SHOWERS ON SOME SHAMROCKS...
Fantastic spring weather prevailed around the Midwest Wednesday with highs reaching 70 along and south of I-80. Mostly sunny skies and a gentle breeze added to the overall perfection of the day. Now it's St Patrick's day and while Irish eyes are smiling, our run of weather luck is quickly running out. By the end of the day, showers may fall on our leprechauns and shamrocks near and north of I-80. Keep your lucky charms and umbrellas handy up that way. The south remains nice and mild. Everybody gets a chance to use the umbrella Thursday night through Friday night as a slow moving storm brings rain, colder temps., and perhaps snow to some in the west.
MUCH NEEDED RAIN...
The change in our weather is tied to an upper air low which briefly closes off at 500mb as it emerges from the Texas Panhandle. The sub-tropical jet generates a nice flow of moisture and a lengthy period of warm air advection. Here's the 500mb jet structure Friday morning as the system enters Missouri.
You can watch the evolution of the surface features and precipitation pattern in this animation of the EURO Thursday morning through Saturday afternoon.
That's a pretty good sized rain shield. With much of my area in abnormally dry to moderate drought conditions and the growing season fast approaching, the rain is needed.
As far as precipitation totals are concerned, models continue to crank out 1/2 to 1 inch amounts on all of my area. However, there is some variability where the heaviest rains occur which you can see in the rainfall forecasts below.
The 3k NAM
The 12k NAM
Another aspect of the storm which is going to be challenging is the threat of wet snow in the northwest third of my area. If snow develops, it's most likely to occur later Friday or more likely Friday night, as temperatures cool after sunset. If I had to make a guess right now, I would say any snow would be just out of my area northwest of Cedar Rapids and Dubuque. Even if snow occurs in the far northwest, with recent warmth it's unsure how much of it would stick to roads. It may very well be that any light accumulations would be on grassy and elevated surfaces. We will have to watch this closely as we obtain more data and get closer to the event. Right now I just don't see much in the way of snow in my area. Here's what models are currently showing for snow totals. Note there is a wide range of solutions and confidence remains very low any one being correct. Also keep in mind that what you are looking at is just raw model output and not official forecasts. This is the data we look at to ascertain trends that eventually lead to forecasts.
The GFS (the snowiest and most ominous out west)
The NAM, close to the GFS
The 3K NAM, lighter but in the same general area as the GFS and 12K NAM. These are all U.S. based models.
The EURO has little in the way of snow.
The GEM spares Iowa entirely keeping any snow in Wisconsin.
Temperatures are going down the next few days with clouds, areas of precipitation, and winds turning to the northeast. The cooling will be most pronounced in the north Thursday where the colder air gets established first. The southern half of my area enjoys another warm day. Here's what the GFS indicates for highs. One more mild day for areas near and southeast of the Quad Cities.
Friday with occasional rain temperatures will be held to the 40s, maybe upper 30s far north. Here's what the EURO shows for highs.
Saturday any lingering rain (or snow) ends early and the rest of the day could be spent fighting clouds. Highs will likely make it back into the upper 40s east to low 50s west. If by chance, the heavier snows of the GFS and NAM verify readings could be quite a bit colder in the NW with it on the ground at least part of the day.
Sunday and Monday it's back to spring with highs climbing well into the 60s under SW flow aloft. Eventually, the next system ejects out of that pattern bringing rain chances back into the area for Tuesday and Wednesday. It does appear that this could be another good rain producer for much of the Midwest. The clouds and rain will gradually cool temperatures those days but readings will still remain above normal.
Beyond that the pattern looks significantly colder for at least the latter half of next week. Plenty of time to figure that out. Happy St. Patty's day and may the luck of the Irish be with you. Roll weather...TS