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April 1-3 Late Season Threat

Ralph Wiggum

By Ralph Wiggum,
in Philadelphia Region

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tcutter

tcutter

Posted
Posted

I'd say N&W of 202 at this point looks golden. Between 202 and I-295 (i.e. the I-95 corrdidor) remain in question. Verbatim, the GFS is the only model showing accumulating snow, simply becuase surface temps are too warm on other models. The column is definitely cold enough but remember, it's not January anymore.

My guess is rain-->heavy snow with poor ratios, a few inches in Philly and major accumulations in higher elevations (typically above 401')

hasn't the euro been a couple of degrees too warm this winter........i thought i remembered that from earlier when we were tracking lots of storms???

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NaoPos

NaoPos

Posted
Posted

hasn't the euro been a couple of degrees too warm this winter........i thought i remembered that from earlier when we were tracking lots of storms???

Someone posted an image earlier. It was running bout 1 degree F too warm.

As far as surface temps, the bigger issue is the thickness level. As the ccb /deform develops, precipitation rates are intense enough to cool the Column dramatically. So verbatim, the euro is snow

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DJ Amenzo

DJ Amenzo

Posted
Posted

Everyone need not forget that most if not ALL of this event occurs in late evening and nighttime! Its definitely cold enough for all snow even into the Pine Barrens, imo. I was initially skeptical, but I'm nearly 100% sold now that a historic April snowfall is imminent. I would not be shocked to see 10-15" in PHL metro. Especially with the a) extreme ccb with deform B) near perfect 500mb vortcity maxima passage c) its April so the suns radiation from the daytime will only act to destabilize the atmosphere, even at night d) the SLP and 850mb low track is perfect right along the BM and concurrent greatest area of baroclinicity. One final thing is that the water in both the DE Bay and the ATL has not warmed much if at all since Feb. This is NOT impossible, it has happened before!

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Thunder Road

Thunder Road

Posted
Posted

hasn't the euro been a couple of degrees too warm this winter........i thought i remembered that from earlier when we were tracking lots of storms???

Yeah amp19psu posted an image that it's been running about 1F too warm lately, so not really enough to invalidate its data.

Right now I'm not worried so much about what the models say verbatim, but the fact that it IS April and that surface warmth will be an issue. Watch for models to under-forecast the effect of the late-season sun angle.

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NaoPos

NaoPos

Posted
Posted

Yeah amp19psu posted an image that it's been running about 1F too warm lately, so not really enough to invalidate its data.

Right now I'm not worried so much about what the models say verbatim, but the fact that it IS April and that surface warmth will be an issue. Watch for models to under-forecast the effect of the late-season sun angle.

Surface warmth has actual been Kept in check the last few days. Highs in the low 40's and lows @ or around freezing is a lot better than highs in the 50's or even a few days in the 60's. While still a concern bc of the solar radiation, we're not as bad off as we normally could have been( strictly going by pAst climo)

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Thunder Road

Thunder Road

Posted
Posted

Surface warmth has actual been Kept in check the last few days. Highs in the low 40's and lows @ or around freezing is a lot better than highs in the 50's or even a few days in the 60's. While still a concern bc of the solar radiation, we're not as bad off as we normally could have been( strictly going by pAst climo)

Yeah I mean we still got a sleetfest in 2007 the day after it was like 72° or something.

I'm just saying that this is a wildcard that, imo, should lower confidence. Not saying it can't or won't stick, just that for now the late-season aspect should lower confidence.

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hazwoper

hazwoper

Posted
Posted

Yeah amp19psu posted an image that it's been running about 1F too warm lately, so not really enough to invalidate its data.

Right now I'm not worried so much about what the models say verbatim, but the fact that it IS April and that surface warmth will be an issue. Watch for models to under-forecast the effect of the late-season sun angle.

Post like yours make me laugh. You do realize that with intense rates being depicted currently on nearly every model and precip occuring for the most part in the over night hours makes your "sun angle" argument nearly moot especially with the temps we are having this week. Just look at what a week 1000mb low on April 9th 1996 did in eastern NJ.

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Thunder Road

Thunder Road

Posted
Posted

Post like yours make me laugh. You do realize that with intense rates being depicted currently on nearly every model and precip occuring for the most part in the over night hours makes your "sun angle" argument nearly moot especially with the temps we are having this week. Just look at what a week 1000mb low on April 9th 1996 did in eastern NJ.

Sorry, when I said to watch for it, I meant in the sense that it's a possibility and should not be ruled out, not in the sense that I guarantee the models will bust or anything like that.

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Yes_Probably_Maybe_No

Yes_Probably_Maybe_No

Posted
Posted

Post like yours make me laugh. You do realize that with intense rates being depicted currently on nearly every model and precip occuring for the most part in the over night hours makes your "sun angle" argument nearly moot especially with the temps we are having this week. Just look at what a week 1000mb low on April 9th 1996 did in eastern NJ.

Take another look at that date. This type of stuff doesn't happen often for a reason and thus many are skeptical. Call it sun angle, low probability, whatever...until I see 6" of snow on my driveway, I'm fully prepared to see a cold rain as I think most are (at least around the immediate PHL area).

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NaoPos

NaoPos

Posted
Posted

Take another look at that date. This type of stuff doesn't happen often for a reason and thus many are skeptical. Call it sun angle, low probability, whatever...until I see 6" of snow on my driveway, I'm fully prepared to see a cold rain, as I think most are (at least around the immediate PHL area).

What has 2 thumbs and is expecting snow in Philly?

THIS GUY!!

On a serious note, the deeper the sytstem, the better chance we have. We got a slushy coating on cars last week in Philly with marginal surface

Temps. Yes, I know, diff set up. But it's possible. Especially with a monster storm. Time will tell though.

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famartin

famartin

Posted
Posted

Post like yours make me laugh. You do realize that with intense rates being depicted currently on nearly every model and precip occuring for the most part in the over night hours makes your "sun angle" argument nearly moot especially with the temps we are having this week. Just look at what a week 1000mb low on April 9th 1996 did in eastern NJ.

Apparently the models did pretty badly with where the big snows were gonna be during that event. Most forecasts leading up to it had the heavy accumulations in NW NJ and NE PA, but instead those areas got totally ripped off. The CCB sat over SE NJ instead. I was on the edge and had ratios of below 5:1.

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hazwoper

hazwoper

Posted
Posted

Apparently the models did pretty badly with where the big snows were gonna be during that event. Most forecasts leading up to it had the heavy accumulations in NW NJ and NE PA, but instead those areas got totally ripped off. The CCB sat over SE NJ instead. I was on the edge and had ratios of below 5:1.

Thanks Ray! Love your site BTW ;)

Just goes to show you that with the right set up (and as currently depicted on many models that set up may just occur in SEPA) 6" snowfall is possible in April. In fact, looking at the surface obs on your site from that event, many of the places seeing snow were in the mid 30s during the height of the event.

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famartin

famartin

Posted
Posted

In the theme of "badly forecast April snow", the April Fool's Day 1997 event was only supposed to be a coating to a couple inches. Instead a widespread swath of central and southern NJ had 6+. Areas in Chester County had over a foot where only a few inches was expected.

April 9th 2000, IIRC, was another bust.

Anyway, bottom line is we can *hope* the models will have a good idea of what's actually gonna happen 24 hours out. April snows are extra finicky because they're typically thread-the-needle events.

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JCT777

JCT777

Posted
Posted

i didn't mean it like that, it was more of a "you're showing me a storm from 15 years ago" type of comment

There was an April 10 storm in 2000 or 2001 (3" of snow for the NW suburbs of Philly), and of course April 7, 2003 which left 4"+ snow and fell mostly during the day. So yes, it's fairly unusual to get 3"+ accumulating snow in the area...but it's possible. And don't forget the March 31 - April 1 storm of 1997 which left 6"+ of snow over most of Bucks and Montgomery counties. :whistle:

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atownwxwatcher

atownwxwatcher

Posted
Posted

atownwxwatcher -- What did the EURO have for NEPA?

AVP

THU 00Z 31-MAR 4.2 -2.9 1015 72 90 0.01 551 538

THU 06Z 31-MAR 0.9 -3.8 1014 98 95 0.06 547 536

THU 12Z 31-MAR 0.8 -3.3 1013 96 72 0.04 546 535

THU 18Z 31-MAR 4.3 -2.9 1011 76 49 0.02 546 537

FRI 00Z 01-APR 2.5 -1.9 1009 91 54 0.02 544 537

FRI 06Z 01-APR 1.2 -1.0 1004 98 89 0.04 540 537

FRI 12Z 01-APR 0.6 -1.7 999 97 90 0.33 535 535

FRI 18Z 01-APR 2.2 -3.7 996 83 95 0.52 530 533

SAT 00Z 02-APR 1.1 -3.0 996 81 86 0.09 530 533

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Allsnow

Allsnow

Posted
Posted

mt holly

COME THURSDAY NIGHT AND EARLY FRIDAY ALL BETS ARE THEN OFF AS THE

LOW IS FORECAST TO INTENSIFY FAIRLY RAPIDLY. THE GFS THERMAL FIELD

IS COLDER THAN THE UKMET OR CAN GGEM (HI RES ECMWF NOT VIEWABLE IN

TIME). BUT TO A CERTAIN EXTENT, IT DEPENDS UPON WHERE THE

DEFORMATION BAND ESTABLISHES ITSELF AS DYNAMIC COOLING WOULD CHANGE

THE RAIN TO SNOW REGARDLESS OF LOCATION. PAY ONE NOW OR PAY ONE

LATER, WE SUPPOSE IF THE LOW WOULD TREND FARTHER TO THE WEST, THIS

WOULD INCREASE THE HYDRO CONCERNS PARTICULARLY IN NJ AS EVENT TOTAL

QPF BY THE GFS/CAN GGEM AND UKMET ARE AVERAGING 1.5 TO 2.5 INCHES.

THE SYSTEM SHOULD BE EXITING OUR AREA AS FRIDAY CONTINUES AND ONCE

THE INTENSITY IS LOST, PRECIPITATION COULD GO BACK TO RAIN. BECAUSE

OF MARGINAL TEMPERATURES THIS HAS THE POTENTIAL TO BE A HEAVY WET

SNOW EVENT, NOT EXACTLY A UTILITY`S DREAM. WE LOADED IN SOME

CONSERVATIVE SNOW AMOUNTS IN THE GRIDS FOR NOW, BUT THIS SHOULD BE

VIEWED AS A VERY FIRST GUESS WITH REVISIONS TO FOLLOW. BROUGHT MIN

TEMPS CLOSER TO FREEZING FASTER OVERNIGHT BECAUSE OF ANTICIPATED

MIXING OR CHANGEOVER AND WITH SNOW PROBABLE ON THE GROUND IN PARTS

OF OUR CWA, WENT BELOW MEX MOS FOR MAX TEMPS

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phlwx

phlwx

Posted
Posted

Does anyone know Philadelphia's top 10 biggest snow events in April? I know of 1915, but besides that, how do 1997, 2001 and 2003 rank? Could we be talking records broken?

Snowiest Aprils on record...

19.4 1915

7.0 1917

6.8 1924

5.1 1916

4.3 1971

4.0 1982

3.1 1898

3.0 1965

2.4 1996

2.4 1990

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