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PHL CWA JAN 26/27 OBS and Discussion Thread


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the ones he posted are 10:1, I posted the ones with ratios because they will be lower, the 10:1 maps usually are way over done on the WRF but here their unrealistic selves are for the area

Vicious gradients there. Going from 2" to 20" in about 50-60 miles.

SREF a little farther west and way more precip to the west when compared to 9z.

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15z SREF has a nice increase in snow accum probablily in area. 4 inch in 12 hour likely accross area. Some 25% chance of 8" in 12-hour starting to show up.

http://www.meteo.psu...robsnwloop.html

The ETA members made a huge jump from the 9z run, the old school ETA operational model also huge jump NW with qpf, 18z NAM will probably follow suit

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Hey Noreaster07 whats your thinking on the Reading area? we were told to expect 5-10" this morning now its 1-3" around here

I don't really forecast too much anymore, my original thinking was 6-10, today made me cut that back in mind to 4-8 for Berks, but if there is a very tight gradient (which I think was over done on the 12z american models) don't be surprised if NW sections (Bernville and NW) of Berks only get like 2-4, while, southeast (Birdsboro and SE) Berks could rake in 7-10"

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Quick question, since I can't interpret VV's and the physics invloved, is there a possibility of low level convection some where in NJ?

Absolutely. Thundersnow is definitely on the table with the level of dynamics we're talking about.

f39.gif

That's some of what's depicted as falling in the upper right image. If you look on the NCEP site at the H7 (700mb) level:

nam_700_036m.gif

look at the tightly packed red lines under the closed contour of the H7 low (over NE MD, NJ, SE PA)--that is omega, which is defined as "A term used to describe vertical motion in the atmosphere. The "omega equation" used in numerical weather models is composed of two terms, the "differential vorticity advection" term and the "thickness advection" term. Put more simply, omega is determined by the amount of spin (or large scale rotation) and warm (or cold) advection present in the atmosphere. On a weather forecast chart, high values of omega (or a strong omega field) relate to upward vertical motion (UVV) in the atmosphere. If this upward vertical motion is strong enough and in a sufficiently moist airmass, precipitation results."

This means that the air in these "high omega" areas is rapidly rising, and that convective potential is there. With a bombing low and being in the CCB, I would definitely think that convection and thunder is definitely possible under this deformation band, whereever it sets up.

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18z NAM snowfall

8-12 makes it pretty far north well west of SE PA nudges midway north into York County but dives south to NE sections of Baltimore cuts over to Wilmington, DE, kisses PHL airport up to Maguire AFB before turning south ACY

4-8 is rule of thumb for entire region line runs well north of Harrisburg, to Hazleton to PA NE point border with NJ and NY,

8-12 doesn't start again til eastern sections of LI

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Hmm ... Mount Holly now thinking the heaviest snows are in NJ?

NJZ001-007>010-PAZ054-055-060>062-068-069-261015-

/O.EXT.KPHI.WS.A.0003.110126T1500Z-110127T0900Z/

SUSSEX-WARREN-MORRIS-HUNTERDON-SOMERSET-CARBON-MONROE-BERKS-

LEHIGH-NORTHAMPTON-MONTGOMERY-BUCKS-

INCLUDING THE CITIES OF...NEWTON...WASHINGTON...MORRISTOWN...

FLEMINGTON...SOMERVILLE...JIM THORPE...STROUDSBURG...READING...

ALLENTOWN...BETHLEHEM...EASTON...NORRISTOWN...DOYLESTOWN

331 PM EST TUE JAN 25 2011...WINTER STORM WATCH NOW IN EFFECT FROM WEDNESDAY MORNING

THROUGH LATE WEDNESDAY NIGHT...

THE WINTER STORM WATCH IS NOW IN EFFECT FROM WEDNESDAY MORNING

THROUGH LATE WEDNESDAY NIGHT.

* PRECIPITATION TYPE: SNOW...WITH POSSIBLY SOME SLEET OR RAIN

MIXED IN DURING THE DAY ON WEDNESDAY.

* ACCUMULATIONS: 4 TO 10 INCHES WITH THE HIGHEST AMOUNTS MOST

LIKELY IN NEW JERSEY.

* TIMING: SNOW WILL SPREAD FROM SOUTH TO NORTH BETWEEN 7 AM AND 1

PM...WITH THE HEAVIEST SNOW EXPECTED BETWEEN 5 PM AND MIDNIGHT.

SNOWFALL RATES COULD AVERAGE 1 TO 2 INCHES PER HOUR. SNOW WILL

END BEFORE THE START OF THE MORNING COMMUTE ON THURSDAY.

* IMPACTS: THE WEDNESDAY EVENING COMMUTE SHOULD BE AFFECTED AS

ACCUMULATING SNOW FALLS. TRAVEL WILL BECOME INCREASINGLY MORE

DIFFICULT AS THE EVENING COMMUTE PROGRESSES. THE THURSDAY

MORNING COMMUTE SHOULD ALSO BE AFFECTED BECAUSE OF RESIDUAL

CLEANUP OF WEDNESDAYS SNOWFALL.

* CONFIDENCE: CONFIDENCE ON SNOWFALL AMOUNTS AT OR ABOVE 6

INCHES IN THE POCONOS AND FAR NORTHWEST NEW JERSEY IS A LITTLE

LESS THAN YESTERDAY DUE TO A SOUTHEASTWARD SHIFT IN STORM

EVOLUTION. CONFIDENCE FROM ALLENTOWN TO TRENTON FOR A

SUBSTANTIAL WINTER EVENT IS ABOVE AVERAGE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT

SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.

CONTINUE TO MONITOR THE LATEST FORECASTS.

&&

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Absolutely. Thundersnow is definitely on the table with the level of dynamics we're talking about.

f39.gif

That's some of what's depicted as falling in the upper right image. If you look on the NCEP site at the H7 (700mb) level:

nam_700_036m.gif

look at the tightly packed red lines under the closed contour of the H7 low (over NE MD, NJ, SE PA)--that is omega, which is defined as "A term used to describe vertical motion in the atmosphere. The "omega equation" used in numerical weather models is composed of two terms, the "differential vorticity advection" term and the "thickness advection" term. Put more simply, omega is determined by the amount of spin (or large scale rotation) and warm (or cold) advection present in the atmosphere. On a weather forecast chart, high values of omega (or a strong omega field) relate to upward vertical motion (UVV) in the atmosphere. If this upward vertical motion is strong enough and in a sufficiently moist airmass, precipitation results."

This means that the air in these "high omega" areas is rapidly rising, and that convective potential is there. With a bombing low and being in the CCB, I would definitely think that convection and thunder is definitely possible under this deformation band, whereever it sets up.

Thanks, I always wondered what height level to look at.for some clue. I'm assuming the red numbers in the closed off low are pretty imprexxive.

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NW NJ....if you look at the Mt Holly forecast snow maps you will see there thinking...see above

Hmm ... Mount Holly now thinking the heaviest snows are in NJ?

NJZ001-007>010-PAZ054-055-060>062-068-069-261015-

/O.EXT.KPHI.WS.A.0003.110126T1500Z-110127T0900Z/

SUSSEX-WARREN-MORRIS-HUNTERDON-SOMERSET-CARBON-MONROE-BERKS-

LEHIGH-NORTHAMPTON-MONTGOMERY-BUCKS-

INCLUDING THE CITIES OF...NEWTON...WASHINGTON...MORRISTOWN...

FLEMINGTON...SOMERVILLE...JIM THORPE...STROUDSBURG...READING...

ALLENTOWN...BETHLEHEM...EASTON...NORRISTOWN...DOYLESTOWN

331 PM EST TUE JAN 25 2011...WINTER STORM WATCH NOW IN EFFECT FROM WEDNESDAY MORNING

THROUGH LATE WEDNESDAY NIGHT...

THE WINTER STORM WATCH IS NOW IN EFFECT FROM WEDNESDAY MORNING

THROUGH LATE WEDNESDAY NIGHT.

* PRECIPITATION TYPE: SNOW...WITH POSSIBLY SOME SLEET OR RAIN

MIXED IN DURING THE DAY ON WEDNESDAY.

* ACCUMULATIONS: 4 TO 10 INCHES WITH THE HIGHEST AMOUNTS MOST

LIKELY IN NEW JERSEY.

* TIMING: SNOW WILL SPREAD FROM SOUTH TO NORTH BETWEEN 7 AM AND 1

PM...WITH THE HEAVIEST SNOW EXPECTED BETWEEN 5 PM AND MIDNIGHT.

SNOWFALL RATES COULD AVERAGE 1 TO 2 INCHES PER HOUR. SNOW WILL

END BEFORE THE START OF THE MORNING COMMUTE ON THURSDAY.

* IMPACTS: THE WEDNESDAY EVENING COMMUTE SHOULD BE AFFECTED AS

ACCUMULATING SNOW FALLS. TRAVEL WILL BECOME INCREASINGLY MORE

DIFFICULT AS THE EVENING COMMUTE PROGRESSES. THE THURSDAY

MORNING COMMUTE SHOULD ALSO BE AFFECTED BECAUSE OF RESIDUAL

CLEANUP OF WEDNESDAYS SNOWFALL.

* CONFIDENCE: CONFIDENCE ON SNOWFALL AMOUNTS AT OR ABOVE 6

INCHES IN THE POCONOS AND FAR NORTHWEST NEW JERSEY IS A LITTLE

LESS THAN YESTERDAY DUE TO A SOUTHEASTWARD SHIFT IN STORM

EVOLUTION. CONFIDENCE FROM ALLENTOWN TO TRENTON FOR A

SUBSTANTIAL WINTER EVENT IS ABOVE AVERAGE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT

SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.

CONTINUE TO MONITOR THE LATEST FORECASTS.

&&

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Hmm ... Mount Holly now thinking the heaviest snows are in NJ?

NJZ001-007>010-PAZ054-055-060>062-068-069-261015-

/O.EXT.KPHI.WS.A.0003.110126T1500Z-110127T0900Z/

SUSSEX-WARREN-MORRIS-HUNTERDON-SOMERSET-CARBON-MONROE-BERKS-

LEHIGH-NORTHAMPTON-MONTGOMERY-BUCKS-

INCLUDING THE CITIES OF...NEWTON...WASHINGTON...MORRISTOWN...

FLEMINGTON...SOMERVILLE...JIM THORPE...STROUDSBURG...READING...

ALLENTOWN...BETHLEHEM...EASTON...NORRISTOWN...DOYLESTOWN

331 PM EST TUE JAN 25 2011...WINTER STORM WATCH NOW IN EFFECT FROM WEDNESDAY MORNING

THROUGH LATE WEDNESDAY NIGHT...

THE WINTER STORM WATCH IS NOW IN EFFECT FROM WEDNESDAY MORNING

THROUGH LATE WEDNESDAY NIGHT.

* PRECIPITATION TYPE: SNOW...WITH POSSIBLY SOME SLEET OR RAIN

MIXED IN DURING THE DAY ON WEDNESDAY.

* ACCUMULATIONS: 4 TO 10 INCHES WITH THE HIGHEST AMOUNTS MOST

LIKELY IN NEW JERSEY.

* TIMING: SNOW WILL SPREAD FROM SOUTH TO NORTH BETWEEN 7 AM AND 1

PM...WITH THE HEAVIEST SNOW EXPECTED BETWEEN 5 PM AND MIDNIGHT.

SNOWFALL RATES COULD AVERAGE 1 TO 2 INCHES PER HOUR. SNOW WILL

END BEFORE THE START OF THE MORNING COMMUTE ON THURSDAY.

* IMPACTS: THE WEDNESDAY EVENING COMMUTE SHOULD BE AFFECTED AS

ACCUMULATING SNOW FALLS. TRAVEL WILL BECOME INCREASINGLY MORE

DIFFICULT AS THE EVENING COMMUTE PROGRESSES. THE THURSDAY

MORNING COMMUTE SHOULD ALSO BE AFFECTED BECAUSE OF RESIDUAL

CLEANUP OF WEDNESDAYS SNOWFALL.

* CONFIDENCE: CONFIDENCE ON SNOWFALL AMOUNTS AT OR ABOVE 6

INCHES IN THE POCONOS AND FAR NORTHWEST NEW JERSEY IS A LITTLE

LESS THAN YESTERDAY DUE TO A SOUTHEASTWARD SHIFT IN STORM

EVOLUTION. CONFIDENCE FROM ALLENTOWN TO TRENTON FOR A

SUBSTANTIAL WINTER EVENT IS ABOVE AVERAGE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT

SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.

CONTINUE TO MONITOR THE LATEST FORECASTS.

&&

Yep, they've decreased snow amounts North and West of the cities on the point and click forecasts. about an hour ago they had us at 4 - 8", now down to 3 - 5".

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