SHOUT IT FROM THE ROOF TOP
- 46 minutes ago
- 4 min read
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PITTER PATTER, YEA BABY THAT'S RAIN...
Shout it from the roof top, rain returns! This vital commodity we take for granted, has been sorely missing from our world since mid-August. On thos day alone, two different rounds are expected that should be enhanced by thunderstorms. If things go the way they are shown, many of us have a crack at an inch. In areas where thunderstorms are active, up to 2 inches are shown in a couple narrow swaths. For many, a 2 inch rain would constitute approximately a third of all the rain we've seen in over last 6 months combined (in a single day).
The period August 15th through March 5th, just 6.48 inches of precipitation has fallen in Dubuque. At the Regional Airport that is the driest ever for that specific stretch of time. Normal is 14.87 inches.
For the same 6+ month time frame, these are the rainfall deficits around Iowa. The southeast half of the state on into NW and WC Illinois has numerous locations with deficits of 8-10 inches. Ironically, there is one little spot in NE Iowa around Decorah where there is a surplus of 8.59 inches. Talk about an island in a sea of dryness!
As you can see, we need to make some hey! Let's get the ball rolling today with a short wave that's ejecting from the main trough further west. Overnight that energy, combined with a healthy low level jet, fueled a mass of showers and thunderstorms that lift northeast across the region Friday morning. There is enough elevated CAPE and shear to generate convection. With low freezing levels, these elevated storms could produce a bit of hail, as well as some wind gusts of 40-50 mph, most likey below severe thresholds.
More important, moisture is expected to be plentiful and the forcing will have water vapor of 1.20 to 1.40 to work on. Not bad at all.
The simulated IR satellite of the HRRR early Friday shows some cold cloud tops in the darker shades of red indicating its sensing some lofty thunderstorms.
The HRRR simulated rainfall product indicates some 50 DBZ returns which also implies some welcome downpours in the stronger updrafts.
By the time the first wave departs my counties in the NE in the afternoon, the HRRR shows much of the area, aside from the far SE picking up .50 to 1.50 inches of rain. Come on down!
The NBM-National Model Blend has this through the day Friday.
The ending of the rain Friday afternoon coincides with the passage of a warm front that sends highs to much warmer levels. It does appear the warm front may be an hour or two slower than in past runs which could delay clearing in the northern 2 tiers of may counties. That could limit heating a bit in that area with highs being held to the mid 60s closer to HWY 20. Otherwise, 70+ looks like a good bet from roughly I-80 south. Here's what the EURO and GFS show.
The EURO
The GFS
This late period of heating will be critical as to what happens with the next round of storms Friday eveing. Moisture will be in place but the atmosphere will need to recover from the initial wave of morning rain. The moisture will be there so it appears the re-charging process should occur. The HRRR has CAPE to HWY 20 by 5 in the evening. However, it is far more pronounced from I-80 south where more heating takes place.
At this point, (early evening) we play the waiting game for the primary energy and a cold front to arrive out of central Iowa where it impinges on water vapor of 1.30 inches. How events unfold is tricky to see at this point because mesoscale details from the earlier convection are not resolved, such a CAPE and outflow boundaries.
That said, SPC continues to highlight the area with a level 2 risk of severe storms. At the very least isolated severe storms seem possible with strong winds the primary threat. I've also seen some indication of organized lewps or bows forming ahead of the front. In such situations, the quasi-linear structures can foster the upscale growth of Quasi Linear Convective Systems (QLCS). While typically know as wind producers, they can produce some brief weak tornado spin ups. Since the line would be arriving after dark that should hinder instability locally and keep the threat minimal. But again, until we see the evolution of the first line of morning storms, this is just educated speculation. Meantime, SPC has the region in a the level 2 risk described above on Friday.
Including the second round of rain Friday night, this is what guidance is showing for rainfall potential through Saturday morning. Keep in mind convection can skew amounts due to its somewhat erratic behavior.
The HRRR
The 3K NAM
The Canadian 10k RDPS
The NBM-National Model Blend
The EURO
The GFS
After midnight Friday, the cold front sweeps east across the region dramatically cutting off moisture and abruptly ending the showers and storms. With a switch to W/NW winds, cooler, drier air settles in for Saturday. Temperatures are mild to start early, but fall in the morning and by afternoon are in the range of 45 to 50, which is about where they remain the rest of the day. At least the sun will be out.
Sunday and Monday look quiet and pleasant. Highs go from 60-65 Sunday to 66 to 73 Monday. Rain chances return Tuesday with similar, to perhaps slightly cooler readings.
It looks as though that rain dance I've been doing the past week is finally paying dividends. I know my wife has seen enough of what she calls "the one legged hokey pokey". Dancing was never my thing. Have a stellar weekend and roll weather...TS
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