Severe Weather Risk

As a cold front approaches from the northwest a few showers and/or thunderstorms are possible this afternoon and evening. The front will slowly move across the state tonight bringing the best chance of showers and thunderstorms. Tomorrow morning parades may be a bit wet from the lingering rain overnight. Shower and thunderstorm chances will diminish in the afternoon and evening tomorrow. The rain amount across the area would be generally 0.50"or less but underneath thunderstorms heavier amounts can be expected. The map to the right is rainfall forecast from 7AM Tue-7AM Thu. Know anyone in south Texas? They could see 3-6" of rain with isolated higher amounts.

Fireworks or T-Storms?

Wednesday Evening
NAM Model (above left)
GFS Model (above right)

Here is where things get tricky...if you look at both computer models at face value the NAM model shows it still raining during the evening but the GFS model is dry. At this point...I would have to side with the GFS model. There doesn't appear to be much upper level support. A cold front will bring a chance of showers Tuesday night through Wednesday. In advance of the cold front the humidity will be high again. Dew points will be in the upper 60s. The amount of rain is is expected to be around 0.50" with heavier amounts east of the Mississippi River.

Rain Amount Forecast 7AM Mon-7AM Wed

Severe Weather Risk
Tuesday (above left)
Wednesday (above right)

Relief On The Way

A slow moving cold front will bring relief from the high humidity we had yesterday. At 8:15 this morning (left map) the cold front was moving through eastern Iowa. Ahead of the front it was still very humid with dew points in the low 70s but behind it across northwest Iowa dew points were down into the 50s...much more comfortable. Not much activity along the front so far when it comes to showers or thunderstorms. There may be a slight chance of t-storms in the southeastern part of the state along and ahead of the front later today.

Heavy Rain Possible

The morning surface map (above left) has an area of high pressure located over southeast Iowa. We had a beautiful start to our last full day of spring with sunshine (above right), low humidity, comfortable temperatures and little or no wind. Our weather has the potential to be pretty wet through early Saturday morning. Below is rainfall forecast from 7AM today through 7AM Saturday. Notice the band of heavy rain possible across Iowa. This doesn't mean that everyone will get this amount of rain but the potential is there for this amount to occur in places.

Severe Weather Threat

6:45 AM Satellite

Early this morning started out sunny as the sun came up. There are showers and a few thunderstorms associated with the clouds in central and western Iowa at this time. Once this area of rain/clouds moves northeast. Most of the day should be dry. These showers/t-storms will be around eastern Iowa mid morning through early afternoon.

4:00 AM Surface Map

High pressure over Indiana this morning was the reason for the beautiful day yesterday and comfortable conditions last night and early this morning. The warm front to our southwest will be moving northeast today. It will move into eastern Iowa this afternoon. South of the front it will be in the 80s and humid while north of it (NE of Waterloo and Cedar Rapids) the humidity level will still be comfortable. The front clears the viewing area this evening with warm and muggy conditions over night through tomorrow.

500 mb & Water Vapor this AM

There is an area of low pressure in the upper levels of the atmosphere across the northwestern part of the United States. The low will strengthen and move east today.

SPC Severe T-Storm Outlook for Today

This is going to help enhance thunderstorms to our west/northwest today. This all moves east and sets the stage for a risk of severe thunderstorms late tomorrow afternoon and evening.

SPC Severe T-Storm Outlook for Thursday

More Chances of Rain

8:45 AM Visible Satellite

Clouds in eastern Iowa are clearing from west to east. There may be a few clouds developing this afternoon but, overall it should be a nice day. More showers/thunderstorms are back in the picture for tomorrow afternoon.

500 mb and Water Vapor Satellie

A large area of low pressure in the upper levels of the atmosphere (centered over the Dakotas) will be slow to move. The low will keep keep the chances of showers/thunderstorms in the forecast through the weekend. It will not rain every hour of every day but, rain is possible at some point each day through early next weekend.

Rainfall Forecast 7 AM Fri - 7 AM Sat

The next round of rain could bring us another .50 to 1.50" across Iowa. The eastern counties could still handle some more rain. Central and eastern Iowa would like to have more dry weather right now than rain.

T-Storms and Severe Weather Risk

The cold front we have been waiting for is now in the western part of the state. It will remain stationary this morning and wait for the low in Kansas to move northeast along the front. As the low and front move into eastern Iowa our shower/thunderstorm chance increases this afternoon. There is also a slight risk for severe weather.

When Will It Rain? How Much?

7 AM Surface Map

A slow moving surface low and trailing cold front will continue to more east east today. In advance of the front a gusty south wind will increase the moisture in the atmosphere. Temperatures today will be similar to yesterday but will feel more uncomfortable. Dew points yesterday were in the 40s...today in the 50s. The higher the dew point...the more moisture in the atmosphere therefore harder for the body to cool itself.

9:01 AM Satellite

This morning, from eastern Iowa...east and north, the sky was clear. The clouds to the west are in advance of the above mentioned cold front. During the heating of the day this afternoon there may be an isolated shower or two to pop up.

500 mb & Water Vapor Satellite

The upper level low and trof in the northern Rockies will continue to slowly move east. The reason why the low is moving slowly is due to the ridge of high pressure in the eastern part of the United States. The timing for the surface front and upper level low to be in the Midwest is Wednesday. This is when we will have our best chance of showers and thunderstorms. Now the question is how much rain will we get?

QPF Rainfall Forecast
7AM Wed-7AM Thu

If this forecast holds true, a beneficial .50" to 1.00" of rain will fall from the clouds as this system moves through the region. Behind the front the temperatures will cool down to near 70 degrees for highs through the weekend.

Forecast Discussion

Iowa Station Plot 8 AM (above right)
Midwest Surface Map 7 AM (above left)

A warm front hung around yesterday across northeast Iowa yesterday and last night. Highs yesterday ahead of the front were in the 60s with 80s behind the front. This morning the front is a little farther northeast. It will continue to slowly move in that direction allowing temperatures to warm into the 80s area wide.

500 mb/6AM Water Vapor

The trof of low pressure in the northwest will bring us a chance of showers and thunderstorms Wednesday into early Thursday morning. There is a threat of severe weather today and tomorrow in advance of the approaching surface cold front. By the time it gets into Iowa the risk of severe weather is minimal at this stage (updates to come).

GFS 7PM Thursday Surface Forecast

The front is expected to slowly move though Iowa on Wednesday. There may be some lingering showers during the morning on Thursday before the sky begins to clear. Ahead of the front the high temperatures will be in the 80s with a drop off to near 70 Thursday through Memorial Day Weekend.

QPF Rain Forecast 7AM Mon-7AM Thu

It has been pretty dry around here lately and rain is not a bad thing. Rain through Thursday morning will be widespread in the middle of the country with the potential for up to one inch across Iowa.

Forecast Discussion

7:45 AM Satellite

The visible satellite over the Midwest shows a clear sky over Iowa with just a few clouds along the Iowa/Minnesota state line. As the day goes on, there will be enough instability in the atmosphere, the sky will become partly cloudy. Notice the swirl in the clouds over northern Minnesota. These clouds are associated with this disturbance. The timing of this with the heating of the day and very cold air aloft may produce a few late afternoon thunderstorms.

7 PM Today 500 mb Forecast
NGM (left)...NAM (center)...GFS (right)

The three above models are for the same time period later today. I circled (blue line) the vorticity maximum as it moves across MN/WI/IL/IA late this afternoon and evening. This will give us the potential for a few t-storms.

Convective Forecast for today from SPC

There is no organize threat for severe weather around the Midwest but, 1 or 2 of the storms that pop up later today may be severe. The above map shows where the small potential of a funnel cloud or brief tornado might occur. The combination of very cold air aloft and the upper level disturbance timed to be over this area during the peak heating of the day might be just the right ingredients for this to occur.

Water Vapor & 500 mb map (this morning)

The disturbance is noticeable on the above map over Minnesota. This will move south and enhance the potential for a few late afternoon/evening t-storms.

Forecast Discussion

7:15 AM Satellite

The sky is cloudy across much of the Midwest. The clouds are generally behind the cold front with sunshine ahead of the cold front. The sunshine will set up the potential for severe weather to our east today.

7:47 AM Radar

Radar shows an area of showers from Wisconsin southwest into Kansas behind the front. The heavies of the rain will be south of Iowa today. The precipitation is moving east/southeast.

Streamlines (above left)
Pressure/Temperature (above right)

The two maps above show the position of the front as of 7 AM. The streamline map shows the change in wind direction from the south (ahead of the front) to the northwest (behind the front). The pressure/temperature map shows where the leading edge of the cooler air is....along and behind the cold front.

BUFKIT Program

We use this program to help analyse data from the computer models. The right hand side is the beginning and moves left in time. The green shaded bars are rain. It is still showing the chance of rain around the noon hour today. The red line is the temperature. Notice how it goes up and down from day to night. The pressure is in white. The trend is upward and a rise in pressure means high pressure moving into the area. High pressure will give us sunshine for the middle and end of the week.

Forecast Discussion

It is going to be a warm day with gusty winds from the southwest as a low pressure system moves east across Minnesota.

3 hr Pressure Change Contoured at 7 AM

I circled the area where the pressure is falling in red. The blue circle is where the pressure is rising. A line from the center of these areas is the direction the low pressure center is moving.

7 AM Pressure Contoured

The low is located over west central Minnesota and is moving along the yellow arrow to the east northeast. The low will drag a cold front through eastern Iowa late tonight.

7AM Dew point Contoured

In advance of the front the wild will be pulling warm air north as well as more moisture. It is not going to be as humid as we are use to around here when the temperature gets to 90 degrees. Today the dew point will be near 60. Usually in July and August (when you usually see 90 degree temps) the dew points are in the mid-upper 60s...very uncomfortable. Don't get me wrong, it is going to be a very warm day but, just not as humid as usual. The map above shows the area shaded in green to have dew points of 60 degrees and higher.

7:45 AM Satellite

In advance of the front there is a large area of high clouds. The sun will be shining through the clouds throughout the day. Along the Nebraska/Kansas state line a few showers have popped up early this morning.

7PM Monday GFS Surface Forecast

The front will be approaching northwest Iowa by this time with showers and a few thunderstorms generally behind the front.

7 AM Tuesday GFS Surface Forecast

Tomorrow morning the front will be to our east with showers and a few thunderstorms. The wind direction will be shifting to the northwest as temperatures will be cooler due to the clouds, showers, wind direction and cooler air mass.

Convective Outlook for Today/Tonight

Because the front is passing through our area at an unfavorable time for severe weather the threat for severe weather looks minimal at best.

7PM Tuesday GFS Surface Forecast

The showers will be ending quickly as the front moves away from the area. Most of the rain will be falling behind the front as it moves into the Ohio Valley at this time.

7AM Wednesday GFS Surface Forecast

High pressure will clear the sky Tuesday night setting the stage for a great stretch of spring weather. It will be sunny, high temperatures will be in the 70s and the humidity level will be low. This should continue through Friday.

HPC QPF 7AM Mon- 7 AM Wed

The forecast amount of rain during this time will range from .25" to .75".