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NYC/PHL Jan 17-19 Forecast Discussion


am19psu

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Looks like it is mostly climatology based probability. Not a bad idea...

and a lot like the last 2 NAM runs, which is another good idea since if anything is going to be right, it would be that model. The 6z gfs seems very suspect. I know mt holly saw the 6z gfs cause they talked about it in their updated afd, yet i didnt see WDrag totally bite on it. I mean, the 6z gfs has ice still going over all of nj thru 21z. scary.

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Guest Patrick

Upton this a.m.:

WINTER WEATHER ADVISORIES WILL LIKELY BE ISSUED FOR MOST IF NOT ALL OF

THE REMAINDER OF THE AREA LATER TODAY...DEPENDING ON CONFIDENCE IN

AT LEAST A GLAZE OF ICE IN A GIVEN ZONE.

I am very surprised that Bergen County, NJ is not included in at least a winter weather advisory.

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Guest Patrick

I guess it is easy to discount the GFS, especially since it basically ignored the last two storms in the short range until they were underway (in a manner of speaking). However, initialization seems fine this go around. Still, that amount of significant icing around these areas is rare, and I believe Snowgoose mentioned this as well: It is far more likely that we get a quick shot of snow following by quick transition to rain, rather than significant icing.

That being said, this is not a typical winter, or a typical decade, or progged to be a typical January. I can't imagine what I would do if people's lives and property depended on my words in this situation, especially in the heavily populated EWR - HPN areas.

and a lot like the last 2 NAM runs, which is another good idea since if anything is going to be right, it would be that model. The 6z gfs seems very suspect. I know mt holly saw the 6z gfs cause they talked about it in their updated afd, yet i didnt see WDrag totally bite on it. I mean, the 6z gfs has ice still going over all of nj thru 21z. scary.

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I guess it is easy to discount the GFS, especially since it basically ignored the last two storms in the short range until they were underway (in a manner of speaking). However, initialization seems fine this go around. Still, that amount of significant icing around these areas is rare, and I believe Snowgoose mentioned this as well: It is far more likely that we get a quick shot of snow following by quick transition to rain, rather than significant icing.

That being said, this is not a typical winter, or a typical decade, or progged to be a typical January. I can't imagine what I would do if people's lives and property depended on my words in this situation, especially in the heavily populated EWR - HPN areas.

The only place north and east of 40N/80W where it is more difficult to see a significant icing event is probably the south shore of Lake Ontario.

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Figured some of you might want to read what Millersville's Eric Horst says, he's usually very spot-on with winter weather events.

A very cold day is on tap as clouds increase over top a large, strong area of high pressure parked over northern New England. Two low pressures systems, one moving in from the Midwest and the other moving up the east coast, will then converge on the region tonight through Tuesday night. The low pressure system along the east coast is the main threat, and with cold air damming in place over most of central and eastern PA (thanks to the New England high pressure) we will have a long duration of frozen/freezing precipitation tonight and Tuesday. Light snow should develop this evening, with a coating to an inch or two possible, before changing to sleet then freezing rain. Here in Lancaster (and points to our west and north), I expect freezing rain to be the primary threat with a 1/4" or more of ice accumulation possible...which could certainly make for significant problems Tuesday. Areas to our south and east will likely change over to plan rain by mid to late morning Tuesday, whereas colder valley areas farther north and west could very well remain at or below freezing all day Tuesday. By late Tuesday afternoon, the steady precipitation will end; so I expect just some lingering freezing drizzle or plain drizzle Tuesday night with temperatures hovering within a couple degrees of freezing.

http://snowball.millersville.edu/~cws/SpecialWeatherDiscussion.html

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What is the best way to see the predicted surface temperatures from the NAM? It is not on any of the default panels on the NCEP NAM graphics. I live about 2 miles from the NWS Andover observation station (K12N) so if there is a way to get predictions for that point it would be great. Thanks.

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What is the best way to see the predicted surface temperatures from the NAM? It is not on any of the default panels on the NCEP NAM graphics. I live about 2 miles from the NWS Andover observation station (K12N) so if there is a way to get predictions for that point it would be great. Thanks.

http://raleighwx.americanwx.com/models/12znam.html

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A half inch of ice is quite difficult to come by unless temps are in the 20's, and ice storm warning criteria is half inch for most of the area north and west of the philly burbs so I'm not suprised to see advisories atm but the scary place to watch is the philly burbs which in my opinion could easily see up to 0.25" of ice = ice storm warning criteria. All ice is extremely dangerous and 0.10" of ice is more than enough to cause roadways to ice over but not enough to cause power outages. My main concern though, is that the models have continued to trend colder and may not be taking into account the modest snow pack still on the ground which will be added to slightly before the warm air alloft arrives. If temps are even 1-2 degrees colder than forecasted, it will make a tremendous difference.

ER_FZ_Rain_WRNG_CriteriaPHI.jpg

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From Mt. Holly AFD - They are definitly leaving the door open for this ending up as a major event.

SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...

***WINTER WEATHER ADVISORY IN EFFECT***

LOW PROB WE MAY EVENTUALLY NEED AN UPGRADE TO A WINTER WARNING FOR

NW NJ OR NE PA EITHER FOR 5-8 INCHES OF WET SNOW OR NEAR ONE HALF

INCH GLAZE.

NO MATTER...COMBINATION OF SNOW AND FREEZING RAIN IS EXPECTED TO

MAKE FOR HAZARDOUS TRAVEL TOMORROW MORNING AND THE ADVISORY IS POSTED.

ADJUSTMENTS IN THIS ADVISORY MAY BE NEEDED THIS AFTERNOON...ESPECIALLY

IN NEW JERSEY AND NE PA.

SNOW AMOUNTS WILL BE HIGHLY DEPENDENT ON THE AMOUNT OF VERTICAL

VELOCITY IN THE IDEAL SNOW GROWTH REGION TUESDAY MORNING. THE 00Z/06Z

NAM AND NOW THE 06Z GFS ALLOWS FOR THE POSSIBILITY OF SNOW EVEN

WITH A SLIVER OF AIR JUST ABOVE 0C NEAR 850 MB... THIS BASED ON

FGEN FORCING CAUSING A PROGRESSIVE NWD MOVING BANDING PATTERN THAT

COULD HAVE AN HR OR 2 OF 1 INCH/HR HEAVY SNOW...ESPECIALLY JUST N

OF PHL TO NRN NJ AND NE PA.

COLD AIR DAMMING WILL ALLOW FOR SOME FREEZING RAIN...ESPECIALLY

WEST OF I95 IN EASTERN PA AND NW NJ TUESDAY AFTER THE PRIMARY LIFT

SHIFTS NORTH OF THE AREA.

MY FEELING IS THAT THIS WILL END UP MOSTLY SNOW IN NE PA AND NW NJ

AND WET SNOW CHANGING TO RAIN ELSEWHERE WITH A NARROW SLIVER OF .2-.4

GLAZE NEAR KABE-KMMU.

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we have had these 2-4 inch sleet events before, is there anything similar to the setups a few years back where the call was for snow but we got 25 and sleet. Could we not even see snow at all with this storm except briefly at the start?

Go back and read previous posts and you will find your info....you could also try www.nws.noaa.gov for an accurate local forecast.

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we have had these 2-4 inch sleet events before, is there anything similar to the setups a few years back where the call was for snow but we got 25 and sleet. Could we not even see snow at all with this storm except briefly at the start?

These events usually come in 2 forms...the ones where you go snow to rain very fast, sometimes not even seeing more than maybe 1-2 hours of snow if that....the other is a prolonged period of snow, sometimes 4-6 hours where you can see as much as 4-5 inches, then maybe 2-3 hours of sleet/freezing rain and then rain....this one I think relies tremendously on when the precipitation gets in, if it arrives by 04-05Z I would not be surprised if we saw 2-4 inches of snow in the NYC area, if it doesnt start til 07-08Z it will be much harder.

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