FXUS61 KALY 152359 AFDALY AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 758 PM EDT TUE MAY 15 2012 .SYNOPSIS... A WEAK LOW PRESSURE SYSTEM WILL MOVE EAST OF THE REGION TONIGHT WITH THE RAIN ENDING. A STRONG COLD FRONT AND ITS ASSOCIATED UPPER LEVEL DISTURBANCE WILL BRING A CHANCE OF STRONG TO SEVERE THUNDERSTORMS TO EASTERN NEW YORK AND WESTERN NEW ENGLAND TOMORROW. HIGH PRESSURE WILL BUILD IN FROM THE GREAT LAKES REGION WEDNESDAY NIGHT WITH SUNNY AND DRY WEATHER THURSDAY INTO THE WEEKEND. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... AS OF 730 PM...A NARROW BAND OF SHOWERS WAS ACROSS THE MOHAWK VALLEY INTO PORTIONS OF THE DACKS. MEANWHILE...DUAL POL RADAR WAS SUGGESTING A REGION OF RAIN/DRIZZLE ADVECTING NORTHWARD ACROSS THE HUDSON RIVER VALLEY INTO THE CAPITAL REGION. LAST VISIBLE IMAGERY OF THE DAY DID REVEAL SOME IMPROVEMENT ACROSS PORTIONS OF HERKIMER COUNTY WITH BINOVCS. SO THIS QUASI-STATIONARY BOUNDARY WAS ALIGNED WELL WITH THE SHOWERS. LATEST RAP/HRRR SUGGEST THIS AREA OF SHOWERS WILL SLOWLY WEAKEN THIS EVENING. WITH AMPLE LOW LEVEL MOISTURE IN PLACE AND THIS BOUNDARY NOT MOVING TOO MUCH...EXPECTATION IS TO CONTINUE ALONG THE CLOUDY-MOCLDY SKIES. FURTHERMORE...STRATUS SHOULD REDEVELOP ALONG WITH THE INCREASE POTENTIAL OF FOG FORMATION PER THE UPS CROSSOVER TECHNIQUE. AS OF 415 PM...A QUASI-STATIONARY FRONTAL BOUNDARY REMAINS SOUTH OF THE REGION OVER THE MID ATLANTIC STATES...AND EAST COAST THIS AFTERNOON. A WEAK LOW PRESSURE SYSTEM AND ITS ASSOCIATED MID LEVEL SHORT-WAVE HAS QUICKLY MOVED ACROSS CNTRL-ERN NY INTO NEW ENGLAND. THE RAIN SHIELD ASSOCIATED WITH THE SHORT-WAVE HAS QUICKLY MOVED ACROSS THE CWA FROM SW TO NE. A FEW SHOWERS HAVE POPPED UP IN THE SW FLOW ALOFT ACROSS THE WRN MOHAWK VALLEY AND CNTRL NY. ANY ISOLATED CONVECTION HAS BEEN HARD PRESSED TO DEVELOP...SO THE ISOLATED THUNDER HAS BEEN REMOVED FROM THE FCST. A SFC TROUGH REMAINS NEAR THE SRN NEW ENGLAND COAST...LONG ISLAND...AND NJ TONIGHT...WHICH WILL KEEP A THREAT OF AN ISOLD-SCT SHOWERS OVER THE SOUTHEASTERN EXTREME OF THE CWA...AND WRN NEW ENGLAND. SOME PATCHY FOG WILL MATERIALIZE IN THE MOIST ENVIRONMENT. ATTENTION WILL SHIFT TO POTENT NORTHERN STREAM SHORT- WAVE OVER THE NRN GREAT LAKES REGION...AND SRN ONTARIO SEEN ON THE LATEST WATER VAPOR LOOP. THIS POTENT SHORT-WAVE AND THE ATTENDANT SFC COLD FRONT WILL BE THE KEEP FOCUSING MECHANISMS FOR STRONG TO POTENTIALLY SEVERE THUNDERSTORMS FOR TOMORROW. MORE DISCUSSION ON THAT IN THE SHORT TERM SECTION. LOW TEMPS TONIGHT WILL MILD WITH THE STRATUS AND PATCHY FOG WITH GENERALLY 50S...AND A FEW MID TO U40S OVER THE SRN DACKS. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... TOMORROW...EXTENSIVE COORDINATION WAS DONE WITH SPC...AND THE NEIGHBORING FORECAST OFFICES FOR THE POTENTIAL SEVERE WEATHER THREAT FOR TOMORROW. THERE WAS A CONSENSUS FOR AN UPGRADE TO A SLIGHT RISK FOR MOST OF THE ALY FCST AREA WITH LARGE HAIL...AND DAMAGING WINDS POTENTIALLY THE MAIN THREATS. THE STRONG COLD FRONT WILL BE APPROACHING FROM THE ST LAWRENCE RIVER VALLEY...AND THE ERN GREAT LAKES REGION IN THE LATE MORNING INTO THE EARLY PM. CLEARING IS EXPECTED AHEAD OF THIS FRONT...AND ITS STRONG SHORT-WAVE TROUGH. THE PATCHY FOG AND STRATUS SHOULD BURN OFF IN THE MID TO LATE MORNING QUICKLY. LOW AND MID-LEVEL HEIGHTS FALLS WILL BE OCCURRING AHEAD OF THE NEGATIVELY TILTED SHORT- WAVE IN THE EARLY PM WITH STEEPENING MID LEVEL LAPSES IN THE H850-500/H700-H500 LAYER TO 6.5/7+C/KM. THE NAM AND GFS BOTH SHOW TWO INSTABILITY AXES ACROSS THE REGION AROUND 18Z. ONE ACROSS THE SRN ZONES...AND ANOTHER ACROSS THE NRN ZONES. THIS IS LIKELY DUE TO A PREFRONTAL SFC TROUGH AHEAD OF THE MAIN FRONT. SFC DEWPTS WILL RANGE FROM THE 50S TO POSSIBLY L60S. SBCAPES ON BOTH THE NAM AND GFS ARE GENERALLY IN THE 1000-1500 J/KG WITH POCKETS SLIGHTLY GREATER. THE 0-6 KM BULK SHEAR VALUES INCREASE TO 35-50 KTS...AND THE FLOW BECOMES UNI-DIRECTIONAL BY THE MID TO LATE PM. ALSO...A FAIRLY SHARP LOW LEVEL THETA-E GRADIENT INCREASES TO 15-20K BY THE AFTERNOON. THE DCAPE VALUES ON THE GFS/NAM AHEAD OF THE STRONG COLD FRONT RANGE FROM 1000-1500+ J/KG ! THE MODEL SOUNDINGS SHOWS AN INVERTED-V SIGNATURE BTWN 18-22Z. THE LEFT FRONT QUAD OF AN H500 JET STREAK /60-70 KTS/ WILL ALSO BE POKING INTO THE FCST AREA TO HELP ENHANCE THE SYNOPTIC LIFT FOR THE CONVECTION. THE THREAT IS THERE FOR LARGE HAIL AND DAMAGING WINDS...AS MULTICELLS WILL LIKELY FORM INTO A LINE OR TWO WITH BOWING SEGMENTS BY THE MID TO LATE PM. THE NCEP 4-KM WRF-NMM BASE REF PRODUCT DONE FOR SPC SHOWS A PRETTY IMPRESSIVE SQUALL LINE SWEEPING ACROSS THE FCST AREA BTWN 18Z-00Z. WE HAVE MENTIONED IN THE TEXT PRODUCTS A CHANCE OF THUNDERSTORMS THAT SOME MAY BE SEVERE. IN THE HWO WE WILL ALSO HIGHLIGHT THE POTENTIAL THREATS. ALSO...THE ENTIRE AREA WILL HAVE ENHANCED WORDING IN THE HWO. SPC HAS THE W-CNTRL MOHAWK AND SRN DACKS OUT OF THE SLIGHT RISK. WE BELIEVE THE THREAT IS STILL POSSIBLE IN THESE AREAS. FINALLY...A QUICK CHECK OF THE LOCAL MAGLENTA EQUATION INDICATES A MAJOR SEVERE EVENT IS POSSIBLE. THE CONDITIONAL EQUATION USED THE FOLLOWING CONSERVATIVE VALUES FROM ALBANY FROM THE NAM: SBCAPE=1000 J/KG MAX SOUNDING WIND=85 KTS EHI=0.5 STORM SPEED=30 KTS SRH (0-3 KM)=100 (M/S)2 THIS WOULD POTENTIALLY BE THE FIRST SEVERE WEATHER EVENT SINCE EARLY LAST FALL /LATE SEPT/. THE POTENTIAL STRONG TO SEVERE CONVECTION WILL END BETWEEN 6-9 PM. MAX TEMPS WILL GENERALLY BE IN THE M70S TO NEAR 80F IN THE VALLEYS WITH U60S TO M70S OVER THE HILLS AND MTNS. WED NIGHT...STRONG COLD AIR ADVECTION OCCURS IN THE WAKE OF THE FRONT WITH H850 TEMPS FALLING TO 0 TO +5C FROM NW TO SE OVER THE FCST AREA. THE SKIES SHOULD RAPIDLY CLEAR DUE TO THE STRONG SUBSIDENCE BEHIND THE BOUNDARY AND UPPER TROUGH. LOWS WILL BE IN THE U30S TO L40S NORTH AND WEST OF THE CAPITAL REGION...AND M40S TO NEAR 50F FROM THE CAPITAL REGION SOUTH AND EAST. THURSDAY...A BEAUTIFUL MID MAY DAY IS EXPECTED WITH HIGH PRESSURE BUILDING IN FROM THE CNTRL AND ERN GREAT LAKES REGION. A FEW-SCT FAIR WX CUMULUS CLOUDS MAY BE AROUND. DESPITE H850 TEMPS OF +2 TO +5C...DECENT MIXING TO H850-800 SHOULD ALLOW MAX TEMPS TO REACH THE U60S TO L70S IN THE VALLEYS...AND 60-65F OVER THE MTNS. THURSDAY NIGHT...SFC HIGH PRESSURE WILL CREST OVER NY AND PA WITH MOSTLY CLEAR/CLEAR AND CALM CONDITIONS. DECENT RADIATIONAL COOLING WILL LIKELY OCCUR. SOME FROST MAY BE POSSIBLE OVER THE SRN DACKS REGION. LOWS IN THE LOWER TO M30S WILL BE COMMON THERE. LOWER TO M40S ARE LIKELY ACROSS THE REST OF THE REGION..EXCEPT THE SRN GREENS...ERN CATSKILLS...AND WRN MOHAWK VALLEY...WHERE SOME U30S WILL ALSO BE POSSIBLE. && .LONG TERM /FRIDAY THROUGH TUESDAY/... A TRANQUIL LONG TERM PORTION OF THE FORECAST AS WE TRANSITION FROM THE COOLER CYCLONIC FLOW ALOFT ON FRIDAY TO BUILDING HEIGHTS AND SURFACE PRESSURES FOR THE WEEKEND. MODEL CONSENSUS IS RATHER HIGH CONFIDENCE FOR A DRY AND SEASONABLE TO ABOVE SEASONABLE TEMPERATURES. MEANWHILE...WE WILL BE MONITORING THE EVOLUTION OF THE CUT OFF UPPER LOW OVER THE SOUTHEAST CONUS LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. HERE...THE MODEL SUITE DIVERGES WITH PLACEMENT...MOISTURE CONTENT...AND EVENTUAL TRACK OF THIS SYSTEM. THE LATEST ECMWF IS THE MOST AGGRESSIVE WITH TRACKING THIS SYSTEM NORTHWARD WITH AN INCREASE PROBABILITY OF SHOWERS LATER MONDAY. THE GFS HANGS ONTO THE RIDGE LONGER LIMITING THE POTENTIAL FOR SHOWERS. THE GGEM IS IN CLOSER AGREEMENT WITH THE ECMWF...WITH A FURTHER INLAND TRACK OF THIS SYSTEM. PER HPC COLLABORATION AND NEIGHBORING OFFICES...WE WILL CONTINUE ALONG THE SLIGHT CHANCE PROBABILITIES AND KEEP TEMPERATURES RATHER MILD. OVERALL...TEMPERATURES WILL AVERAGE AT OR ABOVE NORMAL WITH PRECIPITATION BELOW NORMAL. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... MVFR TO IFR CIGS AND MAYBE VIS EXPECTED TONIGHT FOR THE 4 TAF SITES. ISSUE WILL BE TIMING OF WHEN THESE FLIGHT CATEGORIES WILL BE MET. PER THE LATEST GUIDANCE AND BUFR PROFILES...WE WILL PLACE THESE LOWER RESTRICTIONS TOWARD 03Z. THEN A TEMPO GROUP FOR IFR-LIFR CONDITIONS AFTER MIDNIGHT. THIS LOW STRATUS DECK WILL SLOWLY LIFT SHORTLY AFTER SUNRISE AS SOUTHERLY WINDS INCREASE. AFTER 14Z-15Z WEDNESDAY...CEILINGS AND VISIBILITIES SHOULD LIFT TO VFR. THE UPSTREAM COLD FRONT APPROACHES DURING THE AFTERNOON HOURS WITH AN INCREASED THREAT FOR CONVECTION. AT THIS TIME...TOO LOW CONFIDENCE TO PLACE IN THE TAF. SOUTH TO SOUTHEAST WINDS AT LESS THAN 5 KT TONIGHT...THEN BECOME SOUTH TO SOUTHWEST AT 10 KT OR LESS WEDNESDAY MORNING. .OUTLOOK... WED NT-SUN...VFR...NO SIG WX. && .FIRE WEATHER... A WEAK LOW PRESSURE SYSTEM WILL MOVE EAST OF THE REGION TONIGHT WITH THE RAIN ENDING. A STRONG COLD FRONT AND ITS ASSOCIATED UPPER LEVEL DISTURBANCE WILL BRING A CHANCE OF STRONG TO SEVERE THUNDERSTORMS TO EASTERN NEW YORK AND WESTERN NEW ENGLAND TOMORROW. HIGH PRESSURE WILL BUILD IN FROM THE GREAT LAKES REGION WEDNESDAY NIGHT WITH SUNNY AND DRY WEATHER THURSDAY INTO THE WEEKEND. THE SHOWERS WILL DIMINISH EARLY TONIGHT BUT RH VALUES WILL APPROACH 100 PERCENT WITH SOME PATCHY FOG AROUND. RH VALUES WILL LOWER BRIEFLY TO 35 TO 50 PERCENT TOMORROW AFTERNOON...BEFORE SCATTERED SHOWERS AND THUNDERSTORMS ARRIVE. THE RH VALUES WILL INCREASE TO 70 TO 100 PERCENT THURSDAY MORNING. LIGHT SOUTH WINDS OF 5 TO 10 MPH TONIGHT WILL SHIFT TO THE WEST SOUTHWEST AT 10 TO 20 MPH WITH A FEW GUST TO 25 TO 30 MPH. THE WINDS WILL VEER IN THE WAKE OF THE FRONT TO THE NORTHWEST AT 5 TO 15 MPH. && .HYDROLOGY... AN ADDITIONAL HALF AN INCH TO INCH OF RAIN HAS OCCURRED SO FAR TODAY WITH A LOCALLY HIGHER AMOUNTS OVER THE CATSKILLS. STORM TOTAL RAINFALL AMOUNTS OF 1 TO 3 INCHES OVER THE PAST 24-48 HRS HAVE BEEN COMMON OVER MOST OF THE HSA. SOME WITHIN BANK RISES /1 TO 3 FOOT RISES/ HAVE OCCURRED ON THE RIVERS AND STREAMS. NO FLOODING IS EXPECTED AT THIS TIME BASED ON THE LATEST NERFC HYDROGRAPH FORECASTS. A FEW POINTS HAVE REACHED THE ALERT OR CAUTION STAGE ...BUT NO FLOODING IS EXPECTED. SOME ADDITIONAL RAINFALL IS POSSIBLE ON WEDNESDAY WITH THE COLD FRONT. THE SHOWERS AND THUNDERSTORMS WILL PRODUCE A TENTH TO A THIRD OF AN INCH OF RAINFALL. DRY WEATHER IS EXPECTED THURSDAY THROUGH THE WEEKEND WHICH WILL ALLOW RIVERS TO RECEDE CLOSER TO SEASONAL LEVELS. 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...BGM/WASULA SHORT TERM...WASULA LONG TERM...BGM AVIATION...BGM/NAS FIRE WEATHER...HWJIV/WASULA HYDROLOGY...WASULA WWW.WEATHER.GOV/ALBANY