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Wed, 28 Feb 2007
March Comes in as a Lion
A heavy rain producer for Thursday night into Friday. The NAM has over 2.5 inches water, the GFS has over 1.5 inches. The rain ends during the morning Friday. A cold front will sweep through later Friday, bringing back colder weather to our area for the weekend.
Sat 3/3: Partly sunny with a chance of showers. WINDY and colder. High 45.
Sun 3/4: Mostly sunny, breezy and cold. High 44.
posted: Feb 28 2007 at 7:22 pm
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Tue, 27 Feb 2007Week Weather Outlook
Milder temperatures, but unsettled conditions: Strong low pressure will move through Thursday through Friday, giving us heavy rain, especially early Friday morning. A cold front will sweep through later Friday, bringing back colder weather to our area.
Sat 3/3: Partly sunny with a chance of showers. Windy and colder. High 45.
Sun 3/4: Mostly sunny, breezy and cold. High 44.
posted: Feb 27 2007 at 6:52 pm
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Sun, 25 Feb 2007Winter Storm Update- Sun PM
Latest NAM-WRF just became available....
The worst part of the 'storm' has already occurred. For the balance of the night, another 0.25 inches of water will fall, first as snow, then sleet about midnight and then back to snow before daybreak. Much of the storm will be over by rush hour. Expect another inch or or accumulation in the city. Not much ice or freezing rain expected, just sleet and snow.
posted: Feb 25 2007 at 9:15 pm
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Winter Storm Update- Sun Early Afternoon
See my earlier forecast.
The latest GFS available shows a somewhat colder model solution with perhaps more sleet and snow and less freezing rain. The GFS agrees with the earlier NAM model, with a total QPF value of 0.65 inches water falling, mostly during the later afternoon and evening hours.
Temperatures hover near freezing (31-33) through the storm for the general Philadelphia area. The models differ slightly with the temperatures at 5000 and 7000 feet, which determines the snow/sleet/rain combination. Both models have temperatures aloft not supporting snow by midnight; the latest GFS has a change back to snow around daybreak, while the NAM is a bit later.
The moisture aloft has almost reached us by 1:20 PM, so snow may start before my previous timeframe of 3 PM. Base on the cold temperatures of the latest GFS, I'm raising the accumulations to 2-4 slushy inches on grassy areas by Monday morning for Philadelphia, and back to 4-6 inches north and west.
What should concern us most is the travel conditions Monday morning. Once daylight hours occur, icing will melt on the roadways this time of year: solar insolation is very strong this time of year, even with clouds. So leaving for work a bit later will probably be doable, even if there's a 2-4 inch accumulation of snow and sleet off road.
Next NAM-WRF model output will become available about 9:00 PM tonight. I'll update around that time.
posted: Feb 25 2007 at 1:26 pm
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Winter Storm Update- Sun AM
The models continue to advertise a mixed precipitation event, starting later this afternoon. However there have been some trends apparent since last night. Here they are:
1. The actual low temperatures last night were higher than previously predicted. Temperatures are starting very close to freezing, unlike the storm on Valentines day.
2. The model's QPF values, the amount of water falling, has decreased somewhat over recent model runs and is significantly less than the Valentines day storm.
3. The storm is coming from the west, with less development expected along the coastline.
4. The ground surface temperatures are not as cold as the last storm.
Towards icing problems, the storm will be occurring during the night time hours.
Taking into account these factors, we may luck out and the amount of icing could be significantly less than our recent last storm. Put another way, I think we may get more wet conditions than ice in the immediate Philadelphia area and whatever falls (wet snow, sleet, rain) will be hitting marginally freezing surfaces. (Conditions in the normally colder western/northern suburbs will be much worse.)
Sun 2/25: Bright skies very early, then becoming cloudy with a mix of wet snow and sleet starting between 3-6 PM, changing to freezing rain and plain rain in Philadelphia. About 1 inch slush accumulation on roadways in the immediate Philadelphia area. Driving conditions in Philadelphia will be passable Monday morning, but areas to the north and west will be difficult.
posted: Feb 25 2007 at 8:45 am
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Sat, 24 Feb 2007Winter Storm Update- Sat PM
Low pressure is expected to move across our area from the west late Sunday, with precipitation reaching us around 3-6 PM on Sunday. There are differences between the models, with the NAM-WRF model being much colder and wetter than the GFS.
Let me go through the differences: While both models have precip starting late afternoon. The GFS is warmer aloft than the NAM- the NAM starts things as snow, while the GFS starts things as sleet. The GFS continues with sleet changing to freezing rain with a total precipitation of about 0.60 inches water, then back to snow flurries. The NAM, on the otherhand, has a change to sleet and some freezing rain, but has a changeover back to snow before daybreak Monday with greater storm development and snowfall amounts. The NAM has over 1.00 inch of water falling as a mix of snow, sleet and freezing rain, then with light snow showers possible into early Monday afternoon.
The NAM has the rain/snow line right around Philadelphia...PHL airport has slightly warmer conditions than PNE airport and more snowfall north. Areas to the north and west may have a significant snowfall of 6+ inches with ice accumulation.
Sun 2/25: Bright skies very early, then becoming cloudy with a mix of snow and sleet starting between 3-6 PM, changing to freezing rain later. Possibly 2-4 inches accumulation before a shift to mostly freezing rain with higher amounts north and west. Difficult driving conditions likely Monday morning, especially north and west.
posted: Feb 24 2007 at 10:20 pm
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Ice to Freezing Rain to Snow- Sunday thru Monday- Sat AM Update
During the winter storm last Wednesday, the NAM-WRF did very well in predicting the precipitation type. (The GFS was too warm.)
Last night's NAM (and GFS) has sleet and freezing rain arriving late Sunday afternoon and continuing through Sunday night into Monday morning. Mid morning on Monday, light sleet and rain changes back to snow with some accumulation possible.
Like the last storm, the amount of snow is going to be less important than the difficult travel conditions expected during late Sunday into Monday.
Sat 2/24: Sunny. Windy and cold. High 39
Sun 2/25: Some sun very early, then cloudy with sleet and freezing rain likely starting between 2-4 PM. Icy conditions possible after sunset. High 35. Difficult driving conditions possible Monday morning.
posted: Feb 24 2007 at 8:20 am
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Fri, 23 Feb 2007Weekend Forecast- Difficult weather possible late Sunday- Fri Early PM
Windy weather and cold temperatures to continue on Saturday. Low pressure approaches on Sunday. Temperatures aloft won't support snow, but temperatures at the surface may result in freezing rain.
The current trend is for [freezing] rain to start in the afternoon, but there's uncertainty about the exact timing. Travel conditions may be poor Sunday night and early Monday.
Sat 2/24: Sunny. Windy and cold. High 39
Sun 2/25: Cloudy with sleet and possibly freezing rain later mid-day to the afternoon. High 36.
I'll update tomorrow.
posted: Feb 23 2007 at 9:13 pm
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Thu, 22 Feb 2007Weather Outlook and Weekend Forecast- Thurs AM
Another clipper disturbance will move through today, dragging a cold front through. Rain showers likely, possibly some snow showers this evening as the clipper redevelops off of the coastline. Colder weather returns Friday into Saturday before a deep low pressure moves over us on Sunday. Early Sunday, we may see some sleet before changing to rain.
Sat 2/24: Sunny. Windy and cold. High 37
Sun 2/25: Cloudy with sleet possible early, then rain, possibly heavy. High 36.
posted: Feb 22 2007 at 7:56 am
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Wed, 21 Feb 2007Weather Outlook- Wednesday PM
Another clipper disturbance will move through on Thursday. Rain showers and possibly snow showers later in the afternoon as the clipper redevelops off of the coastline. Colder weather returns Friday into Saturday before a deep low pressure moves over us on Sunday. Early Sunday, we may see some sleet before changing to rain.
Sat 2/24: Mostly sunny. Increasing clouds later in the afternoon. High 40
Sun 2/25: Cloudy with sleet possible early, then rain, possibly heavy. High 42.
posted: Feb 21 2007 at 9:16 pm
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Tue, 20 Feb 2007Weather Outlook- Tues.
A clipper disturbance will bring showers to our area this evening. Another disturbance may bring us some wet snow Thursday evening. Near normal temperatures with highs in the 40s should be with us through the weekend.
Sat 2/24: Mostly sunny. High 40
Sun 2/25: Mostly cloudy. Chance of showers in the afternoon. High 40.
posted: Feb 20 2007 at 6:58 am
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Mon, 19 Feb 2007Weather Outlook- Monday
A transitional period where the amplified pattern of very cold air over our area will relax significantly allowing milder temperatures and small disturbances to move near us. Nothing too exciting...showers possible later Tuesday, possibly some wet snow before daybreak Wednesday. Other periods of clouds later in the week. We'll see the return of 40 degree temperatures during the day.
Sat 2/24: Cloudy and milder. High 48.
Sun 2/25: Cloudy with showers. High 46.
posted: Feb 19 2007 at 7:37 am
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Sun, 18 Feb 2007Weekend Weather Forecast & Week Outlook [Updated Sun AM]
The storm off the coast, will bring in windy conditions by 10 AM through Monday. Colder temperatures later as an arctic front moves through about 5 PM, possibly with snow showers. Monday will be cold and then temperatures moderate for the balance of the week.
A weak disturbance in the northwesterly flow (clipper-like) will bring the chance of a mix or wet snow late Tuesday night into daybreak Wednesday. A small accumulation (1 inch) possible.
The rest of the week looks uneventful at this moment. (The rain storm originally predicted for Thursday won't happen...shunted to our south. Another storm possible for next Sunday afternoon, likely rain.
Sun 2/18: A mix of clouds and sun. Becoming WINDY after 10 AM. Chance of snow showers about 5PM. High 35.
posted: Feb 18 2007 at 8:19 am
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Weekend Weather Forecast & Week Outlook
The storm off the coast, will bring in windy conditions by 10 AM through Monday. Colder temperatures later through Monday will moderate somewhat for the balance of the week.
A weak disturbance in the northwesterly flow (clipper-like) will bring the chance of a mix or wet snow late Tuesday night into daybreak Wednesday. A small accumulation (1 inch) possible.
The rest of the week looks uneventful at this moment. (The rain storm originally predicted for Thursday won't happen...shunted to our south. Another storm possible for next Sunday afternoon, likely rain.
Sun 2/18: A mix of clouds and sun. Becoming WINDY after 10 AM. High 35.
posted: Feb 18 2007 at 7:53 am
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Fri, 16 Feb 2007Weekend Weather Outlook- Fri Afternoon
A weak Alberta clipper type disturbance will move through our area Saturday night. The models are down-playing any precipitation with this system, but some flurries are possible. The clipper will develop into a small storm, but far enough off the coast just to give us windy conditions on Sunday.
Sat 2/17: Partly sunny in the morning, becoming mostly cloudy in the afternoon. Chance of flurries at night. High 37.
Sun 2/18: After some morning clouds, becoming partly to mostly sunny. WINDY. High 35.
A relative warmup is coming next week, about Thursday. Rain likely with our next storm.
posted: Feb 16 2007 at 5:10 pm
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Thu, 15 Feb 2007Weekend Weather Outlook- Thurs PM
High pressure will build in behind the storm that departed today. A cold, northwesterly upper flow will be with us for the weekend. Small disturbances (Alberta clipper type) will be embedded in the northwesterly flow. The GFS has one disturbance approaching Saturday afternoon and another approaching later Sunday. Latest models have this feature very weak, probably not producing anything.
Sat 2/17: Partly sunny in the morning, becoming mostly cloudy later in the afternoon. High 37.
Sun 2/18: Mostly sunny. High 38.
posted: Feb 15 2007 at 7:14 pm
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Wed, 14 Feb 2007Weekend Weather Outlook- Wed PM
High pressure will build in behind the storm that departed today. A cold, northwesterly upper flow will be with us for the weekend. Small disturbances (Alberta clipper type) will be embedded in the northwesterly flow. The GFS has one disturbance approaching Saturday afternoon and another approaching later Sunday. A chance of light flurries with each of these disturbances.
Sat 2/17: Partly sunny in the morning, slight increase in cloudiness during the afternoon with a chance of flurries late. High 34.
Sun 2/18: Partly sunny and windy. High 34.
posted: Feb 14 2007 at 4:27 pm
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Storm Update [2] - Wed AM
Temperatures in Philadelphia and north/west are running much below model guidance this morning. Temperature here is 23.5, having fallen since 6AM. Cold air temperature advection is occurring in this area and I don't expect temperatures to warm up above freezing in Philadelphia and north/west.
posted: Feb 14 2007 at 8:38 am
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Storm Update - Wed AM
Sleet and freezing Rain are falling at this time. High winds, and heavy precipitation rates at this time are causing some flooding on roadways.
The model data has the heaviest freezing rain this morning along with the highest wind gusts. GFS LAMPS statistics has the temps only hitting 32 in Philadelphia. Precipitation ends about 1 PM this afternoon. Things should improve after that time, but windy and cold conditions follow.
That's it for this storm. I hope you've enjoyed my forecasts. I've enjoyed providing them!
posted: Feb 14 2007 at 6:48 am
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Tue, 13 Feb 2007Storm Update - Tues 9:30 PM
Sleet and freezing rain are falling at this time in Philadelphia.
Latest NAM-WRF model data just became available. No change in the forecast. Freezing rain continues through early morning Wednesday in Philadelphia. Freezing rain will be heavy during the morning before changing to plain rain about 9 AM. Significant icing expected, especially north and west where temperatures may not get above freezing at all. Dangerous conditions possible.
Temperatures will rise above freezing in Philadelphia during the morning (about 8-9AM) changing freezing rain to all rain. Heavy rain expected with flooding likely. (Almost an inch of rain expected in a six hour period during the morning.) Latest GFS LAMP MOS data shows that temperatures will not get much above freezing in Philadelphia and will start dropping again after 1 PM Wednesday afternoon.
Temperatures drop rapidly after 1 PM Wednesday with rain tapering off, likely changing to some snow. VERY WINDY. Things freeze over late Wednesday afternoon into evening. Bitter cold Wednesday night.
The GFS data is available in about an hour. I'm not staying up for it :)
posted: Feb 13 2007 at 9:38 pm
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Update - Tues 6 PM
No real change with the models run at 1 PM today with following differences: The GFS has little or no snow at the end of this storm Wednesday afternoon. The NAM has about 1 inch possible. Here's the forecast from this morning, basically still valid:
Temperatures rise in the upper atmosphere earlier in the evening, with snow mixing with sleet and changing over to sleet and then freezing rain between 7-10 PM tonight. (later north and west)
Freezing rain after midnight, becoming heavy freezing rain before daybreak Wednesday continuing into Wednesday morning, with possibly flooding rains. Windy.
Temperatures will rise above freezing in Philadelphia during the morning (about 8-9AM) changing freezing rain to all rain. Areas north and west may have a prolonged period of heavy severe freezing rain. WINDY. The freezing rain will create serious problems later tonight into Wed morning. Flooding Wednesday morning will compound these issues.
Temperatures drop rapidly after 1 PM Wednesday with rain tapering off, possibly some snow. VERY WINDY. Things freeze over late Wednesday afternoon into evening. Bitter cold Wednesday night.
The newest model runs will become available about 9:40 PM. I'll update at that time.
posted: Feb 13 2007 at 6:33 pm
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Weather Update- Tues 2PM
I'm updating this from an office computer...so not sure if this will format well. Somehow it is possible that the models aren't doing well with this storm. We'll have to see. Updates later if I make it home. :-)
I have had an opportunity to check the models and it seems that the NAM is much colder than the GFS. Both have similar amounts of water falling and both support a change to sleet and rain this evening. There is a sense that the secondary low off of the coast hasn't formed yet, so it remains to be seen how this is going to play out.
posted: Feb 13 2007 at 1:13 pm
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About this light snow this morning...
The GFS from last night has this light snow this morning (the NAM doesn't). Not much is really expected to accumulate before this afternoon and later this afternoon. (despite its forboding appearance) As energy shifts to the coastal storm, this light snow should lighten up mid-day before becoming heavier later in the afternoon.
posted: Feb 13 2007 at 7:29 am
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What's wrong with the local news/weather?
I was watching the local news last night. They have the reporters standing there with snow shovels talking about a snowstorm, despite the fact that you're really going to need a boat/ice-breaker on Wednesday. Their own weather forecasters say something different than their own reporters. Go figure. No wonder people are disillusioned and confused with the local weather reports.
To toot my own horn, I got rid of the snow emphasis with my forecast Sunday evening. Accuweather and the local stations took a lot longer to realize this is really going to be a sleet, ice and rain deal.
posted: Feb 13 2007 at 7:03 am
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Storm Update- Tues Early AM
Looking over last night's 1 AM re-run of the models. The NAM-WRF has become similar to the early evening GFS, with light snow with small accumulation this afternoon into this evening, temperatures warming aloft to change-over to sleet early evening, followed by a prolonged period of sleet and then heavy rain and this rain will be freezing rain until sometime Wednesday morning. Serious icing likely.
Here's what's new with the 1 AM models: The NAM has prolonged the precipitation, similar to the 7PM GFS into the afternoon/evening Wednesday with a changeover to snow and a rapid drop temperature Wed afternoon and evening. Several inches possible toward the end of the storm Wed evening, along with a freeze-over of standing water late. Instead, the 1 AM GFS has all the rain/freezing rain ending abruptly in the early afternoon Wednesday after 2 inches of water fall in a six hour period Wed morning! Wow.
With winter weather, the average of the two models often works very well and that translates into the a similar forecast I issued late last night. Here it is again, with modifications:
Light snow Tuesday afternoon...it cranks out .18 inches water (1-2 inches snow) by evening Tuesday. Temperatures rise in the upper atmosphere earlier in the evening, with snow mixing with sleet and changing over to sleet occuring between 7-10 PM Tuesday.
Sleet becomes freezing rain starting after midnight, becoming heavy. Very heavy rain, probably freezing rain, before daybreak Wednesday continuing into Wednesday morning, possibly flooding rains. Windy.
Temperatures will rise above freezing in Philadelphia during the morning, changing freezing rain to all rain. Areas north and west may have a prolonged period of heavy severe freezing rain. WINDY.
Temperatures drop rapidly about 1 PM Wednesday with rain becoming snow again. VERY WINDY. Possible 2-3 inches snow late Wednesday afternoon into the evening Things freeze over late Wednesday afternoon into evening. Bitter cold Wednesday night.
Still a roller coaster. Next model runs will be out later this morning. I have Internet access at work, but I may not be able to update this website until this evening (if I make it home! :) Updates this evening or earlier if I can.
posted: Feb 13 2007 at 6:50 am
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Mon, 12 Feb 2007Storm Update- GFS Model - Mon Late PM Update
Here's the GFS data just becoming available. Some differences between the GFS and NAM-WRF. Most of my regular readers know I prefer the GFS model over the NAM. Here is the latest:
The GFS has more snow Tuesday afternoon than the NAM or its previous runs....it cranks out .028 inches water (2-3 inches snow) BEFORE evening Tuesday. Temperatures rise in the upper atmosphere earlier in the evening, with mixing with sleet occuring between 7-10 PM Tuesday.
Freezing rain starting after midnight, but it has temperatures very warm at the surface by daybreak on Wednesday, so freezing rain should be mostly rain early morning. Very heavy rain before daybreak (0.89 inches water)
HEAVY rain (1.33 inches water) during the morning on Wednesday with high winds. Flooding conditions possible. Temperatures drop rapidly early afternoon Wednesday with rain becoming snow again. Possible 1-2 inches snow late Wednesday afternoon. Windy. Things freeze over late Wednesday afternoon. Bitter cold Wednesday night.
Wow, what a roller coaster! Gonna be interesting! Updates tomorrow morning.
posted: Feb 12 2007 at 10:54 pm
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Light Snow then Sleet Ice and HEAVY Rain - Mon PM Update
Not much has changed since this morning. The upper atmosphere is going to be too warm for snow a short time after is starts Tues eve and the difficulties with this storm will depend on whether the ground warms above freezing.
The raw FOUS data from the tonight's NAM-WRF just became available. Here's the scoop and the trends-
The NAM shows only a light dusting (0.04 inches water) before 7PM Tuesday. That's a light dusting of snow. The drive home shouldn't be too bad Tuesday evening
By midnight, we have about 2 or so inches of snow on the ground, but it will change over to sleet and freezing rain, as the upper atmosphere becomes too warm to support snow just after midnight. Ground temperatures are expected to be below freezing, so sleet and rain will freeze, especially north and west of city. A significant accumulation of ice is possible before daybreak on Wednesday IF the models are correct about the temperatures on the ground.
By 7AM Wednesday, temperatures should move above freezing in Philadelphia, although areas north and west may remain below freezing. HEAVY rain (0.80" water) is predicted to fall in the morning on Wednesday. Depending upon temperatures, it could be a terrible ice storm or just rain storm at that time. Any snow that fell will disappear or become slush with that much rain. If temps remain below freezing in the northern and western suburbs, serious travel problems will result Wednesday morning.
The NAM suggests a brief period of snow again late Wednesday as temperatures rapidly drop late afternoon. This light snow at the end, with pooling water and slush will freeze Wednesday night becoming a different sort of ice problem late Wednesday night and Thursday morning.
The GFS model has been similar to the WRF-NAM with this storm. Its new data won't be available for another hour.
Here's what I'm noticing: The temperatures being predicted by the NAM for right now seem too cold for what the current observations actually are. Perhaps the temperatures when the rain falls late Tuesday night will also be warmer than predicted? That would make things a lot better around here. I'll update tomorrow morning.
posted: Feb 12 2007 at 9:56 pm
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An Ice Storm instead of a Snow storm? - Monday AM Update
The models continue with a change to sleet and rain about midnight Tuesday night. The big issue near Philadelphia will not be the snow-rain line but rather the surface temperatures allowing icing conditions in many areas, both in Philadelphia and especially north and west.
The latest models has some light snow and flurries during the day on Tuesday, not amounting to much. First real snow of about 1 inch will be around drive time Tuesday late afternoon. Snow will become heavier during the evening hours maybe accumulating another 2-3 inches, but will change to sleet and freezing rain both in the city and to our immediate north and west.
Heavy rain will be falling early Wednesday morning in most areas around Philadelphia and immediate suburbs. Whether it will continue to freeze on the ground is the concern in this storm
The big question will be the temperature of the ground/surface. Cold air trapped at the surface from weeks of cold temperatures may allow a significant ice storm to occur in our area before temps rise above freezing later Wednesday morning. This ground freezing potential will occur both in Philadelphia and especially north and west. Above freezing temps should occur in Philadephia by daybreak on Wednesday, but areas north and west may continue to have prolonged icing conditions. Getting above freezing temps in these areas may be delayed.
Again right now, the real concern is an ice storm instead of a snow storm. Predicting exact amounts of snow on the ground at the end completely misses the point.
posted: Feb 12 2007 at 7:28 am
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Sun, 11 Feb 2007Snow turning to Freezing Rain- Sunday PM Update
This afternoon's model runs continue the idea that the coastal low will now form right over the Delmarva area Tuesday night, too close to allow much cold air at 5000 feet to remain entrenched in the storm in Philadelphia.
While the snow will start in the late afternoon Tuesday, allowing about 1-2 inches by rush hour Tuesday, and another 1-2 inches Tuesday evening, temps in the upper atmosphere will warm, causing a change to sleet and freezing rain after midnight. By Wednesday morning, heavy rain will be falling, according to the current models. The big question will be the temperature of the ground/surface. Cold air trapped at the surface from weeks of cold temperatures may allow a significant ice storm to occur in our area before temps rise above freezing later Wednesday. Then cold air comes back in Wednesday night, producing more freezing.
Right now, the real concern is an ice storm instead of a snow storm. This is a big shift from yesterday, where the storm was to form in along the NC coast. Updates later and tomorrow. By the way, next weekend looks very very cold.
posted: Feb 11 2007 at 7:57 pm
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Change in forecast- Snow turning to Rain? - Sun Afternoon
The trend towards warm air moving into our area due to the low pressure developing closer to the coastline seems to be evident in this morning's GFS and NAM-WRF models. Last night's statistical and NAM models suggested this trend.
Based on this morning's models, light snow, starting during the late afternoon on Tuesday will turn to sleet and then heavy rain by Wednesday morning. Based on this scenario, icing, especially in the northern and western suburbs is possible, but snow accumulations will be very limited and difficult to call. So stormy conditions but you may not need the snow plow.
This storm is still 3 days away...we've all seen that things can change dramatically in this time frame. Stay tuned! :-)
posted: Feb 11 2007 at 12:45 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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