It’s Springtime again and with that severe weather season is underway. The graphic above will be used in the warm season to identify the risk for severe weather in the next 5 days. Predicting severe weather beyond day 5 is risky at best (and even at the 3-5 day timeframe it is challenging). The graphic will indicate the risk of severe weather SOMEWHERE in the eastern or western district. The categories will be none, very low, marginal, slight, enhanced, moderate and high. Generally moderate will be events expected within the first two days of the period covered, high is very rare and will always almost be used for events expected the same day the blog is issued. In those situations, there usually be coverage of an expected event and its’s best to monitor local media sources for information.
This week we get a welcome break from the cold weather of late. The eastern district is working on losing the deep snowpack, which will slow the warming there, while out west, there is nothing like that standing in the way. Temperatures were already as high as the 70s Saturday.
Take a look at the upper air flow this next week (click any image to make it more readable): At high latitudes, the cold Hudson’s Bay Low will drift northeast toward Greenland while a cutoff cold core low over the northeast Pacific becomes attached to the jet stream as the week goes on. This has the effect of backing our northwest flow jet stream to westerly, bringing in milder Pacific flow. At subtropical/tropical latitudes, the subtropical high is becoming established in both the eastern Pacific and the Atlantic. In around three months or so, these highs will be over the mid latitudes and will constitute our summer heat dome and Bermuda High. This week, however, the highs push north and help shove the jet stream to the Canadian border as a ridge becomes established out west and over the western Atlantic. We will have a “weakness” in the flow, a weaker trough migrating from the southwest to the middle of the country this coming week. This is overall a mild to warm signal for us with the only weather-producing weather rain chances and mainly for the eastern district.
Next we’ll check the flow of the air masses this week. We’ll have lingering cool over the snowpack to start, but you’ll see a very different picture than the one for most of the last several weeks. These charts show the differences from average for late afternoon temperatures. The reason there is more warmth way up north is that their average temperatures are still much lower, so while the air mass is similar, comparatively they are further above their average than we are above ours. Our average temperatures are now in the 50s for highs.
As you can see, no cold highs moving in from the north this next week. The general surface pattern will bring weak area of low pressure from the Rio Grande Valley through the southeast and then off the Mid Atlantic coast, while a weak clipper low drops through the High Plains, Ohio Valley and also moves off the Mid Atlantic coast. Plenty of moisture is available for the southern system so heavy rains are anticipated for much of the southeastern quarter of the country including the Ohio Valley, and Mid Atlantic. These heavy rains may extend into the eastern forecast district and there is some room for a northward shift, although the northern clipper system may tend to keep this from happening. This is a similar setup to last week, but there is no cold air pre-existing or due in before the storm system moves northeast, so heavy snows are not an issue anywhere in the region. There will be a sharp cutoff between heavy rains and lighter rains and this will be near the eastern forecast district.
Out in the western district, there is very little precipitatable weather expected with the area in between the northern stream system and the moist southern one. Little to no precipitation is currently expected for the next 7-10 days. Kansas City has only had a trace of rain in March and may get into the last third of the month without any measurable rains. The western district sits just to the northeast of an area which has been suffering a multi-year drought centered from Kansas through OK and TX. The dryness has been expanding north and east and with this pattern for the next 7-10 days it looks likely the area will lapse into dryness or drought before the last third of the month arrives. This is not a good place to be heading into the growing season.
March is still one of the drier months in KC, but April/May/June begin the wettest period of the year and it becomes very easy to fall behind. As we head into the warm season, drought tends to propagate itself as heat domes tend to center themselves near drought areas, keeping rain away and intensifying the drought.
We’re jumping ahead into mid summer here, but here’s a big part of the reason we DON’T want to see drought in the Plains when we get into summer. Typically, the majority of the precipitation for the western district comes from nightly thunderstorm complexes. Kansas City’s average rains are 3.7″ in April, jumping to 5.23″ in May and June, and 4.45″ in July and 3.89″ in August. In summer, The subtropical high becomes centered over the hottest part of the country, the Desert Southwest — near the 4 corners at its peak. This produces WNW/NW flow aloft. Thunderstorms form along the High Plains over MT/WY/CO/NE as disturbances rotate around the subtropical high from the tropics, or are generated by thunderstorm complexes in the Southwest Monsoon then round the high and ride SE and in the northwest flow. These disturbances track ESE/SE as organized thunderstorm clusters, moving through the Plains into the Midwest.
When there’s widespread Central Plains drought, the subtropical high becomes centered further north and east, near the Panhandles (or even into OK/KS) because this is the hottest area of the country. By comparison the Desert Southwest is wetter and cooler. This has the effect of shifting the track of the rain-making storm clusters north..heading through the Northern Plains, Upper Midwest and Great Lakes. This leads to hot, rainless summers. The lack of rain reinforces the heat which reinforces the lack of rain..a feedback loop. Often times it takes a tropical cyclone tracking inland from the Gulf in the fall to break the cycle.
The April-June period has averaged dry in 2011, 2012, 2013 and in 2014. Let’s hope things turn around before the month’s done. We can’t forecast a dry and hot summer based on the lack of rain in early to mid March or a drought in the Plains now, but this does show how, should dryness continue another couple months this could become an issue.
The week in review: Winter Storm #3
Winter Storm #3 hit the eastern district this past week with another episode of heavy snow. As was the case with the previous storm there was a sharp cutoff to the snow totals from SE to NW. Take a look at the radar imagery as the storm was in progress. There was also a variety of snow, sleet ice and rain. Very heavy snow (purple) was over the Ohio Valley area. Click any of these images to enlarge:
The final gridded forecast showed totals as low as less than 1″ over STL to as much as 6.5″ SE of Carbondale.
Here’s the snow depth following the storm. Totals ranged from a trace to 2″ north and as much as 8″+ in southern Jackson County, IL.
The heaviest snows fell over W KY where totals approached 20″ over Hopkins CO east of the KY lakes area. The next two maps are visible satellite images showing snow on the ground well into the Mid South and over the eastern district. The grey splotch over SE MO is the forested area of the eastern Ozarks where the trees cut back on the reflectivity of the snowpack. A similar grey area appears over S IL just e of the MS river from Chester southward where the tree-lined bluffs cut back on the brightness of the snow cover.
The snowpack had a big impact on morning lows with subzero readings over the deep snow and single digits elsewhere. This will likely have been the coldest readings for the entire month of March for the east. The west was much milder due to the return of south winds and the lack of snow. Low to mid 20s were common there.
That snow pack’s effects continued into Saturday with the west rising into the 70s with the bare ground while readings were only near 40 or in the 40s over the snow.
The other story is shown here.. a return to Springlike temperatures with readings topping 70 in the western district.
Snowfall Season to date
We can’t yet put the snow season to bed. Although certainly not looking likely this week or next, heavy March snows have occurred. Counting last week’s storm, here’s a generalized map for 2014-2015 snowfall to date. The western district has been shortchanged with only 6-9″ in the southeast portion to 9-12″ west and north. In the east, season totals so far range from 9-12″ west to 12-18″ central and 18-21″ east. Localized higher (and lower) amounts are noted as this is only a very general chart.
Comparing that to the average season snows, typically the western district has anywhere from 18-21″ north to 12-18″ south and the eastern district 12-18″ north to 6-9″ south. This means snow has been near average to above average east and below to well below average west.
That will do it for this week. We’ll have our next weekly update on Sunday the 15th, when we’ll look to see if there’s any hope for some moisture in the west and how much longer the warmer Spring weather will last.