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3/23-3/24 threat OBS


LVblizzard

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Tony's thoughts:

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...

-- Changed Discussion --WARNINGS WILL BE ISSUED FOR OUR THREE NORTHERN COUNTIES WITH

ADVISORIES FOR THE NEXT TWO TIERS SOUTHWARD. LIKE MOST EARLY SPRING

STORMS THIS WILL BE ELEVATION DEPENDENT AND THUS WOULDN`T BE SHOCKED

IF THE RANGES IN ALL OF THE ADVISED/WARNED COUNTIES WITH HIGHER

TERRAIN WILL BE GREATER.

THE GFS INITIALIZATION OVERALL WAS BETTER THAN THE WRF-NMM OFF THE

12Z SOUNDINGS AND VERIFIED QUITE WELL WITH ITS 6 HR PROGS. THE

850MB ERROR AT PBZ IS ALL ABOUT HEIGHT (INVERSION AT 825MB) AND NOT

ABOUT GEOGRAPHY. STILL THE MODEL AND DIURNAL SPLIT CONTINUES WITH

THE GFS THE WARMEST, THE NAM THE SNOWIEST AND MOST OTHER MODELS

BETWEEN. ALSO THE 12Z RUNS HAVE RAN WARMER WHILE THE 00Z RUNS HAVE

RUN COOLER. THE GFS IN SPITE OF ITS INITIALIZATION REMAINS THE

WARMEST MODEL WITH THIS EVENT. THE OTHER MODELS ARE ALL CLUSTERED

MUCH CLOSER TO THE WRF-NMM. FOR THIS FCST PACKAGE WE ARE SIDING

WITH THE CONSENSUS AVERAGE WHICH IS CLOSER TO THE WRF-NMM THAN THE

GFS. FOR ABOUT THE SOUTHERN HALF OF OUR CWA MOST OF THE PTYPE

PROBLEMS ARE ABOUT WEDNESDAY NIGHT. FOR THE NORTHERN HALF OF OUR

CWA THIS HAD THE LOOKS OF THE JAN 26-27 EVENT OF SNOW, A LULL AND

THEN MORE SNOW, BUT WITH A WARMER GROUND AND A MID SEPTEMBER SUN

ANGLE TO FACTOR IN.

WHETHER CONSENSUS BREEDS ACCURACY OR NOT WOULD HAVE LIKED IF THE GFS

AND WRF-NMM THERMALLY WERE CLOSER, BUT ITS DECISION MAKING TIME. THE

WRF-NMM HAS EDGED WARMER, BUT ITS A DIURNAL CYCLE AS THE 00Z RUNS

HAVE BEEN COOLER. THE THERMAL FIELDS 1000-500MB THICKNESSES LESS

THAN 5460M AND 1000-850MB THICKNESSES OF LESS THAN 1300M HAVE BEEN

VERIFYING AS THE SNOW NOT SNOW LINE IN THE UPPER MIDWEST. WE USED

A COMBINATION OF THIS AND THE WRF-NMM THERMAL FIELDS TO ARRIVE AT

PCPN TYPE. IN GENERAL OUTSIDE OF FAR NORTH PCPN SHOULD START AS

RAIN TONIGHT BEFORE WE EVAP COOL TO SNOW, OR EVAP COOL TO SNOW

DURING HEAVIER PCPN PERIODS. EVEN THE GFS IS SHOWING A FGEN AXIS

THAT PRODUCES HIGHER QPF BY MORNING IN THE NORTHERN HALF OF OUR

CWA. THE FCST ISENTROPIC LIFT AND DEEP QVEC CONVERGENCE LOOKS

STRONGER THAN IT WAS ON MONDAY MORNING. SO A BURST WHERE PCPN GOES

FROM RAIN TO SNOW MAY GO PRETTY SOUTH INTO OUR CWA (MAYBE FARTHER

THAN WE HAVE), ALTHOUGH SFC TEMPS FROM PHL SOUTHWARD WILL MAKE IT

HARD FOR SNOW TO ACCUMULATE ON ROADWAYS.

BECAUSE OF GREATER PROXIMITY TO THE FGEN BAND WE HAVE ISSUED AN

ADVISORY FOR THE MORNING COMMUTE FOR BERKS, (REALLY UPPER) BUCKS,

HUNTERDON AND SOMERSET COUNTIES. IT LOOKS AS THOUGH THEY WILL HAVE

A WIDER GAP OF NON SNOW PCPN DURING THE DAY ON WEDNESDAY THAN

PLACES FARTHER TO THE NORTH. WE USED THE NAM SFC TEMPS AND THUS

OUR MINS ARE GOING TO BE LOWER THAN STAT GUIDANCE.-- End Changed Discussion --

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...

-- Changed Discussion --DURING THE DAY ON WEDNESDAY WE WILL HAVE THE EARLY SPRING DILEMMA OF

SNOW FALLING AND HOW MUCH WILL BE STICKING. AFTER THE FGEN BURST

GOES THRU IN THE MORNING, THERE IS A FORECAST GENERAL LULL BEFORE

THE STRONGER SHORT WAVE ARRIVES AND THE SFC LOW STARTS TO INTENSIFY.

THIS IN A TWO-FOLD SENSE SHOULD HOLD ACCUMULATIONS DOWN DURING THE

LATE MORNING AND AFTERNOON AS THE INTENSITY SHOULD NOT BE THERE AND

THE INDIRECT SUN WILL NOT ALLOW IT. ALSO SOME SOUNDINGS ARE SHOWING

THE LOSS OF ICE BEARING CLOUDS. THE NAM FORECAST SOUNDINGS ARE MOST

BULLISH ABOUT THE POSSIBILITY OF SLEET AS IT RAISES TEMPERATURES

ABOVE FREEZING JUST BELOW 700MB THROUGHOUT THIS EVENT. WE WERE A

LITTLE BIT CONSERVATIVE WITH THE MENTION OF SLEET AS PER THE LACK

OF WIDESPREAD PROLONGED SLEET WITH THE LAST EVENT. MODELS ARE

STILL SHOWING INSTABILITY ALOFT AND WHILE WE USED THE GFS

INSTABILITY FIELDS AS A GUIDE, WE LOWERED THEIR LOCATION BY ABOUT

50 MILES TO THE SOUTH TO ACCOUNT FOR PROBABLY A TOO NORTHWARD

PLACEMENT BY THE MODEL. YESTERDAY I BUSTED BIG TIME WITH MAX TEMPS

AT ABE, MY CHANCES OF BUSTING BIG TIME WITH MAX TEMPS TOMORROW

WILL SWITCH TO DELMARVA AS THEY WILL BE CLOSE TO THE WARM FRONTAL

BOUNDARY.

THE PROCESS REVERSES ITSELF ON WEDNESDAY NIGHT WITH THE WRF-NMM

AGAIN THE MOST BULLISH ABOUT THE TRANSITION BACK TO SNOW THROUGHOUT

OUR CWA. FOR NOW NO OTHER MODEL IS EITHER THAN HIGH IN QPF OR THAT

COLD FOR THAT MUCH SNOW AND WE LEANED CLOSER TO AN ECMWF/GFS QPF

COMPROMISE, BUT INCORPORATING THE NAM`S THERMAL FIELDS. CONFIDENCE

ABOUT THE PTYPE EVOLUTION FOR THIS TIME PERIOD IS LOWER THAN

AVERAGE.

EVENT QPF SHOULD AVERAGE HALF AN INCH TO AN INCH AND AS SUCH SHOULD

NOT CAUSE ANY FLOODING PROBLEMS AS LONG AS WE DO NOT HAVE TRAINING

THUNDERSTORMS. WE REALLY DID NOT MAKE TOO MANY CHANGES TO THE REST

OF THE SHORT TERM AS MODEL GUIDANCE HAS NOT DIFFERED MUCH. IT

STILL LOOKS LIKE ONE FINAL SHORT WAVE TROF HAS TO CLEAR THE CWA ON

THURSDAY. AFTER THAT OTHER THAN SPRING GOING AWOL, IT LOOKS DRY

INTO FRIDAY.

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Huh? Not the NAM I am looking at...

12 Z

18 Z

12 Z

18 Z

Looks more or less like it has held serve with the position of the low and the tracking ..perhaps slowed down a bit...but not north IMHO

The 0Z-6Z QPF field is significantly further north and closer to the GFS/EC. NAM is starting to wake up about that false back-end thump.

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The 0Z-6Z QPF field is significantly further north and closer to the GFS/EC. NAM is starting to wake up about that false back-end thump.

Well..it does not look to me like HPC is going with the GFS /EC nor the NAM as far as QPF is concerned.... but rather a blend of guidance as that is usually what it comes down to.

For example ECM thru 48 hrs has .25-.50 into CT

18 Z NAM only has .10-,25 into NE CT more to the SW...

18 Z NAM is also wetter then the ECM for here into NYC ...

GFS(12 Z) was much drier then the NAM (18Z)

Since it always comes down to a blend the HPC makes the most sense..

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Well..it does not look to me like HPC is going with the GFS /EC nor the NAM as far as QPF is concerned.... but rather a blend of guidance as that is usually what it comes down to.

For example ECM thru 48 hrs has .25-.50 into CT

18 Z NAM only has .10-,25 into NE CT more to the SW...

18 Z NAM is also wetter then the ECM for here into NYC ...

GFS(12 Z) was much drier then the NAM (18Z)

Since it always comes down to a blend the HPC makes the most sense..

I'm going with Tony's thoughts, which throw out the back-end thump idea of the NAM in favor of the GFS/EC blend.

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Hopefully...provided it's not an 18z "burp" that comes back at 0z or later.

Any run can be a burp when it comes to the NAM. Granted, probably a bit more likely on the 6Z/18Z suites, but I've witnessed some colossal fails of the NAM out here in the last month. One day a couple weeks ago, the 12Z NAM spit out a ridiculous 1" of QPF in the following 24 hours... the 18Z NAM woke up and cut that down to a quarter inch. The 18Z was much better than the 12Z... it ended up being slightly less than a quarter inch.

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high was 52.8° today. even if we get any frozen pcpn it won't stick down here

I have seen countless examples of where the idea frozen won't accumulate after a warm day gets totally destroyed.

For example: I got lectures on Eastern back in October 2009 how central PA wasn't going to see any snow on the ground due it being in the 60s for much of the week prior. Six inches later....

That snow accumulated in the afternoon, too. It really depends on time of day/night, rates, and cloud thickness. You have to get it started. Once it does, previous day highs mean nothing.

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I have seen countless examples of where the idea frozen won't accumulate after a warm day gets totally destroyed.

For example: I got lectures on Eastern back in October 2009 how central PA wasn't going to see any snow on the ground due it being in the 60s for much of the week prior. Six inches later....

That snow accumulated in the afternoon, too. It really depends on time of day/night, rates, and cloud thickness. You have to get it started. Once it does, previous day highs mean nothing.

True. If it went to 1/4SM +SN, it could start to accumulate during midday. Tend to think that's unlikely in his area, though. Best shot is near and before dawn around TTN.

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I'm going with Tony's thoughts, which throw out the back-end thump idea of the NAM in favor of the GFS/EC blend.

That is all fine and dandy ;) As i do not believe i mentioned anything about the back end thump . My questioning was on how you said that the NAM was further north when the track was actually the same and the QPF field oriented and shifted differently..not so much the actual low position...

I essentially would take a blend of all the guidance such as NAM/UK/GGEM/ECM/Nogaps since they are all quite similar and let the GFS alone out in the field to play...Perhaps it scores a home run...but i would not be counting on it...

All 12 Z 42 hrs

18 Z

Which one looks a little out of place?

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That is all fine and dandy ;) As i do not believe i mentioned anything about the back end thump . My questioning was on how you said that the NAM was further north when the track was actually the same and the QPF field oriented and shifted differently..not so much the actual low position...

That's what I was referring to. When I talk about weather here, I tend to focus on actual results that, you know, all the weenies care about.

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Hoping for an excuse to work from home tomorrow...Monday morning's 0530 am drive to Mt. Arlington was not fun. There were at least 2-3 inches of snow on the roads toward that area Monday and I think road crews in some spots were caught off guard. I also noticed today that the roads in my town were pre-treated today.

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I was thinking of Bensalem, not State College. But even in Bensalem it can accumulate at 1/4SM +SN during midday this time of year. April 2003 is a good example.

Love the shout-out! :thumbsup:

Heh, State College and Bensalem, AccuWeather office locations.

The weirdest damn thing in that Oct snow Ray was it accumulating even on roads at midday and it was just moderate snow - someone at Eastern said it had to do with cloud thickness?

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Heh, State College and Bensalem, AccuWeather office locations.

The weirdest damn thing in that Oct snow Ray was it accumulating even on roads at midday and it was just moderate snow - someone at Eastern said it had to do with cloud thickness?

There's an AccuWX office in my humble little township? :huh:

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Heh, State College and Bensalem, AccuWeather office locations.

The weirdest damn thing in that Oct snow Ray was it accumulating even on roads at midday and it was just moderate snow - someone at Eastern said it had to do with cloud thickness?

That may be part of it. Lord knows the clouds here never seem thick enough... we were down to 1/4 yesterday midday and it barely stuck.

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