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Sat, 31 Jan 2009
Philadelphia Winter Weather-Sat PM [2]
Tonight's GFS model has joined with the NAM model in predicting a major snow for Philadelphia on Tuesday. 7-12 inches possible. Stay tuned.
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posted: Jan 31 2009 at 11:09 pm
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Philadelphia Winter Weather- Snow for Tues?
The models have been predicting a fast moving but deep coastal low, starting in the southeastern states Monday night and intensifying along the coastline on Tuesday. Today's NOGAPS and GFS models have kept this storm fairly far offshore, with only some light snow impacting the immediate Philadelphia area.
This morning's NAM model had a more westward track of the low and more snow for our area. The latest NAM data from tonight shows an even more impressive snow possible, 5-9 inches, for Philadelphia and areas west of Philadelphia for Tuesday. Even areas in NJ will likely receive snow on this one. The NAM did better today on the cold temperatures than the GFS.
The reliability of this winter's predictions from the models has been anything but stellar. However, this is the first storm this season that is developing in the southeastern US, (as compared to the previous ones that were expected to develop from impulses that developed in the the midwest). These previous scenarios (include Alberta Clippers in this category) are notorious for being handled poorly by the models.
This would be a more classic coastal nor'easter. I'm inclined to believe the NAM on this one.
That said, with the GFS and Navy NOGAPS still with an eastward track, confidence is still low for the forecast of snow on Tuesday. Look for updates tomorrow.
Sun 2/1: Partly cloudy/sunny and milder. High 44.
posted: Jan 31 2009 at 10:30 pm
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Philadelphia Weekend Weather- Sat AM Update
High pressure will build in again this weekend, but the amplified trough that has been with us for most of the past month will relax enough to allow some slightly above normal temperatures to be with us for Sunday.
On Monday, the upper trough will reamplify and a fast moving low is expected to develop in Georgia and move up and phase with an upper disturbance moving through PA developing a very deep coastal low. The NOGAPS and the GFS has this coastal low fairly far offshore, so it's unclear whether we will get much (or any) snow from this low in Tuesday. A more westward track or faster development will mean snow for us, starting before daybreak on Tuesday.
Sat 1/31: Mostly sunny, windy and very cold. High 29.
Sun 2/1: Partly cloudy/sunny and milder. High 44.
posted: Jan 31 2009 at 9:23 am
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Fri, 30 Jan 2009Philadelphia Weekend Weather- Fri PM Update
High pressure will build in again this weekend, but the amplified trough that has been with us for most of the past month will relax enough to allow some slightly above normal temperatures to be with us for Sunday.
For the beginning of February, the trough will reamplify on Monday and a deep low is expected to bring precipitation to our area on Tuesday. The latest NAM suggests SNOW. Cold air returns for the balance of next week.
Sat 1/31: Mostly sunny, windy and very cold. High 28.
Sun 2/1: Partly sunny and milder. High 44.
posted: Jan 30 2009 at 11:25 pm
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Thu, 29 Jan 2009Philadelphia Weekend Weather- Thurs PM Update
High pressure will build in again this weekend, but the amplified trough that has been with us for most of the past month will relax enough to allow some slightly above normal temperatures to be with us for Sunday.
For the beginning of February, the trough will reamplify on Monday and a deep low is expected to bring rain to our area on Tuesday. Cold air returns for the balance of next week.
Sat 1/31: Mostly sunny, windy and very cold. High 30.
Sun 2/1: Partly sunny and milder. High 44.
posted: Jan 29 2009 at 7:49 pm
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Tue, 27 Jan 2009Philadelphia Winter Weather- Tues 7PM Update
The model runs from this morning and this afternoon are remarkably consistent with timing and amounts of precip.
That said, both models maintain that the bulk of the precipitation will hold off until later this evening and night time hours, with heavy precip starting about midnight.
Although we may wake up to 2-3 inches of snow very early Wednesday morning, the changeover will occur before daybreak, and any accumulations will quickly get beaten down by sleet, freezing rain and then all rain. The commute Wednesday morning will still be challenging due to lingering icing conditions and heavy sleet/freezing rain, especially north and west of the city.
Rain will continue through most of Wednesday, perhaps changing back to a brief period of light snow Wed evening.
posted: Jan 27 2009 at 8:13 pm
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Philadelphia Winter Weather- Tues 7AM Update
The light snow falling this morning due to over-running of warm air aloft ahead of the main low, has already exceeded the model predictions, specifically the NAM, which underestimated this early snow in last night's models.
That said, both models maintain that the bulk of the precipitation will hold off until later this evening and night time hours, with heavy precip starting about midnight. Both models put out over an inch of water falling Wednesday, mostly as sleet and then all rain.
Although we may wake up to 2-4 inches of snow Wednesday early morning, the changeover will occur before daybreak, and any accumulations will quickly get beaten down by sleet, freezing rain and then all rain. The commute Wednesday morning will still be challenging.
Rain will continue through most of Wednesday, perhaps changing back to a brief period of snow Wed evening.
The next model runs will be out later this morning. Busy day at work so I may not be able to update the website until evening.
posted: Jan 27 2009 at 7:07 am
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Mon, 26 Jan 2009Philadelphia Winter Weather- Mon 10:50 PM Update
The latest NAM data now available...here are the trends. The model delays the precipitation until later Tuesday evening, with very little during the day on Tuesday. Upper temperatures warm, but ground temperatures remain cold through Tuesday night. A period of heavy icing is possible by daybreak Wed, according to the NAM.
Tonight's latest GFS joins the NAM with delaying the heavier precipitation well into the late evening. Temperatures at the surface are very cold, with sleet and snow and considerable icing probable as rain mixes and freezes at the surface after midnight Tuesday. The change to all rain likely on Wednesday, but surface temperatures, especially north of the city, will cause significant icing.
Cold air returns at the end of the storm later Wednesday afternoon with a change back to snow before evening on Wednesday.
posted: Jan 26 2009 at 10:49 pm
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Philadelphia Winter Weather- Mon 10 PM Update
The latest NAM data now available...here are the trends. The model delays the precipitation until later Tuesday evening, with very little during the day on Tuesday. Upper temperatures warm, but ground temperatures remain cold through Tuesday night. A period of heavy icing is possible by daybreak Wed, according to the NAM.
Cold air returns at the end of the storm later Wednesday afternoon with a change back to snow before evening on Wednesday.
To really get an idea on the forecast trends, we'll have to wait for the GFS. The latest GFS data not available until about 10:45 PM.
posted: Jan 26 2009 at 10:12 pm
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Philadelphia Winter Weather Update- Mon Early PM
The latest models have another fixed precipitation event for Philadelphia. Overruning moisture will cause to light snow to form (a coating to an inch) during the daytime on Tuesday. The approaching low will bring more direct effects late Tuesday afternoon and evening with several inches of snow possible before a changeover to sleet and freezing rain after midnight. Perhaps 4 inches of snow is possible before the changeover after midnight.
The question will be how warm surface temperatures get on Wednesday, both at daybreak and during the day. While the changeover to sleet and rain is fairly certain to occur before daybreak on Wednesday, cold air damming and very cold established surface temperature may cause this mix to freeze on roadways and already fallen snow. This will cause very slippery conditions for Wednesday morning and a more extended period of icing to our north.
Cold air returns at the end of the storm later Wednesday afternoon with a change back to snow before evening on Wednesday.
Updates to follow.
posted: Jan 26 2009 at 7:52 pm
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Philadelphia Winter Weather Update- Mon AM
Latest model has light snow for Tuesday, but an eventual turnover to sleet and then rain by Wednesday. Perhaps some slippery driving Wed morning, but forget the snowstorm.
I'll keep an eye on this one.
posted: Jan 26 2009 at 7:06 am
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Sun, 25 Jan 2009Philadelphia Winter Weather Update- Sun PM
Well, the later runs of the NAM and GFS are less in agreement, with the GFS warmer than the NAM. The NAM has precip coming in sooner (early Tues) while the GFS holds it off. This is beginning to remind me of the storm several weeks ago that fell apart.
I'll keep an eye on this one.
posted: Jan 25 2009 at 7:17 pm
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Philadelphia Winter Weather Update- Sun AM
Our first likely significant snow is showing on the latest models for Tuesday into Wednesday. That said, the models have been wrong several times this season, but this is the first time the NAM and GFS have had some agreement in advance this winter.
A stalled frontal boundary to our south will allow a wave to develop and intensify as it moves east. The latest NAM has snow starting as early as Tuesday morning and increasing during the day. Several inches are possible by evening. There is the possibility that warm air will mix in changing to sleet and rain Tuesday night into Wednesday. The exact track and the degree of warming needs to be evaluated with future model runs.
Updates as needed.
A deep trough follows this storm with return to very cold weather. The position of this deep upper trough may allow another storm to affect us in the Friday time period.
Sun 1/25: Partly sunny and cold. High 33.
posted: Jan 25 2009 at 11:49 am
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Philadelphia Weekend Weather Forecast- Sat PM
The cold front passed through and cold temperatures have returned.
The upper air pattern is less amplified and the frontal boundary will be stalling to our south eventually allowing disturbances to develop and ride across the boundary causing snow or ice or rain. This is forecast for late Tuesday as light snow will transition to sleet and freezing rain and then back to snow. Difficult driving is possible Wed morning. lastest GFS has a potential snowstorm for Philadelphia on Wed. Very cold weather returns next weekend.
Sun 1/25: Partly sunny and cold. High 28.
posted: Jan 25 2009 at 3:28 am
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Sat, 24 Jan 2009Philadelphia Weekend Weather Forecast- Sat PM
The cold front passed through and cold temperatures have returned.
The upper air pattern is less amplified and the frontal boundary will be stalling to our south eventually allowing disturbances to develop and ride across the boundary causing snow or ice or rain. This is forecast for late Tuesday as light snow will transition to sleet and freezing rain. Difficult driving is possible Wed morning. Maybe some snow Thurs. Very cold weather returns next weekend.
Sun 1/25: Partly sunny and cold. High 28.
posted: Jan 24 2009 at 9:05 pm
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Fri, 23 Jan 2009Philadelphia Weekend Weather Forecast- Fri AM
Today is our January Thaw!
But our January Thaw will be short-lived because a cold front will pass through late tonight as the upper pattern reamplfies into the persistent cold trough we have had for nuch of this winter. This trough will not be as deep and the boundary will be stalling to our south eventually allowing disturbances to develop and ride across the boundary causing snow or ice. Currently, this is expected to occur next Tues or Wed.
Sat 1/24: Partly Sunny and cold. High 32.
Sun 1/25: Partly sunny and cold. High 28.
posted: Jan 23 2009 at 8:12 am
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Tue, 20 Jan 2009Philadelphia Winter Weather Outlook- Tues AM
The amplified upper trough remains with us. The models underestimated the snow yesterday and didn't capture the temperatures properly last night.
There will be some relaxation of the upper trough later this week, as a thaw might occur Thurs and Fri. (Not the significant January thaw that was depicted a week or so ago.) Amplification of the upper trough will again occur over the weekend, giving dry and cold conditions.
Sat 1/24:Tentative: Partly Sunny and cold. High 32.
Sun 1/25:Tentative: Partly sunny and cold. High 30.
posted: Jan 20 2009 at 7:37 am
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Sun, 18 Jan 2009Philadelphia Winter Weather Outook- Sun PM
A series of upper air disturbances in the cold upper flow will affect us. One of these will develop over us Monday afternoon. The models have been underestimating the snow amounts. The latest GFS has 0.12 inches water. Expect 1-2 inches of snow Monday afternoon.
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posted: Jan 18 2009 at 10:59 pm
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Sat, 17 Jan 2009Philadelphia Winter Weather Forecast- Sat AM
The amplified trough over the eastern US will maintain it's grip. Low pressure approaching and passing to our north through the Great Lakes will give the chance of light snow on Sunday, but the models are not very impressive with precip amounts. Current GFS qpf amount are 0.01 inches water, very low.
The models have shifted the storm that was forecast to move up the coast on Monday farther eastward. Much of the precip will miss us, according to the current track. (about 1 inch snow Sunday night).
Sat 1/17:Sunny and very cold in the morning. Increasing clouds during the later afternoon. High 22.
Sun 1/18:Cloudy and not as cold. Chance of light snow or flurries during the day. Somewhat heavier snow may begin in the evening, accumulating 1 inch or so. High 37.
posted: Jan 17 2009 at 8:38 am
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Fri, 16 Jan 2009Philadelphia Winter Weather Forecast- Fri PM
The amplified trough over the eastern US will maintain it's grip. Low pressure approaching and passing to our north through the Great Lakes will give the chance of light snow on Sunday, but the models are not very impressive with precip amounts.
I just want to mention that the models haven't been doing too great lately. The models were inconsistent with last week's storm that fizzled. This past Thursday's snow squalls weren't captured all that well with either model.
Speaking of the models: Of greater interest is the prospect of a coastal storm developing on Sunday night into Monday. This could provide our first significant snow, with considerably more in NJ. Will keep an eye on this.
.
Sat 1/17:Sunny and very cold in the morning. Increasing clouds during the afternoon. High 23.
Sun 1/18:Cloudy and not as cold. Chance of light snow or flurries during the day. Snow may begin in the evening. High 37.
posted: Jan 16 2009 at 9:23 pm
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Wed, 14 Jan 2009Philadelphia Winter Weather Outook- Wed PM
The extremely ampllfied upper air pattern, has started building into our area.
The latest models have a clipper disturbance moving through on Thursday and again on Saturday and Sunday. For tomorrow, Thursday, the NAM has a coating of snow for our area. The GFS is virtually dry.
For this Saturday, very little if any precip is showing with the next clipper. But this sort of thing can change.
Sat 1/17:Considerable cloudiness and very cold. Chance of flurries. High 24.
Sun 1/18:Considerable clouds. Chance of light snow flurries. High 36.
From Jan 21st through Jan 25th, the classic January thaw will occur, with mild conditions for several days. Cold and stormy weather returns after this thaw.
posted: Jan 14 2009 at 7:42 pm
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Philadelphia Winter Weather Outook- Wed AM
The extremely ampllfied upper air pattern, has started building into our area.
Very cold conditions will be with us through January 20th. Very cold and windy conditions expected through early next week, with clipper disturbances passing through causing light snow, possibly Thursday and possibly Saturday.
From Jan 21st through Jan 25th, the classic January thaw will occur, with mild conditions for several days. Cold and stormy weather returns after this thaw.
For this coming weekend, expect very cold temperatures. Very light snow possible on Saturday.
posted: Jan 14 2009 at 7:13 am
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Tue, 13 Jan 2009Philadelphia Winter Weather Outook- Tues AM
The extremely ampllfied upper air pattern, allowing a deep trough to develop in our area will allow very cold air to move into the Philadelphia area and the eastern US later this week. Very cold conditions will even affect Florida.
I believe this anomalous pattern is consistent with what was expected due to the chilling of the upper atmosphere over months due to a lull in the sunspot cycle as mentioned in my October blog. Only recently has the sun's activity begun to see signs of increase. (See my winter climate prediction from my October 17th blog entry..)
Very cold and windy conditions expected through early next week, with clipper disturbances passing through causing light snow, possibly Thursday and possibly Saturday.
posted: Jan 13 2009 at 6:52 am
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Mon, 12 Jan 2009Philadelphia Winter Weather Outook- Mon PM We need to watch this pattern since coastal storms may develop in this pattern.
An extremely ampllfied upper air pattern will allow very cold air to move into the Philadelphia area and the eastern US later this week.
posted: Jan 12 2009 at 9:15 pm
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Sat, 10 Jan 2009Philadelphia Winter Weather Update- Sat Eve Update
The temps here, northwest of the city, haven't warmed up as much as anticipated, so the turnover to plain rain hasn't occurred. Nonetheless, precipitation amounts have been very light (even less than previously expected).
The latest NAM data shows temps remaining or falling back to freezing, even in Philadelphia proper, before ending about daybreak. About a coating to an inch of snow/sleet may accumulate in the city and immediate Northern/western suburbs by daybreak.
Overall, the models didn't do too well on this storm, especially when the time frame was greater than 24 hours.
Sun 1/11: Considerable cloudiness, some sun, windy and colder. Temps drop during the day into the low 30s and into the 20s by evening.
posted: Jan 10 2009 at 10:22 pm
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Philadelphia Winter Weather Update- Early Sat AM Update
See prior discussion from Friday afternoon for detail and trends.
The 1 AM runs of the NAM and GFS continue with the current forecast: Light snow in this morning, perhaps an inch, then a break in the action during the afternoon. Warm air comes in and rain/sleet in the evening and night. Temperatures rise at night. Possibly back to a brief period of snow showers before daybreak Sunday morning. Little, if any, final accumulation in the immediate PHL/suburban areas when all is said and done.
Sat 1/10: Cloudy. Light snow in the morning. Perhaps a coating to an inch. Very little activity in the afternoon, then Rain and maybe mixed with sleet at night. Temperatures rise during the day into the mid 30s by evening. Little if any final accumulation by Sunday morning.
Sun 1/11: Becoming partly cloudy/sunny, windy and colder. Temps drop during the day through the low 30s and then into the 20s.
posted: Jan 10 2009 at 8:21 am
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Fri, 09 Jan 2009Philadelphia Winter Weather Update- Fri Eve Update
See prior discussion from this afternoon for detail and trends.
Tonight's NAM confirms the afternoon model trends: Light snow in the morning, perhaps an inch, then a break in the action during the afternoon. Warm air comes in and rain/sleet in the evening and night. Temperatures rise at night. Changes back to a brief period of snow very early Sunday morning. Little accumulation in the PHL immediate area when all is said and done.
I'll update when the GFS data comes out about 10:45PM if there are changes.
Sat 1/10: Cloudy. Light snow in the morning. Very little in the afternoon. Rain and sleet at night. Temperatures rise during the day into the mid 30s by evening.
Sun 1/11: Becoming partly cloudy, windy and colder. Temps drop during the day through the low 30s.
posted: Jan 09 2009 at 9:27 pm
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Philadelphia Winter Weather Update- Fri Afternoon Update
There are now some significant changes and uncertainty with Saturday's snow. The trends from this morning's models have snow, mostly in the afternoon, mixing with sleet and rain late afternoon and evening. The models depict warmer air aloft moving in late in the afternoon and evening, before cold air moves back in after midnight. QPF (quantity of water falling) values were similar to last night's runs, but with most precipitation occuring later-- late afternoon and evening. So, there's a delay in the development of this storm and there's a trend towards less snow and more sleet and rain in the immediate PHL area.
To add to uncertainty, the latest 1 PM run of the NAM model has almost no precipitation at all during the day on Saturay and very little sleet and rain (and then snow) at night. Less than a coating! So there are strong trends that this 'storm' may become a big hype.
The afternoon model runs are notoriously fickle and erratic, so we'll have to wait for this evening's runs. The early GFS data will be available about 10:45 PM, the NAM an hour earlier. Check back about 10:45 PM.
Sat 1/10: Forecast very uncertain: Cloudy with flurries possible early, then snow more likely developing later in the afternoon into the evening, mixing with sleet and rain in and around PHL. Precip amounts are looking much lower and warmer temps may signficantly reduce accumulations. High 32.
Sun 1/11: Mostly sunny, windy and very cold. High 31.
posted: Jan 09 2009 at 4:12 pm
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Thu, 08 Jan 2009Philadelphia Winter Weather Update- Thurs Eve Update
This evenings's model runs are have returned to over 0.60 inches water falling mostly afternoon and evening. Warm air aloft may reduce accumulations as snow mixes with sleet.
The statistical models from this morning's models are showing a strong likelihood of anywhere from 0.50 to 1.00 inches water (more in NJ).
Sat 1/10: Cloudy with light snow starting in the morning, then heavier in the afternoon. May mix with sleet, then back to snow in the evening. As much as 3-6 inches possible. High 32.
Sun 1/11: Mostly sunny, windy and very cold. High 31.
posted: Jan 08 2009 at 11:14 pm
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Philadelphia Winter Weather Update- Thurs Afternoon Update
This afternoon's model runs are less impressive with precip on Saturday, with total water amounts less than 0.20 inches (GFS model). However, the 1 PM model runs are notoriously erratic and not always reliable.
The statistical models from this morning's models are showing a strong likelihood of anywhere from 0.50 to 1.00 inches water (more in NJ).
So with the 1 PM models showing a significant decline in potential snowfall for Sat, we'll wait for tonight's model runs. Will keep the forecast tentative.
Sat 1/10: Tentative: Cloudy with snow likely. As much as 4-5 inches possible. High 32.
Sun 1/11: Mostly sunny, windy and very cold. High 31.
posted: Jan 08 2009 at 6:59 pm
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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.
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