Thursday, September 23, 2010

More rain tonight

Today will remain cloudy with highs in the upper 70's to low 80's around the area. There is band of rain stretching northward through central Kansas, and some showers and maybe a thunderstorm will be possible by late this afternoon based on the current radar trends.

The National Weather Service has locations along and north of I-70 in a Flash Flood Watch.

This Flash Flood Watch is in antisipation of possibly some very heavy rain as a strong cold front meets up with a plume of tropical moisture from Mexico. 1-2 inches of rain may fall across parts of northern Missouri tonight as rounds of thunderstorms move through the area. The ground in this area is saturated from recent rounds of heavy rain and thunderstorms, so more flash flooding looks likely. With MLCAPE of 500-750 J/kg, the risk for severe thunderstorms is pretty low as the atmosphere may be too stable, but a few isolated strong to severe thunderstorms may develop. The main risk would be some gusty winds and marginally severe hail.

As a result the Storm Prediction Center has a slight risk for severe thunderstorms from Kansas, northeast through Iowa and Michigan.

20100923 2000 UTC Day 1 Outlook Graphic

Late tonight the strong cold front will sweep through with a long line of thunderstorms. They should be under severe limits, but a few parts of the line may produce winds gusty enough to become severe. The rain chance should be completely out of the area by Friday morning.

Friday should be great with temperatures in the low to mid 70's and no rain. The forecast gets tricky Saturday into Sunday as an upper level low becomes "cut off" and moves south over us Saturday night. The computer models are not consistant on where it will end up tracking, but it looks like it will either be cool and dry, or cool and wet. It will take a couple more days to figure this out. This would definitely be a cool and wet scenario.

image of 500mb Vort, Ht

Alex Pickman

Wednesday, September 22, 2010

Very busy week of weather

Lets look back in the past few days. A storm system moved into the area on Saturday, Septemeber 18, 2010 with a cold front stalling out along I-70. The temperature gradient was pretty impressive with around 90 degrees in Kansas City and 40's across Nebraska. Dewpoints south of the front were also near or above 70 degrees. Conditions were very favorable for thunderstorms to form.

Around 3:00 PM thunderstorms started lining up right over the Kansas City Metropolitan area, creating a very dangerous situation. With the favorable conditions, they quickly turned severe with damaging winds and hail. The storms were training over the same area so flash flooding was also a concern. What was amazing, was in a couple of the stronger stroms, the updrafts went crazy, and were strong enough to support hail over 5 inches! The storms also produced damaging microbursts to add to the damage around Kansas City. The thunderstorms continued around the area into the very early morning hours of Sunday the 19th. Here are some images from the NWS in Pleasant Hill, MO.

(5.5 inch hail producing thunderstorm)

Hail StoneHail stone
Hail stoneHail damage

Yesterday, a weak cold front stalled out across southeast Nebraska. Temperatures were well into the 80's and dewpoints neared 70 degrees. Everything seemed right for thunderstorms to form across southeastern Nebraska, northeast Kansas, and northern Missouri. I expected a Severe Thunderstorm Watch to be issued across northern Missouri by early afternoon and as expected a watch was issued. The threat for severe thunderstorms was pretty slim, and the only reports were in northeast Kansas, but take a look at the radar around 7:40 PM Tuesday.

(Source: NBC Action

Numerous thunderstorms formed and the main threat became flooding. These thunderstorms were moving over the same areas and many locations picked up over 3 inches of rain, and some locations in northeast Kansas picked up over 6 inches according to radar estimates. And with the ground already saturated by previous rains, the potential for flash flooding was great. It took a while for these storms to push southward as the front was stalled in Nebraska, but eventually they did as an outflow boundary drug them toward I-70. Take a look at the estimated precipitation totals:

After all that, what is next? Well there is a couple things I am tracking. On Thursday a strong cold front will approach the area and push into southern Missouri by Thursday night. Right now it looks like rain and thunderstorms, heavy at times will push southeast. Some of the thunderstorms may be severe, but more heavy rain looks likely.

Friday and during the day on Saturday should be very nice with highs in 70's, but an upper level low is forecast to drop southward right over Missouri by Saturday night.

This "Cut off" Upper Level Low will likely create a cool rainy day on Sunday. and lows in northern Missouri could dip into the 40's Monday morning. have a good first day of Fall.

Alex Pickman