769
FXUS61 KALY 221737
AFDALY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
1237 PM EST SUN NOV 22 2009
SYNOPSIS
A LARGE RIDGE OF HIGH PRESSURE WILL COVER THE NORTHEAST TO START THE
WEEK. IT WILL SLIDE EAST INTO THE MARITIMES AND OFFSHORE LATE MONDAY.
OUR WEATHER WILL TURN UNSETTLED MUCH OF THE UPCOMING WEEK. THE FIRST
LOW PRESSURE AREA WILL MOVE NORTHEAST FROM THE CAROLINA COAST
OFFSHORE MONDAY NIGHT AND TUESDAY. THEN MIDWEEK A SERIES OF MUCH
STRONGER STORMS WILL MOVE THOUGH THE MIDWEST AND GREAT LAKES.
NEAR TERM /UNTIL 6 PM THIS EVENING/
MOISTURE IS CONTINUING TO BE TRAPPED UNDER AN INVERSION...AND
CLOUD COVER EXTENDS FROM THE NY AND NEW ENGLAND BORDER WESTWARD
ACROSS NY AND NORTHERN PA. BASED ON UPSTREAM CONDITIONS...AND
LIGHT WIND FLOW THROUGH THE BOUNDARY LAYER...CLOUD COVER SHOULD
PERSIST MUCH OF THE DAY. SOME SLIGHT EROSION SEEN IN WESTERN NEW
ENGLAND PERHAPS SLOWLY BUILDING WEST DURING THE DAY...BUT MIX OF
CLOUDS AND SUN LIKELY FROM PSF TO AQW AND DDH...RIGHT ALONG THE
EDGE OF THE CLOUDS. SOME DEEPER SUBSIDENCE SHOULD BUILD INTO THE
REGION TOWARD AND THROUGH THE EVENING...SO ACKNOWLEDGING SOME
BETTER EROSION TO THE CLOUDS FROM EAST TO WEST LATE THIS AFTERNOON
AND EVENING. SO...SOME BREAKS IN THE CLOUDS ARE POSSIBLE FROM THE
HUDSON VALLEY LATE THIS AFTERNOON OR AROUND SUNSET. NUDGED HIGH
TEMPERATURES DOWN A DEGREE OR TWO BASED ON THE CLOUD COVER...WHICH
WAS EXPANDED. THE REST OF THE FORECAST REMAINS UNTOUCHED.
PREV AFD BELOW...
MOISTURE TRAPPED BENEATH LOW LEVEL SUBSIDENCE INVERSION WILL KEEP
PATCHY LOW CLOUDS AROUND THROUGH AT LEAST LATE THIS MORNING. IN
FACT...WHERE SOME BREAKS HAVE DEVELOPED...CLOUDS MAY ACTUALLY
REDEVELOP AROUND OR JUST AFTER SUNRISE ONCE SHALLOW MIXING
DEVELOPS. EVENTUALLY...AS THE LOW LEVEL FLOW VEERS INTO A MORE NE
DIRECTION...SOME DOWNSLOPING OFF THE HIGHER TERRAIN TO OUR N/E
SHOULD ALLOW FOR MORE BREAKS IN THE CLOUDS TO DEVELOP THIS
AFTERNOON...ESP FROM THE HUDSON RIVER VALLEY EASTWARD. CLOUDS MAY
PERSIST LONGER...PERHAPS WELL INTO THE AFTERNOON...ACROSS WESTERN
PORTIONS OF THE REGION...FROM THE SW DACKS...WESTERN MOHAWK VALLEY
INTO THE SCHOHARIE VALLEY AND NE CATSKILLS.
AS FOR MAX TEMPS...GIVEN THE EXPECTATION FOR SHALLOW MIXING...MAINLY
TO 925-950 MB...WE EXPECT MAXES TO BE A BIT COOLER THAN SAT...ESP
GIVEN A SLIGHTLY COLDER START...ALONG WITH THE EXPECTATION FOR
CLOUDS THROUGH THE MORNING. SO...GENERALLY SIDED CLOSE TO THE COOLER
MET MOS...WITH MAXES GENERALLY REACHING AROUND 50 WITHIN MUCH OF THE
HUDSON RIVER VALLEY...EXCEPT LOWER/MID 50S ACROSS THE MID HUDSON
VALLEY...WITH MAINLY 40S ACROSS HIGHER ELEVATIONS WITHIN WESTERN NEW
ENGLAND AND WESTERN PORTIONS OF THE REGION.
SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/
PERIOD STARTS WITH RIDGING AND SUBSIDENCE THROUGHOUT THE
ATMOSPHERE WITH 572DM HIGH EVEN AT 500HPA. 500HPA TROF LINGERS
SOUTH OF RGN FM MASON DIXON LINE TO LONG IS NY WHILE IMPRESSIVE
SFC HIGH DOMINATES THE NORTHEAST QUARTER OF THE NATION AND IS
CENTERED OVER THE MARITIMES. WHILE THE DIRTY HIGH PHASE WITH
MOISTURE TRAPPED UNDER THE INVERSION WILL HAVE ENDED EARLY SUNDAY
THE NEW GUIDANCE SUGGESTS THE MOIST BOUNDARY LAYER REMAINS AND
SHOWS MARINE LAYER MOISTURE OR FOG/STRATUS CREEPING BACK UP THE
HUDSON VALLEY EVEN AS EARLY AS LATE SUNDAY NIGHT EARLY MONDAY
MORNING. THE WITH ALL THE MODELS AND STATISTICAL GUID KEEPING THE
FLOW EAST TO NORTHEAST BELOW THE INVERSION LAYER...WILL BRING
CLOUDS INTO THE SOUTHEAST. THE NAM IS THE ONLY LESS AGGRESSIVE
MODEL WITH ADVECTING THIS MARINE LAYER MOISTURE WHILE THE
WRF/GEM/GFS SHOW IT BLO 900HPA.
MUCH LIKE LAST WEEK WHEN THIS SAME SCENARIO OCCURRED CLOUDS SHOULD
BARELY MAKE ALBANY MONDAY MORNING AND THESE MAY ERODE FOR A TIME.
FROM ALB N & W WILL STAY FAIR A GOOD PART OF THE DAY TILL BOUNDARY
LEVEL FLOW TURNS SE-S AND MOISTURE STREAMS NORTH. IN SOUTHEAST
LOOKING AT AREAS OF MORNING STRATUS AND FOG THAT MAY OR MAY NOT
BURN OFF BEFORE THE CLOUDS FROM NEXT SYSTEM OVERSPREAD THOSE
AREAS.
MARINE LAYER MOISTURE ADVECTION SHOULD BE WEAK TILL 500HPA TROF
THAT WAS LAYING DORMANT ACROSS THE MID ATLC BEGINS MOVES NORTH
INTO OUR REGION MONDAY. MODELS SUGGEST A COASTAL DEVELOPMENT BUT
ITS WELL OFFSHORE AND ITS MAIN IMPACT IS TO ENHANCE THE MARINE
LAYER INFLOW. THIS MOISTURE AND THE PASSAGE OF SEVERAL 500HPA
SHORT WAVES WILL PRODUCE CLOUDS ACROSS THE AREA AND AN INCR CHC
OF -RN AND DZ MONDAY NIGHT AND TUES MAINLY IN THE SOUTHEAST.
INITIALLY TUESDAY NIGHT THE SFC LOW DEPARTS WELL OFFSHORE. 500HPA
RIDGE REBUILDS ALONG THE SEABOARD. WELL TO OUR WEST THE STAGE IS
BEING SET FOR A COMPLEX PATTERN TO END THE WEEK. TUES NT WERE
STUCK WITH MORE RESIDUAL LOW LEVEL MOISTURE AND NOT MUCH MORE THAN
DRIZZLE AND CLOUDS.
MEANWHILE TUESDAY NIGHT TWO CUTOFFS WILL BE SETTING UP. ONE IN
THE MISSISSIPPI VALLEY THE OTHER IN SOUTH CENTRAL CANADA. LOOKING
AT THE 1.5PVU SFCS THE ORIGINS OF THESE SYSTEMS ARE THREE
PART. 1) JUST OFF THE BRITISH COLUMBIA ALASKA PANHANDLE
COAST...2) IN THE FAST FLOW IN THE CENTRAL PACIFIC NORTH OF
HAWAII AND 3) ALONG ALASKA'S BROOKS RANGE. OBVIOUSLY MANY
QUESTIONS REMAIN ABOUT THE PHASING PROCESS AND THE RESULTANT SFC
WEATHER. MORE IN THIS IN LONG TERM SECTION.
THROUGH TUESDAY NIGHT THERES A FAIR AMOUNT OF MODEL CONSISTENCY
EXCEPT WITH REGARD TO THE MAGNITUDE OF THE MARINE LAYER INFLOW
MONDAY AS DISCUSSED ABOVE.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
THE LONG RANGE FORECAST PERIOD IS THE RESULT OF THE ORGANIZATION OF
TWO MAJOR CUT OFFS AND THEIR INTERACTION AND EVENTUAL MERGER. GIVEN
THE LOCATIONS OF THE VORTICITY THAT WILL GIVE RISE TO THIS SCENARIO
(GIVEN AT END OF SHORT TERM)...MUCH REMAINS UNCERTAIN AND SUBJECT
TO CHANGE BASED ON THE PHASING TIME...DEGREE...LOCATION AND THEN THE
ULTIMATE SFC RESPONSE.
THERE ARE SOME GENERAL THEMES IN MOST OF THE GUIDANCE. ONE CUT
OFF OVER THE MID WEST LIFTS NORTHEAST INTO THE RIDGE OVER THE
EASTERN SEABOARD WEDNESDAY. THE SECOND DIVES SOUTH OUT OF CENTRAL
CANADA. THEY DUMBBELL AROUND EACH OTHER AND MERGE BY THEN END OF
THE WEEK. HWVR POSITIONS RANGE FM CENTERED N OF YUL (GEM)..TO NJ
(GFS) TO OHIO (ECMWF).
WHAT IS MOST CONCRETE AT THIS POINT IS WEDNESDAY THE FIRST 500HPA
CUT OFF MOVES FM MIDWEST INTO GRT LAKES AND PUSHES AN OCCLUDED
FRONT INTO NYS LATE IN THE DAY. THE GFS/GEM AND ECMWF SHOW THIS
SCENARIO WITH THAT CANADIAN ABOUT 6 HOURS FASTER WITH PCPN. WILL
KEEP IT DRY IN THE MORNING WITH CHC POPS AFTN AND WED NIGHT.
THE TIMING ISSUES BECOME MORE ACUTE FROM THURSDAY ON. THURSDAY
THE GFS PUTS FCA IN DRY SLOT AHEAD OF NEXT FRONTAL SYSTEM PUSHING
ACROSS FCA. THE GEM/ECM BRING THE NEXT FRONTAL SYSTEM THROUGH.
IN SUMMARY THE LONG RANGE PERIOD GENERAL THEMES ARE FAIRLY
CLEAR...BUT TIMING IS ALL OVER. OTHER THAN WED WILL LEAVE MUCH OF
THE EARLIER HPC BASED LONG RANGE IN PLACE WITH JUST SOME TWEAKS TO
IMPROVE COORDINATION. TO CHANGE IT TO GMOS AT THIS TIME WILL JUST
INCREASE THE FLIP FLOP FACTOR.
AVIATION /18Z SUNDAY THROUGH FRIDAY/
CLOUDS SHOWING SIGNS OF ERODING FROM WEST TO EAST...WITH THE
CLEARING LINE TRENDING TOWARD THE HUDSON VALLEY EARLY THIS
AFTERNOON. THE MVFR CEILING SHOULD BREAK UP AND BECOME SCATTERED
BY 22-23Z AT KGFL AND KALB...BUT BECOME SCATTERED AT POU BY 19Z.
ONCE THE CLOUDS HAVE ERODED...THE EVENING THROUGH THE OVERNIGHT
PERIOD SHOULD BE MOSTLY CLEAR...WITH NO CEILING. SOME PATCHY FOG
COULD DEVELOP...BUT NOT WIDESPREAD ENOUGH TO INCLUDE BORDERLINE
OFR IN TAFS AT THIS TIME.
HOWEVER...NEXT TAF ISSUANCE WILL HAVE MORE DATA TO EVALUATE THE
FOG POTENTIAL...WHICH MAY NEED TO BE ENHANCED IN TAFS FOR
TONIGHT..STAY TUNED. WINDS WILL BE LIGHT NORTH TO NORTHEAST...AT
10 KT OR LESS THIS AFTERNOON AND TONIGHT. THE NEXT SYSTEM TO OUR
SOUTH AND SOUTHWEST APPROACHES TOWARD SUNRISE...AND CLOUDS WILL
REFORM AS BOUNDARY LAYER MOISTURE INCREASES. SO..BETWEEN
10-14Z...MVFR CEILING WILL DEVELOP AT POU...WHILE VFR CEILING WILL
SPREAD ACROSS KALB AND KGF TOMORROW MORNING. WINDS TOMORROW
MORNING WILL REMAIN NORTHEAST AT 10 KT OR LESS.
OUTLOOK...
MON-TUE...VFR-MVFR...CHC OF RAIN MON NT-TUE.
WED...VFR...CHC OF SHOWERS.
THU-FRI...MVFR/IFR...RAIN POSSIBLE LATE THU THROUGH FRI.
HYDROLOGY
WITH DRY CONDITIONS EXPECTED TO LAST AT LEAST INTO MONDAY RIVERS
WILL CONTINUE RECEDE THROUGH MONDAY. THE NEXT THREAT OF RAIN WILL
BE LATE MONDAY INTO TUESDAY. CONSENSUS OF MODELS IS FOR 0.10 TO
0.30 INCHES MAINLY IN THE SOUTHEAST. THIS EVENT SHOULD HAVE MODEST
IMPACT ON RIVERS AND STREAMS. FURTHER OUT AN UNSETTLED PERIOD OF
WEATHER THURSDAY INTO THE WEEKEND COULD RESULT IN SIGNIFICANT
PRECIPITATION AMOUNTS.
FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING
OBSERVED AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE
VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON
OUR WEBSITE.
ALY WATCHES/WARNINGS/ADVISORIES
CT...NONE.
NY...NONE.
MA...NONE.
VT...NONE.
AVIATION...NAS
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