THE CALM BEFORE THE "SNOW"-STORM...
A SECOND PRINTING OF MY NEW BOOK IS ON THE WAY...
250 NEW COPIES OF DERECHO 911, IOWA'S INLAND HURRICANE ARE AVAILABLE. Around Christmas we sold the last of the 1500 copies of our book on this historic thunderstorm, the most damaging in U.S. history. Due to continued demand we have ordered a limited number of 250 for those of you interested in having the most authoritative account of this extreme event. You can get yours at derechobook.com
IT'S SNOW JOKE, HEAVY SNOW IS KNOCKING ON THE DOOR.......................
For almost a week I've been preaching to the choir (that's you whether you sing or not) that a major winter storm was in the offering to start the week. There's been a lot of give and take regarding the potential amounts but since Thursday there's been general agreement that much of my area, especially the region from HWY 20 south was prime picking's for the worst of the snow.
Heading into the event later today winter storm warnings remain in effect for my region from HWY 20 south. Snow will develop late morning in the far south and spread into the north during the late afternoon. Here's the winter storm warnings as of the time of this posting which are out until noon Tuesday.
The storm itself is rapidly coming together early Monday as the 500mb energy lifts out of the southwest. The GOES water vapor imagery shows the colder (enhanced clouds) surging northward ahead of the vigorous dynamics centered in WC Texas.
The big challenge with this system is the fact the mid-level circulation which starts moisture rich Monday is expected to get sheared and stretched as the day progresses. With time the heavy snow producing trowel which begins with focused lift, convergence, and moisture slowly but steadily weakens as the storm drifts east. For that reason amounts will be heaviest west of the Mississippi rather than off to the east where the storm grows less intense.
The tricky part of the forecast is determining how soon the disturbance weakens as that will have an impact on accumulations throughout my area. As it stands now the storm should be strong enough to dump 5-10" of accumulation on the majority of my area. The far north and south will see the lower totals. Again, depending on intensity, a few places near I-80 in SE Iowa could see amounts in narrow convectively induced bands that reach 10 to 12". At the time of this posting this is the official forecast from the NWS.
Since that forecast was issued, new runs of the operational models have come down and these will be analyzed overnight along with additional data and trends to generate updated snowfall forecasts as the snow approaches Monday. I will of course have that for you in updated posts as the day and the event unfolds. For now, here's the latest raw data from the 0Z models. Again, these are not snowfall forecasts, just the raw model data that is used to create a forecast. What we look for is consistency in the various solutions. One thing they all show is totals decreasing from west to east as the storm slowly but steadily weakens . Here you go using the Kuchera method which takes into account where snow ratios are expected be greater than the standard average of 10:1.
The Canadian GEM
The 12k NAM
The 3k NAM
I will be back with you around mid-day with fresh models, snowfall forecasts, and my thoughts on the latest trends as the storm gets set to strike. Until then, roll weather...TS