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PHL CWA JAN 26/27 OBS and Discussion Thread


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.SHORT TERM /7 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...

-- Changed Discussion --***WATCH EXPANSION INTO NE MD...N DEL AND MUCH OF NJ EXCEPT FAR

SOUTH PROBABLE AT 1115 AM PENDING NEW GFS***

PLEASE GIVE US TIME ON THIS. WE ALL SAW THE NEW 12Z NAM WITH HUGE

SNOWGROWTH AND QPF AMTS UNDER THE DEFORMATION ZONE NW OF THE NAMS

MORE DEFINED 500MB STRUCTURE. COULD BE THUNDER SNOW WED EVE. COLLAB

WITH HPC AT 8AM REGARDING MY UNCERTAINTY FURTHER NW IN NE PA AND

NW NJ BUT AWAITING ALL THE MODELS BEFORE ANY POSSIBLE TRIM THERE.

FOCUS "MAY" BE SHIFTING SEWD 30 MILES.

MORE AT 1115 AM.

http://forecast.weather.gov/product.php?site=NWS&issuedby=PHI&product=AFD&format=CI&version=1&glossary=0&highlight=off

That's essentially a post from the NWS to this thread, lol. I can understand them not wanting to simply rush in and make changes, though. Seems to make sense to wait another hour or so for the GFS and if there's confirmation, then to extend the WS Watches S/E-ward. Starting to look interesting...

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Where was his map?

DT updated his map for NC/VA/MD/DE at 8:45 am this morning and said he'd update later this morning for points to the N. However, you can see his contours extending into parts of NJ/PA and it's clear that most of NJ/EPA is in his 6-12" swath, while areas to the S/E of Philly in NJ are in his 3-6" swath.

http://www.wxrisk.com/

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12z NAM, per WxCaster...

For PNE, 1.15" all levels below freezing

0.68" in 3 hours, 0.98" in 6 hours.

For PHL, 1.26" all levels below freezing. Although the surface rises to 31.9 as the precip is starting.

0.75" in 3 hours, 1.02" in 6 hours.

For DYL, 0.71" all levels below freezing.

0.39" in 3 hours, 0.64" in 6 hours.

For NYC, 0.87" all levels below freezing while precip is falling.

0.85" in 9 hours.

For DCA, 1.13" entire column above surface below freezing, surface starts out at 33.6 but falls to 32.5 when heavy precip hits.

0.86" in 6 hours.

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.SHORT TERM /7 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...

-- Changed Discussion --***WATCH EXPANSION INTO NE MD...N DEL AND MUCH OF NJ EXCEPT FAR

SOUTH PROBABLE AT 1115 AM PENDING NEW GFS***

PLEASE GIVE US TIME ON THIS. WE ALL SAW THE NEW 12Z NAM WITH HUGE

SNOWGROWTH AND QPF AMTS UNDER THE DEFORMATION ZONE NW OF THE NAMS

MORE DEFINED 500MB STRUCTURE. COULD BE THUNDER SNOW WED EVE. COLLAB

WITH HPC AT 8AM REGARDING MY UNCERTAINTY FURTHER NW IN NE PA AND

NW NJ BUT AWAITING ALL THE MODELS BEFORE ANY POSSIBLE TRIM THERE.

FOCUS "MAY" BE SHIFTING SEWD 30 MILES.

MORE AT 1115 AM.

http://forecast.weat...0&highlight=off

That's essentially a post from the NWS to this thread, lol. I can understand them not wanting to simply rush in and make changes, though. Seems to make sense to wait another hour or so for the GFS and if there's confirmation, then to extend the WS Watches S/E-ward. Starting to look interesting...

That's Walt Drag, the latest addition to the Mt. Holly All-Star team.

Continuing on from Walt:

"WHILE THERE ARE CERTAINLY STILL SOME DETAILS THAT NEED TO BE

WORKED OUT FOR THE UPCOMING EVENT...THERE IS NOW ENOUGH EVIDENCE

IN THE OPERATIONAL AND ENSEMBLES RUNS TO START PUTTING TOGETHER A

FRAMEWORK. WITH DRY AIR IN PLACE TO START...THE TIMING OF THE

PRECIPITATION WAS SLOWED DOWN SOME TUESDAY NIGHT. FOR MOST AREAS

THAT SEE THE PRECIPITATION...SURFACE TEMPERATURES SHOULD STILL BE

ABOVE FREEZING...SO MAINLY RAIN IS EXPECTED. PATCHY FREEZING RAIN

IS POSSIBLE FOR NORTHEAST MARYLAND AND SOUTHEAST

PENNSYLVANIA...BUT THE PRECIPITATION CHANCES DO WARRANT HITTING

THIS TOO HARD.

ELSEWHERE...SOME CLEARING IN THE EVENING WILL FADE BY INCREASING

CLOUDINESS. THE CLEARING SHOULD ALLOW FOR SOME RADIATIONAL COOLING

IN THE EVENING...AND THIS MAY RESULT IN LOWS BEING CLOSER TO THE

COOLER GFS MOS NUMBERS.

PRECIPITATION SHOULD PROGRESS NORTH INTO THE DRIER AIR WEDNESDAY...

MAKING IT INTO THE NORTHERN ZONES BY LATE WEDNESDAY AFTERNOON. BASED

ON THE 850 MB LOW TRACK...IT WOULD APPEAR AS THOUGH MOST OF SOUTHERN

AND CENTRAL NEW JERSEY...NORTHEAST MARYLAND AND DELAWARE WOULD BE

WARMING TO THE POINT WHERE SNOWFLAKE PRODUCTION WOULD BECOME

DIFFICULT.

IN THESE AREAS...A MAINLY RAIN EVENT IS EXPECTED FOR THE DAY

WEDNESDAY. AS PRECIPITABLE WATER VALUES APPROACH ONE INCH NEAR KACY

WEDNESDAY AFTERNOON (WHICH IS 2 STANDARD DEVIATIONS ABOVE NORMAL)...

HEAVY RAIN BECOMES POSSIBLE. THIS MAY NOT BE MENTIONED YET AS ONLY

NUISANCE FLOODING WOULD BE EXPECTED.

FURTHER NORTHWEST...THE COLUMN STARTS COLD ENOUGH FOR SNOW...BUT ALL

MODELS ARE SHOWING A WARM LAYER AROUND 6000 FEET...WHICH COULD

RESULT IN SLEET AS WELL. SO...FOR THE DAY WEDNESDAY...MOST OF THE

QPF NORTH AND WEST OF PHILADELPHIA COULD FALL IN THE FORM OF SNOW

AND SLEET. AT THIS JUNCTURE...THE SNOW AND SLEET AMOUNTS WOULD LOOK

TO BE LESS THAN 4 INCHES THROUGH DUSK WEDNESDAY.

THE ABOVE DOES CONTAIN SOME UNCERTAINTY...AS INDIVIDUAL OPERATIONAL

RUNS SHOW A SIGNIFICANT SPREAD IN THE AMOUNT OF LOW LEVEL WARMING.

BECAUSE OF THIS...A BLENDED APPROACH WAS USED FOR HIGH TEMPERATURES

WEDNESDAY.

THE EVENT STARTS TO BECOME MORE INTERESTING LATE WEDNESDAY INTO

WEDNESDAY NIGHT. AS THE MID LEVEL CLOSED LOW APPROACHES THE AREA...

A COUPLE OF THINGS HAPPEN. FIRST...THE COLUMN ITSELF GETS COLDER DUE

TO DYNAMIC COOLING. BASED ON A BLEND APPROACH TO THE COLUMN

TEMPERATURE PROFILES...THIS COULD BE ENOUGH FOR AREAS SEEING RAIN TO

CHANGE TO SNOW DURING THE EVENING ACROSS NORTHEAST MARYLAND...

NORTHERN DELAWARE...AS WELL AS SOUTHWEST AND CENTRAL NEW JERSEY,

COULD BE THUNDER SNOW AND 1 TO 2 INCH PER HOUR SNOWFALL RATES FOR

SEVERAL HOURS WITHIN 30 MI EITHER SIDE OF I95.

WINDS WILL INCREASE AS THE SURFACE LOW APPROACHES WEDNESDAY

AFTERNOON. MODEL SOUNDINGS SUGGEST 35 TO 40 KNOTS OF WIND WILL BE

AVAILABLE AT THE TOP OF THE INVERSION AS THE SURFACE LOW GETS GOING.

FOR NOW...WILL INDICATE THE POTENTIAL FOR WINDS TO GUST TO 35 TO 40

MPH...BUT IT IS TOO EARLY TO CONSIDER WIND HEADLINES AT THIS TIME."

And that's him going conservative and not buying the 12Z NAM hook, line, and sinker. We'll see more with the 12Z GFS.

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DT updated his map for NC/VA/MD/DE at 8:45 am this morning and said he'd update later this morning for points to the N. However, you can see his contours extending into parts of NJ/PA and it's clear that most of NJ/EPA is in his 6-12" swath, while areas to the S/E of Philly in NJ are in his 3-6" swath.

http://www.wxrisk.com/

thanks

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Yeah, quite the gradient there. But let's see if the other 12z models follow suit, or have more precip to the northwest of the NAM's sharp cutoff.

Was prepped for a foot up our way.... we'll see.

Hey - can you send me the code you used to set up your wunderground sig? Mine just displays a link....

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That's essentially a post from the NWS to this thread, lol. I can understand them not wanting to simply rush in and make changes, though. Seems to make sense to wait another hour or so for the GFS and if there's confirmation, then to extend the WS Watches S/E-ward. Starting to look interesting...

I thought the exact same thing. Who else would they be directly addressing to give them time on the forecast? Certainly not your average person who catches the evening news forecast.

The gradients on these storms over the last year have been ridiculous. It is a forecaster's nightmare I'm sure! :arrowhead:

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I thought the exact same thing. Who else would they be directly addressing to give them time on the forecast? Certainly not your average person who catches the evening news forecast.

The gradients on these storms over the last year have been ridiculous. It is a forecaster's nightmare I'm sure! :arrowhead:

Tony (rainshadow) and Walt (Walt Drag) are both registered members here, along with Mike Gorse (MGorse). Tony and Walt wrote the disco--Walt the part that we're talking about. Not sure if they can post at work (lol), but if they can see the board, message received. Thanks guys!

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Tony (rainshadow) and Walt (Walt Drag) are both registered members here, along with Mike Gorse (MGorse). Tony and Walt wrote the disco--Walt the part that we're talking about. Not sure if they can post at work (lol), but if they can see the board, message received. Thanks guys!

Message might also be aimed at local media outlets...who try to coordinate to get latest watches warnings out as they do their noontime broadcasts and afternoon radio packages...

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