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Late Weekend Storm Threat


IsentropicLift

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No blocking, strengthening S/W and departing high. It's a movie we've all seen before.

The high isn't really retreating...the problem is the models don't know how far to dig the shortwaves. 18z NAM has the lead vort over Lake Superior whereas the 12z GFS has the vort swinging through Illinois. NAM is probably wrong as usual, should be a decent storm over here.

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I am thinking little or nothing Sunday as the overrunning is north of the city.  I see that a Dynamic Destabilization Event over running and these typically happen in upstate NY or in central to northern New England.  As for Monday it is anyone's guess.on how the upper levels develop.  It could be a decent size coastal low or it could just be like the models have it now or a little stronger.  It will depend on how much energy digs into the eastern Midwest.

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MT HOLLY 341 PM

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
HIGH PRESSURE WILL PUSH FARTHER TO OUR SOUTH INTO FRIDAY NIGHT, BUT
DRY WEATHER WILL CONTINUE INTO THE NIGHT. GUSTY CONDITIONS FROM THE
DAY WILL DIMINISH AFTER SUNSET. OVERNIGHT LOWS WILL BE MUCH WARMER
FROM THURSDAY NIGHT`S, BUT MAY STILL END UP A FEW DEGREES BELOW
NORMAL IN SOME PLACES.

ON SATURDAY, GUIDANCE CONTINUES TO INDICATE A COLD FRONT SAGGING
DOWN ACROSS THE AREA, THEN STALLING ACROSS OUR SOUTHERN AREAS OR
JUST TO OUR SOUTH. SEVERAL SHORT WAVE/VORTICITY IMPULSES ARE
FORECAST TO MOVE ACROSS THE AREA SATURDAY, SATURDAY NIGHT, AND
AGAIN ON SUNDAY WHICH COULD LEAD TO A COUPLE OF SEPARATE PERIODS
OF ENHANCED PRECIPITATION CHANCES. RIGHT NOW, IT LOOKS LIKE THE
BEST CHANCE FOR PRECIPITATION THROUGH SUNDAY MAY OCCUR ACROSS THE
NORTHERN HALF/THIRD OF THE AREA WHERE THE HIGHEST LOW/MID LEVEL
MOISTURE RESIDES.

THEN AS WE MOVE INTO SUNDAY NIGHT AND MONDAY, AN AREA OF LOW
PRESSURE THAT DEVELOPS ALONG THE FRONT TO THE WEST OVER THE
WEEKEND CONTINUES TO SLIDE EAST THEN OFF THE MID ATLANTIC COAST
AND SLOWLY DRIFT EASTWARD INTO MONDAY NIGHT. THERE IS SOME SLIGHT
TIMING DIFFERENCES WITH THE MODELS WITH GFS BEING MORE PROGRESSIVE
AND THE ECMWF A LITTLE SLOWER AND LAGGING THE LOW SLIGHTLY. THIS
LEADS TO SOME TIMING DIFFERENCES IN HOW LONG THE PRECIPITATION
LASTS. HOWEVER, IT STILL LOOKS LIKE THE MAIN FOCUS FOR
PRECIPITATION IS SUNDAY NIGHT INTO MONDAY. THE ACTUAL TRACKS IN THE
MODELS ARE PRETTY CLOSE AND ARE TRYING TO CONTINUE TO PUSH THE LOW
NORTHWARD. A FARTHER NORTHWARD TRACK AS USUAL WOULD LEAD TO A
MULTITUDE OF PTYPES AS THERE IS AN INDICATION OF SOME WARM AIR AT
925-850 MB. IT SILL LOOKS LIKE OUR FAR NORTHERN AREAS SHOULD SEE
MOSTLY SNOW, WHILE FAR SOUTHERN AREAS MAY SEE MOSTLY RAIN. IN
BETWEEN, THE TRANSITION ZONE IS STILL DIFFICULT TO DISCERN AS OF
NOW
. WE WILL KEEP THE SNOW/SLEET MIXTURE AND HAVE ADDED A CHANCE
OF FREEZING RAIN DURING THIS PERIOD FOR SOME AREAS.

BY MONDAY NIGHT, BOTH THE GFS AND ECMWF HAVE THE LOW OFFSHORE,
AND MOVE IT EASTWARD INTO TUESDAY. THERE COULD BE SOME LINGERING
PRECIPITATION INTO MONDAY NIGHT AS THE LOW PULLS EASTWARD AND THE
MAIN SHORT WAVE MOVES ACROSS THE AREA. ALSO, PRECIPITATION SHOULD
HAVE CHANGED TO ALL SNOW IN ALL AREAS BY MONDAY NIGHT.
TUESDAY
COULD END UP BEING PRECIPITATION FREE AS DRIER AIR MOVES IN BEHIND
THE DEPARTING SYSTEM. WINDS WILL LIKELY INCREASE TUESDAY INTO
TUESDAY NIGHT AS THE PRESSURE GRADIENT TIGHTENS BETWEEN THE
DEPARTING LOW AND HIGH PRESSURE TO THE WEST.

HIGH PRESSURE MAY BRIEFLY BUILD ACROSS THE AREA TUESDAY NIGHT INTO
WEDNESDAY WHICH WILL BRING A BRIEF PERIOD OF DRY WEATHER AND LIGHTER
WINDS TO THE AREA.

ANOTHER CLIPPER SYSTEM AND ASSOCIATED FRONTAL BOUNDARY IS CURRENTLY
FORECAST TO MOVE ACROSS THE NORTHEAST AROUND THURSDAY OF NEXT WEEK
WHICH COULD BRING ANOTHER CHANCE OF PRECIPITATION. 

 

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One thing goes without saying this winter. The models have been AWFUL outside of 3 days. Bad. REALLY bad.

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Not really, weve just been on the border of all the storms. New England always knew they were getting good storms and they did, PHL/DC always knew they were getting nothing and they did. Just our area has been on the border of every storm so small shifts make big differences for us.

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And Upton  just proved my point  in their  afternoon AFD - only took until the next scheduled model runs at 12Z - they are forecasting model run to model run and changing their outlook and forecast every cycle - so throwing around snowfall totals of 8 inches in their A.M. AFD looks kind of foolish now - nothing like flip flopping - expect changes again later tonight.........

Upton Just updated their AFD a few minutes ago - IMO throwing around snow totals in this very complex setup this early is nonsense . They are once again leaning heavily on the GFS which give close to 0.90 total qpf

 

143  

FXUS61 KOKX 051221  
AFDOKX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW YORK NY  
721 AM EST THU FEB 5 2015  
   

   
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
 
 
FAIRLY GOOD AGREEMENT IN THE LONG TERM WITH A COLD FRONT APPROACHING  
THE AREA FRIDAY NIGHT AND THEN MOVING THROUGH LATE SATURDAY INTO  
SATURDAY NIGHT. IT WILL THEN STALL WELL SOUTH OF THE AREA...AND A  
WEAK LOW PRESSURE SYSTEM WILL DEVELOP ALONG THE FRONTAL BOUNDARY OFF  
THE MID-ATLANTIC COAST ON MONDAY. IT WILL THEN HEAD NORTHEAST  
PASSING WELL SOUTH AND EAST OF LONG ISLAND BY TUESDAY. THERE IS THE  
POTENTIAL FOR 8"+ OF SNOW.
HOWEVER...THIS WILL FALL OVER AN  
EXTENDED PERIOD OF TIME...FROM SATURDAY NIGHT THROUGH TUESDAY. IF  
THE MODELS CONTINUE TO SHOW THIS EXTENDED PERIOD OF  
SNOW...QUESTION REMAINS AS TO WHETHER WE RECEIVE 8"+ IN A 24 HOUR  
PERIOD TO CONSIDER WATCHES/WARNINGS OR ADVISORIES IF IT FALLS IN  
A PERIOD LONGER THAN 24 HOURS. THERE IS UNCERTAINTY WITH QPF...AS  
THE 00Z GFS HAS ABOUT HALF AN INCH LESS QPF THAN THE 12Z ECMWF.  
THIS MAY BE DUE TO THE STRENGTH OF THE H5 TROUGH...WHICH IS WEAKER  
IN THE GFS THAN THE ECMWF. THIS WOULD LEAD TO A WEAKER SURFACE  
LOW. THE TREND HAS BEEN TO WEAKEN THIS TROUGH FROM RUN TO RUN IN  
BOTH MODELS. MORE CONFIDENT THAT PRECIPITATION TYPE WILL BE ALL  
SNOW EVERYWHERE.  
 
HIGH PRESSURE BUILDS IN AT THE SURFACE TUESDAY NIGHT...WITH A WARM  
FRONT APPROACHING THE AREA ON WEDNESDAY.  
 

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Not really, weve just been on the border of all the storms. New England always knew they were getting good storms and they did, PHL/DC always knew they were getting nothing and they did. Just our area has been on the border of every storm so small shifts make big differences for us.

Small shifts? Even you know that's not accurate.

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On the 12z Euro the high moves east from central Quebec toward Newfoundland on Monday, as the S/W strengthens. That's a position that would encourage SE flow from the ocean. There's a 50-50 feature early but it's lifting out. All in all the pattern still looks very progressive and transient. The shifting positions of these highs makes it possible that what storm does form does so too far north and as flow is reversing to easterly. It's possible the high is in a better place or the 50-50 feature stabilizes, but I don't see anything to ensure a cold outcome near the coast. Also, these initial overrunning deals overshoot the NYC area to the north 9 out of 10 times, so it's hard to count on snow from that. That will likely be light and favor I-90.

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