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NYC/PHL Jan 17-19 Forecast Discussion


am19psu

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URGENT - WINTER WEATHER MESSAGE

NATIONAL WEATHER SERVICE NEW YORK NY

343 AM EST MON JAN 17 2011

...POTENTIAL WINTER STORM FOR INTERIOR PORTIONS OF THE LOWER

HUDSON VALLEY...SOUTHWESTERN CONNECTICUT...AND NORTHEAST NEW

JERSEY FROM LATE TONIGHT THROUGH TUESDAY NIGHT...

CTZ005-006-NJZ002-NYZ067>070-171645-

/O.NEW.KOKX.WS.A.0003.110118T0600Z-110119T1100Z/

NORTHERN FAIRFIELD-NORTHERN NEW HAVEN-WESTERN PASSAIC-ORANGE-

PUTNAM-ROCKLAND-NORTHERN WESTCHESTER-

343 AM EST MON JAN 17 2011

...WINTER STORM WATCH IN EFFECT FROM LATE TONIGHT THROUGH LATE

TUESDAY NIGHT...

THE NATIONAL WEATHER SERVICE IN UPTON HAS ISSUED A WINTER STORM

WATCH...WHICH IS IN EFFECT FROM LATE TONIGHT THROUGH LATE TUESDAY

NIGHT.

* LOCATIONS...INTERIOR PORTIONS OF THE LOWER HUDSON

VALLEY...SOUTHWESTERN CONNECTICUT...AND NORTHEAST NEW JERSEY

* HAZARDS...SNOW...SLEET...AND FREEZING RAIN

* ACCUMULATIONS...2 TO 4 INCHES OF SNOW AND SLEET INTO TUESDAY

MORNING...THEN UP TO A HALF AN INCH OF ICE ON TOP OF THE SNOW

AND SLEET FROM TUESDAY MORNING INTO TUESDAY NIGHT.

* TEMPERATURES...TEMPERATURES AT THE ONSET OF PRECIPITATION MONDAY

NIGHT WILL BE IN THE TEENS TO LOWER 20S...THEN SLOWLY RISE

TOWARDS THE FREEZING MARK TUESDAY. THERE IS SOME QUESTION OF

WHETHER THE FREEZING MARK IS REACHED...OR POSSIBLY EXCEEDED. ANY

AREAS WHICH WERE TO GO ABOVE FREEZING TUESDAY...WILL FALL BELOW

FREEZING TUESDAY NIGHT.

* TIMING...SNOW SHOULD DEVELOP MAINLY AFTER MIDNIGHT MONDAY

NIGHT...THEN MIX WITH AND CHANGE TO SLEET AND PRIMARILY FREEZING

RAIN BY AFTERNOON. SOME LOCATIONS COULD CHANGE TO RAIN FOR A

PERIOD OF TIME IN THE AFTERNOON...BEFORE CHANGING BACK TO

FREEZING RAIN TUESDAY EVENING. PRECIPITATION SHOULD TAPER OFF BY

LATE TUESDAY NIGHT.

* IMPACTS...TRAVEL COULD BECOME HAZARDOUS BY THE RUSH HOUR TUESDAY

MORNING...THEN BECOME TREACHEROUS BY TUESDAY AFTERNOON. IN

ADDITION...THE WEIGHT OF THE SNOW AND ICE COMBINED COULD BRING

DOWN TREE BRANCHES AND POWER LINES.

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Mt Holly

Winter Weather Advisory

URGENT - WINTER WEATHER MESSAGENATIONAL WEATHER SERVICE MOUNT HOLLY NJ411 AM EST MON JAN 17 2011NJZ001-007-008-PAZ054-055-060>062-171715-/O.NEW.KPHI.WW.Y.0004.110118T0600Z-110118T1800Z/SUSSEX-WARREN-MORRIS-CARBON-MONROE-BERKS-LEHIGH-NORTHAMPTON-INCLUDING THE CITIES OF...NEWTON...WASHINGTON...MORRISTOWN...JIM THORPE...STROUDSBURG...READING...ALLENTOWN...BETHLEHEM...EASTON411 AM EST MON JAN 17 2011...WINTER WEATHER ADVISORY IN EFFECT FROM 1 AM TO 1 PM EST

TUESDAY...

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY HAS ISSUED A WINTERWEATHER ADVISORY FOR |SNOW AND FREEZING RAIN...WHICH IS IN EFFECT FROM 1 AM TO 1 PM EST TUESDAY.

* PRECIPITATION TYPE: SNOW AND FREEZING RAIN.*

ACCUMULATIONS: 2 TO 4 INCHES OF SNOW AND THEN POSSIBLY 2 TENTHS OF AN INCH OF GLAZE.*

TIMING: SNOW BEGINS AROUND OR SHORTLY AFTER MIDNIGHT AND CONTINUES INTO THE MORNING RUSH HOUR. IT CHANGES TO FREEZING RAIN BETWEEN 7 AM AND 11 AM FROM SOUTH TO NORTH AND THEN PROBABLY TO NON FREEZING RAIN DURING MIDDAY OR EARLY TUESDAY AFTERNOON.*

IMPACTS: HIGH CONFIDENCE THAT TRAVEL WILL BE SLOW AND DIFFICULT TUESDAY MORNING.PRECAUTIONARY/PREPAREDNESS ACTIONS...A WINTER WEATHER ADVISORY MEANS THAT PERIODS OF SNOW...SLEET...OR FREEZING RAIN WILL CAUSE TRAVEL DIFFICULTIES. BE PREPARED FOR SLIPPERY ROADS AND LIMITED VISIBILITIES...AND USE CAUTION WHILE DRIVING.&&$DRAG

(Should be added in here)

OF GREATER CONCERN IS SNOWFALL AND OR ICE ACCUMULATION IN THELEHIGH VALLEY NORTHEASTWARD INTO SUSSEX...WARREN AND PARTS OFMORRIS COUNTIES. FOR NOW WE PLAY IT CONSERVATIVE.

USING THE NAM SOLN SOLELY...A STRIPE OF 5-8 SNOW FALL COULD OCCURFROM VCNTY KMPO TO JUST N OF FWN. WE`RE NOT ACCEPTING THISSOLN...AT LEAST NOT RIGHT NOW.

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I'm not sure the variations in advisory/nothing in NE NJ between MT Holly and Upton is more because 2 inches qualifies as an advisory in the Mt Holly zones and not in Upton or not....the snowfall alone for NYC/NE NJ won't reach 4 inches but 1-2 inches of snow combined with some sleet and FZRA may qualify for a WWA.

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per gfs this run, abe on north doesnt get abv freezing, A lot less qpf though.

Its funny how the 06Z GFS looks more like the 00Z NAM than the 06 NAM does...the off hour NAM runs have been getting so bad its almost sad...they might want to look into if perhaps some data feed is not getting in there because I swear they have gotten very bad the last 12-18 months....I'd be surprised if the 12Z NAM does not trend even colder for inland areas from the 00Z.

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Its funny how the 06Z GFS looks more like the 00Z NAM than the 06 NAM does...the off hour NAM runs have been getting so bad its almost sad...they might want to look into if perhaps some data feed is not getting in there because I swear they have gotten very bad the last 12-18 months.

yea i just added in, nyc , atleast the western side doesn't look like it gets abv freezing at all either.

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I'm not sure the variations in advisory/nothing in NE NJ between MT Holly and Upton is more because 2 inches qualifies as an advisory in the Mt Holly zones and not in Upton or not....the snowfall alone for NYC/NE NJ won't reach 4 inches but 1-2 inches of snow combined with some sleet and FZRA may qualify for a WWA.

impact (Tuesday AM commute)...Mount Holly has had a couple of advisories that have been more for impact criteria as opposed to amount.

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prb_24hicez_ge.25_2011011712f024_sm.gif

prb_24hicez_ge.25_2011011712f048_sm.gif

Mt Holly forecast for my area (see dot on map in signature):

Tonight: Snow before 5am, then snow and sleet. Low around 19. East wind around 6 mph. Chance of precipitation is 100%. New snow and sleet accumulation of 1 to 2 inches possible.

Tuesday: Snow and freezing rain before noon, then rain. High near 34. Northeast wind between 7 and 9 mph. Chance of precipitation is 100%. New ice accumulation of 0.1 to 0.3 of an inch possible. New snow accumulation of 1 to 3 inches possible.

Tuesday Night: Rain likely before 3am, then a chance of snow. Cloudy, with a low around 31. North wind between 3 and 6 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Wednesday: A chance of snow showers before 9am, then a slight chance of rain and snow showers between 9am and noon, then a slight chance of snow showers after noon. Mostly cloudy, with a high near 37. West wind between 3 and 10 mph, with gusts as high as 20 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

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I do like this blurb in the AFD

LOW PROB WE MAY EVENTUALLY NEED AN UPGRADE TO A WINTER WARNING FORNW NJ OR NE PA EITHER FOR 5-8 INCHES OF WET SNOW OR NEAR ONE HALFINCH GLAZE.

.....

MY FEELING IS THAT THIS WILL END UP MOSTLY SNOW IN NE PA AND NW NJAND WET SNOW CHANGING TO RAIN ELSEWHERE WITH A NARROW SLIVER OF .2-.4GLAZE NEAR KABE-KMMU.

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I do like this blurb in the AFD

LOW PROB WE MAY EVENTUALLY NEED AN UPGRADE TO A WINTER WARNING FORNW NJ OR NE PA EITHER FOR 5-8 INCHES OF WET SNOW OR NEAR ONE HALFINCH GLAZE.

.....

MY FEELING IS THAT THIS WILL END UP MOSTLY SNOW IN NE PA AND NW NJAND WET SNOW CHANGING TO RAIN ELSEWHERE WITH A NARROW SLIVER OF .2-.4GLAZE NEAR KABE-KMMU.

Walt Drag FTW

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Mt Holly is on top of the forecast down here. I can't find anything to quibble with what they have out.

They said about all that can be said and covered all the bases regarding possible detailed outcomes. Definitely a touchy forecast that will change hour by hour early tomorrow morning on. It may very well end up an either heavy snow or rain event with a smaller area of mixed snow sleet & freezing rain in between. Always difficult to say just how much lower levels will warm and how quickly. The retreating high argues for quicker warming but if winds keep a more northerly then easterly component then it will be a nail biter for areas N&W.

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Latest Wxsim off of 6z runs continues to paint a somewhat snowier (2" to 4" of snow before changeover then icing for most of the event) picture by Tuesday AM here in the NW Philly burbs...here is the breakdown

Flurries by 10pm

Moderate Snow by 1130pm (temp 27.6)

Heavy Snow by 330am (temp 26.9)

Heavy Snow and IP mix at 6am (temp 27.9)

Transition to IP/ZR by 8am

ZR all morning temp rises above freezing by around noon - by that time 0.99" of precip has fallen. Another .09" falls while temps are just above freezing before ending in early afternoon.

Paul

www.chescowx.com

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Latest Wxsim off of 6z runs continues to paint a somewhat snowier (2" to 4" of snow before changeover then icing for most of the event) picture by Tuesday AM here in the NW Philly burbs...here is the breakdown

Flurries by 10pm

Moderate Snow by 1130pm (temp 27.6)

Heavy Snow by 330am (temp 26.9)

Heavy Snow and IP mix at 6am (temp 27.9)

Transition to IP/ZR by 8am

ZR all morning temp rises above freezing by around noon - by that time 0.99" of precip has fallen. Another .09" falls while temps are just above freezing before ending in early afternoon.

Paul

www.chescowx.com

That sounds like no fun at all, your main worries would be power outages with this. How much would be with it being ZR accumulations wise? And the rise above freezing and plain rain really wont help promote much of any melting of the snow or IP or ZR might just have some sort of small run-off of the regular rain but not much taken away from the rest of which has already accumulated.

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Lee

I am not buying this forecast verbatim...I think the qpf may be a bit overdone and my experience shows we will probably get above freezing a little quicker then late morning. But either way I do have an automatic generator that kicks in when we lose power.

Certainly looks like a messy commute all over tomorrow

Take care

Paul

That sounds like no fun at all, your main worries would be power outages with this. How much would be with it being ZR accumulations wise? And the rise above freezing and plain rain really wont help promote much of any melting of the snow or IP or ZR might just have some sort of small run-off of the regular rain but not much taken away from the rest of which has already accumulated.

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Guest Patrick

The 11Z RUC explodes the precip up the coast from 00Z onward.

Snowfall map remains in line with NWS thinking as well.

post-177-0-92622700-1295269118.png

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Imagine if the sfc high was parked to our NW instead of retreating to the NE? As it is, the damming signature as it departs is troublesome. The arctic air in place is the key to any setup like this where the high is departing. If we had a stale air mass in place, this wouldn't even be a discussion about a threat for big icing.

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I love how the 6z GFS now shows all of Northern New Jersey staying below freezing for the entire storm tomorrow.

the 6z run did this the other day. I would lean twds the higher res models with this one but if they agree with this colder solution then it is something to watch.

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I think the NWS has a great handle on things in the PHI area in terms of changeover times from frozen to non-frozen precipitation. It should be interesting to see how things play out.

I think once you get north of Rt 422 (north of Pottstown) and north of exit 31 (Lansdale) on the PA Turnpike NE Extension the cold air will be stubborn to scour out.

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