Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 271830
AFDBUF

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

.SYNOPSIS...
THIS AFTERNOON SHOULD BE MAINLY DRY...HOWEVER CONDITIONS WILL
DETERIORATE RAPIDLY THIS EVENING AS LOW PRESSURE PIVOTS FROM
EASTERN MICHIGAN TO NEW YORK STATE. THIS WILL BRING HEAVY RAINS TO
PORTIONS OF WESTERN NEW YORK...WITH EMBEDDED THUNDERSTORMS. THIS
WILL LAST INTO MONDAY BEFORE A COOLER PATTERN SETS UP FOR THE
FIRST HALF OF THE WORK WEEK WITH A FEW SHOWERS POSSIBLE FROM TIME
TO TIME. THEN TEMPERATURES WILL BEGIN TO MODERATE TOWARD THE END
OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
THE REMAINDER THE AFTERNOON SHOULD LARGELY BE DRY...WITH VISIBLE
SATELLITE SHOWING A SIGNIFICANT DRY SLOT WHICH IS ROUGHLY ALIGNED
WITH WEAK MID-LEVEL RIDGING. SHOWERS AND POSSIBLY A THUNDERSTORM
MAY 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 AXIS 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 THE
SAME TRACK. THE UPPER LEVEL TROUGHING AND DIFLUENCE 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 THIS MOISTURE...AND IT WILL BE THESE
MESOSCALE FEATURES WHICH 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.
FORECAST FOLLOWED A CONSENSUS OF ALL GUIDANCE...WHICH SUPPORTS THE
CURRENT LOCATION OF THE FLOOD WATCH. THE AREA MOST VULNERABLE IS
THE BUFFALO CREEKS AND URBAN AREAS...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. 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 TUESDAY NIGHT/...
ANY LINGERING SHOWERS EAST OF LAKE ONTARIO EARLY MONDAY EVENING
WILL END. THERE MAY BE SOME PARTIAL CLEARING AT FIRST BEHIND THE
DEPARTING LOW...BUT THEN SOME WRAP AROUND MOISTURE AND LAKE EFFECT
CLOUDS WILL DEVELOP OVERNIGHT IN THE NORTHWEST UPSLOPE FLOW
REGIME. LAKE INDUCED INSTABILITY WILL BE GREAT ENOUGH FOR SOME
CLOUD COVER...BUT SHOULD NOT BE HIGH ENOUGH FOR SHOWERS GIVEN THE
SHORT FETCH AND LACK OF SYNOPTIC SCALE FORCING.

ON TUESDAY THE LONGWAVE TROUGH WILL BE WELL ESTABLISHED ACROSS THE
GREAT LAKES AND NORTHEAST. THE NEXT LOW LEVEL TROUGH AND DEEPER
MOISTURE WILL REMAIN ACROSS THE CENTRAL AND UPPER LAKES TUESDAY.
THIS WILL LEAVE LITTLE IN THE WAY OF ORGANIZED ASCENT OVER THE LOWER
LAKES. COLD AIR ALOFT AND WEAK LAKE AND TERRAIN INDUCED CONVERGENCE
ZONES MAY SUPPORT A FEW WIDELY SCATTERED SHOWERS DURING THE MIDDAY
AND AFTERNOON...MAINLY INLAND FROM THE LAKESHORES. IT WILL REMAIN ON
THE COOL SIDE...WITH HIGHS ONLY IN THE VERY LOW 70S AT LOWER
ELEVATIONS AND MID 60S ACROSS HIGHER TERRAIN.

TUESDAY NIGHT THE DIURNAL SHOWERS SHOULD END DURING THE EVENING.
OVERNIGHT DEEPER WRAP AROUND MOISTURE AND WEAK ASCENT WILL BEGIN TO
OVERSPREAD WESTERN NY...WHICH MAY SUPPORT A FEW SCATTERED SHOWERS. A
CYCLONIC SOUTHWEST FLOW AND DEEPER MOISTURE COMBINED WITH COOL MID
LEVEL TEMPS MAY ALSO SUPPORT A FEW LAKE EFFECT SHOWERS EAST AND
NORTHEAST OF LAKE ERIE BY WEDNESDAY MORNING.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
A DEEP LONGWAVE TROUGH WILL REMAIN OVER THE GREAT LAKES AND
NORTHEAST THROUGH MIDWEEK BEFORE SLOWLY DE-AMPLIFYING AND RETREATING
INTO QUEBEC BY THE END OF THE WEEK. THE MOIST CYCLONIC FLOW WILL
ALLOW A SERIES OF LOW AMPLITUDE SHORTWAVES AND LOW LEVEL TROUGHS TO
CROSS THE REGION. EACH ONE OF THESE WILL SUPPORT SCATTERED SHOWERS
AND THERE WILL ALSO BE THE POTENTIAL FOR SOME LAKE ENHANCEMENT AS
WELL EARLY WEDNESDAY MORNING AND PERHAPS AGAIN LATER WEDNESDAY NIGHT
WITH COOL AIR ALOFT. TEMPERATURES WILL ONLY SLOWLY IMPROVE WEDNESDAY
AND THURSDAY WITH HIGHS IN THE MID 70S AT LOWER ELEVATIONS AND
AROUND 70 ACROSS HIGHER TERRAIN.

THE TROUGH WILL FINALLY RELAX ITS GRIP BY FRIDAY WITH WEAK SURFACE
HIGH PRESSURE BUILDING INTO THE LOWER LAKES. THIS SHOULD FINALLY
BRING A MAINLY DRY DAY WITH TEMPERATURES SLOWLY MOVING BACK CLOSER
TO AVERAGE. 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 ANOTHER CHANCE OF
SHOWERS AND A FEW THUNDERSTORMS.

&&

.AVIATION /18Z 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...
WINDS WILL AVERAGE BETWEEN 10 AND 15 KNOTS TODAY...WITH SOME MODEST
CHOP ALONG THE WESTERN SHORES OF BOTH LAKES...BUT WAVES SHOULD
STAY BELOW SCA CRITERIA THROUGH THIS EVENING.

LOW PRESSURE WILL PIVOT SOUTH OF THE REGION TONIGHT AND THEN WILL
STRENGTHEN ACROSS EASTERN NEW YORK ON SUNDAY. 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.

&&

.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...HITCHCOCK
LONG TERM...HITCHCOCK
AVIATION...APFFEL
MARINE...APFFEL







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