-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBGM 210251
AFDBGM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BINGHAMTON NY
1051 PM EDT MON MAY 20 2013

.SYNOPSIS...
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A WARM WEATHER PATTERN HAS SET UP ACROSS THE AREA AND WILL
CONTINUE THROUGH WEDNESDAY, WITH HIGH TEMPERATURES NEAR TO JUST
ABOVE 80 AND LOWS MAINLY IN THE 60S. SCATTERED SHOWERS AND
THUNDERSTORMS CAN BE EXPECTED, ALTHOUGH MOST OF THE PERIOD WILL
BE DRY. A COLD FRONT WILL TRACK ACROSS THE AREA ON THURSDAY WITH A
SHOWERS AND THUNDERSTORMS. MUCH COOLER WEATHER WILL FOLLOW BEHIND
THE FRONT FRIDAY AND SATURDAY.
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&&

.NEAR TERM /THROUGH TUESDAY/...
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10 PM UPDATE...
GRIDS IN GOOD SHAPE. MADE MINOR ADJUSTMENTS. A LINE OF
THUNDERSTORMS CONTINUES TO TRACK TOWARD WRN NY WITH LITTLE SIGN OF
WEAKENING. MESO MODELS DO NOT AGREE WHETHER IT WILL GET HERE OR
NOT. LOCALLY STILL UNSTABLE. UPPED POPS FOR MID TO 3 AM THEN
DROPPED THEM. CONSENSUS WOULD HAVE THE LINE CONTINUING INTO WRN NY
THEN HEAD EAST ALONG THE LAKE PLAIN. LITTLE MAKING IT TO THE SRN
TIER AND NE PA. NO ADJUSTMENTS TO TUESDAY AND BEYOND.

PREVIOUS DISCUSSION...
SUMMER-LIKE AIR MASS IS BECOMING ESTABLISHED ACROSS THE AREA THIS
AFTERNOON WITH TEMPERATURES CLIMBING TO NEAR 80 AND DEW POINTS
INTO THE 60S. HIGH RESOLUTION MODELS HAVE BEEN ADVERTISING
ISOLATED SHOWERS AND THUNDERSTORMS WHICH SO FAR HAVE NOT OCCURRED.
WITH LITTLE IN THE WAY OF A TRIGGER AND SOME DRY AIR INDICATED ON
CURRENT WATER VAPOR LOOP EXPECT ANY SHOWERS OR STORMS TO BE VERY
ISOLATED INTO EARLY THIS EVENING. BASED ON THIS HAVE KEPT POPS
BELOW 20 PCT THROUGH THIS EVENING. A LINE OF SHOWERS AND
THUNDERSTORMS CURRENTLY DEVELOPING OVER MICHIGAN WILL MOVE EAST
ACROSS MICHIGAN AND SOUTHERN ONTARIO THIS EVENING... PROBABLY
REACHING WESTERN NEW YORK AROUND MIDNIGHT. THESE SHOWERS WILL BE
WEAKENING AS THEY APPROACH CENTRAL NY AFTER MIDNIGHT BUT COULD
PRODUCE A BRIEF PERIOD OF SHOWERS TOWARD DAWN... ESPECIALLY OVER
THE NORTHERN AND WESTERN PART OF THE FORECAST AREA.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
TRICKY FORECAST SETTING UP FOR TUESDAY THROUGH WEDNESDAY AS A
MODERATELY UNSTABLE AIRMASS WILL INTERACT WITH WEAK UPPER-LEVEL
SHORT WAVES ROTATING AROUND THE NORTHERN RIM OF A LARGE- SCALE
UPPER RIDGE... PRODUCING SCATTERED SHOWERS AND THUNDERSTORMS. IN
MANY WAYS THE PATTERN OVER THE NEXT COUPLE OF DAYS WILL BE MORE
TYPICAL OF MID-SUMMER INSTEAD OF MAY. THE PRIMARY LOW- LEVEL SURFACE
BOUNDARY WILL START OUT NORTH OF OUR AREA TONIGHT BUT MAY SAG SOUTH
TUESDAY INTO WEDNESDAY... AIDED BY CONVECTIVELY INDUCED OUTFLOW
BOUNDARIES PUT DOWN BY ANY CONVECTION.

THE FIRST ROUND OF SHOWERS WILL BE WEAKENING AND PUSHING EAST OF
OUR AREA EARLY TUESDAY MORNING. HOWEVER THESE SHOWERS COULD HELP
TO ESTABLISH A LOW-LEVEL BOUNDARY SOMEWHERE ACROSS CENTRAL NY...
WHICH MAY HELP TO TRIGGER ANOTHER ROUND OF SHOWERS AND
THUNDERSTORMS TUESDAY AFTERNOON AS A WEAK SHORT WAVE TRACKS EAST
AROUND THE NORTHERN RIM OF AN UPPER RIDGE. MODELS DISAGREE
SOMEWHAT ON AMOUNT OF INSTABILITY THAT WILL DEVELOP TUESDAY
AFTERNOON... BUT WITH A WARM AND SOMEWHAT HUMID AIRMASS IN PLACE
EXPECT THAT CAPES AROUND 1000 J/KG WOULD BE REASONABLE. GFS
FORECAST VALUES OVER 2000 J/KG IN NORTHEAST PA ARE BASED ON SFC
DEW POINTS REACHING ABOVE 70 AND DO NOT APPEAR REASONABLE. HOWEVER
EVEN THE 1000 J/KG SCENARIO WOULD BE ENOUGH TO KICK OF A FEW
HEALTHY STORMS. DEEP LAYER SHEAR VALUES OF 20-30 KTS WOULD BE
MARGINALLY LARGE ENOUGH FOR A FEW STORMS TO APPROACH SEVERE
LIMITS... AND THEREFORE OUR AREA IS OUTLINED IN A SEE TEXT AREA IN
THE LATEST SPC GUIDANCE. COVERAGE OF STORMS IS ALSO A TRICKY ISSUE
FOR TOMORROW. LATEST WPC PROBABILISTIC GUIDANCE IS INDICATING POPS
NEAR 80 PCT BASED ON ENSEMBLE DATA... HOWEVER WITH WEAK WARM
SECTOR-TYPE FORCING SUSPECT THAT THE COVERAGE MAY NOT BE THAT
LARGE. HAVE GONE WITH HIGH CHC POPS FOR CENTRAL NY AND LOW CHC
POPS FOR NORTHEAST PA.

BOTH CAPE AND SHEAR ARE FORECAST TO INCREASE ON WEDNESDAY... WITH
CAPE VALUES GENERALLY 1000-1500 J/KG AND DEEP LAYER SHEAR 25 TO 30
KTS IN NORTHEAST PA AND 35 TO 40 KTS ACROSS CENTRAL NY. QUESTION
WILL BE WHETHER A TRIGGER WILL BE AVAILABLE TO KICK OFF STORMS IN
THE WARM SECTOR OF A CYCLONE OVER THE LOWER GREAT LAKES. OVERALL
PATTERN IS SIMILAR TO TUESDAY WITH WSW FLOW ALOFT AND WOULD NOT BE
SURPRISED TO SEE ANOTHER ROUND OF SHOWERS AND STORMS... THIS TIME
WITH A LITTLE MORE SEVERE POTENTIAL.

BEST SYNOPTIC SCALE FORCING WILL BE THURSDAY AS A COLD FRONT
FINALLY MOVES EAST ACROSS THE AREA. AGAIN A ROUND OF SHOWERS AND
STORMS LOOKS LIKE A GOOD BET AS THE FRONT MOVES ACROSS THE AREA
WITH SEVERE POTENTIAL PROBABLY A FUNCTION OF FRONTAL TIMING...
WITH AN AFTERNOON FRONTAL PASSAGE MORE CONDUCIVE TO SEVERE
WEATHER.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
MEDIUM RANGE MODELS CONTINUE TO SHOW A DEEP UPPER LEVEL TROF OVER
THE NORTHEAST THROUGH MOST OF THE PERIOD WITH HEIGHTS GRADUALLY
BUILDING LATE AS THIS TROF LIFTS EAST. THIS WILL KEEP TEMPERATURES
5-10 DEGREES BELOW NORMAL WITH MIN TEMPS COLD ENOUGH FOR POSSIBLE
FROST BOTH FRIDAY/SATURDAY NIGHTS AND MAYBE EVEN SUNDAY NIGHT.

AT THE SFC, POST COLD FRONT SHOWERS/THUNDERSTORMS WILL LINGER
THROUGH THE OVERNIGHT PERIOD WITH BEST CHC FOR THUNDER DURING THE
EARLY EVENING. AS THE UPPER LEVEL TROF BUILDS IN ON FRIDAY THE CHC
FOR SHOWERS WILL CONTINUE WITH THE HIGHEST POPS IN THE SOUTHERN
CATSKILLS AND NE PA. REMAINDER OF PERIOD WILL BE DRY WITH PARTLY
TO MAINLY CLEAR CONDITIONS AS SFC HIGH PRES FROM CENTRAL CANADA
DROPS SOUTH ACROSS THE GREAT LAKES REGION TO OUR VCNTY BY MONDAY.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
LOW CONFIDENCE FORECAST DURING THE TAF PERIOD IN REGARDS TO
PLACEMENT OF THUNDERSTORMS...BUT OUTSIDE OF ANY THUNDERSTORMS MAINLY
VFR OVERALL. EXCEPTIONS WILL BE SHALLOW MOISTURE MOVING INTO KAVP
AND KBGM FOR POSSIBLE LOW END MVFR CIG FOR A TIME EARLY
MORNING...AND PERHAPS MVFR CIG SNEAKING FOR KRME AS WELL.
ALSO...KELM MAY HAVE A PERIOD OF EARLY MORNING MVFR VALLEY FOG.
LIGHT AND VARIABLE WIND THROUGH TONIGHT BECOMING WEST- SOUTHWEST
AT 5-10 KNOTS TUESDAY MORNING. A THUNDERSTORM CANNOT BE RULED OUT
OVERNIGHT TOWARDS KSYR-KRME DUE TO INSTABILITY ALOFT...BUT NOT
ENOUGH CONFIDENCE TO INCLUDE IN TAF. MODELS HAVE STRUGGLED...WITH
SOME EVEN DEPICTING A LITTLE ACTIVITY OVER THE AREA NOW /00Z/
WHICH OBVIOUSLY IS NOT OCCURRING. BETTER CHANCES FOR THUNDER ARE
EXPECTED DURING TUESDAY...ESPECIALLY AFTERNOON...SO PROB30 TSRA
GROUPS HAVE BEEN INCLUDED DURING THE MORE LIKELY TIMES IN MOST
TAFS ACCORDINGLY. TAFS MAY BE AMENDED AS NECESSARY SHOULD
THUNDERSTORMS TRY TO FIRE UPSTREAM LATER THIS EVENING.

OUTLOOK...

WEDNESDAY NIGHT/THURSDAY...MVFR POSSIBLE IN SHOWERS/THUNDERSTORMS.

FRIDAY/SATURDAY...VFR.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NY...NONE.

&&

$$
SYNOPSIS...MSE
NEAR TERM...MSE/TAC
SHORT TERM...MSE
LONG TERM...RRM
AVIATION...MDP