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Philadelphia Weekend Weather and Storm Forecasts
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Miscellaneous
Mon, 31 Jan 2011
Philly Winter Weather Update- Mon 11 PM
The latest NAM and HRRR models now show only an inch or less of snow for the immediate Philadelphia area by daybreak Tuesday. The atmosphere warms in the upper levels, but the NAM continues with temperatures at or below freezing near the surface for much of the day and evening Tuesday. Very light precipitation will fall as sleet and freezing rain from about 7 AM onward on Tuesday.
If the cold NAM model is correct, a significant ice buildup is possible for Philadelphia and north/west of the city for much of Tuesday and early Tuesday night. During the daylight hours, road surfaces may be just wet, although other surfaces may develop significant ice buildup.
During the evening hours Tuesday, untreated road surfaces may become icey as well. Temps rise before daybreak Wednesday as heavy rain falls into the early afternoon.
posted: Jan 31 2011 at 10:53 pm
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Philly Winter Weather Update- Mon AM
Today's model runs have been consistent with a forecast of a warm-frontal type light snow for Tuesday in advance of the main low pressure system that will affect us on Wednesday.
The NAM is predicting 1-3 inches of snow on Tuesday morning, becoming sleet in the afternoon and then light freezing rain by Tuesday evening and then heavy rain for Wednesday. The majority of this storm will be rain for us, in marked contrast to our last storm. There is little uncertainty about this being a mostly rain event for Philadelphia on Wednesday.
What is uncertain is the amount of ice buildup late Tuesday and Tuesday night. It may be a bit dicey for the evening commute of Tuesday and possibly the early commute hours of Wednesday morning, where a freezing rain situation might make driving difficult. For areas north and west of Philadelphia, a significant ice accumulation is possible by early Wednesday morning.
So while the major part of this storm will be a mostly rain event on Wednesday, there will be an ice component for Tuesday night and early Wednesday morning. The amount of ice may be significant in areas north and west of Philadelphia. It does not appear that it will change to snow at the end.
posted: Jan 31 2011 at 7:26 am
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Sun, 30 Jan 2011Philly Winter Weather Outlook- Sun PM
Today's model runs have been consistent with a forecast of a warm-frontal type light snow for Tuesday in advance of the main low pressure system that will affect us on Wednesday.
The GFS model is predicting 2-4 inches of snow on Tuesday, becoming light freezing rain Tuesday evening and then heavy rain for Wednesday. The majority of this storm will be rain for us, in marked contrast to our last storm. There is little uncertainty about this being a mostly rain event for Philadelphia.
What is a bit dicey is the very early evening commute hours of Tuesday and possibly the very early commute hours of Wednesday, where a freezing rain situation might make driving difficult. It's not certain how much freezing precip will fall before the transition to all rain. Again, for our area, I would expect this storm to be a mostly rain event on Wednesday. It does not appear that it will change to snow at the end.
posted: Jan 30 2011 at 8:39 pm
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Sat, 29 Jan 2011Philadelphia Weekend Weather Forecast -Sat PM
The area of snow flurries is entering Philadelphia and it will be with us into the early evening. Skies clear later and it will be mostly sunny on Sunday.
As for the storm approaching Tuesday into Wednesday, it looks like we will get some light snow early on Tuesday with another warm frontal type system. The major storm for Wednesday looks much warmer in the upper atmosphere than our last storm, I do expect much of the storm to be sleet and then rain. Not much snow expected at this time.
Sun 1/30: Mostly sunny, some clouds late in the afternoon. High 35
posted: Jan 29 2011 at 2:48 pm
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Thu, 27 Jan 2011Philadelphia Weekend Weather Forecast- Thur PM
While the models didn't accurately predict the Wed morning warm frontal-type snow, the NAM was fairly accurate with the heavy snow that fell during the 6 hour period last night. Total snows were in the 14-17 inch range.
The upper air flow will bring three areas of vorticity through Philadelphia over the next three days. Clouds, light snow or flurries are predicted with the first two passing through, Friday and Saturday.
For Friday the GFS has only flurries while the NAM model cranks out an inch or so of light snow. For Saturday, both have light snow flurries. Just some clouds for Sunday.
Sat 1/29: Mostly cloudy, chance of snow flurries in the afternoon. High 36.
Sun 1/30: Some sun, increasing clouds in the afternoon. High 37.
posted: Jan 27 2011 at 5:58 pm
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Wed, 26 Jan 2011Philly Winter Weather Update- Wed 7PM
As everyone knows, the models underestimated the precipitation this morning. But the rest of the scenario seems to be verifying as predicted by the NAM model.
For the time period from now (7PM) to midnight, the NAM has been very consistent in pumping out almost 1 inch of water this six hour period! This is translating into an incredibly heavy snowfall until just past midnight. Final totals could easily approach 9-12 inches if the NAM verifies.
The latest High Resolution Rapid Refresh model predicts similar amounts (8-12) inches of snow for the Philadelphia area by the time things end before after midnight. Areas in NJ to the east, less. Areas just to the west of Philadelphia (Chester County, Upper Montgomery County) may have well over 12 inches.
posted: Jan 26 2011 at 7:34 pm
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Philly Winter Weather Update- Wed 10 AM
The storm is already more impressive than any of the models predicted last night.
The latest NAM data just available continues a cold thermal profile (for PHL airport area gridpoint). Upper atmosphere temps warm a bit early afternoon, but key temps in the lower atmosphere support wet snow, freezing rain until about 4-5 PM. Temps on the ground may warm to 35 degrees during the early afternoon.
For the time period after 6 PM tonight, the NAM has been very consistent in pumping out almost 1 inch of water in a 6 hour period! That looks like it may translate into an incredibly heavy snowfall during the evening up until midnight. Final totals could easily approach 9-12 inches if the NAM verifies.
The latest High Resolution Rapid Refresh model predicts similar amounts (9-12) inches of snow for the Philadelphia area by the time things end before after midnight. Stay tuned.
posted: Jan 26 2011 at 9:59 am
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Philly Winter Weather Update- Wed 7 AM
The storm is already more impressive than any of the models predicted last night. The NAM FOUS data from the 1 AM model run has temps remaining in the all-snow range even for Philadelphia. But the new experimental HRRR has the snow changing to freezing rain for the immediate PHL area, then back to snow after 4 PM. In past storms, the NAM FOUS has been reliable.
The same NAM FOUS data, if correct, would give us well over a foot of heavy snow by daybreak Thurs morning. Stay tuned.
posted: Jan 26 2011 at 7:43 am
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Tue, 25 Jan 2011Philly Winter Weather Outlook- Tues 9 PM
Tonight's NAM model raw data has just become available. It shows very light wet snow, freezing rain and sleet early morning and then a mix of light rain, sleet during the afternoon, changing to wet snow about 5-6 PM. Temperatures drop below freezing during the early evening as the atmosphere aloft also cools. During the evening heavy precip falls as snow, with a rapid accumulation of snow. It looks like 5-9 inches of snow falls before daybreak Thurs.)
Stay tuned!
posted: Jan 25 2011 at 9:17 pm
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Philly Winter Weather Update- Tues 1 PM
Latest computer models have a period of heavy snow Wed evening and night. Difficult to judge amounts with surfaces wet and icey from the day but 6 inches or more possible especially north and west of the city. Stay tuned!
posted: Jan 25 2011 at 1:22 pm
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Mon, 24 Jan 2011Philly Winter Weather Outlook- Mon 10 PM
Tonight's NAM model has shifted the storm well into late Wednesday and Wednesday night. The latest thermal profile is looking colder and wetter, with ice and sleet more likely and a significant snow accumulation possible by Thursday morning,
There has been considerable model run to run inconstancies and model differences. The trend today has been back towards a more intense low pressure system, similar to that predicted several days ago. Still much uncertainty.
Stay tuned!
posted: Jan 24 2011 at 10:10 pm
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Philly Winter Weather Outlook- Mon PM
The storm scenario for Wednesday continues to change, as the major part of this storm intensifies late Wednesday into Thursday night. It looks like things start as light sleet and rain early Wednesday morning, (except north and west of the city) and becomes heavy rain Wednesday afternoon. It then transitions back to snow, from west to east Wednesday evening with several inches possible when things clear out very early Thursday morning.
There has been considerable model run to run inconstancies and model differences. The trend today has been back towards a more intense low pressure system, similar to that predicted several days ago. For our area, the track and deformation of the jet continues to show mostly rain for the most of the storm, as warm air pushes in, but stay tuned!
posted: Jan 24 2011 at 8:45 pm
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Sun, 23 Jan 2011Philly Winter Weather Outlook- Sun PM
As mentioned yesterday, the storm being talked about for this week continues to remain much more of an uncertainty.
In fact, today's GFS and NAM models keep the precipitation off to our east, missing us. The NOGAPS has the storm brushing us, but brings in warm air for sleet and rain. None of the models are not predicting the explosive development that had been predicted several days ago. So the predicted big snow storm may not materialize.
That said, we certainly have seen the difficulties the models have had this season in accurately predicting snow totals in advance. (Just last week, only the 12 hour forecast range proved reliable for Friday's "storm".)
So stay tuned.
posted: Jan 23 2011 at 6:29 pm
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Sat, 22 Jan 2011Philly Winter Weather Outlook- Sat
Just as we have started to focus attention on the upcoming storm next week, the models have changed its likely timing and configuration.
It now appears that the storm will be delayed until Wednesday, instead of Tuesday, with considerable differences in track between the GFS, the EMCWF, and the NOGAPS. All show a deep storm, but most show more warm air and a less amplified jet stream, causing a mixed bag of precipitation, more rain and less snow.
That said, we certainly have seen the difficulties the models have had this season in accurately predicting snow totals in advance. (Just last week, only the 12 hour forecast range proved reliable for Friday's "storm".)
So stay tuned.
posted: Jan 22 2011 at 3:16 pm
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Fri, 21 Jan 2011Philadelphia Weekend Weather Forecast- Fri PM
High pressure will build in during the weekend, as a deep upper air trough allows cold air to spill into the area. A weak upper air disturbance will bring some mid-level clouds on Saturday morning, with some sunshine in the afternoon. Temps will be in the 20s, with winds about 10 mph.
An interesting scenario developing during the Tuesday through Wednesday timeframe next week, as an upper air low brings light snow to our area on Tuesday, then spawns the development of blocked low pressure off of the coast, giving us heavy snow Tuesday night into Wednesday. The details are changing but the likelihood of a significant snowfall is taking shape for this time period. Stay tuned.
Sat 1/22: Some mid level cloudiness in the morning, more sun in the afternoon. Breezy and very cold. High 21.
Sun 1/23: Mostly sunny, continued breezy and cold. High 27.
posted: Jan 21 2011 at 6:05 pm
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Thu, 20 Jan 2011Philly Winter Weather Update- Thur 9 PM
The latest NAM model data is in line with the experimental HRRR model. Only 1-2 inches snow tonight, ending daybreak Fri. Less in NJ.
The rest of the weekend will be very cold with highs in the 20s.
posted: Jan 20 2011 at 9:09 pm
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Philly Winter Weather Update- Thur PM
Latest model outputs for PHL airport show about .27 inches water (NAM model), the QPF value (quantity of precip falling) and 0.23 inches water (GFS model). The NAM has been remarkably consistent with its QPF value, but today, the GFS model dropped back a bit. This still translates into about 2-4 inches of snow, ending daybreak on Friday.
A new experimental model, the High Resolution Rapid Refresh model, predicts only 1-2 inches for our area, keeping the heavier snowfall in central PA. I'll look at this again later on, since this model is an ultra short range model, predicting only 15 hours ahead.
The rest of the weekend will be very cold with highs in the 20s.
posted: Jan 20 2011 at 7:42 pm
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Wed, 19 Jan 2011Philly Winter Weather Update-
Both the NAM and GFS models have been predicting a storm to move just our south late Thursday night/Friday morning and blossom off of the coast as it moves away.
Both models have remarkably similar QPF values -- approximately .30 inches water falling as snow and ending about daybreak on Friday. This translates into about 3-6 inches with 4-5 most likely.
The rest of the weekend will be very cold with highs in the 20s.
posted: Jan 19 2011 at 8:29 pm
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Sun, 16 Jan 2011Difficult Commute Tues Morning-
The models have been suggesting a difficult commute for early Tuesday morning, as a mix of precipitation is expected to start before daybreak on Tuesday. Warm air is expected to mix in at 5000 feet, but temperatures at the ground are expected to stay at or just above freezing. With precipitation commencing before any sun angle can heat through the clouds (insolation) and with ground temperatures so very cold for so long, a period of ice and freezing rain/sleet is likely, especially north and west of Philadelphia.
posted: Jan 16 2011 at 4:56 pm
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Sat, 15 Jan 2011Philadelphia Weather Update- Sat AM
A frontal boundary will pass through Saturday evening. The chance of snow showers tonight looks minimal at this time. Temps will remain below normal.
An interesting weather scenario for Tues morning, as moisture moves in perhaps before temps rise above freezing. A period of sleet and freezing rain is possible Tues morning before and during the rush hour.
Sat 1/15: Cloudy and cold. High 35.
Sun 1/16: Sunny and occasional clouds, windy and cold. High 32.
posted: Jan 15 2011 at 9:23 am
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Fri, 14 Jan 2011Philadelphia Weather Update- Fri PM
A frontal boundary will pass through Saturday evening, possibly producing some snow showers. Additional areas of vorticity will rotate through on Sunday causing some cloudiness. Temps will remain below normal.
An interesting weather scenario for Tues morning, as moisture moves in perhaps before temps rise above freezing. A period of sleet and freezing rain is possible Tues morning before and during the rush hour.
Sat 1/15: Cloudy, with a chance of snow showers in the evening. High 35.
Sun 1/16: A mix of sun and clouds, windy and cold. High 31.
posted: Jan 14 2011 at 7:50 pm
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Tue, 11 Jan 2011Philly Winter Weather Update- Tues 9PM
The latest NAM model data is just becoming available. For Philadelphia, it has 0.31 inches water falling between now and 1 AM. This is about 3-5 inches of snow for most of immediate Philadelphia, with more north and east of the city (around Trenton, eastern portions of Bucks county and northeast), less south and southwest. Areas of Chester county will have much less. The NAM has the storm dry-slotting after 1 AM, so little additional accumulation is expected around PHL during the early morning hours.
The snow should certainly be over by daybreak tomorrow.
posted: Jan 11 2011 at 9:16 pm
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Philly Winter Weather Update- Tues 7PM
This afternoon's models look very unimpressive for Philadelphia. Calling this a major storm appears to be hype.
Based on today's models, it looks like 3-5 inches is the most likely amount in and around Philadelphia. It will essentially end near daybreak tomorrow. The predictions of higher amounts look unlikely. I'll update later.
posted: Jan 11 2011 at 7:28 pm
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Philly Winter Weather Update- Tues 12PM
Both the NAM and the GFS has a minimal 3-4 inches.
Both models are confronting a situation where two storm centers redevelop into one coastal storm. I've seen past situations where this scenario is handled poorly by both models---specifically where energy transfers from the western storm to the coastal storm and almost 'jumps' over us, giving us minimal snow totals. So, unlike the storm of two weeks ago which had a single low pressure center, the snow totals for this system are very uncertain for us here.
While not a cop-out, the forecast range of 3-4 inches may be as good a guess as we can make with this storm. Later model runs today may (or may not) clarify this situation.
posted: Jan 11 2011 at 12:22 pm
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Philly Winter Weather Update- Tues 7AM
The 1 AM reruns of the GFS and NAM models continue with the differences in precipitation totals expected from tonight's storm with the NAM. The NAM continues with a significant snowfall (>8 Inches) while the GFS has a minimal 3-4 inches.
The precip differences in these models with this storm has less to do with storm track and more to do with differences in physics of the models. Both models are confronting a situation where two storm centers redevelop into one coastal storm. I've seen past situations where this scenario is handled poorly by both models---specifically where energy transfers from the western storm to the coastal storm and almost 'jumps' over us, giving us minimal snow totals. So, unlike the storm of two weeks ago which had a single low pressure center, the snow totals for this system are very uncertain for us here.
While not a cop-out, the forecast range of 3-9 inches may be as good a guess as we can make with this storm. Later model runs today may (or may not) clarify this situation.
posted: Jan 11 2011 at 7:44 am
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Mon, 10 Jan 2011Winter Weather Update- Mon 9 PM
Tonight's NAM model data has just rolled in. (Those supercomputers keep getting faster.) For PHL airport grid point, the NAM is showing about .55 inches water falling as snow which is about 8-9 inches snow, starting about 6 PM Tuesday and ending by daybreak Wed morning.
The GFS has been consistent with much lower amounts, about 4 inches. (That's why the commercial Forecasts have been saying 4-8 inches.). The average of 6 inches is most likely.
The GFS data will be available later.
posted: Jan 10 2011 at 9:26 pm
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Sun, 09 Jan 2011Winter Weather Update- Sun PM
Today's models show the development of a coastal storm, late Tuesday afternoon into Wednesday morning.
As is often the case, there are differences with the models regarding strength and speed, with the latest NAM being significantly wetter (or whiter as the case may be) than the GFS. The NAM has a major snow for us (>8 inches) while the GFS has a light snow of 2-4 inches.
10 PM update- latest NAM has snow starting tues night. >12 inches possible.
posted: Jan 09 2011 at 10:50 pm
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Winter Weather Update- Sun PM
Today's models show the development of a coastal storm, late Tuesday afternoon into Wednesday morning.
As is often the case, there are differences with the models regarding strength and speed, with the latest NAM being significantly wetter (or whiter as the case may be) than the GFS. The NAM has a major snow for us (>8 inches) while the GFS has a light snow of 2-4 inches.
We won't have a complete handle until later Monday or early Tuesday, but some snow, possibly significant, appears likely Tuesday night, ending early Wed.
posted: Jan 09 2011 at 6:49 pm
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Sat, 08 Jan 2011Winter Weather Update- Sat 7 AM
The latest NAM has dropped the snow totals back to about 1 inch for today.
posted: Jan 08 2011 at 7:52 am
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Fri, 07 Jan 2011Winter Weather Update- 10 PM
The latest NAM model now cranks out 3-5 inches of snow for Saturday.
posted: Jan 07 2011 at 10:26 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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