LET THE WARM-UP BEGIN...
After another sub-par day day Wednesday (damp, dreary, and depressing by all accounts), our ship is is getting set to sail to warm-up land as the week enters its final phases. The change can't come fast enough for me. Here's Dubuque's April temperatures and 14 of the months 20 days have had highs at or below 50 degrees. Average temperatures are running close to 6 degrees below normal.
You know its not good when Easter is colder than Christmas, which was the case this year by far. In the graphic below from the Iowa Mesonet, you can see in the shades of blue where that was the case. Some areas also had a white Easter but a brown Christmas. Another weird oddity....
At least for a few days, we're gonna buck the trends and get that temperature on the plus side of average. Here's what the EURO and GFS operational models are showing for temperature trends in the Quad Cities the next few days. If things go well Saturday, some areas could register their first 80 degree high of the year. Oh I like that party!
Here's the change in the storm track at 500mb that brings the warm-up. First though, the cool set-up that brought a record low to Cedar Rapids of 19 degrees Monday morning.
Now the 500mb pattern going into the weekend that brings the chance of an 80 degree high.
The set up above also brings moisture into the Midwest. Look what happens in that regard. Water vapor stands at a paltry 0.15 inches Tuesday.
By Friday amounts have increased to nearly 1.50 inches in southeast Iowa.
With moisture, warmth, and a couple fronts to interact with, the weather will also remain active. I see no weather problems Thursday with partly sunny skies and highs reaching the mid to perhaps upper 60s. However, issues arise Thursday night when a strong warm front enters the picture. It's tight baroclinic boundary combined with an increasing low level jet sets up the potential for active showers and thunderstorms to develop, especially in the southern half of my area. If storms fire, which seems likely, they have the potential to be hailers in spots. SPC shows a 5 percent risk of damaging hail in my far SW counties later Thursday night. Not a huge threat but conditions are ripe for hail that would have less significant impacts.
Those areas that miss the storms in the north Thursday night will get a chance Friday near and north of the warm front which continues it's slow but steady trek through Iowa and northern Illinois. Again, a few storms could contain some hail but I think the greatest threat from any storms Thursday night or Friday will be heavy rain. It would not surprise me to see a band of 2"+ rains near or north of I-80. The HRRR is very bullish on that potential. Here's what models are suggesting for rain totals over that period. This could vary significantly and is nothing more than raw guidance. It does however help to establish trends. You will notice there is still variance among models where the heaviest rains set up.
The Weather Prediction Center
The 12k NAM
Another challenge with this forecast is how far north the warm front gets by Friday evening (which dictates how warm temperatures end up). I am still of the opinion that the outflow from morning storms and a southeast wind will make it difficult for the front to get much past I-80, perhaps as far north as HWY 30. That sets up a big temperature range of up to 20 degrees from north to south. The EURO matches my thinking best and so that's what I'm leaning on. Here's what it shows for highs Friday. I'm confident the south gets warm but the potential for a bust is there in my central counties where the cool air could be difficult to dislodge. The strength of Thursday night's storms will have a say in the outcome. Something we just won't know until it happens.
The GFS is much warmer all the way to HWY 20. I hope it happens but I have serious doubts.
It does appear the warm front skips north out of the area Friday night and into the warm sector we all go Saturday. Chances for storms look small as forcing remains to the west during the day. However, with dew points in the low 60s and highs in the upper 70s (potentially 80), it will feel like spring. It will be a blustery day but that's the price you pay for a warmth in April.
Saturday night with moisture and mild air in place the potential exists for a band of thunderstorms to develop ahead of a cold front which marches into the area. These would arrive in my far western counties between late evening and midnight. A strong storm is possible but by that point we will be losing instability as temperatures cool after sunset. That would indicate a weakening trend in storms as they enter my area and approach the Mississippi later Saturday night. For that reason, the severe weather threat looks relatively low in my central and eastern counties. In fact, the broken line of showers and storms may not reach my counties southeast of the Quad Cities until Sunday morning.
The Storm Prediction Center does have a slight risk outlook in effect for severe storms Saturday just to my west.
Any lingering rain ends early in the NW Sunday but may take most of the morning to move out of my SE counties. Temperatures to start early Sunday will be in the low to mid 60s but will begin falling in the morning in eastern Iowa before doing the same in Illinois by afternoon. With a brisk NW wind readings will be in the 50s by evening.
That leads us into another chilly period Monday and Tuesday. But hey, as the saying goes, "it was nice while it lasted". Have a productive day and roll weather...TS