Chris's Corner - March Snow Likely - But Not Much
Mar 9, 2022 21:54:09 GMT -6
BRTNWXMAN, jeepers, and 2 more like this
Post by Chris Higgins on Mar 9, 2022 21:54:09 GMT -6
Ok... been off from TV this week and had a long week of military time from Friday through yesterday so I haven't been all that interested in getting into forecasting. But I figured I need to throw something out there for folks. And since it's a new system for a new month... how about a new thread.
The look of the system has changed a little bit since I posted last about this thing. We went through a couple of days where forecast soundings failed to saturate in the layers that were cold enough for snow and it looked like any icy mix was possible. Now, the soundings have come into agreement that we should go from a brief period of rain rain at the onset (very brief) and then a quick transition to wet snow.
This is not a classic winter storm in any way, shape or form. There is no deformation zone, no low pressure, not a lot of anything except the mid-level front brushing up against bursts of moisture and warm air advection. I'm just not terribly impressed here.
Major limiting factors across most of my viewing area include...
1) warm ground after a couple of days of fairly mild...although not super warm temperatures
2) time of year and time of day... the sun angle is getting up there now and daytime snow accumulation is tough... especially on roads and even more so with marginal surface temperatures.
3) Marginal surface temperatures...likely near freezing...and maybe even above freezing Friday for any snow that falls southeast of I-44 in MO and south of I-70 in Illinois.
These limiting factors lead me to believe model snowfall forecasts are much too generous. Snow depth change products are a better fit... and even those may be too beefy when you consider my standard "wet QPF" deduction of around 20% off the top.
Some factors that do favor some enhanced snowfall...
1) Temperatures are cold aloft and there is some modest lift through the DGZ...although the greatest lift is above it. The problem is that this happens during the day for areas along and southeast of I-44 in MO and south of I-70 in Illinois and this will limit effective accumulations despite what should be a few hours of decent snowfall rates.
2) Northwest of I-44 in MO and north of metro STL... that better alignment of DGZ and lift occurs at night... and this will allow for a greater opportunity to get a "base" down that will allow the snow to stick longer and begin to accumulate. This fact, along with what appears to just be better dynamics leads me to cover the western and northern parts of my viewing area with 2-3 inches... much of which will be on the grass... but slushy roads are likely...especially those roads that get little sun.
Further south... there's just too many things arguing against effecient snowfall... so I'm going to go with a general 1" and spots of 2" for the northern and western STL metro... and taper to 1" or less for STL City and points east.
As the sun goes down and the band of snow slithers east... accumulations may ramp up a bit south towards the Kaskaski River because of the lowering sun angle Friday afternoon and evening. But even there... 1-2 seems the best call to me at this juncture.
The look of the system has changed a little bit since I posted last about this thing. We went through a couple of days where forecast soundings failed to saturate in the layers that were cold enough for snow and it looked like any icy mix was possible. Now, the soundings have come into agreement that we should go from a brief period of rain rain at the onset (very brief) and then a quick transition to wet snow.
This is not a classic winter storm in any way, shape or form. There is no deformation zone, no low pressure, not a lot of anything except the mid-level front brushing up against bursts of moisture and warm air advection. I'm just not terribly impressed here.
Major limiting factors across most of my viewing area include...
1) warm ground after a couple of days of fairly mild...although not super warm temperatures
2) time of year and time of day... the sun angle is getting up there now and daytime snow accumulation is tough... especially on roads and even more so with marginal surface temperatures.
3) Marginal surface temperatures...likely near freezing...and maybe even above freezing Friday for any snow that falls southeast of I-44 in MO and south of I-70 in Illinois.
These limiting factors lead me to believe model snowfall forecasts are much too generous. Snow depth change products are a better fit... and even those may be too beefy when you consider my standard "wet QPF" deduction of around 20% off the top.
Some factors that do favor some enhanced snowfall...
1) Temperatures are cold aloft and there is some modest lift through the DGZ...although the greatest lift is above it. The problem is that this happens during the day for areas along and southeast of I-44 in MO and south of I-70 in Illinois and this will limit effective accumulations despite what should be a few hours of decent snowfall rates.
2) Northwest of I-44 in MO and north of metro STL... that better alignment of DGZ and lift occurs at night... and this will allow for a greater opportunity to get a "base" down that will allow the snow to stick longer and begin to accumulate. This fact, along with what appears to just be better dynamics leads me to cover the western and northern parts of my viewing area with 2-3 inches... much of which will be on the grass... but slushy roads are likely...especially those roads that get little sun.
Further south... there's just too many things arguing against effecient snowfall... so I'm going to go with a general 1" and spots of 2" for the northern and western STL metro... and taper to 1" or less for STL City and points east.
As the sun goes down and the band of snow slithers east... accumulations may ramp up a bit south towards the Kaskaski River because of the lowering sun angle Friday afternoon and evening. But even there... 1-2 seems the best call to me at this juncture.
