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Glenn F. Schreiber DMD and Glenn Schreiber is theweatherguy writing about Philadelphia Weather [radar] [surface map] [disclaimer]

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Glenn F Schreiber
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Sat, 12 Jan 2008
Storm Update - Sat 11 PM
The models are still showing temps above freezing in the immediate Philadelphia area for Sunday evening and night. The statistical models also show less than a 40% chance of snow for the immediate PHL area as well, with probabilities increasing near Allentown. Significant snow is possible in the far northern areas. That said, the temperatures above 2000 feet support snow. So it might fall as snow and then melt or mix with rain in the lower part of the atmosphere. Predicting accumulations in this scenario isn't really possible, but if the models are correct about the surface temps, this won't be much of a storm, except for the heavy rain mixed with snow.
Here are the trends as of 11 PM:
Upper atmosphere temps are remaining cold enough to support snow, BUT ground temps above freezing.
Amount of precipitation falling (QPF values) are as high as over 1.0 inches water, according to the GFS. The NAM has joined the GFS with about 1.0 inches of water.
The precip will likely reach us between 5 and 7 PM. The storm is a rapid mover.

With precipitation rates so high between 7PM and 1AM, will dynamic cooling bring temps down enough to have snow here? Don't know.
Let me say that with all the years I've been looking at snow storms, this is the first time I can remember where temperatures aloft are so low , precip rates so high, and the ground temperatures expected to be several degrees above freezing. I'll be the first to say that I don't have much confidence in calling this storm.
The storm also depends on a transfer of energy between a low in the Great Lakes and a developing low, a situation often missed by the models. There is no 'large cold high' expected to move in behind the coastal low.
Sun 1/13: Some sun early, becoming cloudy late morning. Precipitation begins as rain or rain mixed with snow about 5-7PM. Likely becoming very wet snow, but may not accumulate. Accumulations not able to be determined High 47.

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posted: Jan 12 2008 at 11:06 pm

[/weather/jan08] permanent link

Storm Update - Sat Evening
The models are still showing temps above freezing in the immediate Philadelphia area for Sunday evening and night. The statistical models also show less than a 40% chance of snow for the immediate PHL area as well, with probabilities increasing near Allentown. That said, the temperatures aloft support snow. So it might fall as snow and then melt or mix with rain in the lower part of the atmosphere. Predicting accumulations in this scenario isn't really possible.
Here are the trends:
Upper atmosphere temps are remaining cold. Ground temps above freezing.
Amount of precipitation falling (QPF values) are as high as over 1.0 inches water, according to the GFS. The NAM has about .65 inches
The precip will likely reach us late afternoon or early evening. The storm is a rapid mover.
The models haven't shown great consistency. The storm also depends on a transfer of energy between a low in the Great Lakes and a developing low, a situation often missed by the models (precipitation is sometimes much less than forecast if the energy 'skips' over us.)
Sun 1/13: Some sun early, becoming cloudy late morning. Precipitation begins as rain or rain mixed with snow. Likely becoming wet snow, but may not accumulate. Accumulations not able to be determined High 47.

Like these forecasts? Improve my Yahoo ratings by clicking on an ad of interest at the top of the page! If you receive this report via RSS feed, please visit the site http://theweatherguy.net and click. Thanks!

posted: Jan 12 2008 at 6:38 pm

[/weather/jan08] permanent link

Storm Update- Saturday AM
The latest GFS model is in and it again shows over 1 inch of precipitation for Philadelphia. (The NAM shows less) Temperatures at all levels of the atmosphere support snow, but temperatures at the ground in Philadelphia are 2 degrees above freezing. Needless to say, an error of ground temperature will make a whole world of difference here.
Here are the trends:
Upper atmosphere temps are trending colder, as more cold air aloft is forecast.
The track of the storm is now closer to the coast.
The precip will likely reach us late afternoon. The storm is a rapid mover.
That said, temperatures this morning are running lower than predicted by the models, suggesting temps tomorrow may be off. The GFS overestimates temperatures.
We need to watch this, since small changes will make a big change in the forecast. The precip will definitely change to wet snow in Philadelphia and north and west. Whether we have a winter storm will depend on ground surface temps, which are, at this time, expected to be above freezing.
The models haven't shown great consistency. Look for changes in the forecast.
Sat 1/12: Partly sunny. High 52
Sun 1/13: Some sun early, becoming cloudy late morning. Precipitation begins as wet snow late afternoon. Snow may accumulate during the evening. Accumulation amounts not certain at this time, but several inches possible, even a significant storm. High 47.

posted: Jan 12 2008 at 12:22 pm

[/weather/jan08] permanent link

Weekend Weather Forecast- Sat AM
There is still uncertainty with the expected development of the coastal storm on Sunday.
Here are the trends:
Upper atmosphere temps are trending colder, as the storm is expected to track somewhat more easterly.
As a result of the easterly track, less precipitation will reach our area. Despite the track, the major models show a surface maxima of precipitation over our area as energy from a Great Lakes low is transfered to the coastal low.
The precip will likely reach us early evening. The storm is a rapid mover.
That said, temperatures this morning are running lower than predicted by the models, suggesting temps tomorrow may be off.
The models continue to show a low pressure system developing along the coastline. Upper air temperatures will support snow, but the models suggest temperatures at the surface will not be below freezing, although there are trends towards lower temps.
We need to watch this, since small changes will make a big change in the forecast. The precip will definitely change to wet snow in Philadelphia and north and west. Whether we have a winter storm will depend on ground surface temps, which are, at this time, expected to be above freezing.
The models haven't shown great consistency. Look for changes in the forecast. This is NOT a storm that is definite.
Sat 1/12: Partly sunny. High 52
Sun 1/13: Some sun early, becoming cloudy late morning. Precipitation begins as wet snow. Snow may accumulate during the evening. Accumulations not certain at this time, but several inches possible. High 47.

posted: Jan 12 2008 at 8:32 am

[/weather/jan08] permanent link

Disclaimer: I am not a meteorologist and provide this information as a hobby and for entertainment (mostly my own :-) . While attempts are made to predict the weather as best as I can, use at your own risk! I am NOT responsible for any direct or indirect consequential injury/damages due to your use of these forecasts. Always check the NWS Official Forecast for your final plans.

The weatherguy.net home page has been visited times since October 2003.

theweatherguy's website
		Philadelphia Weekend Weather and Storm Forecasts
Glenn F. Schreiber DMD and Glenn Schreiber is theweatherguy writing about Philadelphia Weather [radar] [surface map] [disclaimer]
	About this blog theweatherguy's website, "Thoughts and comments on Philadelphia Weather and Daily Life." Glenn F Schreiber aka "theweatherguy" Photos Weather Definitions Copy link for RSS feed Links These are a few of my favorite links. National Weather Service Official Forecasts Meteorology Glossary Archives Weather Archives: 13: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 12: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 11: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 10: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 09: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 08: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 07: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 06: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 05: Apr May Jun July Aug Sept Oct Nov Dec Commentary: Miscellaneous Find	Sat, 12 Jan 2008 Storm Update - Sat 11 PM The models are still showing temps above freezing in the immediate Philadelphia area for Sunday evening and night. The statistical models also show less than a 40% chance of snow for the immediate PHL area as well, with probabilities increasing near Allentown. Significant snow is possible in the far northern areas. That said, the temperatures above 2000 feet support snow. So it might fall as snow and then melt or mix with rain in the lower part of the atmosphere. Predicting accumulations in this scenario isn't really possible, but if the models are correct about the surface temps, this won't be much of a storm, except for the heavy rain mixed with snow. Here are the trends as of 11 PM: Upper atmosphere temps are remaining cold enough to support snow, BUT ground temps above freezing. Amount of precipitation falling (QPF values) are as high as over 1.0 inches water, according to the GFS. The NAM has joined the GFS with about 1.0 inches of water. The precip will likely reach us between 5 and 7 PM. The storm is a rapid mover. With precipitation rates so high between 7PM and 1AM, will dynamic cooling bring temps down enough to have snow here? Don't know. Let me say that with all the years I've been looking at snow storms, this is the first time I can remember where temperatures aloft are so low , precip rates so high, and the ground temperatures expected to be several degrees above freezing. I'll be the first to say that I don't have much confidence in calling this storm. The storm also depends on a transfer of energy between a low in the Great Lakes and a developing low, a situation often missed by the models. There is no 'large cold high' expected to move in behind the coastal low. Sun 1/13: Some sun early, becoming cloudy late morning. Precipitation begins as rain or rain mixed with snow about 5-7PM. Likely becoming very wet snow, but may not accumulate. Accumulations not able to be determined High 47. Like these forecasts? Improve my Yahoo ratings by clicking on an ad of interest at the top of the page! If you receive this report via RSS feed, please visit the site http://theweatherguy.net and click. Thanks! posted: Jan 12 2008 at 11:06 pm [/weather/jan08] permanent link Storm Update - Sat Evening The models are still showing temps above freezing in the immediate Philadelphia area for Sunday evening and night. The statistical models also show less than a 40% chance of snow for the immediate PHL area as well, with probabilities increasing near Allentown. That said, the temperatures aloft support snow. So it might fall as snow and then melt or mix with rain in the lower part of the atmosphere. Predicting accumulations in this scenario isn't really possible. Here are the trends: Upper atmosphere temps are remaining cold. Ground temps above freezing. Amount of precipitation falling (QPF values) are as high as over 1.0 inches water, according to the GFS. The NAM has about .65 inches The precip will likely reach us late afternoon or early evening. The storm is a rapid mover. The models haven't shown great consistency. The storm also depends on a transfer of energy between a low in the Great Lakes and a developing low, a situation often missed by the models (precipitation is sometimes much less than forecast if the energy 'skips' over us.) Sun 1/13: Some sun early, becoming cloudy late morning. Precipitation begins as rain or rain mixed with snow. Likely becoming wet snow, but may not accumulate. Accumulations not able to be determined High 47. Like these forecasts? Improve my Yahoo ratings by clicking on an ad of interest at the top of the page! If you receive this report via RSS feed, please visit the site http://theweatherguy.net and click. Thanks! posted: Jan 12 2008 at 6:38 pm [/weather/jan08] permanent link Storm Update- Saturday AM The latest GFS model is in and it again shows over 1 inch of precipitation for Philadelphia. (The NAM shows less) Temperatures at all levels of the atmosphere support snow, but temperatures at the ground in Philadelphia are 2 degrees above freezing. Needless to say, an error of ground temperature will make a whole world of difference here. Here are the trends: Upper atmosphere temps are trending colder, as more cold air aloft is forecast. The track of the storm is now closer to the coast. The precip will likely reach us late afternoon. The storm is a rapid mover. That said, temperatures this morning are running lower than predicted by the models, suggesting temps tomorrow may be off. The GFS overestimates temperatures. We need to watch this, since small changes will make a big change in the forecast. The precip will definitely change to wet snow in Philadelphia and north and west. Whether we have a winter storm will depend on ground surface temps, which are, at this time, expected to be above freezing. The models haven't shown great consistency. Look for changes in the forecast. Sat 1/12: Partly sunny. High 52 Sun 1/13: Some sun early, becoming cloudy late morning. Precipitation begins as wet snow late afternoon. Snow may accumulate during the evening. Accumulation amounts not certain at this time, but several inches possible, even a significant storm. High 47. posted: Jan 12 2008 at 12:22 pm [/weather/jan08] permanent link Weekend Weather Forecast- Sat AM There is still uncertainty with the expected development of the coastal storm on Sunday. Here are the trends: Upper atmosphere temps are trending colder, as the storm is expected to track somewhat more easterly. As a result of the easterly track, less precipitation will reach our area. Despite the track, the major models show a surface maxima of precipitation over our area as energy from a Great Lakes low is transfered to the coastal low. The precip will likely reach us early evening. The storm is a rapid mover. That said, temperatures this morning are running lower than predicted by the models, suggesting temps tomorrow may be off. The models continue to show a low pressure system developing along the coastline. Upper air temperatures will support snow, but the models suggest temperatures at the surface will not be below freezing, although there are trends towards lower temps. We need to watch this, since small changes will make a big change in the forecast. The precip will definitely change to wet snow in Philadelphia and north and west. Whether we have a winter storm will depend on ground surface temps, which are, at this time, expected to be above freezing. The models haven't shown great consistency. Look for changes in the forecast. This is NOT a storm that is definite. Sat 1/12: Partly sunny. High 52 Sun 1/13: Some sun early, becoming cloudy late morning. Precipitation begins as wet snow. Snow may accumulate during the evening. Accumulations not certain at this time, but several inches possible. High 47. posted: Jan 12 2008 at 8:32 am [/weather/jan08] permanent link Disclaimer: I am not a meteorologist and provide this information as a hobby and for entertainment (mostly my own :-) . While attempts are made to predict the weather as best as I can, use at your own risk! I am NOT responsible for any direct or indirect consequential injury/damages due to your use of these forecasts. Always check the NWS Official Forecast for your final plans. The weatherguy.net home page has been visited times since October 2003.