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FXUS61 KALY 091141 AFDALY AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 641 AM EST TUE MAR 9 2010 .SYNOPSIS... HIGH PRESSURE WILL BUILD IN ACROSS THE REGION TODAY...THEN BEGIN TO SHIFT EASTWARD ON WEDNESDAY. AN APPROACHING WARM FRONT WILL BRING A CHANCE OF SOME LIGHT RAIN THURSDAY AND ESPECIALLY THURSDAY NIGHT. A SPRAWLING STORM SYSTEM OVER THE CENTRAL PLAINS WILL TRACK EASTWARD INTO OUR REGION FRIDAY AND INTO THE WEEKEND...BRINGING THE POTENTIAL FOR WIDESPREAD SIGNIFICANT PRECIPITATION. THE EFFECTS OF THIS STORM MAY LAST INTO EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 330 AM...TRANQUIL WEATHER WILL PERSIST TODAY AND TONIGHT...AS HIGH PRESSURE BUILDS IN. TEMPS ALOFT ARE FORECAST TO COOL BY A FEW DEG C...SO SURFACE MAX TEMPS SHOULD BE AROUND 2-5 DEGREES COOLER THAN YESTERDAY BUT STILL ABOVE NORMAL. WIND SPEEDS WILL BE A BIT WEAKER AS WELL AS THE PRESSURE GRADIENT SLACKENS. WITH HIGH PRESSURE MOVING OVERHEAD TONIGHT...MIN TEMPS SHOULD BE A BIT COOLER THAN RECENT NIGHTS DUE TO CLEAR SKIES BUT ALSO NEAR CALM WINDS EVEN DOWN THE MOHAWK VALLEY AND IN THE HIGHER TERRAIN. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 330 AM...HIGH PRESSURE WILL START TO SHIFT EAST OF THE AREA ON WED...WITH A WEAK SOUTHEAST FLOW DEVELOPING. TEMPS ALOFT WILL BE WARMING...SO SURFACE TEMPS SHOULD RESPOND WITH LOWER 50S POSSIBLE IN MOST VALLEY LOCATIONS AND EVEN MID 40S IN THE HIGHER ELEVATIONS. CLOUDS WILL BE ON THE INCREASE WED NIGHT AS A WARM FRONT APPROACHES FROM THE OHIO VALLEY REGION...BUT WILL LIKELY NOT REACH AREAS NORTH AND EAST OF THE CAPITAL DISTRICT UNTIL MORNING. AS A RESULT...TEMPS WILL BE COLDEST WHERE CLEARING HOLDS ON THE LONGEST WITH GENERALLY 20S...BUT MILDER LOWER 30S FROM THE CAPITAL DISTRICT SOUTH AND WEST. THUR WE WILL SEE OUR FIRST CHANCE OF MEASURABLE PRECIP IN AT LEAST A WEEK...AS WEAK ISENTROPIC LIFT COMMENCES ACROSS THE AREA. SOME DIFFERENCES IN GUIDANCE IN TERMS OF TIMING AND PLACEMENT OF QPF...BUT THERE IS AGREEMENT THAT ANY PRECIP THAT FALLS WILL BE LIGHT. WENT CLOSER TO LOWER NAM POPS WITH SLIGHT CHANCE FROM ALBANY NORTH AND EAST AND LOW CHANCE SOUTH AND WEST. 00Z ECMWF IS MORE SIMILAR TO THE NAM...WITH THE GFS SEEMINGLY A BIT TOO AGGRESSIVE WITH HIGHER POPS DESPITE VERY WEAK FORCING. EVEN WITH INCREASING CLOUDS...A MILD AIR MASS WILL BE IN PLACE SO EXPECTING MAX TEMPS TO BE SIMILAR TO WEDNESDAY'S READINGS. IT APPEARS THERE WILL BE A BETTER CHANCE FOR AT LEAST GREATER COVERAGE OF RAIN THUR NIGHT...AS ISENTROPIC LIFT INCREASES AND SOUTHERLY FLOW STRENGTHENS WHICH SHOULD HELP TRANSPORT BETTER MOISTURE INTO THE REGION. WILL MENTION LIKELY POPS AFTER MIDNIGHT. ALL GUIDANCE SUGGESTING 850/925 TEMPS ABOVE FREEZING THROUGHOUT THE AREA...SO WILL MENTION PLAIN RAIN FOR PTYPE. && .LONG TERM /FRIDAY THROUGH MONDAY/... HIGH CONFIDENCE CONTINUES THAT A LONG DURATION AND HIGH IMPACT STORM SHOULD STILL BE AFFECTING THE REGION FRIDAY THROUGH MONDAY. GUIDANCE CONTINUES TO GRADUALLY PUSH THE HEAVIEST PRECIPITATION SLIGHTLY LATER WITH EACH RUN...BUT REGARDLESS OF TIMING...THE PERIOD BETWEEN FRIDAY AND SUNDAY NIGHT SHOULD FEATURE THE PERIODS OF THE HEAVIEST PRECIPITATION. WHAT WE KNOW: THREE STRONG UPPER SYSTEMS CURRENTLY EXIST THAT WILL INTERACT WITHING THE LARGE SCALE UPPER LOW AS IT DEVELOPS AND TRACKS INTO THE EASTERN U.S. ONE IS ABOUT TO ENTER WESTERN CANADA...ANOTHER IS IN THE SW U.S. AND THE ONE AT THE FRONT OF THE LINE IS CURRENTLY PRODUCING RESPECTABLE CONVECTION IN THE CENTRAL U.S. DIRECT TROPICAL AND SUBTROPICAL MOISTURE FEED SEEN IN WATER VAPOR IMAGERY INTERACTING WITH THE LEAD SYSTEM...AND GUIDANCE SUGGESTS THIS WILL CONTINUE AS THE UPPER LOW STRENGTHENS AND TRACKS EAST. RELATIVELY LITTLE COLD AIR FROM THE SURFACE THROUGH THE BOUNDARY LAYER THROUGH MUCH OF THE EVENT...SO MOST OF THE PRECIPITATION ACROSS THE REGION SHOULD BE RAIN THROUGH SUNDAY. HIGH CONFIDENCE BUT NO GUARANTEES: LOW LEVEL U WIND ANOMALIES EXCEED -4 SD IN MOST INDIVIDUAL ENSEMBLE MEMBERS AND DETERMINISTIC GUIDANCE...BUT SPREAD AMONG MANY ENSEMBLE MEMBERS DAMPENS OUT MAGNITUDE IN ENSEMBLE MEANS. V WIND ANOMALIES APPROACH AND IN SOME CASES EXCEEDS 4 SD AS WELL. PWAT ANOMALIES ARE 1-3 SD ABOVE NORMAL. SO...LOTS OF LOW LEVEL AND BOUNDARY LAYER MOISTURE AND CONVERGENCE TO SUPPORT UNUSUALLY HIGH PRECIPITATION AMOUNTS IN AREAS OF MAXIMA. PROLONGED EAST TO SOUTH BOUNDARY LAYER FLOW SUGGESTS ENHANCED PRECIPITATION IN AND AROUND THE CATSKILLS...BERKSHIRES AND SOUTHERN VT. BASED ON RUN TO RUN CONSISTENCY IN GUIDANCE/ENSEMBLES...THE MULTIPLE UPPER IMPULSES ROTATING AROUND THE UPPER LOW SUGGESTS THAT PRECIPITATION OVER THE COURSE OF MULTIPLE DAYS WILL BE INTERMITTENT...WITH SOME PERIODS OF LULLS...BETWEEN UPPER IMPULSES. STILL...THE LONG TERM PRECIPITATION TOTALS OVER THE SEVERAL DAYS LOOKS TO BE SIGNIFICANT. BELOW AVERAGE CONFIDENCE: AGEOSTROPHIC WINDS AND ISALLOBARIC FLOW COULD BE QUITE STRONG OUT OF THE NORTHEAST TO NORTHWEST...SUGGESTING RELATIVELY COLDER AIR COULD BE REINFORCED AND ENTRENCHED...ESPECIALLY OVER NORTHERN AREAS FROM THE ADIRONDACKS TO SOUTHERN VT. TEMPERATURES COULD BE ON THE LOWER SIDE OF GUIDANCE AND IN SOME CASES A LITTLE BELOW GUIDANCE FOR HIGH TEMPERATURES. AREAS OF VERMONT INTO THE NORTHERN BERKSHIRES...NORTHERN LAKE GEORGE SARATOGA REGION AND ADIRONDACKS MAY SEE PERIODS OF MIXED PRECIPITATION FRIDAY NIGHT...SATURDAY NIGHT. TEMPERATURES WILL BE VERY BORDERLINE FRIDAY NIGHT AND SATURDAY NIGHT...AND THERE MAY BE NO MIX...BUT WITH TEMPERATURES DROPPING TO AROUND FREEZING OR JUST BELOW IN SOME SCATTERED AREAS...KEEPING MIX IN FORECAST FOR NOW. BETTER CHANCE OF TRANSITION TO SNOW SUNDAY NIGHT WHEN DEEPER COLD ADVECTION MAY BEGIN. TOO EARLY TO GET SPECIFIC AT THIS POINT. TIMING OF THE DEEPER COLD ADVECTION SUNDAY NIGHT INTO MONDAY MAY NEED TO BE ADJUSTED ONE WAY OR ANOTHER AS NEWER DATA AND GUIDANCE WILL BE CONSULTED DURING THE NEXT FEW DAYS. BUT ONCE DEEPER COLD ADVECTION BEGINS...SOME AREAS COULD SEE SOME MINOR ACCUMULATING SNOW BEFORE ALL PRECIPITATION ENDS. VERY STRONG BOUNDARY LAYER WINDS THROUGHOUT THE EVENT SUGGESTS SOME AREAS COULD SEE ENOUGH BOUNDARY LAYER MIXING FOR VERY STRONG SURFACE WINDS AT TIMES...PERHAPS IN THE HIGHER ELEVATIONS OF THE CATSKILLS... BERKSHIRES AND SOUTHERN VT. TOO EARLY TO ZERO IN ON EXPECTED MAXIMUM WINDS AND EXACT AREAS OF GREATEST THREAT. SO SUMMARIZING POTENTIAL HAZARDS: HEAVY RAIN FALLING ON DEEP SNOW PACK WITH TEMPERATURES AND DEW POINTS LIKELY AT OR ABOVE THE LOWER 40S IN THE CATSKILLS...SOUTHERN BERKSHIRES AND NW CT...SUGGESTS FLOODING POTENTIAL IN SOME AREAS. STRONG WINDS COULD AFFECT SOME REGIONS AS WELL...WITH EMPHASIS ON HIGHER ELEVATIONS. SOME MIXED PRECIPITATION POSSIBLE AT TIMES IN AREAS FROM THE ADIRONDACKS EAST TO SOUTHERN VT. POSSIBLE MINOR ACCUMULATIONS OF SNOW IN SOME AREAS BEFORE PRECIPITATION ENDS. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... EXPECT VFR CONDITIONS TO PERSIST THE NEXT 24 HOURS FOR THE MID AND UPPER HUDSON VALLEY TERMINALS. THE WINDS WILL BE LIGHT TO CALM AT KPOU AND KGFL THROUGH THE EARLY MORNING HOURS. THEY WILL INCREASE FROM THE N/NW AT 5-10 KTS IN THE LATE MORNING THROUGH THE AFTERNOON. FOR KALB...THE WINDS WILL PERSIST FROM THE W/NW AT 5 TO 10 KTS THROUGH THE EARLY MORNING HOURS. THEY WILL INCREASE FROM THE N/NW AROUND 10 KTS IN THE WAKE OF THE FRONT BY THE LATE MORNING...CONTINUING THROUGH THE AFTERNOON. WINDS AT ALL SITES WILL DIMINISH TO LIGHT THIS EVENING. OUTLOOK... TUE NIGHT-WED NIGHT...VFR. NO SIG WX. THU...VFR/MVFR. SLIGHT CHC -RA THU NIGHT...VFR/MVFR. CHC -RA FRI-SAT...MVFR/IFR...LIKELY -RA. && .HYDROLOGY... NO HYDRO PROBLEMS EXPECTED THROUGH AT LEAST THURSDAY ACROSS THE AREA. SOME MINOR FLOW INCREASES ARE OCCURRING FROM MELTING SNOW DURING THE AFTERNOONS...WITH TEMPERATURES DIPPING TO NEAR OR BELOW FREEZING AT NIGHT. A LARGE AND COMPLEX STORM SYSTEM WILL IMPACT OUR REGION WITH POTENTIALLY SIGNIFICANT PRECIPITATION FROM FRIDAY THROUGH THE WEEKEND. SOME LIGHT RAIN IS POSSIBLE THURSDAY INTO THURSDAY NIGHT...BUT THE TIME FRAME OF CONCERN FOR HEAVY RAINFALL IS DURING THE WEEKEND. THE COMBINATION OF RAIN...AND MELTING SNOW...COULD RESULT IN SOME FLOODING PROBLEMS. MANY AREAS IN THE HUDSON VALLEY...INCLUDING THE GREATER CAPITAL DISTRICT...HAVE LOST MUCH OF THEIR SNOWPACK. HOWEVER...SNOW WATER EQUIVALENTS ACROSS MOUNTAIN AREAS REMAIN VERY HIGH...WITH 4 TO 10 INCHES OF WATER IN THE SNOW PACK. THE FIFTH SPRING FLOOD POTENTIAL OUTLOOK WAS ISSUED FRIDAY. PLEASE SEE /ESFALY/ FOR DETAILS. 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. && $$ AVIATION...NAS