So Long Snow & Hello Spring!
Snow Is Going, Going, Soon Gone
Meteorological spring is now just two days away! As I mentioned yesterday, this last weekend of winter should be its warmest. Today will be the sixth day in a row with above average temperatures. The recent winter warmth has done a number on our snowpack. The snow depth at O'Hare has dropped 15" from its peak of 21" on the 16th. It has fallen 11" in just this past week. Since the melting hasn't been too rapid and there has not been an significant rain over the past several days, we have avoided flooding. More on the spring flood risk below.
Southwest winds and some sunshine should push todays highs into the lower to middle 50s. Average highs for this date are around 40°.
Mild Start To March
After our "warm" weekend we do drop back below average on Monday. Aside from that the first week of March should be fairly mild. Longer range forecasts keep this pattern going well into at least the middle of the month.
The temperature anomaly forecast has us warming back up by Wednesday from 10° to 15° above average. Most of the country will be mild for early March.
No Significant Snow
The latest GFS model's meteogram does not show any significant snow for at least the next ten days. Some light rain is possible early Sunday morning, a little light snow Monday, light rain on Friday and then some light rain a week from Monday.
The GFS model total snowfall accumulation all the way through the next fifteen days only squeezes out around a dusting of snow north and west of the city. That snow would fall early on Monday. Any show that does stick will melt off quickly as highs Monday will be above freezing.
Strong Signal For Mild Pattern
The signal is growing stronger for a relatively mild first and second week of March. Average highs for this period in Chicago are in the lower 40s. The latest 6-10 day temperature probability forecast has us outlooked for above average temperatures overall from March 4th through March 8th. The longer range 8-14 day forecast keeps us favored for above average temperatures overall from March 6th through March 12th. The highest probabilities are centered almost directly over Chicago.
From Quiet To More Active Pattern
The long range precipitation probability forecasts keeps this relatively quiet pattern going through the first week of March and then favors a more active pattern by the middle of the month. The 6-10 day forecast favors us for below average precipitation overall from March 4th through February March 8th. The longer range 8-14 day forecast has us outlooked for above average precipitation overall from March 6th through March 12th. The risk for spring flooding is above average for many area rivers. More on that below.
The Climate Prediction Center's seasonal forecast for spring suggests a mild and moist pattern overall here. The temperature probability forecast for the months of March, April and May have us outlooked for above average temperatures overall. The precipitation probability forecast for the same period has us outlooked for above average precipitation overall.
Spring Flood Risk Forecast
The National Weather Service considers many risk factors for spring flooding. They include snow cover, soil moisture, and current river conditions.
"A significant snow cover with high water content can increase the chances of flooding once warmer weather melts the snow. Elevated soil moisture conditions reduce the amount of rainfall that is soaked up by the ground and increase the amount of water that then runs off into area streams. Above average river levels reduce the river rise required to reach flood stage, while below average river levels would require an increased amount of river rise to reach flood stage."
Their latest forecast suggests the flood risk is above average for many of our area rivers. The Des Plaines and Fox rivers in particular need to be watched closely.
Here is my 7 day forecast:
Today: Partly to mostly sunny High: 52
Sunday: Light rain possible early, windy, partly to mostly cloudy Low: 38 High: 50
Monday: Mostly sunny Low: 26 High: 38
Tuesday: Partly to mostly sunny Low: 25 High: 45
Wednesday: Partly to mostly sunny Low: 34 High: 52
Thursday: Partly to mostly sunny Low: 38 High: 50
Friday: Partly to mostly sunny Low: 33 High: 50