Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 162351
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
651 PM EST TUE DEC 16 2014

.SYNOPSIS...
PERIODS OF RAIN SHOWERS WILL CONTINUE ACROSS THE AREA TONIGHT AS A
LOW PRESSURE SYSTEM MOVES THROUGH THE REGION. COLDER AIR WILL MOVE
IN BEHIND THIS SYSTEM FOR WEDNESDAY INTO THURSDAY...RESULTING IN A
MIX OF RAIN AND SNOW TRANSITIONING TO LAKE EFFECT SNOW SHOWERS EAST
AND SOUTHEAST OF THE GREAT LAKES. HIGH PRESSURE WILL RETURN BY
FRIDAY AND SATURDAY WITH DRYING CONDITIONS AND NEAR-NORMAL
TEMPERATURES.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
SURFACE ANALYSIS THIS EARLY EVENING PLACES AN AREA OF LOW PRESSURE
BETWEEN LAKES HURON AND ERIE. THE INITIAL BATCH OF RAIN SHOWERS
ALONG A WARM FRONT ARE NOW ACROSS THE EASTERN LAKE ONTARIO
REGION...AND BECOMING LESS INTENSE THIS EVENING. SURFACE
TEMPERATURES EAST OF LAKE ONTARIO ARE IN THE MID 30S SO THE THREAT
OF FREEZING RAIN WILL BE MINIMAL FOR THE THREE COUNTIES EAST OF LAKE
ONTARIO.

WATER VAPOR IMAGERY DISPLAYS A COMPLEX UPPER LEVEL LOW OVER THE
GREAT LAKES REGION. A SHORTWAVE STACKED OVER THE CENTRAL GREAT LAKES
SURFACE LOW IS NOTED WITH BROAD CYCLONIC FLOW...WHILE A SECOND
SHORTWAVE IS MORE SUBTLY NOTED OVER THE WESTERN GREAT LAKES...ONE
THAT WILL MAINTAIN THIS UPPER LEVEL LOW OVER THE EASTERN GREAT LAKES
REGION THROUGH TOMORROW NIGHT.

FOR THE REMAINDER OF THIS EVENING AND OVERNIGHT LIGHT RAIN SHOWERS
ON THE PERIPHERY OF THIS UPPER LEVEL LOW OVER THE CENTRAL GREAT
LAKES WILL PASS ACROSS WESTERN NEW YORK. WILL MAINTAIN HIGHEST
POPS...CATEGORICAL OVER FAR WESTERN NEW YORK...WHILE TOWARDS THE
GENESEE VALLEY AND FARTHER FROM THE SURFACE LOW/BETTER CONVERGENCE
MOST OF THE NIGHT WILL FEATURE LITTLE PRECIPITATION ACTIVITY AND
WILL COVER THIS POTENTIAL WITH CHANCE POPS. LOWS TONIGHT WILL REMAIN
MILD WITH OVERNIGHT LOWS RANGING FROM THE MID 30S TO LOWER
40S...WITH WARMEST OVERNIGHT TEMPERATURES FOUND NEAR THE LAKE
PLAINS.

ON WEDNESDAY A FRESH SHOT OF COLD AIR WILL ARRIVE ACROSS THE REGION
AS WESTERLY FLOW INCREASES ON THE BACK SIDE OF THE SURFACE LOW
CENTERED JUST NORTH OF LAKE ONTARIO. THE LOW CENTER WILL REDEVELOP
ALONG THE NEW ENGLAND COAST THROUGH THE DAY AS THE AXIS OF THE UPPER
LEVEL TROUGH SHIFTS ACROSS THE NORTHEAST. PERSISTENT COLD AIR
ADVECTION WILL KEEP TEMPERATURES ON A SLOW DOWNWARD TREND THROUGH
THE DAY FROM WEST TO EAST AND FROM HIGH ELEVATIONS TO LOW
ELEVATIONS. UPPER 30S TO LOW 40S EARLY WILL FALL TO UPPER 20S AND
LOW 30S BY THE LATE AFTERNOON.

WEAK SYNOPTIC LIFT FROM THE SURFACE LOW AND UPPER LEVEL TROUGH AXIS
CROSSING THE REGION COMBINED WITH PLENTY OF LOW LEVEL MOISTURE WILL
KEEP SHOWERS IN THE FORECAST THROUGH THE DAY WITH HIGHEST CHANCES
FOCUSED EAST OF THE LAKES WITH SOME LAKE ENHANCEMENT AND UPSLOPE.
AS 850MB TEMPS FALL TO AROUND -6C LAKE INDUCED EQUILIBRIUM LEVELS
WILL CLIMB TO AROUND 5KFT. PTYPE WILL BE RAIN EARLY IN THE DAY AND
ACROSS LOW ELEVATIONS MIXING WITH SNOW GOING INTO THE AFTERNOON.
ACROSS HIGHER ELEVATIONS A MIX EARLY ON WILL CHANGE OVER TO ALL SNOW
THROUGH THE DAY WITH ACCUMULATIONS UP TO AN INCH. COLD ADVECTION
WILL BRING GUSTY WINDS DURING THE DAY UP TO AROUND 35 MPH.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AN ELONGATED SURFACE LOW WILL CONSOLIDATE NEAR NOVA SCOTIA WEDNESDAY
NIGHT. THIS WILL SET UP A WESTERLY FLOW WEDNESDAY EVENING...WHICH
WILL SHIFT TO THE WNW LATER IN THE NIGHT. EQUILIBRIUM LEVELS WILL BE
LOW THROUGHOUT THE PERIOD...WITH A PERSISTENT INVERSION FORECAST TO
REMAIN NEAR OR JUST ABOVE 5K FT THROUGH FRIDAY. THIS WILL RESULT IN
SMALL LAKE INDUCED CAPES WITH CLOUD TOPS MARGINALLY COLD ENOUGH FOR
DENDRITIC SNOW GROWTH. THE MOST SIGNIFICANT LIFT WILL COME FROM
UPSLOPING RATHER THAN LAKE INDUCED INSTABILITY...WITH THE GREATEST
SNOW ACCUMULATIONS INLAND FROM THE LAKES ACROSS HIGHER TERRAIN.

THE STEADIEST SNOW WILL LIKELY BE WEDNESDAY EVENING WHEN MOISTURE
ASSOCIATED WITH AN EXITING UPPER LEVEL LOW HELPS ENHANCE LAKE SNOWS.
OFF LAKE ERIE A SHARPER INVERSION WILL BE IN PLACE BUT AIR BENEATH
THIS WILL BE COLDER. 12Z NAM/RGEM GUIDANCE BOTH HINT AT A LAKE
HURON MOISTURE CONNECTION...WHICH COULD ENHANCE SNOWFALL ON THE
CHAUTAUQUA RIDGE AND BOSTON HILLS. GENERALLY EXPECT 1 TO 3 INCHES IN
THESE AREAS....BUT IT IS NOT OUT OF THE QUESTION THAT A PROLONGED
UPSTREAM LAKE CONNECTION COULD RESULT IN LOCALLY HIGHER AMOUNTS
WEDNESDAY NIGHT. LAKE ONTARIO IS A BIT MORE STRAIGHTFORWARD WITH A
LESS PRONOUNCED INVERSION AND DEEPER MOISTURE. THE W-WNW FLOW WILL
UPSLOPE THE HIGHER TERRAIN...ESPECIALLY THE TUG HILL. FORECAST
CONFIDENCE FALLS JUST SHY OF ANY WINDER HEADLINES...BUT IF
NOTHING CHANGES COULD SEE 3 TO 6 INCH ADVISORY AMOUNTS ON THE TUG
HILL WEDNESDAY NIGHT INTO THURSDAY.

AS WINDS SHIFT TO THE WSW LATE WEDNESDAY NIGHT INTO THURSDAY...THIS
WILL PUSH WHATEVER MOISTURE THIS IS ON LAKE ONTARIO SOUTH INTO THE
LAKE PLAINS. THIS IS LIKELY TO BRING SNOW SHOWERS TO THE I-90
CORRIDOR FROM BUF-ROC-SYR...BUT ACCUMULATIONS SHOULD BE
LIGHT...GENERALLY AN INCH OR LESS. MEANWHILE...THE EXIT OF THE UPPER
LEVEL TROUGH WILL RESULT IN A LOWERING INVERSION AND LESS ORGANIZED
LAKE EFFECT SNOW. WHAT DOES LAST WILL AGAIN FOCUS ON HIGHER
TERRAIN...WITH MINIMAL ACCUMULATION NEAR THE IMMEDIATE LAKESHORES
EAST OF LAKE ERIE AND ONTARIO.

THE NORTHWEST FLOW WILL CONTINUE THURSDAY NIGHT AND FRIDAY. LOW
EQUILIBRIUM LEVELS AND LIMITED MOISTURE WILL RESULT IN LIGHT
ACCUMULATIONS WHICH WILL MAINLY BE CONFINED TO THE CHAUTAUQUA RIDGE
OFF LAKE ERIE AND JUST EAST OF ROCHESTER TO OSWEGO COUNTY AND THE
TUG HILL OFF LAKE ONTARIO. TEMPERATURES AT THE TOP OF THE 5K
EQUILIBRIUM LEVEL WILL BE MARGINALLY COLD ENOUGH FOR DENDRITIC SNOW
GROWTH WITH A SMALL CHANCE FOR SOME FREEZING DRIZZLE THURSDAY NIGHT.
GIVEN FORECAST THERMAL PROFILES AND SPOTTY MID-LEVEL MOISTURE EXPECT
PRECIPITATION WILL PRIMARILY BE LIGHT SNOW OR FLURRIES...AND WILL
MAINTAIN THIS IN THE FORECAST.

TEMPERATURES WILL CONTINUE TO BE CHILLY...WITH A MINIMAL DIURNAL
RANGE DUE TO PERSISTENT CLOUD COVER WITH STRATUS TRAPPED BENEATH THE
INVERSION. HIGHS ON THURSDAY AND FRIDAY WILL GENERALLY BE NEAR
FREEZING...WITH OVERNIGHT LOWS IN THE MID TO UPPER 20S.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
HIGH PRESSURE WILL BUILD ACROSS THE REGION FRIDAY NIGHT AND
SATURDAY...WHICH WILL DIMINISH WINDS AND END THE LAKE EFFECT. LOW
MOISTURE WILL LINGER...BUT THERE SHOULD BE AT LEAST SOME BREAKS OF
SUNSHINE ON SATURDAY.

SATURDAY NIGHT AND SUNDAY THE FOCUS TURNS TO A SOUTHERN STREAM
SYSTEM. MODEL GUIDANCE HAS STRUGGLED WITH THE TRACK AND INTENSITY
DETAILS OF THIS FEATURE OVER THE PAST FEW DAYS. FOLLOWING A SHIFT IN
THE OTHER DIRECTION YESTERDAY...12Z GUIDANCE HAS TRENDED TOWARD A
WEAKER NON-PHASED SOLUTION INSTEAD OF A STRONG COASTAL LOW. IF THIS
PLAYS OUT...IT WOULD BRING SOME LIGHT SNOW TO WESTERN NEW YORK WITH
MINIMAL ACCUMULATION. GIVEN THE TIMEFRAME...THERE IS STILL A CHANCE
FUTURE RUNS WILL CHANGE...SO FORECAST UPS THE POPS A BIT...BUT STILL
REMAIN IN THE CHANCE CATEGORY TO REFLECT THE UNCERTAINTY IN MODEL
GUIDANCE. EITHER WAY...THE SYSTEM DOES NOT APPEAR LIKELY TO HAVE A
MAJOR IMPACT ON OUR REGION...WITH SEASONABLY COOL TEMPERATURES
EITHER WAY.

BEHIND THIS SYSTEM WEAK HIGH PRESSURE SHOULD BRING A RETURN TO DRY
WEATHER FOR MONDAY AND MONDAY NIGHT. TEMPERATURES WILL BE VERY CLOSE TO
AVERAGE FOR MID TO LATE DECEMBER WITH NO PUSH OF ARCTIC AIR THROUGH
EARLY NEXT WEEK.

LOOKING A LITTLE FARTHER AHEAD...12Z GUIDANCE IS FAIRLY CONSISTENT
WITH PREVIOUS RUNS OF THE GFS/ECMWF WITH A DEEP TROUGH FORECAST TO
EXTEND DOWN THE MISSISSIPPI...THEN SWING AROUND AND CLOSE OFF AS A
COASTAL LOW DEVELOPS IN THE NORTHEAST ON CHRISTMAS DAY. IF THIS PLAYS
OUT...THIS WILL BRING A CHANCE OF RAIN SHOWERS ON TUESDAY OR
WEDNESDAY...FOLLOWED BY COOLER WEATHER THE LATTER HALF OF THE WEEK.
THE GEFS ENSEMBLE MEAN TRENDS THE NAO INDEX STEADILY DOWNWARD
THROUGH THE END OF THE MONTH INDICATING A GREATER POTENTIAL FOR HIGH
LATITUDE BLOCKING. EXPECT MID WINTER COLD TO ARRIVE NEAR CHRISTMAS
AND HAVE SOME STAYING POWER.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
THIS EVENINGS 00Z TAF PACKAGE WILL START WITH VFR TO IFR FLIGHT
CONDITIONS ACROSS THE TAF AREA. IFR FLIGHT CONDITIONS WITHIN A
PERIOD OF RAIN ASSOCIATED WITH A WARM FRONT OVER THE EASTERN LAKE
ONTARIO REGION WILL CONTINUE FOR THE NEXT SEVERAL HOURS. BEHIND THIS
WARM FRONT A LULL IN PRECIPITATION WITH VFR FLIGHT CONDITIONS FOUND
ACROSS THE GENESEE VALLEY.

FARTHER TO THE WEST AND CLOSER TO THE SURFACE AND UPPER LEVEL LOW
PERIODS OF LIGHT SHOWERS/DRIZZLE WILL PASS ACROSS FAR WNY. THIS WILL
BRING ADDITIONAL HOURS OF IFR FLIGHT CONDITIONS FOR KJHW/KBUF/KIAG.
IFR FLIGHT CONDITIONS ARE EXPECTED TO LAST THE LONGEST ACROSS THE
KJHW AIRFIELD.

IFR FLIGHT CONDITIONS WILL ONLY MODESTLY IMPROVE DURING THE DAYLIGHT
HOURS TOMORROW...WITH WIDESPREAD LOW END MVFR FLIGHT CONDITIONS
LIKELY ACROSS THE CWA. THE EXCEPTION WILL BE AGAIN BE KJHW WHERE IFR
FLIGHT CONDITIONS MAY JUST VERY WELL CARRY THROUGH THE ENTIRE 00Z
TAF PERIOD.

COLDER AIR WILL SWEEP ACROSS THE REGION DURING THE DAY TOMORROW WITH
SCATTERED RAIN SHOWERS BECOMING MIXED WITH AND CHANGING TO LIGHT
SNOW SHOWERS. WITHIN THESE SNOW SHOWERS TOWARDS THE END OF THE TAF
CYCLE MVFR/IFR VSBYS ARE AGAIN LIKELY.

WINDS WILL PREVAIL FROM THE SOUTHWEST THIS PERIOD. WITH THE COLD AIR
SWEEPING ACROSS THE EASTERN GREAT LAKES EXPECT SOME GUSTS TOWARDS 30
KNOTS ACROSS THE KBUF/KIAG/KROC AIRFIELDS....WITH 20 KNOT OR SO
GUSTS ACROSS KJHW AND KART.

OUTLOOK...
WEDNESDAY NIGHT AND THURSDAY...VFR/MVFR WITH SCATTERED TO
OCCASIONALLY MORE NUMEROUS SNOW SHOWERS.
FRIDAY...MAINLY VFR WITH A CHANCE OF SNOW SHOWERS.
SATURDAY...VFR.
SUNDAY...VFR/MVFR WITH A CHANCE OF SNOW SHOWERS.

&&

.MARINE...
SOUTHERLY WINDS IN PLACE TONIGHT WITH LOW PRESSURE CENTERED NEAR THE
WEST END OF LAKE ERIE. THE LOW PRESSURE WILL PIVOT NORTH AND EAST
ACROSS THE LOWER GREAT LAKES TONIGHT WITH A COLD FRONT THEN BRINGING
WIDESPREAD ADVISORY WINDS AND WAVES LATER TONIGHT THROUGH THURSDAY
NIGHT. GIVEN HIGH CONFIDENCE IN THESE HIGHER WINDS AND WAVES SMALL
CRAFT ADVISORIES ARE ISSUED FOR BOTH LAKES FROM TONIGHT THROUGH
THURSDAY NIGHT. HIGH PRESSURE BUILDS IN FRIDAY AND SATURDAY WITH A
RETURN TO MORE RELAXED CONDITIONS.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 7 AM WEDNESDAY TO 4 AM EST THURSDAY
         FOR LEZ020.
         SMALL CRAFT ADVISORY UNTIL 10 PM EST THURSDAY FOR LEZ040-
         041.
         SMALL CRAFT ADVISORY FROM 7 AM WEDNESDAY TO 4 AM EST
         THURSDAY FOR LOZ030.
         SMALL CRAFT ADVISORY FROM 10 AM WEDNESDAY TO 4 AM EST
         FRIDAY FOR LOZ043-044.
         SMALL CRAFT ADVISORY FROM 8 AM WEDNESDAY TO 10 PM EST
         THURSDAY FOR LOZ042.
         SMALL CRAFT ADVISORY FROM NOON WEDNESDAY TO 4 AM EST
         FRIDAY FOR LOZ045.

&&

$$

SYNOPSIS...SMITH
NEAR TERM...SMITH/THOMAS
SHORT TERM...APFFEL
LONG TERM...APFFEL/HITCHCOCK
AVIATION...THOMAS
MARINE...SMITH






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