Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 040024
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
824 PM EDT FRI JUL 3 2015

.SYNOPSIS...
A WEAK SYSTEM WILL BRING SCATTERED SHOWERS AND POSSIBLY A FEW
THUNDERSTORMS TO AREAS MAINLY SOUTHEAST OF BUFFALO...ROCHESTER...
AND WATERTOWN OVERNIGHT AND SATURDAY...WITH HIGH PRESSURE AND DRY
WEATHER THEN RETURNING FOR SATURDAY NIGHT THROUGH MONDAY. THE NEXT
WEATHER SYSTEM IS EXPECTED TO ARRIVE TUESDAY OR TUESDAY NIGHT.

&&

.NEAR TERM /THROUGH SATURDAY/...
TONIGHT...A LONGWAVE TROUGH CURRENTLY DRAPED ACROSS THE WESTERN
AND CENTRAL GREAT LAKES WILL SLOWLY MOVE EASTWARD...WITH AN
ATTENDANT WEAK SURFACE REFLECTION SLIDING ACROSS THE OHIO VALLEY
AND MID ATLANTIC STATES...WHILE REMAINING MAINLY SOUTH OF OUR
REGION. WHILE SOME MOISTURE ASSOCIATED WITH THIS FEATURE WILL
ADVECT NORTHWARD INTO OUR REGION...ANY PRECIPITATION MAY HAVE A
HARD TIME MAKING IT MUCH FURTHER NORTH THAN OUR SOUTHERNMOST TWO
TIERS OF ZONES AS IT ENCOUNTERS PROGRESSIVELY DRIER AIR TO THE
NORTH. OTHERWISE...CLOUDS FROM THIS DISTURBANCE WILL HELP TO LIMIT
RADIATIONAL COOLING TONIGHT.

LOOKING AT SOME OF THE MODEL DETAILS...SOME OF THE HIGHER
RESOLUTION OPERATIONAL MODELS SUCH AS THE NAM AND EVEN THE GFS
APPEAR TO BE SUFFERING FROM CONVECTIVE FEEDBACK WITH EXCESS
INSTABILITY NOT BEING WELL HANDLED BY CONVECTIVE PARAMETERIZATION
AND THUS BEING DUMPED IN THE FORM OF EXCESSIVE PRECIPITATION. THIS
CONTINUES TO BE MOST EVIDENT IN THE NAM WHICH DEPICTS A COUPLE OF
1+ INCH QPF BULLSEYES ALONG THE NORTHWESTERN FRINGE OF THIS SYSTEM
BETWEEN LATER TONIGHT AND SATURDAY MORNING. IN CASES SUCH AS
THIS...THE MODELS DO NOT APPEAR TO KNOW WHAT TO DO... AND THUS
DUMP OUT ALL THE PRECIPITATION AT ONCE. CONVECTIVE ALLOWING
MEMBERS OF VARIOUS ENSEMBLE PACKAGES...THE NCAR AND SSEO... APPEAR
TO HAVE A BETTER HANDLE...WITH MOST MEMBERS NOT SHOWING OVERNIGHT
CONVECTION EXCEPT TOWARD THE SOUTHERN TIER.

WITH THE ABOVE IN MIND...HAVE CONTINUED TO LEAN MORE HEAVILY
TOWARD OUR DRIER CONTINUITY FOR THE OVERNIGHT HOURS AND FIRST
PORTION OF SATURDAY...THOUGH AT THE SAME TIME HAVE ALSO ELECTED TO
BRING SHOWER CHANCES A LITTLE FURTHER NORTH THAN BEFORE BASED ON
UPSTREAM OBS/RADARS. WITH THIS CHANGE...WE NOW HAVE BONA FIDE
CHANCES FOR SHOWERS AS FAR NORTH AS THE CHAUTAUQUA-ONTARIO COUNTY
CORRIDOR...WITH SCATTERED SPRINKLES POSSIBLE AROUND THE NORTHERN
FRINGES OF THIS.

INDEPENDENCE DAY/SATURDAY...ANY PRECIPITATION ASSOCIATED WITH THE
WEAK SYSTEM SHOULD QUICKLY MOVE OFF TO THE EAST DURING THE
MORNING. BEHIND THIS...THERE MAY BE ENOUGH INSTABILITY AND WEAK
LIFT ALONG LAKE BREEZE BOUNDARIES DURING THE AFTERNOON TO KICK OFF
SOME ADDITIONAL SCATTERED SHOWERS AND POSSIBLE THUNDERSTORMS
INLAND FROM THE LAKES DURING THE AFTERNOON...WITH THIS ACTIVITY
TRACKING EASTWARD WITH TIME AND NOT TENDING TO LAST TOO LONG AT
ANY GIVEN LOCATION.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
RIDGING ALOFT AND A DRIER AIRMASS MOVE INTO THE REGION FOR SUNDAY.
WITH NORTHWESTERLY FLOW BEHIND A COOL FRONT AND 850 MB TEMPERATURES
AROUND +12 TO +14C... EXPECT THAT FULL SUNSHINE AND MIXING UP TO
ABOUT 850 MB WILL RESULT IN HIGH TEMPERATURES IN THE UPPER 70S TO
LOW 80S. LIGHT MEAN FLOW UNDER THE SURFACE HIGH WILL ALLOW LAKE
BREEZES TO DOMINATE OFF BOTH LAKES ERIE AND LAKE ONTARIO... BUT
SHOULD MAKE FOR AN EXCELLENT RECREATION DAY AS PART OF THE HOLIDAY
WEEKEND.

BY MONDAY...SOUTHERLY FLOW INCREASES ACROSS THE FORECAST AREA IN
RESPONSE TO A WAVE TRACKING ACROSS THE UPPER GREAT LAKES AND
ATTENDANT SURFACE LOW INTO THE MIDWEST. INCREASED WARM ADVECTION AND
DOWNSLOPE / OFF SHORE FLOW WILL PUSH TEMPERATURES SOLIDLY INTO THE
80S ON MONDAY... WITH MID TO UPPER 80S POSSIBLE IN THE MOST
DOWNSLOPE PRONE LOCATIONS LIKE THE GENESEE VALLEY. MONDAY NIGHT WILL
REMAIN WARM /LOW IN THE UPPER 60S TO AROUND 70/... WITH SOUTHERLY
DOWNSLOPE WINDS AHEAD OF THE SURFACE FRONT KEEPING THE BOUNDARY
LAYER MIXED OVERNIGHT. THIS ALONG WITH DEW POINTS CLIMBING INTO THE
60S WILL MAKE FOR AN UNCOMFORTABLE NIGHT TO SLEEP WITH THE WINDOWS
OPEN.

TUESDAY INTO TUESDAY NIGHT... AS THE PARENT SHORTWAVE TROUGH TRACKS
NORTH OF THE FORECAST AREA... THE ATTENDANT COLD FRONT WILL EITHER
PUSH AN AREA OF SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE
FORECAST AREA... OR INCREASE THE CHANCE FOR AN MCS TRACKING OUT OF
MICHIGAN / MIDWEST TO MOVE ACROSS THE AREA. THE TIMING OF WHICH
REMAINS FAIRLY UNCERTAINTY AT THIS LEAD TIME. STILL TEMPERATURES
WILL LARGELY REMAIN IN THE LOW 80S ON TUESDAY WITH 850 MB
TEMPERATURES SURGING TO AROUND +17C AHEAD OF THE FRONT... ALTHOUGH
HEATING WILL BE LIMITED BY INCREASE CLOUD COVER AND CHANCE OF
SHOWERS AND STORMS.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
WEAK HIGH PRESSURE WILL BUILD INTO ACROSS THE AREA WEDNESDAY THROUGH
FRIDAY... THIS WILL KEEP TEMPERATURES IN THE 70S TO NEAR 80 WITH
BELOW NORMAL CHANCES OF PRECIPITATION TO END THE WORK WEEK. FORECAST
CONFIDENCE INTO THE WEEKEND REMAINS BELOW NORMAL... AS VARIOUS
FORECAST MODELS DISAGREE ON THE TIMING A SHORTWAVE THAT COULD BRING
INCREASED SHOWER/THUNDERSTORM CHANCES TO ONE OF THE DAY OF THE
WEEKEND. WHILE SATURDAY OR SUNDAY COULD SEE SOME SHOWER/THUNDERSTORM
ACTIVITY... THE WEEKEND LOOKS FAR FROM A WASHOUT.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
TONIGHT...A LONGWAVE TROUGH CURRENTLY DRAPED ACROSS THE WESTERN
AND CENTRAL GREAT LAKES WILL SLOWLY MOVE EASTWARD...WITH AN
ATTENDANT WEAK SURFACE REFLECTION SLIDING ACROSS THE OHIO VALLEY
AND MID ATLANTIC STATES...WHILE REMAINING MAINLY SOUTH OF OUR
REGION. THESE FEATURES WILL BRING INCREASING/LOWERING VFR CLOUD
COVER TO MOST AREAS...THOUGH ANY ASSOCIATED SCATTERED LIGHT
SHOWERS WILL LIKELY REMAIN CONFINED TO AREAS SOUTHEAST OF
KBUF/KROC/KART...WITH THE BEST CHANCES FOR THESE FOUND NEAR THE
NY/PA BORDER. ACROSS THE SOUTHERN TIER...SOME MVFR CIGS CANNOT BE
COMPLETELY RULED OUT VERY LATE TONIGHT/EARLY SATURDAY.

ON SATURDAY...THE AFOREMENTIONED SURFACE WAVE WILL SLIDE OFF TO
THE EAST...RESULTING IN A GENERAL DECREASE IN SHOWER ACTIVITY AND
CLOUD COVER DURING THE MORNING. WITH DIURNAL HEATING...SOME
ADDITIONAL SCATTERED SHOWERS AND THUNDERSTORMS MAY THEN FIRE ALONG
LAKE BREEZE BOUNDARIES AND PUSH EASTWARD DURING THE
AFTERNOON...THOUGH THESE /AND ANY ATTENDANT BRIEF LOCAL
REDUCTIONS/ SHOULD AGAIN REMAIN LARGELY SOUTH AND EAST OF
KBUF/KROC/KART.

OUTLOOK...
SATURDAY NIGHT THROUGH MONDAY...VFR.
TUESDAY AND WEDNESDAY...MAINLY VFR WITH A CHANCE OF SHOWERS AND
THUNDERSTORMS.

&&

.MARINE...
A WEAK PRESSURE GRADIENT WILL REMAIN IN PLACE ACROSS THE LOWER
GREAT LAKES THROUGH THE HOLIDAY WEEKEND. THIS WILL GENERALLY
RESULT IN RELATIVELY LIGHT WINDS AND MINIMAL WAVES...WITH LOCAL
LAKE BREEZE CIRCULATIONS DEVELOPING EACH AFTERNOON.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...NONE.

&&

$$

SYNOPSIS...JJR/ZAFF
NEAR TERM...JJR/ZAFF
SHORT TERM...CHURCH
LONG TERM...CHURCH
AVIATION...JJR/ZAFF
MARINE...JJR/ZAFF


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