Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 271947
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
347 PM EDT SUN JUL 27 2014

.SYNOPSIS...
LOW PRESSURE ACROSS EASTERN MICHIGAN WILL PIVOT AROUND AN UPPER
LEVEL DISTURBANCE...REACHING EASTERN NEW YORK STATE MONDAY MORNING. THIS
WILL BRING HEAVY RAINS TO PORTIONS OF WESTERN NEW YORK...WITH SOME
EMBEDDED THUNDERSTORMS. RAIN WILL LAST INTO MONDAY AND THEN A COOLER
PATTERN WILL SET UP FOR THE FIRST HALF OF THE WORK WEEK.

&&

.NEAR TERM /THROUGH MONDAY/...
THE REMAINDER THE AFTERNOON SHOULD LARGELY BE DRY...WITH VISIBLE
SATELLITE SHOWING A SIGNIFICANT DRY SLOT ACROSS CENTRAL NEW YORK
WHICH IS ROUGHLY ALIGNED WITH WEAK MID-LEVEL RIDGING. A FEW SHOWERS
AND THUNDERSTORMS WILL CLIP THE SAINT LAWRENCE VALLEY...WITH SOME
LIGHT SHOWERS OR SPRINKLES POSSIBLE IN THE SOUTHERN TIER...BUT THE
VAST MAJORITY OF THE REGION SHOULD BE DRY WITH A FAIR AMOUNT OF
SUNSHINE THROUGH 700 PM. TEMPERATURES WILL BE IN THE UPPER 70S TO
LOWER 80S WITH THE COOLER TEMPERATURES ALONG THE LAKESHORES AND
ACROSS HIGHER TERRAIN.

CONDITIONS WILL DETERIORATE RAPIDLY THIS EVENING...AS STEADIER
RAINS MOVE INTO THE REGION FROM THE OHIO VALLEY. THERE CONTINUES
TO BE A POTENTIAL FOR FLOODING...WITH MOST MESOSCALE 12Z GUIDANCE
CONTINUING TO FORECAST LOCALIZED RAINFALL AMOUNTS OF 2 TO 3
INCHES. THE FORECAST CHALLENGE IS DETERMINING EXACTLY WHEN AND
WHERE THESE AMOUNTS WILL FALL...GIVEN THE CONVECTIVE ELEMENTS OF
AN OTHERWISE SYNOPTIC EVENT.

AN ANOMALOUSLY DEEP 500 MB TROUGH ACROSS THE CENTRAL GREAT LAKES
THIS AFTERNOON WILL PIVOT ACROSS THE LOWER LAKES...WITH THIS
FORECAST TO STRENGTHEN A SURFACE LOW WHICH WILL TAKE ROUGHLY A
SIMILAR TRACK. THE UPPER LEVEL TROUGHING AND DIFFLUENCE WILL ALIGN
WITH DEEP LOW LEVEL MOISTURE TO PRODUCE LARGE SCALE LIFT ACROSS OUR
REGION TONIGHT INTO MONDAY. ON TOP OF THIS...SUBTLE LOW AND MID
LEVEL BOUNDARIES WILL FOCUS RAINFALL...AND IT WILL BE THESE
MESOSCALE FEATURES WHICH COULD PUSH RAINFALL AMOUNTS OVER THE 2 INCH
THRESHOLD. 12Z RUNS OF THE NAM/RGEM HAVE SHIFTED SOUTHEAST WITH THE
HEAVIEST RAINFALL FROM PREVIOUS RUNS...WHILE THE GFS SEEMS TOO DEEP
WITH THE SURFACE LOW. 09Z SREF ENSEMBLES REFLECT 00/06Z GUIDANCE AND
PUT THE BULLS-EYE ACROSS THE NIAGARA FRONTIER...WITH THE LATEST RUNS
OF THE HRRR TENDING TO SUPPORT THESE SOLUTIONS. BASED ON THIS...HAVE
HIGH CONFIDENCE THAT THERE WILL BE HEAVY RAIN...BUT DO NOT HAVE HIGH
CONFIDENCE ON EXACTLY WHERE IT WILL BE...SINCE IT IS ONLY LIKELY TO
IMPACT A PORTION OF THE REGION. THE FORECAST FOLLOWS A CONSENSUS OF
ALL GUIDANCE...WHICH SUPPORTS THE CURRENT LOCATION OF THE FLOOD
WATCH. THE AREA MOST VULNERABLE IS URBAN AREAS AND THE BUFFALO
CREEKS...WHICH WOULD PROBABLY REACH FLOOD STAGE IF RAINFALL
TOTALS TOP 2 INCHES. LARGER BASINS ARE LESS LIKELY TO FLOOD...SINCE
THE AXIS OF HEAVY RAIN IS LIKELY TO BE TOO SMALL TO FILL A LARGER
BASIN SUCH AS THE GENESEE RIVER. ALSO...MOST RIVERS AND CREEKS ARE
AT FAIRLY LOW FLOWS TO START WITH.

EXPECT STEADY RAIN WITH EMBEDDED THUNDERSTORMS TO REACH WESTERN
PORTIONS OF THE SOUTHERN TIER AROUND SUNSET...THEN SLOWLY SPREAD
NORTHEAST TO BUFFALO LATE THIS EVENING AND ROCHESTER AROUND
MIDNIGHT. THERE IS A LIMITED SEVERE WEATHER POTENTIAL THIS
EVENING...HOWEVER WINDS ALOFT ARE FAIRLY LIGHT...AND NOT TERRIBLY
FAVORABLE FOR SEVERE WEATHER THOUGH A FEW STRONG STORMS CANNOT BE
RULED OUT. LATER TONIGHT...INSTABILITY WILL BECOME ELEVATED AS A
NORTHERLY SURFACE FLOW BECOMES ESTABLISHED.

THE AXIS OF HEAVY RAIN WILL SHIFT EASTWARD LATE TONIGHT INTO MONDAY
MORNING. MEANWHILE...MODERATE NORTHERLY FLOW WILL BE IN PLACE...WITH
GUSTS TO 25 MPH. THIS UPSLOPE COMPONENT COMBINED WITH COOLER
TEMPERATURES ALOFT AND UPPER LEVEL TROUGHING WILL CAUSE CLOUDS AND
POSSIBLY SHOWERS TO LINGER FOR MUCH OF THE DAY. COOLER AIR AND
CLOUDS KEEP TEMPERATURES IN THE 60S ON MONDAY...WHICH IS
UNSEASONABLY COOL FOR THIS TIME OF YEAR.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
COOL AIR WILL REMAIN ACROSS THE EASTERN GREAT LAKES ON MONDAY
NIGHT...BUT THE DRIER AIR ALOFT AND SUBSIDENCE WILL SUPPRESS ANY
LAKE EFFECT RESPONSE OTHER THAN A THIN LAYER OF LAKE INDUCED
STRATOCU TO THE SOUTHEAST OF LAKES ERIE AND ONTARIO. EXPECT A COOL
AND DRY NIGHT WITH LOWS IN THE MID 40S TO NEAR 50 ACROSS THE
INTERIOR OF THE SOUTHERN TIER AND THE TUG HILL PLATEAU...TO THE MID
TO UPPER 50S ALONG THE SHORES OF LAKES ERIE AND ONTARIO.

IT WILL BE A LITTLE WARMER ON TUESDAY WITH HIGHS N THE MID/UPR 60S
INLAND TO THE LOWER 70S ALONG THE LAKESHORES AND LOWER TERRAIN.
HOWEVER...THE WARMER SURFACE TEMPS COINCIDE WITH A COOLING ALOFT TO
AROUND +5C AT 850MB AS THE AXIS OF THE PERSISTENT CANADIAN TROUGH CROSSES
THE REGION. THIS WILL YIELD THE CHANCE OF DAYTIME SHOWERS ON TUESDAY
WITH SOME NIGHTTIME LAKE EFFECT RAIN TUESDAY NIGHT...AND EVEN THE
ISOLATED RISK OF WATERSPOUTS.

THE LOW CHANCE OF DIURNAL CYCLE SHOWERS CONTINUES ON WEDNESDAY AS
THE UPPER TROUGH ROTATES ANOTHER SPOKE OF VORTICITY ACROSS THE
REGION. THE HIGH TEMPS WILL BUMP UP ANOTHER NOTCH...TO THE UPPER 60S
TO MID 70S...SO WILL BRING BACK A CHANCE OF THUNDERSTORMS DURING
WEDNESDAY AFTERNOON. THE 850MB TEMPS WARM SUFFICIENTLY TO EXCLUDE
THE RISK OF WATERSPOUTS. WEDNESDAY NIGHT WILL BE LESS COOL WITH
OVERNIGHT LOWS IN THE 50S ACROSS THE REGION...AND A LOW CHANCE OF AN
OVERNIGHT SHOWER AS WELL.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
THE DEEP LONGWAVE TROUGH OVER THE GREAT LAKES AND NORTHEASTERN STATE
DURING MIDWEEK WILL SLOWLY DE-AMPLIFY AND RETREAT INTO QUEBEC BY THE
END OF THE WEEK. THE LOW CHANCE OF SHOWERS ON THURSDAY WILL GIVE WAY
TO NIL POPS ON THU NIGHT AND FRIDAY. HIGH TEMPS WILL RISE FROM MID
70S THURSDAY TO THE UPPER 70S ON FRIDAY.

THE SLOW WARMING TREND WILL CONTINUE ON SATURDAY...BUT A CLOSED LOW
DEVELOPING OVER THE OHIO VALLEY MAY FORCE ATLANTIC MOISTURE TO
SPREAD NORTH INTO OUR REGION WITH A CHANCE OF SHOWERS AND A FEW
THUNDERSTORMS SATURDAY AND SUNDAY AFTERNOONS.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
WEAK UPPER LEVEL RIDGING SHOULD KEEP CONDITIONS VFR FOR THE
REMAINDER OF THE AFTERNOON.

LOW PRESSURE WILL APPROACH THE REGION TONIGHT...WHICH WILL BRING
STEADY AND SOMETIMES HEAVY RAINFALL TO THE REGION TONIGHT. EXPECT
CIGS/VSBY TO GRADUALLY LOWER TO MVFR THIS EVENING FROM SW- NE AS
THIS LOW APPROACHES THE REGION. THE STRENGTHENING LOW WILL SET UP
A NE FLOW...WHICH IS LIKELY TO BRING EVEN LOWER CONDITIONS LATE
TONIGHT...WITH IFR OR LOWER CIGS A GOOD POSSIBLY. CIGS WILL BE
SLOW TO LIFT ON MONDAY MORNING...WITH A NORTHERLY UPSLOPE FLOW
AND LINGERING MOISTURE.

OUTLOOK...
MONDAY AFTERNOON...GRADUAL IMPROVEMENT FROM IFR/MVFR LATE
AFTERNOON AND EVENING.
TUESDAY THROUGH THURSDAY...MAINLY VFR WITH A CHANCE OF SHOWERS.
FRIDAY...VFR.

&&

.MARINE...
LOW PRESSURE WILL PIVOT SOUTH OF THE REGION TONIGHT AND THEN WILL
STRENGTHEN ACROSS EASTERN NEW YORK ON MONDAY. THIS WILL TIGHTEN THE
PRESSURE GRADIENT AND ESTABLISH A MODERATE NORTHERLY FLOW LATE
TONIGHT AND MONDAY. THE 12Z GFS APPEARS OVERDONE...BUT EVEN SO THE
NAM/RGEM ARE STRONGER THAN PREVIOUS RUNS AND SUPPORTS SMALL CRAFT
HEADLINES FOR LAKE ONTARIO...AND THE LOWER NIAGARA RIVER. EVEN LAKE
ERIE BEARS WATCHING...WITH WINDS/WAVES LIKELY TO APPROACH SMALL
CRAFT CRITERIA LATE TONIGHT AND MONDAY MORNING. WINDS WILL DIMINISH
MONDAY NIGHT...WITH A WEAKER FLOW FORECAST FOR MID-WEEK. COOLER
TEMPERATURES ALOFT SUGGEST THERE IS A CHANCE FOR WATERSPOUTS ON
TUESDAY NIGHT INTO WEDNESDAY.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...FLOOD WATCH FROM 10 PM EDT THIS EVENING THROUGH MONDAY
     AFTERNOON FOR NYZ001>004-010>014-019>021-085.
MARINE...SMALL CRAFT ADVISORY FROM 5 AM TO 2 PM EDT MONDAY FOR LOZ030.
         SMALL CRAFT ADVISORY FROM 2 AM TO 8 PM EDT MONDAY FOR
         LOZ042>044.
         SMALL CRAFT ADVISORY FROM 5 AM TO 6 PM EDT MONDAY FOR
         LOZ045.

&&

$$

SYNOPSIS...APFFEL
NEAR TERM...APFFEL
SHORT TERM...WCH
LONG TERM...WCH
AVIATION...APFFEL
MARINE...APFFEL







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