As we get ready to celebrate our nation's independence and take part in lots of outdoor fun this weekend, it's time for me to take a look back at June's climate data.  This very well could be the year without a summer and I would like to explore that in another blog next week.  For now though, let's look back and see what type of month we had in June.

Our average temperature last month was 70.2 degrees which is 0.5 degrees below normal.  Keep in mind that number takes into account both the high and low temperatures for each day.  Obviously last month was cool for June.  We had no days where the temperature reached 90 degrees.  The highest number was 89 on June 25 and the lowest value was 45 on June 1.  This tied the old record for that date set back in 1930!  The record high for the month as a whole was 100 set back on June 27, 1966.  The record low for the month was 40 back on June 11, 1980.  Could we see a summer without a 90 degree temperature?  This year, that might just be possible.

Not only was June a cool month, but it was also quite wet!  We measured 6.14 inches of rainfall at Harrisburg International Airport.  That is 2.15 inches above normal!  The record rainfall for the month came back in 1972 with the remains of Agnes bringing the total to 18.55 inches!  The driest June was back in 1966 with only 0.07 inches of rainfall.  A record rainfall occurred on June 10 with 1.70 inches.  This broke the old record of 1.66 set back in 1944.  We had at least some measurable rain for 16 of the 30 days last month.  All in all, June 2009 will be remembered as a cool and damp start to summer.

Join me next week as I take a look at climate trends for the rest of the summer.  Don't be surprised if we stay cool and wet.  It looks like that type of weather is here to stay!  Have a great holiday weekend and enjoy all the fireworks around the region!  See you next week!

It's that time of year when showers and thunderstorms become a daily threat.  Last evening brought a little bit of everything across central Pennsylvania.  We had some gusty winds, heavy rains, and even some hail reports.  Several areas, especially in York County, also had flash flooding problems.  As we head into this afternoon, evening, and overnight we should brace ourselves for more of the same.

I mentioned yesterday in my blog that the Storm Prediction Center would probably extend their slight risk area into Pennsylvania for today.  They didn't disappoint me...take a look:

Once again we are in the slight risk area for severe thunderstorms through the overnight.  Our greatest risk tonight will come in the form of potentially damaging winds.  Yesterday, I talked about the lifted index and CAPE as good measures of whether or not severe weather would develop.  Both the lifted index and CAPE values were pretty impressive at this time yesterday afternoon.  Today we are socked in with some clouds and that could help keep the atmosphere more stable.  If any sunshine does manage to cut through these clouds later today, the atmosphere would rapidly destabilize and that would be the fuel that is needed to fire some decent storms.  For now though, I expect the lifted index and CAPE values to be a little lower than yesterday.  Let's have a look:

CAPE values for central Pennsylvania this afternoon are significantly lower than yesterday.  I am only seeing around 500 J/kg for our area.  This doesn't indicate a great chance for severe weather today.  However, if the sun breaks out, expect the CAPE values to soar and the atmospheric stability to deteriorate quickly.

With lifted index values only around -1 or -2 across the lower Susquehanna Valley this afternoon, I do not expect anything too intense to develop immediately.  The main front is still out over the Ohio Valley and it will be sometime before it crosses the region.  This may not happen until the overnight.  With the loss of daytime heating by that point, we could still see some thunderstorms, but the severe threat would be incredibily limited.  The cloud cover today is really helping stabilize the atmosphere.  As I mentioned yesterday, I would like to see lifted index numbers between -3 and -6 for some really juicy storms to form.  That doesn't appear to be the case right now, but again, if we get some sun later today that could all change. 

Any heavy showers or thunderstorms that do form this evening or overnight have the potential to create some flash flooding problems across the region.  Remember to take extra precaution if you live near a small stream or creek.  Flash flooding is a very dangerous situation and is not to be taken lightly.  Stay safe out there and let's hope for a break from this weather at some point in the near future. 

Yesterday brought a potent round of heavy showers and thunderstorms across the Midstate.  Many areas dealt with strong, gusty winds, torrential rain, and large hail.  Over 20 separate hail reports came in from across our area yesterday afternoon and evening.  We even had a rotating cell over Lancaster county for a brief period.  Dewpoints are high once again this afternoon and it looks like thunderstorms will plague us through the end of this work week.  Let's take a look at our chances for a repeat of yesterday afternoon.

The Storm Prediction Center has shifted their risk area to the east and that means that some of south-central Pennsylvania is now included for this afternoon and this evening.

I am not anticipating another round like yesterday, however, there could certainly be a few strong to severe storms around as we head into the evening hours.  A better chance for some thunderstorms will come tomorrow afternoon and evening...more on that in just a bit. 

One of the factors that we use to determine whether or not an environment is capable of producing thunderstorms is called the lifted index.  This is the result of an equation that uses many atmospheric variables to help predict where and if thunderstorms may form and how strong they could become.  The more negative the number, the better chance for strong thunderstorms to form. 

Usually, a lifted index at or below -3 indicates the environment is ripe for producing strong thunderstorms.  Notice that we have some -5s just to our south across the Virginias this afternoon and our area is located within the -3 and -4 contours.  This is relatively impressive and indicates to me that we need to keep our guard up heading into the evening hours.  The muggy and humid air is present and higher dewpoint air keeps getting funneled into southern Pennsylvania as a warm front lifts to our north. 

Another parameter we use to determine atmospheric instability is the CAPE.  CAPE stands for convective available potential energy.  Without getting into the complicated specifics about how this number is calculated, we like to see CAPE values around 1000 J/kg for a good thunderstorm environment.  Let's see how we are doing so far this afternoon.

Once again we have some rather juicy numbers sitting across the lower Susquehanna Valley.  With CAPE values approaching 2500 J/kg already, this environment clearly favors thunderstorm formation.  If we can get some good lift this afternoon, we may just get some decent cells to fire over the southern part of the viewing area.  Time will tell.

As I write this, a cell has just popped up over Adams county that looks fairly impressive.  Keep an eye across the southern tier!  I still think tomorrow offers a great chance for active severe weather as the trailing cold front will cross Pennsylvania.  Here is the Storm Prediction Center risk chart for tomorrow:

While the slight risk is not quite in Pennsylvania, I think there is a good possibility that by tomorrow we will be in a slight risk.  I will post another update tomorrow afternoon and let you know what I am thinking for our severe chances.  In the mean time, stay tuned to abc27 and abc27.com for weather updates.  Also, send in your storm photos to weather@abc27.com or brettsblog@abc27.com and include your name and hometown so we can show them on the web or on air!  Keep an eye to the sky this afternoon!