theweatherguy's website
Philadelphia Weekend Weather and Storm Forecasts
About this blog
theweatherguy's website,
"Thoughts and comments on Philadelphia Weather and Daily Life."
aka "theweatherguy"
Copy link for RSS feed
These are a few of my favorite links. Meteorology Glossary
Weather Archives:
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
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
Commentary:
Miscellaneous
Fri, 28 Feb 2014
Philadelphia Weekend Weather Forecast - Fri PM
March will come in like a lion. The cold air mass over us will provide continued cold temperatures on Saturday. An approaching frontal boundary on Sunday will bring clouds followed by light rain towards evening. The frontal boundary is expected to sink to our south during the nighttime hours and by Monday morning a developing wave along the frontal boundary will bring snow. The GFS model cranks out quite a bit of precipitation, as snow, ending Monday evening.
Of all of the weather 'events' of this winter, this potential snowfall has the greatest amount of uncertainty regarding precipitation amounts and precipitation type (snow sleet freezing rain). With some of the energy still off of the CA coastline, an accurate prediction is not possible at this time. The interplay between cold air moving in and moisture approaching from the southwest will be complex and slight changes will result in big weather differences. Additionally, location will be a factor, where 50 miles can make a significant difference in heavy snow vs sleet vs freezing rain. Stay tuned.
Sat 3/1: Sunny in the morning. Some cloudiness mixes in during the afternoon. High 30.
Sun 3/2: Cloudy with rain or sleet developing late afternoon. High 37. Sleet, rain or freezing rain changes to snow at night, towards Monday morning. Snow, 6 inches or more during Monday. Stay tuned.
posted: Feb 28 2014 at 4:30 pm
[/weather/feb14] permanent link
Mon, 17 Feb 2014Philly Winter Weather Update - Mon 11 PM
snow totals for tomorrow looking very uni mpressive. maybe an inch.
posted: Feb 17 2014 at 10:52 pm
[/weather/feb14] permanent link
Philly Winter Weather Update - Mon 5 PM
This afternoon's models are looking less impressive. Based on the afternoon model runs, expect only 2-3 inches.
posted: Feb 17 2014 at 5:12 pm
[/weather/feb14] permanent link
Philly Winter Weather Update - Mon 12 PM
Once again, the Philadelphia area will be threatened by snow. The latest NAM model shows a small disturbance moving across our area, but undergoing intensification as it reaches the coast. QPF values over 0.60 inches water, falling as snow. The GFS has much less intensification and much lower QPF values (0.25). This winter, the NAM has been remarkably good at predicting snowfall. So right now, 3-6+ inches of snow possible for our area, starting before daybreak and ending late morning.
Both models have snow starting before daybreak, so we will wake up to about 3-4 inches of snow. Updates later.
posted: Feb 17 2014 at 12:43 pm
[/weather/feb14] permanent link
Fri, 14 Feb 2014Philadelphia Weekend Weather Forecast - Fri PM
Low pressure moving to our south on Saturday will bring snow to our area. The NAM has the snow in the afternoon, while the GFS has has snow in the morning and afternoon. Both models crank out about .30 inches water, but temps near or above freezing and insolation through clouds with the higher February sun will limit accumulations on roadways. 2-4 inches looks possible on surfaces other than roadways.
A cold front moves through after the low passes, dropping temperatures for Saturday night through Monday. A significant warming trend starts midweek.
Sat 2/15: Cloudy with snow, 2-4 inches on grassy surfaces. Deep cold returns at night.
Sun 2/16: Sunny and very cold. High 28.
posted: Feb 14 2014 at 7:32 pm
[/weather/feb14] permanent link
Thu, 13 Feb 2014Philly Winter Weather Update - Thurs 4 PM
The latest NAM has become available- another 4-6 inches of snow tonight! Temperatures to get colder and support a change back to snow.
Even more incredible- the NAM is showing about 3-5 inches of snow for Saturday morning!
posted: Feb 13 2014 at 5:07 pm
[/weather/feb14] permanent link
Philly Winter Weather Update - Thurs 11 AM
The QPF values for the NAM were a much closer to the snowfall totals this morning compared to the GFS model. In the Chestnut Hill area, we have about 10 inches of snow.
The latest NAM model data has little if anything for the afternoon with temps near or above freezing. The NAM shows snow starting again this evening as temperatures fall- another 3-5 inches of snow this evening by about midnight!
Even more incredible- the NAM is showing about 3 inches of snow for Saturday morning!
posted: Feb 13 2014 at 11:02 am
[/weather/feb14] permanent link
Wed, 12 Feb 2014Philly Winter Weather Update - Wed 7 PM
Still huge differences in the models. If the NAM is correct, we will wake up tomorrow to a foot of snow with heavy snow falling. If the GFS is correct, we will wake up to 3 or 4 inches. Both have a changeover to sleet and rain during the day, then a few inches of snow Thursday night.
In past years, huge differences between the GFS and the NAM models have often resulted in storms did not live up to the hype. Will be interesting to see how things play out. The next model runs come out about 9 PM and 10:30 PM tonight.
posted: Feb 12 2014 at 7:24 pm
[/weather/feb14] permanent link
Tue, 11 Feb 2014Philly Winter Weather Update - Tue 11 PM
Big differences between NAM and GFS models- the latest GFS has only a few inches of snow mixing with sleet during the day.
In past years, huge differences between the GFS and the NAM models have often resulted in storms that fizzled out and did not live up to the hype. Will be interesting to see if things come into better agreement tomorrow.
posted: Feb 11 2014 at 10:51 pm
[/weather/feb14] permanent link
Philly Winter Weather Update - Tue 10 PM
Big differences between NAM and GFS models, with the NAM predicting colder temperatures and significantly more snow. A fair amount of snow will be on the ground by daybreak Thursday and continue through the morning, tapering in the afternoon, with additional wrap around snow in the evening.
This coming storm is a more typical nor'easter than the other systems that have made this winter so 'distinguished'. With that comes all the uncertainty of track and temperature. The NAM has done better this winter with the other storms. The latest NAM data just available shows quite a storm with at least 12-17 inches of heavy snow. The GFS is warmer (sleet) during the day. Both models dry slot us in the afternoon with light snow returning in the evening.
posted: Feb 11 2014 at 9:40 pm
[/weather/feb14] permanent link
Fri, 07 Feb 2014Philadelphia Weekend Weather Forecast - Fri PM
An overall cold pattern will be with is for the coming week. The current configuration of the jet stream is preventing the models from reliably forecasting more than a few days in advance. Even for the coming weekend, the GFS is showing snow late Sunday (2-3 inches) while the NAM shows nothing.
An Alberta clipper system will pass over us on Sunday. It's unclear whether there will be enough moisture to allow for any snow.
Sat 2/8: Mostly cloudy and cold. High 30.
Sun 2/9: Cloudy. High 35. Chance of light snow late in the day, possibly 1-3 inches by midnight.
posted: Feb 07 2014 at 8:15 pm
[/weather/feb14] permanent link
Mon, 03 Feb 2014Philly Winter Weather Update - Mon 10 AM
Latest NAM model continues with almost 1 inch of water (QPF= quantity of precipitation falling) between 7AM and about 4 PM.
Apparently, it can snow with 1000-500 mb thickness levels above 540! Interestingly, the NWS forecast discussion last night about 10PM addressed this question and I appreciated hearing their explanation. So a whopper of a snowfall this is turning out to be!
posted: Feb 03 2014 at 10:07 am
[/weather/feb14] permanent link
Sun, 02 Feb 2014Philly Winter Weather Update - Sun 10 PM
Latest NAM model has increased QPF to over an inch. Still maintains marginal temps for snow and a bit warm in the upper atmosphere.
It would not surprise me if the storm is more of a messy mix of snow, sleet and rain during the time of heaviest precipitation in the morning. So the bottom line-- the predicted high snow total for this storm is not that certain. Could be a whopper in snow totals or could be a bust.
posted: Feb 02 2014 at 10:03 pm
[/weather/feb14] permanent link
Philly Winter Weather Update - Sun 6 PM
Low pressure will move up along a stalled frontal boundary to our south with precipitation starting about 3AM Monday and continuing through early afternoon on Monday.
The models continue to crank out significant amounts of water falling tomorrow morning. QPF values are now in the 0.80 inch range. The big question in my mind- will the temperatures really support snow for our area?? The models keep the critical temperatures at or below freezing in the lower 10,000 feet of the atmosphere. HOWEVER, 500-1000 mb thickness levels, which reflect the coldness and density of the upper levels of the atmosphere are predicted to be significantly warmer than those that usually support snow in our area. Thickness levels are predicted to fall during the daytime, but during the time of maximum precipitation, that parameter just seems a bit warm to me.
I'm sure the NWS knows why it's predicting snow, but it would not surprise me if the storm has more of a messy mix of sleet and rain during the time of heaviest precipitation. So the bottom line-- the predicted snow total for this storm is not that clear-cut this time around.
posted: Feb 02 2014 at 6:30 pm
[/weather/feb14] permanent link
Philly Winter Weather Update - Sun 6 PM
Low pressure will move up along a stalled frontal boundary to our south with precipitation starting about 3AM Monday and continuing through early afternoon on Monday.
The models continue to crank out significant amounts of water falling tomorrow morning. QPF values are now in the 0.80 inch range. The big question in my mind- will the temperatures really support snow for our area?? The models keep the critical temperatures at or below freezing in the lower 10,000 feet of the atmosphere. HOWEVER, 500-1000 mb thickness levels, which reflect the coldness and density of the upper levels of the atmosphere are predicted to be significantly warmer than those that usually support snow in our area. Thickness levels are predicted to fall during the daytime, but during the time of maximum precipitation, that parameter just seems a bit warm to me.
I'm sure the NWS knows why it's predicting snow, but it would not surprise me if the storm has more of a messy mix of sleet and rain during the time of heaviest precipitation. So the bottom line-- this is storm and the predicted snow totals are not that clear-cut this time around.
posted: Feb 02 2014 at 6:27 pm
[/weather/feb14] permanent link
Philly Winter Weather Update - Sun 8 AM
Low pressure will move up along a stalled frontal boundary to our south with precipitation starting about 3AM Monday and continuing until about noon or so.
The NAM has consistently produced about 0.60-0.70 inches water QPF for the event with the GFS somewhat lower. The big question mark will be the vertical temperature profile of the atmosphere and whether this falls as snow or a mix. The NAM brings temperatures under 10,000 feet to near or below freezing but temperatures in the upper atmosphere remain marginally too warm for snow at PHL. (We have had snow fall recently with this thermal profile, but often it gets mixed with rain or sleet.)
Temperatures in the warm upper atmosphere are expected to fall as the morning continues, so a turn-over to snow is expected, sometime in the mid-morning. Surface temperatures at the freezing level of 32 and marginal temperatures in the upper atmosphere for snow formation for much of the storm will result in very wet snow possibly mixed with sleet, heavy and quite different than recent storms.
Roadways, already covered with salt and near-freezing temperatures will result in low slushy, messy accumulations. Grassy surfaces more likely to pickup higher accumulations. Too many factors to guess the exact accumulation, but 4 inches on grassy surfaces possible with less on roadways. As always, colder areas to the immediate north and west of PHL will have greater accumulations. Areas far northwest will be colder, but will miss the main slug of precipitation.
posted: Feb 02 2014 at 8:08 am
[/weather/feb14] permanent link
Sat, 01 Feb 2014Philly Winter Weather Update - Sat 1 PM
As mentioned last night, there's been an upper air pattern change which distills down to the likelihood of frontal boundaries stalling just to our south. When this sort of pattern sets up, whether it be summer or winter, areas near the stalled front become exposed to low pressure waves that develop and move along the stalled frontal boundary.
The front that moves through Sunday has been expected to stall in the Virginias with a low pressure wave riding up along the front. Originally, our area was to be too far north to be affected, but the latest model runs are showing the low pressure wave to more directly affect our area. The latest NAM shows a QPF of over 0.70 inches water for PHL which translates into 10+ inches. The temperature profile (snow vs rain) is unclear, but the latest NAM favors snow Philadelphia and northward. Stay tuned.
posted: Feb 01 2014 at 1:25 pm
[/weather/feb14] 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.