GOING UP, THEN WAY DOWN LOW...
No question this is one of those good news, bad news forecasts. Generally, I like to find out the bad news first and get it out of the way. However, in this case, from a timeline stand point it makes sense to start with the good and so we shall.
EMBRACE THE WARMTH
A potent storm is gathering over the Rockies that will bring a blizzard to North Dakota and sub zero temperatures later in the week. We, are fortunately on its warm side (at least initially) and that results in another big warm-up with the potential for near record highs, mainly Thursday. Here's what the storm looks like at 500mb Wednesday evening,
This surge of warm air never made it to the Midwest Tuesday but it arrives Wednesday morning in the form of a strong warm front. The warm advection associated with it could spark some widely scattered showers and storms that might dot parts of the region Wednesday morning. These would quickly come to an end from south to north during the morning as the warm front and its forcing moves into Wisconsin. The afternoon turns breezy and mild with highs of 69 north to 75 in the south, pushing records.
By Thursday morning look at the warm air the storm is drawing into its center over South Dakota. Departures of 25-35 degrees above normal are common over the central Midwest.
Actual temperatures to start Thursday will be near or slightly above 60. The GFS shows this for lows.
That should blow away the exisiting records for "warm" low temperatures on November 10th. 48 is the record in Dubuque and 53 is the mark in Moline.
As Thursday progresses, a powerful cold front approaches dishing out SW winds that could gust 35-40 mph. That is expected to send highs into the range of 70 north to 78 south. Here's what the GFS indicates. As you can see in the graphic above that should give record highs a real run for their money.
The combination of the impinging strong jet and gusty surface winds also increases moisture with dew points approaching 60.
That's a significant level of moisture by November standards and should be enough for thunderstorm development when the front streaks towards the area late in the day. Depending on the timing and amount of heating, strong to even a few severe thunderstorms are possible. The low CAPE (instability) and high shear environment could even spin up a couple brief tornadoes. Not a great threat but something to watch. The 3k NAM shows the storms lined up along the cold front in the late afternoon.
SPC shows a the slight risk area for severe weather just catching my western counties in Iowa. I still think given the speed of the front this may be moved slightly further east in later outlooks reaching as far east as the Mississippi.
TIME TO GET DOWN...
Thursday night it's time to get down, way down thanks to the passage of the strong polar front. Any showers and storms end early as the front hits bringing sharply colder and drier air into the region. After those near record highs in the low to mid 70s in the afternoon, temperatures free fall into the upper 20s to low 30s by Friday. Here's the 24 hour change showing the 30-45 degree cool-down around the central Midwest.
During the day Friday and into Saturday, strong cold air advection will see to it that wintry temperatures grip the region into next week. After sunshine to start Friday, low clouds will wrap around the passing system and invade the region Friday afternoon. Some minor vorticity Friday night and steep lapse rates Saturday should keep periods of clouds going along with some hit and miss snow showers or flurries. Nothing to worry about except the fact that snow is a four letter word some of you do not like to hear even in the lightest context. As for weekend highs, they will likely remain in the low to mid 30s Friday-Sunday. Lows Saturday morning should be in the mid to upper 20s with some upper teens possible Sunday morning if clouds break.
Below you can see the energetic pattern across N. America with our system wrapping up over California.
From the data I've seen, it appears the coming cold snap will prevail for much of the next 10 days. The EURO average 10 day temperature departure for the period November 10th-20th shows cold across the country.
Overall, after Thursday night precipitation appears to on the light side. However, some of what ends up falling could come as snow. The EURO ensemble mean has this for total snowfall through November 20th. Confidence is low we would see anything more than snow showers or flurries but I like our chances of seeing our first dusting somewhere between November 15th-20th. Fingers crossed!
Speaking of chances, the EURO indicates 50-60 percent odds of 1 inch or more of snow in my area during the period ending November 23rd.
HOW LONG DOES THE COLD LAST?
If you aren't ready for winter to lock in just yet there is some positive news. The MJO which heralded the coming chill with its tour of phase 7 is projected to work its way into phase 6 November 18th. That would imply temperatures getting back to more seasonal levels around November 20. In December that is a blast furnace so as one who likes snow, I hope it departs that phase quickly if indeed it gets there.
Additionally, the EPO by the end of its phase forecast below is going from an extremely negative (cold phase) to a more neutral state which implies at least a temporary breakdown of the huge ridge off the Pacific NW. Another sign the cold should ease around November 20th.
Meantime we are rolling into phases 8 and 1 of the MJO. The associated temperature analogs in November are cold and that is exactly what's on the table starting Friday.
Well, then, get ready for a couple of windy warm days. Odds are high we won't be this warm again for at least 3 months. Then again, the way things are going, who's to say? Nothing shocks me much anymore! Roll weather...TS
