000
FXUS61 KBUF 201805
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
205 PM EDT MON MAY 20 2013

.SYNOPSIS...
A SOUTHWESTERLY FLOW OF WARM AND MORE HUMID AIR WILL CONTINUE ACROSS 
THE REGION FOR MUCH OF THIS WEEK...WHILE A FRONTAL BOUNDARY ALSO 
STALLS OUT ACROSS NEW YORK STATE AND SETS THE STAGE FOR INCREASING 
CHANCES OF SHOWERS AND THUNDERSTORMS. THE MORE UNSETTLED CONDITIONS 
WILL LAST THROUGH THURSDAY...BEFORE A COLD FRONT CROSSES THE AREA 
AND USHERS IN COOLER AND DRIER WEATHER FOR THE END OF THE WEEK AND 
THE MEMORIAL DAY WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
THE INLAND REGIONS HAVE FILLED IN WITH SHALLOW CUMULUS OR STRATOCU 
THIS AFTERNOON. THE MID LEVEL AND UPPER RIDGE SHOULD BE STRONG 
ENOUGH TO SUPPRESS FURTHER VERTICAL DEVELOPMENT THUS ONLY A SLIGHT 
CHANCE OF ANY SHOWERS OR THUNDERSTORMS. THE ONLY EXCEPTION SHOULD  
BE THE NORTH COUNTRY WHERE THERE IS A WEAK SURFACE BOUNDARY WHICH 
MAY PROVIDE ENOUGH FOCUS AND LOW LEVEL LIFT TO FIRE OFF A COUPLE OF 
SHOWERS OR THUNDERSTORMS. WILL CARRY LOW CHANCE POPS FOR JEFFERSON 
AND LEWIS COUNTIES AND MUCH OF THE SAINT LAWRENCE VALLEY.

THIS EVENING...EXPECT FAIRLY QUIET CONDITIONS FOR THE FIRST HALF OF 
THE NIGHT...THEN CONVECTIVE CHANCES WILL BEGIN TO INCREASE AGAIN 
FROM NORTHWEST TO SOUTHEAST AS LOW PRESSURE DEVELOPS ACROSS THE 
WESTERN AND CENTRAL LAKES AND SENDS INCREASING MOISTURE AND LIFT 
EASTWARD ALONG THE SAGGING FRONTAL BOUNDARY. WITH THE SHORT TERM 
MODEL GUIDANCE HAVING DIFFICULTY IN RESOLVING/AGREEING ON THE TIMING 
AND PLACEMENT OF THE RESULTANT AREAS OF CONVECTION...FOR NOW HAVE 
JUST INDICATED A GENERAL INCREASE IN POPS BACK TO THE LOW CHANCE 
RANGE OVERNIGHT.

WITH RESPECT TO TEMPERATURES...850 MB TEMPS WILL CONTINUE TO CLIMB 
TO THE +13 TO +15C RANGE TODAY...AND THIS SHOULD BE ENOUGH TO 
SUPPORT WIDESPREAD HIGHS IN THE LOWER-MID 80S AWAY FROM LAKE 
INFLUENCES...WITH COOLER READINGS FOUND NEAR THE LAKESHORES...AND IN 
THE VICINITY OF THE FRONTAL BOUNDARY SAGGING INTO THE NORTH COUNTRY. 
A RATHER WARM NIGHT WILL THEN FOLLOW FOR TONIGHT...WITH READINGS 
ONLY DROPPING INTO THE LOWER TO MID 60S. WITH SFC DEWPOINTS ALSO 
RISING INTO THE LOWER 60S...IT WILL ALSO BEGIN TO FEEL SOMEWHAT 
HUMID.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
A CLOSED H5 LOW PARKED OVER THE NORTHERN PLAINS AT THE START OF THIS 
PERIOD WILL KEEP A WARM RIDGE IN PLACE ACROSS OUR REGION THROUGH AT 
LEAST WEDNESDAY. THIS WILL NOT ONLY SUPPLY US WITH SOME SUMMER LIKE 
WARMTH BUT WILL GIVE US A TASTE OF SUMMER HUMIDITY AS WELL. WHILE WE 
CAN SAY THIS WITH A HIGH DEGREE OF CERTAINTY...IT WILL CONTINUE TO 
BE CHALLENGING TO PINPOINT THE TIMING AND EXTENT OF THE SHOWERS AND 
THUNDERSTORMS THAT ARE EXPECTED DURING THIS TIME FRAME. 

ON TUESDAY...THE CONTROLLING RIDGE THAT UP TO THIS POINT HAD BEEN 
PROTECTING MOST OF THE REGION WITH ITS ASSOCIATED SUBSIDENT FLOW 
WILL START TO WEAKEN. MEANWHILE AT THE SFC...A SLOW MOVING FRONTAL 
BOUNDARY WILL SAG SOUTH FROM SOUTHERN ONTARIO...LIKELY STALLING OVER 
OUR WESTERN COUNTIES. CONVECTION IS LIKELY TO DEVELOP ALONG AND 
SOUTH OF THIS BOUNDARY WHERE DEW POINTS IN THE LOW-MID 60S SHOULD 
HELP TO ESTABLISH AFTERNOON CAPE VALUES >1000 J/KG AWAY FROM THE 
LAKES ALONG WITH LI'S IN THE VCNTY OF -4/-5. THE DIURNALLY DRIVEN 
CONVECTION WILL BE AIDED BY INCREASING AMOUNTS OF LOW LEVEL MOISTURE 
OUT OF THE OHIO VALLEY...WITH PWAT VALUES POSSIBLY CLIMBING OVER 1.5 
INCHES. GIVEN THE LACK OF CONFIDENCE ON THE FRONTAL POSITION...WILL 
HAVE TO BROAD BRUSH WITH LIKELY POPS FOR THE AFTERNOON. OTHERWISE AS 
ALREADY MENTIONED...IT WILL BE WARM AND HUMID TUESDAY WITH HIGHS OF 
80 TO 85 OVER THE WRN COUNTIES AND 70S EAST OF LK ONTARIO. 

THE SHOWERS AND THUNDERSTORMS OVER THE WESTERN COUNTIES WILL TAPER 
OFF EARLY TUESDAY NIGHT AS THE BOUNDARY LAYER WILL PARTIALLY 
STABILIZE WITH THE REMOVAL OF DIURNAL HEATING. MID LEVEL RIDGING 
WILL BECOME RE-ESTABLISHED OVER OUR FORECAST AREA DURING THE NIGHT 
AS WELL...SO THIS SHOULD ALSO HELP IN TEMPORARILY ENDING ANY PCPN. 
SHOWERS AND POSSIBLE THUNDERSTORMS SHOULD BE A LITTLE MORE COMMON IN 
THE VCNTY OF THE FRONTAL BOUNDARY EAST OF LK ONTARIO DURING THE 
OVERNIGHT THOUGH. OTHERWISE...THIS WILL LEAVE A RELATIVELY WARM AND 
HUMID NIGHT ACROSS THE REGION...ESPECIALLY OVER THE WESTERN COUNTIES 
(SOUTH OF LK ONTARIO AND THE FRONTAL BOUNDARY).

THE EARLY SUMMER AIRMASS WILL REMAIN IN PLACE ACROSS THE FORECAST 
AREA ON WEDNESDAY AS THE CLOSED LOW OVER THE NORTHERN PLAINS WILL 
GRADUALLY OPEN UP WHILE KEEPING A MOISTURE RICH LOW LEVEL INTACT 
FROM THE OHIO VALLEY. THIS LOW LEVEL FEED WILL BE ENHANCED BY BROAD 
LOW PRESSURE THAT WILL APPROACH OUR FORECAST AREA FROM LOWER 
MICHIGAN. THIS SHOULD LEAD TO MORE EXTENSIVE CLOUD COVER...WHICH IN 
TURN WILL MINIMIZE DIURNAL INSTABILITY OVER OUR REGION. 
NEVERTHELESS...SBCAPES OF 500 J/KG SHOULD BE MORE THAN ENOUGH TO 
GENERATE SOME SHOWERS AND THUNDERSTORMS WITH PWAT VALUES OF >1.5 
SUPPORTING SOME LOCALIZED HIGH QPF. WILL ONCE AGAIN BROAD BRUSH WITH 
LIKELY POPS.  

IN TERMS OF THE POTENTIAL FOR STRONG TO SEVERE STORMS...WILL 
REITERATE THE THINKING FROM THE PREVIOUS DISCUSSIONS. MID LEVEL 
LAPSE RATES FOR BOTH TUESDAY AND WEDNESDAY ARE ONLY IN THE VCNTY OF 
6 DEG C/KM WITH EQUALLY UNIMPRESSIVE KINEMATIC FIELDS (EX. 0-3KM 
SHEAR <25 M/S). 

THE AFOREMENTIONED SFC LOW WILL CROSS TO OUR NORTH WEDNESDAY NIGHT 
WHILE ITS TRAILING FRONTAL BOUNDARY WILL HANG BACK TO A FRONTAL WAVE 
IN THE VCNTY OF WRN LK ERIE. THIS WILL KEEP SHOWERS AND POSSIBLE 
THUNDERSTORMS OVER OUR REGION...BUT DO NOT EXPECT STRONG ENOUGH 
FORCING TO SUPPORT SIGNIFICANT QPF. 

ON THURSDAY AND THURSDAY EVENING...THE WAVY FRONTAL BOUNDARY WILL 
SLOWLY DRIFT ACROSS OUR FORECAST AREA. FROM THE 00Z MODEL RUNS...
THE GFS WAS SOME 3-6 HOURS FASTER WITH THIS PASSAGE THAN ITS 
EUROPEAN COUNTERPART. IN ANY CASE...THIS WILL LIKELY GENERATE 
ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS WITH DAYTIME TEMPERATURES 
AVERAGING SOME 10 DEG F LOWER THAN THE PREVIOUS FEW DAYS. THIS WILL 
TRANSLATE INTO EARLY AFTERNOON HIGHS IN THE LOWER 70S FOR MOST 
AREAS. 

WHILE THURSDAY NIGHT SHOULD PROVE TO BE NOTICEABLY COOLER...THERE 
WILL BE SOME LINGERING SHOWERS WITH SKIES STUBBORN TO CLEAR. IN 
FACT...MOST AREAS MAY KEEP THEIR LOW CLOUD COVER RIGHT THROUGH 
DAYBREAK ON FRIDAY. THIS WILL ESPECIALLY BE TRUE FOR SITES EAST OF 
THE GENESEE VALLEY. TEMPERATURES ARE EXPECTED TO DROP INTO THE 
40S...WHICH WILL BE AT LEAST 15 DEG LOWER THAN PREVIOUS OVERNIGHT 
LOWS.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
THE VARIOUS MEDIUM RANGE GUIDANCE PACKAGES ARE IN STRONG AGREEMENT 
THAT GENERALLY FAIR AND SEASONABLY COOL CONDITIONS WILL BE IN PLACE 
DURING THIS PERIOD...INCLUDING THE BULK OF THE MEMORIAL DAY WEEKEND. 
A BROAD BASED RIDGE WILL BE POSITIONED OVER THE NATIONS MID SECTION 
AND THIS WILL LEAVE TWIN TROUGHS OFF THE COASTS OF VANCOUVER AND 
EASTERN QUEBEC...WHERE COOLER THAN AVERAGE TEMPERATURES ARE 
EXPECTED. 

A MORE DETAILED LOOK AT OUR REGION REVEALS THAT WE WILL HAVE SOME 
LEFTOVER LOW CLOUDS AND LIGHT SHOWERS FRIDAY MORNING (MAINLY EAST OF 
GENESEE VALLEY) IN THE WAKE OF THE DEPARTING FRONTAL SYSTEM...BUT AS 
LOW LEVEL RIDGING BUILDS SOUTH ACROSS THE GREAT LAKES...OUR SKIES 
WILL CLEAR OUT. H85 TEMPS WILL DROP TO AROUND 5C...SO FRIDAY WILL BE 
MUCH COOLER WITH AFTERNOON TEMPS GENERALLY IN THE LOWER 60S (50S 
ACROSS THE NORTH COUNTRY).

EXPANSIVE HIGH PRESSURE WILL BUILD SOUTH ACROSS THE REGION FROM 
CANADA SATURDAY AND SUNDAY...WITH H85 TEMPS FORECAST TO BE IN THE 
VCNTY OF 4C BOTH DAYS. THIS WILL KEEP THE AFTERNOONS COOL AND THE 
NIGHTS CHILLY WITH SOME FROST POSSIBLE...MAINLY ACROSS THE SOUTHERN 
TIER AND EASTERN LAKE ONTARIO REGIONS.

A PEEK AHEAD TO MEMORIAL DAY SUGGESTS THAT FAIR DRY WEATHER WILL BE 
IN PLACE WITH A MODERATION IN TEMPERATURES TO NEAR SEASONAL LEVELS.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
AFTERNOON WARMTH DEVELOPING SCT/BKN SKY CONDITION ACROSS THE INLAND 
REGION OF THE FORECAST AREA WITH MOST OF THE TAF SITES TO REMAIN 
BEHIND LAKE BREEZE BOUNDARIES AND THUS IN MORE STABLE AIR...WITH VFR 
CONDITIONS CONTINUING. 

TONIGHT...EXPECT VFR CONDITIONS TO CONTINUE TO PREVAIL FOR MUCH OF 
THE NIGHT...BEFORE SOME ADDITIONAL CONVECTION POSSIBLE ACROSS THE 
NORTH COUNTRY LATE. WITH THE TIMING AND PLACEMENT OF THIS  VERY 
UNCERTAIN AT THIS POINT...FOR NOW HAVE JUST ADDED VCSH TO THE TAFS 
TO COVER THIS POTENTIAL.

THE UPPER AND MID LEVEL RIDGE AXES TO PASS ACROSS THE REGION AND TO 
THE EAST ON TUESDAY. WILL HAVE A SLIGHTLY BETTER CHANCE OF AFTERNOON 
AND EVENING CONVECTION...ALONG THE LAKE BREEZE BOUNDARIES AND OVER 
THE INTERIOR OF THE FORECAST AREA.

OUTLOOK...  
TUESDAY THROUGH THURSDAY...NUMEROUS SHOWERS AND THUNDERSTORMS WITH 
ASSOCIATED BRIEF MVFR/IFR...OTHERWISE VFR. 
FRIDAY...MAINLY VFR WITH A CHANCE OF SHOWERS.
SATURDAY...VFR.

&&

.MARINE...
THROUGH MUCH OF THIS WEEK...WINDS WILL REMAIN RELATIVELY LIGHT AND 
VARIABLE IN DIRECTION DUE TO A NEARLY STATIONARY FRONTAL BOUNDARY 
THAT WILL REMAIN DRAPED ACROSS THE REGION...AS WELL AS THE DAILY 
DEVELOPMENT OF LAKE BREEZES. AS A RESULT...WAVE HEIGHTS SHOULD ALSO 
REMAIN MINIMAL. OTHERWISE...AFTER A MAINLY DRY DAY TODAY...SHOWER 
AND THUNDERSTORM CHANCES WILL INCREASE MARKEDLY FOR THE TUESDAY 
THROUGH THURSDAY TIME FRAME.

&&

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

&&

$$

SYNOPSIS...JJR
NEAR TERM...WCH
SHORT TERM...RSH
LONG TERM...RSH
AVIATION...WCH
MARINE...JJR