Our upper trough is holding strong over the Great Lakes today.  This is keeping us cooler than average… and keeping humidity in check:

And take a look at the 500mb forecast for Wednesday… it doesn’t budge:

So we are going to continue with the comfortable weather.  It will certainly feel pleasant over the next few days… but this also comes along with the chance of showers.  Think of that big low like a wheel, spinning over the Great Lakes.  There are “spokes” around that wheel… which are areas of enhanced lift.  As each one approaches us, it will increase the chance of rain here… aided by daytime heating.  You can see these “spokes” below… broken yellow lines… (valid Wed AM):

The low finally pulls away during the end of the week… drying us out just in time for the holiday weekend!  We’ll also enjoy a warming trend… with highs in the lower 80s.   Join us at Riverscape over the 4th of July… free fun for everyone!  Fireworks are Friday night… get there before 10pm.  For a full schedule of fireworks around the Miami Valley… check out WDTN.com.

Have a good day!
Jamie

Last week temperatures in the upper 80s and low 90s kept air conditioners humming across the Miami Valley but this week, whether your a fan of summer or not, temperatures will break.  The reason?  an upper level low… but it isn’t all peaches and cream.  Every once in a while a set up like this can breed strong to even severe storms.

Here is why.  An upper level low is pressing the jetstream south of our area.  While that will bring in cooler temperatures and drier air it also lowers the temperature in which a parcel (imaginary balloon of air) needs to rise too in order to go up (thats how clouds form, rising air). 

With plenty of cold air around in the upper levels of the atmosphere temperatures in the mid to upper 70s will be all that we need to get those afternoon clouds going and as the low moves further south on Wednesday the chances for those clouds, showers and thunderstorms will dramatically rise.  Since the air is cooler then normal, hail can form in much weaker showers/thunderstorms.  So perhaps in a normal situation this time of your you would need a 30,000 foot tall storm to create some 1 inch hail, with so much cool air around a 20,000 foot tall storm can do the same.  Also with winds at the surface and aloft generally out of the same direction, straight line winds could also be a concern.

Another important factor to watch will be weak little boundaries circulating around the upper level low.  These can also enchance rotation leading to stronger storms and in some cases tornadoes.  So while temperatures may be cooler then average if we see enough sun in the morning conditions may be right for some pop-up severe.

This temperature profile of the United States also give you a good idea of whats going on. (by the way these temperatures are in Celsius).  Last week  850mb temperatures varried from 18 to 21C.  This week come Tuesday and Wednesday they will be close to 8-10C.

Cooler… yes.  Severe weather free…  possibly not.  One way or another enjoy the Summer time version of the January thaw….  or the June cool down!

We had some very heavy rain fall overnight, as thunderstorms moved through the area.  Here is the radar image from 9pm… you can see the storms forming to our northwest:

Here’s what it looked like at the height of heavy rain in Montgomery County… what a lightning show!

And now for some rainfall totals…

The heaviest fell along and south of I-70.  Unfortunately for those of you that missed it to the north… it looks like you’ll be dry for today.  The cold front is passing through this morning, so there is the slight chance of something spotty… in the south… late this morning.  Even though a cold front is passing through, there’s not much relief from the hot and humid weather!  We will be into the upper 80s again today and tomorrow.

The next chance of rain comes with a cold front late Saturday night into Sunday morning.  Here’s the GFS at 8am Sunday:

This front will finally bring in some more comfortable air… with temperatures falling below normal early next week.  And here’s the kicker… LOWER HUMIDITY!! 

I hope you enjoy your weekend!

Jamie

Sorry for the late blog today… sometimes I really don’t know where the time goes!  I have been working on some new graphics this afternoon…

Today, another scorcher… with highs in the lower 90s.  The humidity is definitely higher this afternoon, as well… with our dew points in the low 70s!  Ouch!  Use caution outside today, as heat index values could get into the mid-to-upper 90s.

A cold front is approaching… it should get here late today.  As the afternoon goes on, the chance of thunderstorms increases.  As of noon, there is nothing going on… but we’re waiting for development to our Northwest.  Thunderstorms likely won’t impact us until sometime after 3pm today.  But any thunderstorm that does move in will have the potential to become severe.  Damaging winds are the main threat… with the potential for some hail… and VERY heavy rain!!  Keep an eye to the sky late afternoon/evening.

Unfortunately, the cold front will NOT bring in colder air for the weekend.  Friday and Saturday we’ll be back in the upper 80s to near 90 degrees.  The humidity will come down a bit, but it will still be a little muggy.  A stronger cold front will move through Saturday night, bringing much more comfortable air into the area for next week.  Lower temps AND lower humidity.  I can’t wait!!

Jamie

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Yesterday we climbed to 85 degrees… and if you thought it felt hot… it’s only going to get worse for you today and tomorrow.  At least it is good pool weather!  If you’re heading out to the pool… perhaps the lake… or maybe you just want to run through the sprinkler… the next 2 days look good.  Changes will come on Thursday:

While our heat it not quite out-of-control… it is opressive across the central part of the country.  This is where a big ridge of high pressure is in control, allowing the heat and humidity to build.  Here is a look at the ridge, at about 18,000 feet up in the atmosphere:

We are warm, on the very edge of the ridge.  But under the core of the ridge, we find the most uncomfortable air… thus, some Heat Advisories and Excessive Heat Warnings are in effect:

Out in Kansas and Missouri, they will see heat index values of 105 to 110 today and tomorrow!  Not much relief for them at night, either, as temperatures will only drop into the 80s for lows.  At least here in the Dayton area, we’ll get to cool off after the sun sets… our lows will dip down into the 60s!

No rain is in the forecast for us until Thursday, when we could see some scattered showers and thunderstorms move through with a weak cold front.  I do expect some places to miss out on the rain, as the nature of the activity will be scattered.  Hopefully the places that have missed out in the past will get a little chance to catch up…

This week is Lightning Safety Awareness Week!  More people are hurt by lightning then by tornadoes or hurricanes, and lightning kills more people in the U.S. than any other weather event except flooding.   On average, lightning strikes 400 people every year.  As of today, 15 people in the US have already died this year, from lightning strikes.  Here are the stats from NOAA:

Click to enlarge

Remember, the safest place to be during a thunderstorms is indoors!  If you are outside and you see lightning… apply the 30/30 rule.  When you see a strike… count how many seconds before you hear the thunder.  If it’s less than 30 seconds, take cover!  Once indoors, wait 30 minutes after the last sound of thunder before heading back outside. 

Jamie

This morning, the radar is our weather story!  We have been tracking thunderstorms throughout the morning.  There was a line of severe thunderstorms heading RIGHT for us earlier… but a transfer in energy has us dodging the strongest storms.  Here is what the radar looked like right before we started our 5am newscast:

The strongest thunderstorms around Chicago/Northern Indiana had been producing damaging winds, and were heading in our direction.  But then we saw some thunderstorms develop RIGHT over the Miami Valley.  You can see three hours later, the energy moved from the stronger thunderstorms to the developing thunderstorms:

Now a closer look at that line of thunderstorms as it developed right over us on Live Doppler 2X.  You can see we had a brief heavy downpour in Montgomery County as the line was getting organized… around 5:20am:

The line was strongest in the Northern counties, however… and Auglaize and Logan counties saw the worst of it.  A ton of lightning, and very heavy rain.  As the line moved east, it really strengthened, prompting warnings just as it left our area:

And you can see what’s left of the first line of severe weather (the weakening line) entering our northwest counties on the image above.  SO… the storms that were heading our way weakened.  AND… the storms that formed right over us didn’t strengthen until they were out of our area.  We really lucked out this morning!!

But we’re not out of the woods just yet.  We have a MODERATE risk for severe weather over the next 24-hours… damaging winds seem likely, with the potential for hail and an isolated tornado.  The chance of spotty/isolated thunderstorms will be there this afternoon… but the main show will again be overnight into the early morning hours of Saturday.  We’ll let you know if we have any more watches or warnings issued, both on the air… and at www.wdtn.com

Saturday, still hot and humid… and we’ll continue to see the chance of showers and thunderstorms through the afternoon.  But it does look like we’ll dry out a bit for Father’s Day!

Jamie

The next 48 hours are going to be quite active across the Midwest… including right here in the Miami Valley.  We will be affected by a series of thunderstorm complexes… each of which bring the potential for severe weather and heavy rain.  We have a pretty good shot of strong thunderstorms both today and Friday.  The Storm Prediction Center (SPC) has us with a slight risk today:

And a moderate risk Friday/Friday night:

This will be our best chance of severe weather.  It looks like an outbreak of damaging winds… could be some hail… and we can’t rule out an isolated tornado.  It will be a busy 2-days in the forecast center, I am sure.  We’ll be staying late/getting up early to keep you posted on any severe weather that strikes.  Keep tabs on-air and online… at www.wdtn.com!

To break it down… during the daylight hours, we’re running a slight chance of showers/thunderstorms… and it increases each evening and overnight:

At any time over the next 2 days, thunderstorms will have the potential to become strong to severe… and to produce heavy rain.  By Friday night, we could have some flooding on our hands.  Stay with us for updates and further details as this event unfolds…

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UPDATE… 9am THURSDAY… area of rain over Indiana is holding together quite well, and will spread across the Miami Valley between 10am and noon.  Steady rain for awhile… then a break later today.  Stronger stuff still possible overnight.

Jamie

A little meso low spun up along our warm front leading to some very heavy rain.  Rainfall rates greater then 2 inches an hour fell across much of the Miami Valley.  While no official flood advisories or flood warnings were issued places like Union and Bellbrook were inundated with over 1.5 inches of rain in 2 hours.  Here are some of the totals.

This noon hour, an MCS Mesoscale Convective System is falling apart as it continues to move east and into the western Miami Valley.  It was quite healthy looking this morning, when it was in southwestern Indiana:

But now, you can see it has weakened… as it is just across the Indiana/Ohio state line:

The reason… 1) Time of day.  This is the usual time of day for thunderstorm complexes to weaken.  They tend to do so as the low level jet weakens a bit.  2) East wind.  A wind from the East is usually a “dry” wind.  Note our dew points are only in the lower 50s right now… it feels pretty comfortable outside. 

That line of thunderstorms near St. Louis has held together pretty good… but will stay south of the Dayton area.  We are not out of the woods yet, however.  We will have to watch for additional thunderstorms to develop during the afternoon.  A warm front is south of us and will slowly move north… keeping us with the chance of rain.  It seems the clouds from this morning’s MCS will help keep us a bit more “stable” this afternoon… but we’ll keep an eye out for any stronger thunderstorms.  Strong winds and/or hail would be the main threat today.

Tomorrow, we’ll be on the other side of the warm front… the juicy side!  We’ll continue with a chance of scattered showers and thunderstorms.  It will also feel much more humid… and temperatures will be warmer.  Lower-80s Wed… mid-80s Thu… and upper 80s Fri!  Here comes Summer!  Which, by the way, officially starts at 1:45am on Sunday.

Jamie

Here is what the Storm Prediction Center has posted for us as of Monday night..

SPC keeps most of the severe weather to our south… with a slight risk for extreme southern Ohio.  While I agree the best threat for severe weather is south of here, I think we will have enough instability to get a few showers and storms that could be on the severe side as well by the time Tuesday evening rolls around.

Here is what the NAM and GFS have to say…

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Both models are showing heavy rain building with a shortwave Tuesday evening and early Wednesday morning… that means we will have to be on our toes for possible severe weather.   Look for SPC to adjust that slight risk further north on Tuesday morning.

We had some rain around the area Sunday late afternoon/evening.  Here is a picture sent in by Dot Baker, of a thunderstorm in Champaign County:

Those showers and thunderstorms actually set us up for fog this morning.  We had a lot of moisture around, thanks to that rain.  Skies partially cleared overnight… and we didn’t have much wind at all.  These are the perfect conditions for fog formation… and early this morning, visibilities were down to a quarter of a mile in spots.  Rob Lunsford sent me this pic from Phillipsburg, in Northwest Montgomery County:

But as the sun came up, it helped to burn away the fog, and we have a pretty nice day in the works!  The pattern this season has been a stationary front to our south… and that is, again, what we have today:

I think it’s far enough south that the rain will stay away today… but there could be something isolated in our extreme southern counties (Butler, Warren, Clinton).  The front will lift a bit farther north on Tuesday… and an upper level disturbance will move in as well… increasing our rain chances.  The week won’t be a wash-out… but a little active, again, with the front nearby.

Jamie

With 2-3 inches of rain falling in some areas Thursday night flooding on area streets was quite common but in some areas front lawns turned into small lakes!  Take a look at the pictures below!

These pictures are from Germantown and Clayton Oh… plenty of rain.  Now if we could only see some sun!  I’m sure there are plenty of garden that need to dry out and lawns that need to be mowed!

We had rain and thunderstorms move through the area this morning.  Some of the thunderstorms were producing rainfall rates of more than 2″ per hour!  Here are Weatherbug Network totals from around the Miami Valley, as of 8:am:

Keep in mind, much of this rain fell in one hour!  Our weatherchecker in between Beavercreek & Xenia reported .9″ in just 30 minutes!  Because of this, we had a few Flood Warnings and Advisories issued… as high water is an issue.  For the latest watches and warnings, be sure to stay with us on Channel 2 and right here on wdtn.com.

The flooding concerns are not over just yet!  While we’re going to see a break in the rain during the late morning/early afternoon… we have rain and thunderstorms that will move in later today.  Any thunderstorm will have the potential to produce heavy rain again, as this airmass has a lot of moisture!  We also have a “Slight Risk” of severe weather this afternoon… we’ll keep you posted on that, too.  Damaging winds and hail would be the main threats.

I got an email this morning from a viewer… she had a great question.  She wanted to know how the relative humidity can be less than 100% when it’s raining.  The answer lies in understanding what relative humidity is.  You can have a relative humidty of 100% when it’s not even raining… and when it IS raining, the RH could be less than 100%.  It just depends on how saturated the air is.  That’s what RH is… the amount of moisture in the air, as a percentage of the most moisture that the air could hold at a certain temperature.  Our RH was pretty close to 100% this morning, but it stayed right around 95%.  It only reaches 100% when it can’t hold any more moisture… when the maximum amount of moisture has evaporated into the air.   

The dew point is a better measure of how much moisture is in the air… how it feels.  We know dew points higher than 60 degrees are going to feel humid!  And we certainly do today… with dew points in the lower-to-mid 60s.  Yes, more heavy rain is possible in a juicy airmass like this!

Jamie

During the mid-late morning hours, showers and thunderstorms will spread into the Miami Valley.  The strongest thunderstorms will stay to the south… but we will likely still hear a few rumbles of thunder through the early afternoon.  The image of Live Doppler 2 X below is from 7:30 this morning.  Click on it to be linked to the current radar loop:

This initial batch of rain may be a very good thing… helping us remain more “stable” this afternoon… so as to limit severe weather a bit.  We are still in a “Slight Risk” with the SPC, however, so it is a situation we will be watching closely as the day goes on.  If we get a break (with some sun) after this first batch of rain, any additional thunderstorms will have the potential to become strong to severe!  Hail and damaging winds will be the main threats… and we could see some pretty heavy downpours!

A stalled front to our south will lift north today, increasing the humidity again this afternoon:

Notice a surface low back in Illinois.  That will ride along the front, bringing more showers and thunderstorms on Thursday.  Finally, we’ll dry out Friday afternoon, and it will become less humid as we head into the weekend!  Good, just in time for Poultry Days! 

Have a good one!
Jamie

Looks like I missed a lot of severe weather last week while I was on vacation!  We went to Hilton Head Island, and the weather there was boring (but nice!).  I was actually watching the radar the night you had hail and tornado warnings in the Miami Valley!  I enjoyed looking at all of the pictures you sent in, and wanted to post the link to Wilmington’s summary of the storm, in case you haven’t seen it:

JUNE 2nd, STORM SUMMARY

Now onto our weather today!  We’re in the warm sector… with a warm front to the north and a cold front to the west:

As the storm continues to move East, some mid/upper level energy will also move across the region… keeping us with the chance of scattered showers and even some thunderstorms.  Any thunderstorm that develops this afternoon/evening will have the potential to become severe.  Damaging winds and large hail would be the main threats… but once again, this will all be determined with how much sunshine/destabilization we see.  If we are cloudy most of the day, the chance for severe weather will be less likely.  But we are in a “Slight Risk”… so it’s something we’ll be watching through the day:

You can send severe weather reports or pictures to weather@wdtn.com. 

Tuesday morning, there could be a lingering shower… but the rest of the day looks dry and rather nice, with a high near 80.  Rain is back in the forecast both Wednesday and Thursday, as our next system moves in!  We still need all of this rain… we’re just about a half-inch below average for the month… and still 4″ below average for the year…

Have a good one,
Jamie

Here are just a few of the Hail pictures that we used on the air earlier this week!  Between the strong storms morning morning, Hail and severe weather Tuesday afternoon and steady rains Wednesday we are finally getting a break.

Speaking of rain.. here are some of the rainfall totals from Wednesday… most spots coming in with .25 to .5 inches.  Just enough rain to perk up those flowers and green up the grass.

Over the next few days High pressure will dominate bringing perfect late spring weather for the weekend!  And dont forget the Strawberry Festival up in Troy!

A strong cold front moved through the Maimi Valley Tuesday afternoon.  With surface winds and winds aloft on the weak side long lived super cells were not possible… but one cell popped up over Preble county prompting a tornado warning and dropping 2.00 to 2.5 inch hail across the county.

Here is a link to some more of the pictures posted on our site.

http://www.wdtn.com/dpp/weather/WDTN_Severe_Weather_Pictures_June_2