A WINTER STORM IN THE WORKS...
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LAST DAY OF FEBRUARY (meteorological winter)
Another February has come and is on its way out.The final hours will end Tuesday with a dry day but perhaps some light showers towards evening. The drier weather will be welcome as February has turned into a wet month with some areas seeing 3 to 4 times thier normal precipitation. Here's what the monthly amounts look like with less than a day to go.
The associated precipitation departures are signficant for February, normally a relatively light month for totals with moisture limited by cold air.
Monday's storm was a wet one despite the fast movement of the system. Water vapor (PWAT'S) reached close to all time February maximums around 1.3 inches. Many areas picked up an inch or more of rain. These are the Doppler estimates.
We should tack a little more on to monthly totals Tuesday evening thanks to a fast moving disturbance that kicks up some showers to end the month. Totals will be light but a few locations could wring out a 1/10th of an inch. The south seems to be favored for the heavier showers.
THE NEXT WINTER STORM UP....
That leads us to an impressive closed low that is expected to eject out of the mean trough situated over the southwest U.S. It promises to generate another very energetic storm with a 976mb surface low emerging and tracking northeast towards St. Louis Friday morning. This is another one of those storms that causes models fits due to complex phasing between the northern and southern streams. The EURO shows a closed negatively tilted 500mb circulation center situated over SC Missouri early Friday.
As with recent storms, the gulf is wide open and a tremendous fetch of moisture surges north ahead of the system. Available water vapor (PWAT'S) reach 1.50 inches in southeast Illinois with nearly an inch up to SE Iowa.
Remarkably, those levels are once again 400% higher than normal in EC Illinois.
The big question now is where does the storm track? The EURO ensemble mean, comprised of 51 members shows the uncertainty that exists by plotting the surface low location of all its members Friday morning. For a high confidence forecast we would like these to all be clustered within 100 miles of a specific location. In other words, the smalller the spread the more predictable the atmosphere is. Right now we have a signficant range that could put my area directly in the path of the storm or have us miss it altogether.
The control, which is the most likely solution of the ensembles (an average if you will) shows the low in this postion at noon Friday. On the EURO that puts us in the snow on the NW flank (or cold sector) of the storm.
For comparison purposes it currently indicates this for snowfall, (far from a sure thing as you will see below).
The associated odds off 3 or more inches of snow is at 70-80 percent for the majority of my area.
COMPARING THE EURO TO THE GFS
The GFS is not quite as intense and is a little further southeast on its depiction of the storm. Its ensemble members show the surface low about 175 miles further southeast than the EURO. It's not as strong on the central pressure as well.
That relegates the odds of 3 or more inches of snow to more like 40-60 percent with the highest threat in the southeast.
The GFS solution points to totals like this. They are lighter and focused further to the southeast on a line from Burlington to a little east of DeKalb.
I will say this, the plots of the surface low by the various GFS ensemble members show about a third of them further NW and stronger, closer to what the EURO is indicating. In general, the clustering is tighter than what the EURO indicates so at least on the GFS, confidence is higher the low is headed on a track close to St Louis.
The Canadian GEM is basically warmer and a miss to the southeast.
The national model blend is snowy for my entire area.
In summation, it appears a winter storm is going to impact the central Midwest and chances have increased significantly that it will impact my area late Thursday night and Friday. If current trends hold advisories/watches may be issued by the NWS around Wednesday. That said, if phasing is not realized to the degree currently indicated, this would significantly weaken the system and take the worst of its impacts east of my region. Conversely, a stronger solution could shift it a but further northwest. All we can do now is play the waiting game. We will know more in the next 24 hours as the storm begins to enter the data rich terrain of the west coast. Stay tuned and roll weather...TS