Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 261137 AFDBUF AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BUFFALO NY 737 AM EDT SUN APR 26 2015 .SYNOPSIS... A PERSISTENT UPPER LEVEL LOW WILL CONTINUE TO SPIRAL OVER NEW ENGLAND TODAY...SENDING ONE LAST WAVE OF MOISTURE...CLOUDS AND LIGHT SHOWERS ACROSS THE REGION TONIGHT AND MONDAY MORNING BEFORE EXITING THE REGION TUESDAY. MAINLY DRY WEATHER WITH NEAR NORMAL TEMPERATURES ARE EXPECTED FOR TUESDAY AND WEDNESDAY BEFORE ANOTHER WEAK SYSTEM BRINGS A ANOTHER CHANCE OF SHOWERS BY THURSDAY. && .NEAR TERM /THROUGH TONIGHT/... ON THE WATER VAPOR IMAGERY THIS MORNING AN UPPER LEVEL LOW SPINS JUST OFF THE NEW ENGLAND COASTLINE. THIS IS THE SAME LOW THAT HAS SLOWLY CROSSED EASTERN NORTH AMERICA THIS PAST WEEK. A SHORTWAVE IS SEEN ON WATER VAPOR OVER FAR SW QUEBEC. IR SATELLITE IMAGERY DISPLAYS SEVERAL AREAS OF MID LEVEL CLOUDS NOW OVER LAKE ONTARIO AND AREAS SOUTH. A BRIEF CLEAR SLOT HAS DEVELOPED OVER THE EASTERN LAKE ONTARIO REGION. FOR TODAY AFTER A MIX OF SUN AND CLOUDS THIS MORNING...EXPECT A FAIRLY CLOUDY DAY TO DEVELOP AS MOISTURE FROM THE NORTH CONTINUES TO ADVECT SOUTHWARD...AND DAYTIME INSTABILITY AND STEEPENING LAPSE RATES EXPANDS A STRATO-CU LAYER. AS DISPLAYED ON IR SATELLITE IMAGERY...THERE ARE SOME BREAKS IN THE UPSTREAM CLOUD COVER AND SOME SUNSHINE WILL BE POSSIBLE THIS MORNING. THE REGION SHOULD REMAIN DRY TODAY...THOUGH A FEW SPRINKLES/LIGHT RAIN SHOWER ARE POSSIBLE LATE IN THE AFTERNOON EAST OF LAKE ONTARIO AS MOISTURE FIELDS INCREASE THIS AFTERNOON. AFTER A COOL START HIGHS SHOULD REBOUND INTO THE UPPER 40S AND LOWER 50S. COOLEST AREAS WILL BE SOUTH OF THE LAKES WHERE A LIGHT NORTHWESTERLY FLOW OVER THE YET STILL COOL LAKE WATERS KEEPS AREAS NEAR THE SOUTHERN LAKE SHORES IN THE LOWER TO MID 40S. TONIGHT A SHORTWAVE TROUGH WILL PASS ACROSS THE REGION FROM THE NORTH. THIS FEATURE COMBINED WITH INCREASING LOW LEVEL MOISTURE WILL BRING A FEW LIGHT RAIN SHOWERS/DRIZZLE TO THE REGION. WITH LITTLE FORCING ALOFT AS WIND FIELDS REMAIN WEAK WILL CONTINUE JUST CHANCE POPS OVERNIGHT. THE LIGHT MOIST NORTHERLY FLOW THROUGH THE NIGHT WILL UPSLOPE SUCH THAT LOW CLOUDS AND PATCHY AREAS OF FOG AND DRIZZLE (POSSIBLE FREEZING DRIZZLE) WILL BE POSSIBLE OVER HIGHER TERRAIN OF SOUTHERN NY. THE TRADITIONALLY COLDER VALLEYS OF SOUTHERN NEW YORK MAY DROP PAST THE FREEZING MARK OVERNIGHT AND WITH LITTLE MOISTURE IN THE SNOW GROWTH ZONE...FREEZING DRIZZLE WILL BE POSSIBLE. EAST OF LAKE ONTARIO THE MOISTURE FIELD SHOULD BE DEEP ENOUGH TO SUPPORT EITHER RAIN OR SNOW SHOWERS OVERNIGHT. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... MODEL CONSENSUS CONSISTENTLY KEEPS AN UPPER-LEVEL LOW STALLED NEAR NOVA SCOTIA THROUGHOUT THE PERIOD. A TROUGH EXTENDING TO THE WEST FROM THIS LOW WILL DROP SOUTHWARD ACROSS OUR REGION ON MONDAY WITH A MORE SUBTLE DISTURBANCE FORECAST TO FOLLOW THIS MONDAY EVENING. LIFT WITH THIS FEATURE WILL BE VERY WEAK...WITH NAM/GFS BUFKIT SHOWING NEARLY ALL THE OMEGA BELOW 850MB. MOST OF THIS IS PROBABLY DUE TO UPSLOPING FROM THE NORTHERLY FLOW. UPSLOPING CAN BE OVERDONE BY MODEL GUIDANCE SINCE PRECIPITATION DEPENDS HEAVILY ON HOW SATURATED THE BOUNDARY LAYER IS. THERE IS A FAIR AMOUNT OF BOUNDARY LAYER MOISTURE UPSTREAM WITH THIS FEATURE...SO WILL MAINTAIN CHANCE POPS MONDAY INTO MONDAY EVENING. ANY PRECIPITATION THAT DOES OCCUR WILL BE LIGHT WITH AMOUNTS BARELY ENOUGH TO WET THE GROUND. THERE SHOULD BE FAIRLY EXTENSIVE CLOUD COVER MONDAY AND MONDAY NIGHT. CONSIDERING THE WARM BIAS OF MOST GUIDANCE THE PAST COUPLE DAYS...AND 850MB TEMPS OF -2C WILL NUDGE HIGHS ON MONDAY DOWN A BIT. UNLESS THERE ARE SIGNIFICANT BREAKS OF SUNSHINE...EXPECT HIGHS TO MAINLY BE IN THE MID TO UPPER 40S. HOWEVER THE CLOUD COVER WILL KEEP TEMPERATURES FROM DROPPING MUCH MONDAY NIGHT WITH LOWS IN THE UPPER 30S TO LOWER 40S. SOME PATCHY UPSLOPE FOG IS POSSIBLE MONDAY NIGHT DEPENDING ON HOW MUCH MOISTURE IS TRAPPED IN THE BOUNDARY LAYER. ALTHOUGH THE UPPER LOW WILL REMAIN NEARLY STATIONARY THE PASSAGE OF THE TROUGH AXIS WILL ALLOW A SUBTLE UPPER LEVEL RIDGE TO BUILD TOWARD THE REGION TUESDAY AND TUESDAY NIGHT. THIS WILL RESULT IN GRADUALLY CLEARING SKIES AND WARMING TEMPERATURES. HIGHS ON TUESDAY WILL DEPEND ON HOW MUCH SKIES CLEAR...WITH MODEL GUIDANCE DIFFERING ON THIS SOMEWHAT. USING A PARTIAL CLEARING MODEL CONSENSUS HIGHS ON TUESDAY SHOULD RISE INTO THE UPPER 50S TO LOWER 60S AWAY FROM THE LAKES...WITH TEMPERATURES 5 TO 10 DEGREES COOLER ALONG THE IMMEDIATE LAKESHORE. THE NW FLOW SHOULD ALLOW KEEP MOST OF THE BUFFALO METRO AREA ON THE WARM SIDE OF THE LAKE BREEZE. BY TUESDAY NIGHT EXPECT MOSTLY CLEAR SKIES WITH DECENT RADIATIONAL COOLING ALLOWING TEMPERATURES TO DROP TO THE MID 30S TO LOWER 40S. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... FAIRLY TYPICAL SPRING WEATHER TO CONTINUE THROUGH THE EXTENDED FORECAST PERIOD. BY WEDNESDAY...THE UPPER-LEVEL LOW THAT HAS BEEN HANGING AROUND WILL FINALLY DEPART OFF THE NEW ENGLAND COAST. MODELS ARE IN AGREEMENT THAT THIS WILL BE FOLLOWED BY A NORTHERN STREAM SHORTWAVE INTERACTING WITH A CUTOFF LOW EXITING FROM THE FOUR CORNERS REGION. HOWEVER...THAT IS WHERE THE AGREEMENT ENDS...AS THE GLOBAL MODELS ALL HANDLE THIS INTERACTION DIFFERENTLY. LOOKING AT RECENT RUNS OF THE GGEM/ECMWF/GFS...ABOUT TWO-THIRDS OF THE GUIDANCE IS SIMILAR TO THE 00Z GGEM/ECMWF WHICH FORECAST A WEAK AND DISORGANIZED TROUGH WITH WARMER TEMPERATURES AND ONLY A LOW CHANCE FOR PRECIPITATION LATE IN THE WEEK. THE LESS LIKELY 00Z GFS SOLUTION HAS A STRONGER CUT-OFF LOW DEVELOPING WHICH WOULD BRING COOLER TEMPERATURES AND A BETTER CHANCE FOR PRECIPITATION. FORECAST WILL USE A CONSENSUS OF ALL GUIDANCE...WHICH SHOULD EVENTUALLY TREND TO ONE OF THESE TWO CAMPS. IN GENERAL...THIS APPROACH LEADS TO SLIGHTLY WARMER TEMPERATURES TO THE PREVIOUS FORECAST WITH LITTLE CHANGE TO POPS. BY NEXT WEEKEND...THE MODEL CONSENSUS IS TO BUILD A RIDGE ACROSS THE UPPER GREAT LAKES...WITH SOME NORTHWEST FLOW IN PLACE ACROSS THE LOWER GREAT LAKES. THIS SHOULD RESULT IN A WARMER WEEKEND AS COLDER AIR WILL BE SUPPRESSED WELL TO THE NORTH. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... AT 12Z VFR FLIGHT CONDITIONS WERE FOUND ACROSS THE REGION...AND THESE CONDITIONS ARE EXPECTED TO PERSIST FOR ANOTHER 18 TO 24 HOURS ACROSS THE REGION. SOME PASSING MID LEVEL CLOUDS THIS MORNING FROM THE NORTH WILL THICKEN THROUGH THE DAY AS DEEPER MOISTURE DROPS SOUTHWARD FROM SOUTHERN CANADA. THIS MOISTURE MAY TRIGGER A FEW SPRINKLES/SHOWERS ACROSS AREAS EAST OF LAKE ONTARIO THIS LATE AFTERNOON...AND AFTER 00Z FOR THE REMAINDER OF THE REGION. AS SUCH WILL NOT INCLUDE ANY WX CODE INTO THE TAFS UNTIL THE DEEPER MOISTURE ARRIVES OVERNIGHT. DUE THE THE SCATTERED NATURE WILL ONLY INCLUDE A VCSH IN THE TAFS. WITHIN THE DEEPER MOISTURE IN THE LOWER LEVELS SOME MVFR CIGS ARE POSSIBLE WITH THE LIGHT NORTHERLY FLOW. ALSO ACROSS THE HIGHER TERRAIN LIGHT DRIZZLE AND IFR FLIGHT CONDITIONS ARE PROBABLE. THESE LOWER CONDITIONS ARE LIKELY NOT TO START UNTIL AFTER 03Z. THE BEST CHANCES FOR ANY SHOWERS THIS TIME PERIOD WILL BE FROM 03Z MONDAY TO 21Z MONDAY. OUTLOOK... MONDAY AFTERNOON...ANY SHOWERS DIMINISHING...MAINLY VFR. TUESDAY THROUGH THURSDAY...MAINLY VFR. && .MARINE... LOW PRESSURE REMAINING OVER NEW ENGLAND TODAY WILL MAINTAIN RELATIVELY LIGHT NORTHWEST WINDS ON THE LOWER LAKES THROUGH THE MIDDLE OF NEXT WEEK. WINDS WILL OCCASIONALLY BECOME STRONG ENOUGH TO PRODUCE CHOPPY WAVE ACTION...BUT SHOULD STAY JUST BELOW SMALL CRAFT ADVISORY CRITERIA. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...NONE. && $$ SYNOPSIS...THOMAS NEAR TERM...THOMAS SHORT TERM...APFFEL LONG TERM...APFFEL/CHURCH AVIATION...THOMAS MARINE...THOMAS

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