Beau Dodson's WeatherTalk Blog

Moonrise will be at 8:25 p.m. and moonset will be at 5:57 a.m.  Full moon.

Monday Night – Partly cloudy.  Warm and humid.  A few evening thunderstorms.  Then, thunderstorms becoming increasingly possible after midnight.  A few isolated storms possible before midnight.  Locally heavy downpours where storms occur.
What impact is expected?   Lightning and wet roadways.  Gusty winds near storms.
Temperatures:  Lows in the 70-75 degree range
Winds: Winds southwest at 4-8 mph with gusts to 12 mph.  Gustier near storms, as always.
What is the chance for precipitation? 30% before midnight.  And, 50%-60% after midnight.
Coverage of precipitation:  Becoming scattered with increasing coverage potential late at night.
Is severe weather expected?  Unlikely.  A couple of storms could produce gusty winds.
My confidence in this part of the forecast verifying:  High
Should I cancel my outdoor plans? No, but monitor radars.

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1.   A complex forecast for the coming seven to ten day period
2.   On and off heavy thunderstorm chances.  Similar to the last few weeks.  Feast or famine.
3.   Heat wave signals?

I posted a long update on Facebook this morning.  And, I will paste it here, as well.  The forecast is entering an unsettled period.  That means on and off thunderstorm chances.  Some of the storms could produce torrential downpours.  Very much like the last few weeks, not everyone will receive rain.  And, some places will pick up a months worth of rain in a couple of hours.  Not all that unusual for the summer months.

I continue to monitor the big heat ridge to our west and south.  This ridge is a beast.  Very hot conditions are occurring under the ridge.  And, we will need to monitor the ridge over the coming weeks.  From time to time it is pushed further south and west.  That is when our thunderstorm chances increase.  Then it nudges back into our area like a camel sticking its nose into a tent.  When it nudges back into the area we heat up.

Here is the post from Facebook.  It goes into detail about the current weather pattern and what is anticipated over the coming days.  Monitor updates.

A complicated forecast over the coming seven to ten days.  And, to make everything more complicated there will be some big differences in the forecast from Poplar Bluff, Missouri to northwest Kentucky.  Everyone’s forecast is not going to be the same.  Keep that in mind, as well.

Scattered storms likely this afternoon.  Lightning and a brief downpour is the main concern.

What is what

Heat ridge?  A ridge if high pressure normally means hot and humid conditions for our region.

Trough?  A trough of low pressure typically means unsettled weather with thunderstorms.

Northwest flow?  When winds are from the northwest.  This means a trough is present in our region.  Northwest flow in the summer can mean active weather with frequent rounds of heavy thunderstorms.

PWAT values?  Precipitable water values.  One way that meteorologists measure moisture in the atmosphere.  PWAT values of 1.7 to 2.2″ means the atmosphere is loaded with moisture.  Slow moving storms can produce flash flooding when PWAT values are high.

CAPE?  Convective available potential energy.  CAPE is a measure of energy in the atmosphere.  High CAPE numbers could mean strong to severe thunderstorms.  CAPE values in the summer months can range from 2000-6000.  Very high because of heat and high dew points.

Dew points?  Dew point degree temperature is a better way to measure moisture in the air vs humidity.  Humidity levels don’t really tell the story when it comes to a muggy atmosphere.  Dew points, however, are a great way to measure the mugginess of air.  Dew points of 70 or above are considered air you wear (as Jim Rasor says).

Let’s dig into the forecast.

At times the forecast may sound worse than it is.  But, there are a few things to remember about June and July weather.  And, these are always in the back of my mind when forecasting summer thunderstorms.

1. It is flash flood season.  June and July typically produce some of the most intense flash flooding our area experiences.  Slow moving thunderstorm clusters can drop 2, 3, 4, 5 or more inches of rain in a matter of a few hours.  PWAT values during the summer months can top two inches.  Very high numbers.

2.  Instability is always going to be high during the summer months.  Hot temperatures and high dew points will equal high CAPE numbers.  CAPE is a measure of instability in the atmosphere.  Higher CAPE numbers indicate the potential for strong to occasionally severe thunderstorms.   The main concern, during the summer months, are down burst winds.  Thunderstorm tops can reach 50,000-60,000 feet.  That is a lot of energy.  And, what goes up must come down.  Occasionally summer thunderstorms can produce pockets of 60-70 mph winds.  Normally these areas are less than a few blocks wide and long.  But, where they occur they can cause damage.  We witnessed that last week (parts of the area).

3.  We are going to ride the heat ridge over the coming weeks.  The heat ridge will deliver actual air temperatures of 94-102 degrees (and heat index values even higher).  And, we will be near a semi-perma eastern United States trough.  When the trough wins you can expect northwest winds with thunderstorm chances.  When the ridge wins out you can expect intense heat and muggy air.

These two elements (the heat ridge and the trough) will make for a complex weather forecast.  It is possible that parts of our region will pick up 2-4″ (or more) of rain over the next seven to ten days.  Meanwhile, other parts of our region (mainly the southwest part which would include parts of southeast Missouri) will pick up less than an inch of rain.

Forecast headaches abound.  I would suggest monitoring frequent updates if you have outdoor plans.  Forecasts will be changeable.  Lower confidence than normal will be the norm!

Let’s tackle the thunderstorm chances

A cold front will push into the region late tonight into Tuesday evening.  This front will be the focus for showers and locally heavy thunderstorms.  Isolated severe thunderstorm risk.

Locally heavy rain is possible.  A soupy air-mass will mean that some storms could produce 1-3″ of rain per hour.  The best rain chances will be along and north of the cold front.  The front will stall out over our region.  It won’t make it all the way through my forecast counties.

Generally, where rain does manage to fall, 0.25″-.0.75″ totals are anticipated.  Then, pockets of 1-3″+ of rain will be possible where slow moving thunderstorms occur.

The cold front moves back north as a warm front on Wednesday morning and afternoon.  A severe weather outbreak is possible over northern Illinois into Indiana and northern Kentucky on Wednesday into Wednesday night.  That will occur outside of my forecast area.

Our region can expect a chance for thunderstorms on Wednesday morning.  Then, slight chances for thunderstorms on Wednesday afternoon and evening.  If a storm does form on Wednesday afternoon or evening then it would be intense.

I will be monitoring several clusters of strong storms moving out of central and northern Illinois on Wednesday and Wednesday night.  It is possible some of that activity clips my northeast forecast counties.  That would include areas such as Carmi, Illinois towards Madisonville, Kentucky.  Again, my northeast counties.

The warm front will return on Wednesday night into Thursday as a cold front.  Scattered showers and thunderstorms will be possible on Thursday and Thursday night.  Some locally heavy rain will be possible.  But, I doubt everyone will experience rain on Thursday and Thursday night.

A few scattered heavy storms are possible on Friday, as well.

Friday night might end up dry.

Lower confidence on Saturday and Sunday’s forecast.  Depending on which guidance package you believe, we will either have widespread thunderstorms with heavy rain or partly sunny sky conditions with a few scattered storms.  I don’t have much confidence in how the weekend forecast pans out.  There will be at least a chance for thunderstorms.  The real question will be coverage.  Plenty of time to fine tune the weekend numbers.

Another concern for the next seven to ten days will be temperatures.  This heat ridge means business.  When the heat ridge nudges into our region you can expect hot and muggy conditions.  Air temperatures well into the 90’s (if not lower 100’s) and heat index values of 95-105 degrees.

The European model guidance is hot.  It is showing 90’s almost daily into the middle of next week.  The GFS (American) guidance shows next week almost cool with several nights in the 50’s.  Not sure I am buying the GFS.  It has performed poorly this month.  The European guidance, on the other hand, has done quite well.

I looked over the model ensembles (large packages of data) and they support us being squeezed between the heat ridge to our west and south and the northwest flow (troughs).  The troughs deliver unsettled weather conditions.

I suspect next week will be unsettled with several rounds of thunderstorms.  But, I also suspect it will be quite warm next week.

Daily highs will depend on cloud cover.  When thunderstorms are present you can expect upper 80’s to lower 90’s.  When sun is plentiful you can expect 90-98 degree weather.  Muggy, as well.

Lot of moving parts to the weather forecast.  Thus, monitor updates each day.  And, don’t be surprised if there are significant swings in the forecast.  Low to medium confidence in the overall forecast through next Monday.

Here are a few maps.

These first maps are showing you future-cast radar from the 4 KM NAM model.   This won’t be exact.  It just gives you an idea of what radar MIGHT look like.  It is guidance and not gospel.  Expect scattered storms on Tuesday into Wednesday morning.

This first map is for Tuesday afternoon around 3 or 4 pm.  You can see some storms near the Ohio River.  I suspect there will be scattered storms just about anywhere in the region.  We will see if a more solid line forms later in the day and evening.  The NAM thinks it will form over extreme southern Illinois and western Kentucky.  Likely from an old outflow boundary moving in from the north.  An outflow boundary is a dying area of thunderstorms that leaves a boundary.  These boundaries can be the focus for new thunderstorm development.

Moving into the early evening hours.  A few storms in the region.  Locally heavy storms.  Isolated severe weather risk.

Moving into Tuesday night.  Notice the band from Iowa into Kentucky?  That is along the old cold front which will become a warm front.  The warm front will move back north and east.  Along and north of the front is where thunderstorms will form on Tuesday night and Wednesday morning.  This will be in response to the low level jet developing.  A low level jet is an increased area of wind speed that develops at night.  This can help produce thunderstorms.  The storms will push north and east on Tuesday night/Wednesday morning.

And, here is the Wednesday morning map.  Notice the heavy storms along the warm front.  The placement of the warm front is an important part of the forecast.  Some of the storms on Tuesday night and Wednesday morning, north of the warm front, could produce hail and strong winds.

Check out these temperatures.  This is the GFS model guidance from weatherbell.com   I have chosen to data set that I think has the best chance of verifying.  Hot is the rule.

These are high temperature forecasts into next week.  If this is correct then heat wave weather has arrived.  EC data shows even hotter temperatures.  Keep in mind that heat index values would top 100 degrees.  These maps are showing you actual air temperatures.

Heat index values are determined by dew points, cloud cover, and air temperatures.  Just because we have temperatures in the 90’s does not necessarily mean we will have heat index values above 100 degrees.  But, when dew points increase our heat index values will go up.

Here are the GFS high temperature forecasts

This is for Wednesday.  Click image for a larger view.

Thursday

Friday

Saturday

Sunday

Monday

Tuesday

Wednesday of next week is the image below

Longer range guidance has our region in above normal temperatures.  This is the GFS ensembles.  Red means above normal temperatures.  This will take us into the first few days of July.  When you average everything out it appears above average will win.  June has been a warm month.

This first map is through June 26th.

This next map is through July 1st.  Days 8-12.

Long range cycle would keep us unsettled the first week of July.

Radar

We have regional radars and local city radars – if a radar does not seem to be updating then try another one. Occasional browsers need their cache cleared. You may also try restarting your browser. That usually fixes the problem. Occasionally we do have a radar go down. That is why I have duplicates. Thus, if one fails then try another one.

If you have any problems then please send me an email beaudodson@usawx.com

WEATHER RADAR PAGE – Click here —

We also have a new national interactive radar – you can view that radar by clicking here.

Local interactive city radars include St Louis, Mt Vernon, Evansville, Poplar Bluff, Cape Girardeau, Marion, Paducah, Hopkinsville, Memphis, Nashville, Dyersburg, and all of eastern Kentucky – these are interactive radars. Local city radars – click here

Live Lightning Data – zoom and pan:  Click here
Live Lightning Data with sound (click the sound button on the left side of the page): Click here

We will have on and off thunderstorm chances over the coming days.  I really don’t like these NOAA maps.  They don’t tell the story.  Last week they had us in small rain amounts.  Some places ended up with 3-4″ of rain.  Unfortunately the NOAA maps do not capture thunderstorms.  Thus, this is very much a broad-brushed outlook.

Over the next seven days some areas will receive almost no rainfall.  Other areas could easily receive 1-3″ of rain.  The problem with summer thunderstorms is that they don’t impact everyone.  And, it is nearly impossible (if not impossible) to tell you how much rain will fall at your exact location.  Keep that in mind.

Here is the official NOAA map for the next seven days.

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