514
FXUS61 KALY 231740
AFDALY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ALBANY NY
140 PM EDT THU MAY 23 2013
SYNOPSIS
A COLD FRONT WILL MOVE SLOWLY ACROSS THE REGION THIS
AFTERNOON INTO TONIGHT...AND STALL ALONG THE ATLANTIC SEABOARD
FRIDAY. LOW PRESSURE WILL ORGANIZE...INTENSIFY...AND LINGER ON THIS
FRONT NEAR THE NEW ENGLAND COAST MUCH OF THE WEEKEND. HIGH PRESSURE
WILL BUILD INTO THE EASTERN GREAT LAKES MEMORIAL DAY AND DRIFT OVER
OUR REGION INTO MIDWEEK WITH FAIR AND DRY WEATHER.
NEAR TERM /THROUGH TONIGHT/
AS OF 130 PM EDT...A COLD FRONT REMAINS WEST OF THE REGION OVER
THE OHIO VALLEY AND THE EASTERN GREAT LAKES REGION EARLY THIS
AFTERNOON...WITH A PREFRONTAL TROUGH MOVING ACROSS CNTRL NY AND
PA. THIS PREFRONTAL TROUGH IN THE WARM SECTOR HAS PRODUCED SCT
SHOWERS OVER THE SRN DACKS AND W-CNTRL MOHAWK VALLEY...AND OTHER
HEAVY SHOWERS AND THUNDERSTORMS OVER THE MID HUDSON VALLEY AND NW
CT IN ADVANCE OF THE MID LEVEL SHORT-WAVE. THE THUNDERSTORMS
APPEAR TO BE TRAINING...AND A FLASH FLOOD WARNING HAS BEEN ISSUED
FOR LITCHFIELD COUNTY CT...AND SE DUTCHESS COUNTY. A 30-35 KT H850
LLJ AND STRONG LOW-LEVEL THETA-E ADVECTION HAVE CAUSED THE
BAND OF CONVECTION. POPS WERE ISSUED FOR CATEGORICAL VALUES. MOST
OF THE REST OF THE FCST AREA IS SANDWICHED BETWEEN THE TWO
BOUNDARIES WITH JUST SOME SCT SHOWERS. ANOTHER BAND IS STARTING TO
REACH THE WRN DACKS...SO HIGHER POPS HAVE PLACED HERE.
THE SATELLITE PICTURE IS CLUTTERED WITH CLOUD COVER WHICH WILL
INHIBIT WIDESPREAD STRONG TO SEVERE CONVECTION AT THIS TIME.
DEWPTS REMAIN IN THE U50S TO M60S...SO ANY HOLES IN THE CLOUD
COVER MAY ALLOW SBCAPES VALUES OF 400-800 J/KG TO DEVELOP. THE MID
LEVEL LAPSE RATES CONTINUE TO LOOK POOR AT THIS TIME...BUT THE
BETTER UPPER LEVEL JET DYNAMICS ARRIVE IN THE LATE PM AND EVENING
/OUR FORECAST AREA GETS IN THE RIGHT REAR QUADRANT OF THE JET
STREAK/...AND THE DEEP SHEAR STRENGTHENS TO 40-50 KTS...ESPECIALLY
FROM THE CAPITAL REGION NORTHWARD BTWN 18Z- 00Z. THE AMOUNT OF
HEATING AND SFC DESTABILIZATION REMAINS THE QUESTION FOR THE
POSSIBILITY OF SEVERE THUNDERSTORMS THIS PM. NO ENHANCED WORDING IN
THE ZONES AND GRIDS YET. SOME MULTICELLS EVOLVING INTO LINES AND
BANDS LOOK POSSIBLE BASED ON THE MODEL SOUNDINGS AND HODOGRAPHS.
THE LOW TO MODEST INSTABILITY AMOUNTS SHOULD LIMIT TALL UPDRAFTS.
THE FLASH FLOOD WATCH REMAINS UP FOR THE NRN HALF OF THE FCST
AREA. ZONAL FFG VALUES IN THE 1/3/6 HR TIME FRAME HAVE LOWERED TO
1-2 INCHES OVER PORTIONS OF THE CAPITAL REGION AND SRN VT DUE TO
THE HEAVY RAINS THE PAST FEW DAYS. THE SLOW MOVEMENT OF THE
BOUNDARY COUPLED WITH THE ANOMALOUS PWAT VALUES COULD PRODUCE SOME
FLASH FLOODING IN A FEW SPOTS. AT THIS TIME...MONITORING FOR
EXPANSION BASED ON THE HEAVY SHOWERS AND THUNDERSTORMS TO THE
SOUTH.
TEMPS WERE LOWERED ABOUT A CATEGORY TO THE M60S TO M70S OVER THE
REGION FOR THE REST OF THE AFTERNOON.
SHOWERS AND THUNDERSTORMS SHOULD EVOLVE INTO JUST AN AREAS OF STEADY
RAIN LATE TONIGHT AS THE LOW LEVEL COOLING GRADUALLY SPREADS
EAST...AND THE STRENGTHENING UPPER FEATURE BEGINS TO CUT OFF AND
TRACK ALONG THE NORTHEAST COAST TOMORROW INTO THE WEEKEND. LOWS
WILL BE IN THE 50S TO L60S.
SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/
THE TREND THAT BEGAN APPEARING IN THE MODEL SUITE TWO DAYS AGO...IS
NOW CONSENSUS FOR THE WEEKEND. 00 UTC GFS/NAM/ECMWF HAVE CDFNT
STALLING ALONG I-95 CORRIDOR BY FRI MORNING. SHARP 500HPA TROF FM
QB TO APPALACHIANS MOVING EAST...AS SERIES OF SHORT WAVES DIVE
SOUTHWARD INTO IT AND CUT IT OFF.
DURING FRI IT CUTS OFF OVER THE MID ATLC STATES...COASTAL
CYCLOGENISUS ENSUES OFF LONG ISLAND...AND THE SLOWLY DEEPENING SFC
LOW AND THE 500HPA CUT OFF BCMG VERTICAL OFF S NEW ENG COAST
SAT...THEN DRIFT SLOWLY N SUNDAY INTO GULF OF MAINE.
NEEDLESS TO SAY THIS IS GOING TO FEEL MORE LIKE A LATE OCTOBER
WEEKEND IN THE NORTHEAST. DURING FRIDAY -SHRA WILL TRANSITION TO
PERIODS OF RAIN IN ANNA TYPE FRONT BTWN SFC FRONT AND 500HPA AXIS.
AT SAME TIME GRADIENT BETWEEN 1031MB HIGH OVER MIDWEST...AND
DEEPENING SFC LOW OFF LONG ISLAND WILL RESULT IN A 14MB WIND
GRADIENT ACROSS NYS FRI & SAT. N WINDS WILL INCR TO 10-20 MPH AND
RESULT WILL BE A RAINY RAW FRI AND SAT.
GFS QPF OF 1-2.5 INCHES...ECMWF 0.75 TO 1.0 FRIDAY NIGHT THROUGH
SAT NT.
DURING THE DAY FRIDAY TEMPERATURES WILL JUST HOLD STEADY NEAR
MORNING LOWS...BEFORE FALLING DURING FRI AFTN IN STRONG CAA. THEY
WILL FALL FURTHER FRI NT INTO THE 40S WITH 30S IN WESTERN
PERIPHERY. SAT HIGHS WILL BE IN THE 50S AND LOW 60S WITH CLOUDS
AND PERIODS OF RAIN. MAX MIN TEMPS IN GUIDANCE ARE PROBABLY NOT
MUCH USE...AS ALOT OF NON-DIURNAL EFFECTS GOING ON FRI INTO SAT.
WILL USE 3 HOURLIES AND LET MAX/MINS FALL OUT.
OF NOTE IS THAT THE WESTERN EDGE OF THE PCPN/CLOUDS WITH THIS
SYSTEM WILL BE A VERY SHARP TRANSITION...SOMEWHERE ON THE WESTERN
PERIPHERY OF FCA. PCPN COULD BE SPOTTY OR NON-EXISTENT ALONG W
EDGE OF FCA...AND THERE MAY BE PERIODS OF THINNING CLOUDS WHICH
WOULD ALLOW TEMPS TO DROP TO NR FREEZING DURING MORNINGS.
SUN THE VERTICAL SYSTEM WILL CONTINUE TO DRIFT THROUGH THE GULF
OF MAINE...INTO THE MARITIMES SUN NT. THE GFS HAS CLOUDS AND -SHRA
DIM SUNDAY WITH INCRG SUN ALONG W PRTNS OF FCA. THE ECMWF KEEPS IT
CLOUDY AND WET INTO SUN EVENING. THE O6UTC NAM/GFS ARE A TAD MORE
PROGRESSIVE WITH THIS SYSTEM AND HAS CLOUDS AND RAIN ONLY FM HUD
VLY EAST SAT...AND THE SYSTEM CLEARLY EXITING REGION SAT NT.
FOR NOW FCST REFLECTS 00UTC MODEL SUITE TIMING...WITH SKIES FINALLY
CLEARING SUN NT ACROSS FCA AS 500HPA RIDGING BUILDS INTO THE GRTLKS
AND SFC HIGH BUILDS INTO E GRTLKS. BUT IF THE EMERGING TREND
CONTINUES ON LATER RUNS...CONDITIONS MIGHT NOTICEABLE IMPROVE
ACROSS FCA FOR SUNDAY.
LONG TERM /MONDAY THROUGH WEDNESDAY/
AFTER A SOGGY HOLIDAY WEEKEND...THE CUTOFF AND SFC SYSTEM DEPART
AS RIDGE AT 500HPA BUILDS INTO GRTLKS AND SFC HIGH BUILDS FROM
GRTLKS TO CAROLINAS MONDAY. THIS PATTERN WILL SHIFT EAST AS LARGE
500 HPA RIDGE BUILDS OVER E USA AND SFC HIGH SETTLES OFF THE EAST
COAST. TEMPS WILL RETURN TO NR NORMAL MONDAY..AND BUILD UPWARD
INTO THE WEEK. FCA IN WAA REGIME THROUGHOUT. THE GFS BRINGS A
WMFNT AND CHC -SHRA/TSTMS LATE TUES AND WED...WHILE ECMWF KEEPS IT
DRY INTO THU. ONLY 6 MEMBERS OF THE GEFS ARE IN LINE WITH THE
OPERATIONAL RUN PCPN WED...THE REST OF THEIR PLUMES ARE FLAT
LINED. WPC HOLDS PCPN OFF TILL END OF EFP ON THUR. SO FOR NOW WILL
HAVE A FAIR WARM EFP...WITH A VERY NOTICEABLE WARMING TREND TO ABV
NORMAL TEMPS. WILL POPULATE WITH WPC FROM MIDNIGHT SHIFT.
AVIATION /18Z THURSDAY THROUGH TUESDAY/
MAINLY VFR CONDITIONS...BUT MVFR-IFR POSSIBLE AT TIMES THROUGH THE
AFTERNOON IN SHOWERS AND A POSSIBLE RUMBLE OF THUNDER.
PREDOMINANTLY MVFR CONDITIONS TONIGHT AND FRIDAY AS A SLOW-MOVING
COLD FRONT SWITCHES SOUTHERLY WINDS AROUND TO NORTHERLY SOMETIME
AROUND DAYBREAK UPON ITS PASSAGE THROUGH THE AIRPORTS. LOW PRESSURE
RIDING UP ALONG THE FRONT WILL KEEP CLOUDS AROUND INTO THE EARLY
AFTERNOON ON FRIDAY. NO SHEAR ISSUES.
OUTLOOK...
FRI PM-SAT...MAINLY VFR. -SHRA LIKELY.
SAT NGT-SUN...VFR...CHC -SHRA.
SUN NGT-TUE...VFR...NO SIG WX.
FIRE WEATHER
NO FIRE WEATHER CONCERNS INTO SUNDAY. PERIODS OF RAIN...MODERATE
TO HEAVY AT TIMES WILL CONTINUE INTO THE HOLIDAY WEEKEND.
RH VALUES WILL INCREASE TO 85 TO 100 PERCENT TONIGHT...AND
FRIDAY NIGHT...AND LOWER TO 45 TO 60 PERCENT THURSDAY AFTERNOON
AND ONLY 60-80 PERCENT FRIDAY AFTERNOON.
WINDS WILL GENERALLY BE SOUTH AT 5 TO 10 MPH TODAY...TURNING NORTH
FRIDAY AND INCREASING TO 10 TO 15 MPH. .
HYDROLOGY
ECMWF AND GFS VERY AGGRESSIVE IN BRINGING HEAVY RAINFALL INTO CWA
INTO THE MEMORIAL DAY WEEKEND. OPERATIONAL ECMWF AND GFS PRODUCE
2.50 TO 5.0 INCHES OF RAIN IN CWA INTO SUNDAY. GEFS SHOW AVERAGE
OF 2.0 INCHES THROUGH WEEKEND WITH 8 MEMBERS PUSHING IN EXCESS OF
3.5 INCHES.
FIRST CHALLENGE FOR HEAVY RAIN WILL COME WITH TODAYS SLOWLY MOVING
FRONT. EASTERN CWA AND CENTRAL CWA HAVE SEEN HEAVIEST RAIN OVER
THE LAST TWO DAYS AND WOULD APPEAR TO BE THE REGION WHERE FLASH
FLOOD THREAT IS AT HIGHEST. A FLASH FLOOD WATCH ISSUED FOR THESE
AREAS.
ALY WATCHES/WARNINGS/ADVISORIES
CT...NONE.
NY...FLASH FLOOD WATCH THROUGH FRIDAY MORNING FOR NYZ032-033-
038>043-047>054-082>084.
MA...NONE.
VT...FLASH FLOOD WATCH THROUGH FRIDAY MORNING FOR VTZ013>015.
SYNOPSIS...SNYDER/WASULA
NEAR TERM...WASULA/NAS
SHORT TERM...SNYDER
LONG TERM...SNYDER
AVIATION...ELH
FIRE WEATHER...SNYDER
HYDROLOGY...SNYDER
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