MASS...AND THE SUPER DRY AIR BEING DAMMED IN BY THE RETREATING ANTICYCLONE. WE KEPT A CHC -FZRA/-IP IN WITH -RA AS THE PREDOMINANT PTYPE. WE PLACED LIKELY TO CATEGORICAL POPS IN FROM THE CAPITAL DISTRICT SOUTH...AND ONLY LOW CHANCE TO THE NORTH. NOT TOO CONFIDENT THE PCPN WILL MAKE IT FARTHER NORTH OF KALB AT THIS TIME. SATURDAY...THE LOW LEVEL JET STRENGTHENS TO 50-70 KTS AT H850 FROM THE E/SE WITH THE WARM FRONT TO THE COMPLEX SYSTEM JUST SOUTH OF LONG ISLAND AND INTO SRN NJ. THE LOW LEVEL BAROCLINIC ZONE STRENGTHENS JUST SOUTH OF THE FCST AREA...AND PERIODS OF RAIN DUE TO THE OVER RUNNING WILL PUSH INTO THE SRN ZONES OF THE FCST AREA IN THE LATE MORNING AND INTO THE AFTERNOON. THE LATEST GLOBAL ENSEMBLES SHOW H925 EASTERLY WINDS ANOMALIES OF 3 TO 5 STANDARD DEVIATIONS GREATER THAN NORMAL OVER THE SRN HALF OF THE FCST AREA. THE H850 EASTERLY ANOMALIES ARE GREATER THAN 5 STANDARD DEVIATIONS ABOVE NORMAL OVER NRN NJ...ERN PA AND SRN NY. THE -U COMPONENT ANOMALIES WILL HELP ADVECT IN ATLANTIC MOISTURE. THE NAM SHOWS TREMENDOUS DOWNSLOPING TO COMMENCE IN THE HUDSON RIVER VALLEY. THE SHADOWING EFFECT COULD SIGNIFICANTLY DECREASE THE PCPN (WITH LESS THAN A TENTH OF AN INCH ADVERTISED BY THE NAM IN A FEW SPOTS/. LATE SATURDAY THE THREAT STARTS TO POTENTIALLY BUILD FOR SOME WIND ADVISORY LEVEL WIND GUSTS TO MATERIALIZE OVER THE SRN GREENS/NRN BERKS/TACONICS. THE SOUNDINGS DO SHOW A LOW LEVEL INVERSION MATERIALIZING INHIBITING FULL MIXING TO THE SFC. ACTUALLY WE THINK THE BETTER CHANCE OF MIXING SOME GUSTS AT LEAST TO 40-45 MPH WILL BE IN THE EVENING PERIOD WHEN THE LOW JET SEGMENT AT H925 STRENGTHENS TO 40-50 KTS OVER THE ERN ZONES. SATURDAY NIGHT...THE PWAT ANOMALIES ARE ONLY 1-2 STANDARD DEVIATIONS ABOVE NORMAL NOW...ESPECIALLY IN THE SOUTHERN ZONES. THE SECONDARY SFC WAVE IS NEAR THE DELMARVA REGION WITH THE BEST QG LIFT DUE TO THE STRONG DIFFERENTIAL THICKNESS ADVECTION COUPLED WITH THE DIFFERENTIAL VORTICITY ADVECTION IMPACTING THE REGION. THE BEST LOW/MID LEVEL FRONTOGENESIS IN THE H850-700 LAYER IS SITUATED NEAR THE ERN CATSKILLS...MID HUDSON VALLEY...AND NW CT. THE STRONG THETA-E ADVECTION FOCUSED BY THE NOSE OF THE LLJ SHOULD BRING RAIN...HEAVY AT TIMES...FROM THE CAPITAL REGION SOUTH /EXCEPT WHERE DOWNSLOPING COMES INTO PLAY/. THE ECMWF SHOWS THE CONVEYOR BELT OF MOISTURE SLOWLY SHIFTING NORTHWARD THROUGH THE NIGHT ACROSS THE REGION. SOME WIND GUSTS COULD APPROACH ADVISORY LEVELS OVER THE HIGHER TERRAIN OF THE SRN GREENS...BERKS...TACONICS...AND CATSKILLS. WILL CONTINUE MENTION IN THE HWO. THE 00Z GEFS PLUME DIAGRAM IS STRANGE FOR KALB WITH MANY SNOW MEMBERS DURING THE LATE SAT-SAT NIGHT TIME FRAME. NOT SURE WHERE ALL THE COLD AIR WILL COME FROM. ACTUALLY THE GFS WITH ITS 00Z SOLUTION WILL WRAP SOME IN FROM THE NORTH AND EAST. BOTTOM LINE HEAVIEST RAINFALL LOOKS TO FALL IN THE OVERNIGHT PERIOD. THIS COULD BRING SOME FLOOD ISSUES. WILL WAIT FOR THE DAY CREW TO COORDINATE WITH THE NERFC ON POTENTIAL LOCATIONS FOR POSSIBLE FLOOD THREAT. RIGHT NOW...THE BEST CHANCE OF 2-4 INCHES OF RAINFALL LOOKS TO BE GREENE...ULSTER...COLUMBIA...DUTCHESS...BERKSHIRE AND LITCHFIELD COUNTIES...WITH A SHARP GRADIENT NORTHWARD...WHERE AROUND AN INCH OCCURS IN THE CAPITAL REGION...MOHAWK VALLEY...AND SRN VT...AND MAYBE A HALF AN INCH TO AN INCH NORTHWARD. DOWNSLOPING COULD PRODUCE SOME VERY LOW TOTALS IN THE UPPER HUDSON/LAKE GEORGE REGION. THE EASTERN SLOPS OF THE CATSKILLS COULD GET THE HEAVIEST RAINFALL. THERE WILL ALSO BE SOME SNOW MELT...BUT LATE MODEL PROJECTIONS DO NOT HAVE DEW POINTS SURGING MUCH HIGHER THAN THE 30S. WE FOLLOWED THE NAM THERMAL PROFILES...AND SOME COLDER AIR MAY MOVE INTO THE BOUNDARY LAYER AFTER MIDNIGHT CHANGING THE PCPN TO SOME SLEET AND FREEZING RAIN...ESPECIALLY OVER THE WRN AND SRN ADIRONDACK REGION. WE PLACED CHANCE VALUES FOR THIS PTYPE TRANSITION. SUNDAY...PERIODS OF RAIN TRANSITION TO SCATTERED SHOWERS IN THE AFTERNOON FROM WEST TO EAST. WE CONTINUED TO FOLLOW THE NAM THERMAL PROFILES WITH A SLIGHT MIX OVER THE NORTHWESTERN ZONES WITH MARGINAL BOUNDARY LAYER TEMPS THAT ARE SUB FREEZING. AS BOUNDARY LAYER TEMPS WARM ABOVE FREEZING THIS WOULD CHANGE TO RAIN. IF THE BOUNDARY LAYER TEMPS COOL ENOUGH WITH COLDER AIR COMING IN ALOFT...THEN THIS COULD BE SOME WET SNOW OVER THE ERN CATSKILLS...PARTS OF THE SRN ADIRONDACKS...AND SRN GREENS AND BERKS. RIGHT NOW...WE HAVE STAYED WITH RAIN AS THE MAIN PTYPE IN THE AFTERNOON. MAX TEMPS WILL GENERALLY BE IN THE 40S...WITH SOME MID TO UPPER 30S OVER THE CATSKILLS. OVERALL...THE HEAVIEST QPF WILL BE DICTATED BY THE TRACK OF THE CUTOFF...WHICH COULD YIELD A TREMENDOUS GRADIENT OF PCPN...WITH SHADOWING/DOWN SLOPING ALSO CUTTING DOWN ON THE PCPN. && .LONG TERM /SUNDAY THROUGH THURSDAY/... STACKED LOW PRESSURE SYSTEM MOVE GRADUALLY MOVE NORTHEAST OUT TO SEA WITH PRECIPITATION LINGERING ACROSS THE EASTERN PORTION OF THE FORECAST AREA SUNDAY NIGHT AND POSSIBLY INTO MONDAY. THE ECMWF IS SLOWER MOVING THE LOW AWAY THAN THE GFS. THERE IS A LARGE SPREAD IN THE GFSENSEMBLE MEMBERS. COLDER AIR IS EXPECTED TO WORK IN CHANGING RAIN TO SNOW SUNDAY NIGHT. AFTER THIS...A SPRAWLING SURFACE HIGH OVER THE PLAIN STATES IS EXPECTED TO BUILD EASTWARD. HOWEVER...ALOFT THE LONGWAVE TROUGH REMAINS THE EASTERN UNITED STATES. AT THIS TIME...LOOKING AT DRY WEATHER WITH SLIGHTLY ABOVE NORMAL TEMPERATURES MUCH OF NEXT WEEK. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... COMPLEX SYSTEM ROTATING ABOUT THE CENTRAL U.S. STILL SLOWLY PROGGED TO MOVE EASTWARD...TRANSLATING ITS ENERGY TOWARD THE DELMARVA AREA ON SATURDAY. ALL TERMINALS WILL START THE PERIOD WITH VFR CONDITIONS. AS MOISTURE AHEAD OF A WARM FRONT ASSOCIATED WITH THE AFOREMENTIONED SYSTEM MOVES NORTH. NORTHERLY AGEOSTROPHIC WIND COMBINED WITH EASTERLY SFC WIND CAUSING SOME DOWNSLOPING WILL KEEP THE TERMINALS DRY FOR THE REST OF THE DAYLIGHT HRS TODAY. KPOU WILL SEE SOME VCSH...BUT NOT MUCH IF ANY RAINFALL ACCUMULATION EXPECTED. AS KPOU IS ALSO FURTHEST TERMINAL SOUTH...PRESSURE GRADIENT STRONGER RESULTING IN GUSTY WINDS AND LLWS OVERNIGHT. CONDITIONS WILL DETERIORATE TO MVFR THIS AFTERNOON WITH CIGS LOWERING AS RAIN APPROACHES THIS EVENING. VSBYS WILL ALSO DETERIORATE TO MVFR WITH THE ONSET OF PRECIP AROUND 23Z. CONDITIONS WILL CONTINUE TO DETERIORATE TO IFR SATURDAY MORNING. KALB CAN EXPECT SOME VCSH OVERNIGHT...WITH CIGS LOWERING TO MVFR AROUND MIDNIGHT/04Z. PRECIP WILL BE DELAYED IN ITS PROGRESSION NORTHWARD...SO HAVE HELD OFF ON -SHRA UNTIL 16Z/SATURDAY. KGFL CAN EXPECT EVEN MORE OF A DELAY...WITH VCSH AT 08Z. PTYPE EXPECTED TO STAY RAIN/RAIN SHOWERS EVEN THOUGH 925HPA WETBULB TEMPS BELOW FREEZING...AS SFC TEMPS WILL BE WARM ENOUGH IN THE VALLEYS TO SUPPORT NON-FREEZING PRECIP DUE TO SOME DOWNSLOPING WINDS. ALSO ANY PRECIP THAT OCCURS OVERNIGHT INTO EARLY MORNING SHOULD BE LIGHT ENOUGH THAT EVAPORATIVE COOLING EFFECTS WILL BE NEGLIGIBLE. OUTLOOK... SAT NT...MVFR/IFR...MOD TO HVY RA LIKELY. SUN...MVFR/IFR...-SHRA LIKELY. MON...MVFR/VFR...-SHRA TAPERING OFF TOWARDS THE AFTERNOON. TUE-WED...VFR...NO SIG WX. && .HYDROLOGY... NO HYDRO PROBLEMS ARE EXPECTED THROUGH FRIDAY NIGHT. A COMPLEX AND FAIRLY LONG DURATION RAIN EVENT WILL OCCUR BEGINNING FRIDAY NIGHT CONTINUING THROUGH THE WEEKEND...WITH THE HEAVIEST RAIN EXPECTED LATE SATURDAY AFTERNOON INTO SUNDAY. CURRENT QPF PROJECTIONS SHOW RAINFALL AMOUNTS WILL RANGE FROM AROUND A QUARTER OF AN INCH ACROSS THE WESTERN ADIRONDACKS TO AS MUCH AS ONE TO TWO INCHES ACROSS WESTERN NEW ENGLAND. SOME ENHANCEMENT OF THE PRECIPITATION WILL OCCUR ALONG THE EAST FACING SLOPES OF THE CATSKILLS...GREEN MOUNTAINS AND BERKSHIRES...WHERE LOCALLY AROUND THREE INCHES OF RAIN IS POSSIBLE THROUGH THE ENTIRE EVENT. THERE ARE 4-8 INCHES OF WATER EQUIVALENT REMAINING IN THE SNOWPACK ACROSS THE CATSKILLS...ADIRONDACKS...GREENS...AND BERKSHIRES...WITH THE HIGHEST VALUES IN THE CATSKILLS AND SOUTHERN GREENS. THIS EXPECTED RAINFALL...ALONG WITH SOME SNOW MELT DUE TO A PERIOD OF TEMPERATURES OVER 40 DEGREES...WILL LIKELY CAUSE SOME FLOODING ON RIVERS AND STREAMS BY SUNDAY AND POSSIBLY INTO EARLY NEXT WEEK...MAINLY FOR AREAS SOUTH AND EAST OF THE CAPITAL REGION. THE TREND IS SLIGHTLY SLOWER WITH THE RAIN AND SLIGHTLY COLDER WITH SOME LIGHT MIXED PCPN OVER THE NRN ZONES. STILL TOO EARLY TO HOIST ANY FLOOD WATCHES AT THIS TIME...AND WE WILL WAIT FOR FULL COORDINATION WITH THE NORTHEAST RIVER FORECAST CENTER LATE FRIDAY MORNING INTO THE EARLY AFTERNOON. 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...WASULA NEAR TERM...WASULA SHORT TERM...WASULA LONG TERM...IAA AVIATION...KGS HYDROLOGY...IAA/WASULA