THE BATTLE OF THE "DRY" BULGE...
A few days ago it looked like more snow, (several inches of it) was in the offering for much of the central Midwest today. However, as I've pointed out since Monday, the system has trending further and further south with each passing day. Now, the system is on our doorstep and while the outcome is on track with my expectations, there's still some doubt about how much snow will fall in my far southern counties.
One thing that's abundantly clear is that snow of any measure of impact will be confined to my far southern counties (a common theme this winter). The overall consensus is that HWY 34 is roughly the 1" line. From there south 1-2 inch totals seem to be a good estimate with the heavier amounts the further south you go from that line. If the heavier totals of the NAM verify a 3" total is possible in extreme SE Iowa and WC Illinois. It will take time for the atmosphere to saturate so snow is not likely to develop until later Thursday afternoon where it will continue into the evening.
North of that threshold, amounts will be minimal with 1/2 inch to perhaps an inch possible as far north as I-80. From there up to HWY 30 a dusting is on the table but suffice it to say, little if any snow will fall north of the Quad Cities. Where it does snow down south, snow ratios will be high (15:1) indicating a dry fluffy snow that will be easy to move or plow. It will accumulate on roads though and some slick travel is likely from approximately HWY 34 south. So far the only counties in my area under winter weather advisories are Lee and Hancock shown below.
Wednesday evening the official NWS snowfall forecast shows 0 to 3 inches in the Quad Cities and 0-2" from Iowa City to Sterling Rock Falls. About the most models are indicating in the Quad Cities is an inch, some as low as 1/2 inch. I will be surprised if the Quad Cities picks up more than an inch.
If you look below, you can see on this graphic the odds of an inch of snow in Iowa City are 15% so my question is, why would you forecast a range up to 2 inches? In Davenport the odds of an inch are 25%, yet the range is up to 3 inches. I believe the data supports a far lower range than what's indicated and that's been my thinking for 48 hours.
As for modeling, here's the latest guidance. My money is on a blend of the EURO and GFS which seem to be handling the influx of dry air best. I expect they will win the battle of the dry air bulge when all is said and done. The hi-res CAM's which just yesterday showed as much as 7-8" around Burlington are now falling in line. Again, I emphasize the models shown below are not official forecasts but rather raw data which helps construct forecasts. They show this.
Here's the HRRR which I like, It's very close to what I think will end up verifying.
The 12K NAM
The 3K NAM
Once this disturbance drifts out of the area Thursday night, it's followed by an Arctic cold front of significant proportions Friday. Behind it brisk NW winds will usher in a stout but quick moving pop of cold air. Temperatures will fall rapidly late Friday and by Saturday morning lows will be in the single digits.
Those readings are at least 20 degrees below normal with some places in Minnesota as much as 44 degrees below their norms.
Wind chills are headed into the range of 5 to 10 below zero, perhaps 15 below in the far north.
As I promised yesterday, after highs in the mid 20s Saturday warming commences Sunday with highs climbing back into the 50s Sunday. Readings will gradually warm early next week before really taking off Wednesday and Thursday when 60s are expected, perhaps even 70 in spots Thursday.
Here's the 7 day temperature departures for the week long period March 15th through the 22nd. That looks good!