Thursday, July 2, 2015

Thursday Night Holiday Weekend Weather Update: Not a Good Trend

Well, it appears now the trend is not in favor of excellent weather for this holiday weekend. As I discussed in my post earlier in the week, we are dealing with a large scale pattern supportive of unsettled weather along with a stalled front to the south of us. I explained how based on how upper air energy interacts with this front will determine if we are wet or dry. The trends in the last 24 hours have been stronger with the upper level energy thus the low pressure system is projected to develop more to the north on Saturday. This means the chance of showers and more clouds than sun.

Lets take a look..

Old GFS for Saturday..

New GFS (other models including the Euro trending north)..

This is NOT the trend I want to see 24 hours out.

Look at the difference in the "Dig" in the upper air energy projection compared to earlier runs..

Old GFS..

New GFS..

It might be hard to see but the bottom image has a sharper dig to it and that is helping bring this low pressure north more along with the stalled front. 

Here is the bottom line:

  • There is an increased chance of rain for Saturday the 4th. 
  • This threat of showers is mainly during the day not at night
  • Expect mostly cloudy conditions Saturday
  • Skies should clear by the time the fireworks go off Saturday night 
  • Sunday looks like a beautiful day 

Thanks for checking in. If anything changes in tonight model runs I will update tomorrow. Enjoy the holiday weekend!

Weekend Weather Looking Good So Far!

Weekend weather update will be live later tonight! Looks like the unsettled weather MIGHT stay south. Of course interpreting model error will be a big part of this. Currently the models keep us dry but I will evaluate how they could change. 

Tuesday, June 30, 2015

Tuesday Morning: Taking a Look at this Week Through the Holiday Weekend

A tricky forecast is in store for the next five days, especially as we head towards the 4th of July. This is all due to the overall synoptic (large scale) pattern that will be in place over the region this week. Looking below you can see a pattern that is charactorized by a western ridge and eastern trough. If this looks like a pattern that is more common in the winter you are correct! In fact, that is why you are seeing temps on the cooler side as the trough over the east brings in cooler air from Canada. 

What this pattern is going to end up being responsible for is multiple upper level disturbances and front crossing through the area. This is what is going to make the forecast difficult. Every model will handle each disturbance differently especially as we get closer to the weekend so the solutions could range from a Sunny 4th to a rainy 4th. At this time I am not calling for rain on the weekend, but acknowledge it could be possible. That is why I will have to have antoher update as the weekend closes in. 

First lets focus on today into tonight as a warm front will cross into the area...

This will give us a chance at showers tonight into tomorrow morning but then should clear for the bulk of the day Wednesday. 

The weather systems corresponding cold front then crosses through Wednesday night but there will be limited shower activity at that time. 

The very difficult part of this forcast comes as that frontal boundry stalls just to our south late in the week. Anytime you have a stalled front, it acts as a boundry between warmer and colder air. This can cause unsettled weather when you get upper level disturbances that spin up this warm and cold air creating precipitation. The problem is every model is handleing this differently. For example lets look at the Canadian..

It models the upper level disturbances will interact with the front and bring rain into the area for Friday and Saturday. In fact, you can see it has two low pressure centers forming as a result of this.

The GFS on the other hand keeps this all to the south..

Again this all will depend on where and how the upper level energy enters the pattern. As an example you can see how in the Canadian example it is modeling a strong wave of upper level energy as seen by the deep yellows and reds near the area..

The GFS much flatter, thus not as wet at the surface..

And there you have it guys, the 4th of July weekend's fate rests on what model ends up being correct! Stay tuned I will update on this as we get closer to Thursday.

Friday, June 26, 2015

Weekend Update: Rain,Rain and More Rain

The rain is going to move in very late tonight/early Saturday morning. as a low pressure develops along a front over our area. The image below is valid for Saturday..

By the time we get to Sunday morning there should still be some lingering showers with heavy rain to the north..

This storm should exit Sunday morning so as the day goes on the weather should improve. I don't expect sunshine but the main rain threat is Saturday.

Total rainfall amounts..

Thats all for now, stay dry!

Thursday, June 25, 2015

Thursday Weather Note

Good morning everyone. We have a big pattern change that is going to take shape this weekend and last through at least next week. What this means is we will see peroids of rain tonight into Friday morning. Then again on Saturday and Sunday. In fact the whole weekend could be a washout. After this unsettled weather moves through we are going to be in a period of temperatures cooler than normal all of next week. That means low to mid 70's!

I am going to have more detail on this in my weekend weather update which will be out by tomorrow morning. Before then, I will leave you with this..

Image above shows the pattern change with a big ridge of high pressure out west and a trough now in the east valid Monday. Heck we even have a nice negative NAO with the high pressure over Greenland. If only this was winter!

More later. 

Tuesday, June 23, 2015

*Strong to Severe Thunderstorms to Effect Area this Afternoon*

Good morning everyone. It looks like we just might still have the dynamics in place for some pretty big storms as we head into this afternoon. As you walk outside today you will notice how hot and humid it is. Heat index values will reach the mid to high 90's in spots ahead of an approaching cold front that will cause these storms to fire up. Below you can see the current radar scan that shows our area of storms out in PA..

This actually is ahead of the cold front and the timing of this complex vs the crossing of the front will determine how severe the storms get. Regardless, I see enough evidence in place to say SOME areas will see severe storms.

Instability values as projected by all the models still look decent. As a reminder instability measures the temperature of an air parcel compared to its surrounding environment. You want that daytime heating to warm things up and cause that air to rise..

Here is the updated projected instability..

Not every model is showing the same degree of instability but I like I said above I think there is enough evidence to support strong to severe storms. I am not on the bandwagon of an all out severe weather outbreak (more widespread) however. 

If we now go to the updated radar projections some pretty nasty storms are popping up this afternoon..

At this point it all will come down to nowcasting. We need to see where the big storm cells develop and what areas they will effect. I think the biggest threat for areas that get hit by the bigger storms will be very strong wind gusts, downpours and some small hail. In terms of tornado development it is not off the table but I do not see widespread support for that. 

 I will be having updates on twitter today with that information. 

Monday, June 22, 2015

Monday Morning Weather Discussion: A Hot Humid Start to the Week, Severe Weather Possible Tuesday

Good morning everyone. I will start by saying the weekend forecast was a disaster. For one it did not rain as much as expected and the timing was completely off.  Models significantly overestimated the rainfall amounts. The good news was that Sunday ended up being an excellent day unexpectedly.

The news this week will be the very hot and humid conditions  along with a potential severe thunderstorm threat tomorrow. By the time we get to the end of the week things will cool down a little but we can see some more showers Friday.

Lets look at tomorrows thunderstorm set up. You can see below the temperatures ahead of an approaching cold front..

This hot moisture filled air is going to be ingredient #1 as a cold front then comes approaching from the west. On the next image below you can see the high resolution NAM model's projection of storms popping up along the front..

Notice the low pressure system up in Quebec. That is what the cold front is associated with. 

To determine how severe a thunderstorm event may be, we need to look at how unstable the atmosphere will be. In other words what is the temperate of an air parcel compared to its surrounding environment. If it is much warmer than the environment then it rises causing those big storm clouds building high up in the atmosphere. We can determine the potential for this by using an index called CAPE. Below shows the instability for tomorrow afternoon. Just know the closer to red the more unstable the atmosphere is..

Could this be one of the bigger severe weather event for the east coast this year? I am not sure yet but it is work monitoring and I will have another update on this tonight or tomorrow morning.

Thanks for checking in.