ENJOY THE PARTY, IT ENDS WITH A BIG THUD...
For nearly 2 weeks I've been pointing towards the period November 11th or 12th for what I believed was to be a significant pattern change that would bring our first real taste of winter. This was before models were seeing it and few others were talking about it. My rational was the MJO (Madden Julien Oscillation) going into a cold November phase, and the EPO (eastern Pacific Oscillation) trending strongly negative. I've explained it several times but the idea was that those 2 drivers in conjunction were a strong teleconnection for cold weather. The models didn't really see it clearly until a week later but they are all over it now.
Check this out, the 10 day temperature departures November 11-21st.
The Surface and 500mb features November 17th
The 500mb anomalies November 17th. Look at that cross polar flow.
Temperature departures the evening of November 17th. Virtually all of Canada, the mainland U.S. and Mexico is below normal. Even the Caribbean! I suspect this is overblown but even a scaled back version would be plenty fresh.
We may also experience wind chills in the 5-10 degree range at some point in the period November 17-22nd.
Between now and November 21st, guidance indicates most areas have a good shot at seeing their first measurable snow. I'm not seeing a good window for that yet (and certainly nothing major) but it is on the table. Here's what the ensemble mean of the EURO is indicating for snowfall the next 15 days.
The GFS ensemble has a similar look.
NOAA and the Climate Prediction Center is now in the game regarding the cold as well.
People, I rest my case. Cold is coming.
The Satellite is telling in that is depicts a deep western U.S. trough loaded with energy sitting off the coast of the Pacific Northwest. That is the system that will open the door for the first wave of cold Friday.
However, ahead of the storm we get one more chance to bask in near record warmth. The strong SW flow that's coming sends another tentacle of mild air into the Midwest. The process is in the initial stages Tuesday so another seasonally cool day is in store with highs in the low to mid 50s.
Wednesday warm air returns with a vengeance as the western energy penetrates the Rockies. Warm air advection may produce a period of clouds and perhaps a few light showers in the morning along a northward migrating warm front. After they move out, the afternoon sees temperatures jump into the range of 65-70 Wednesday. Thursday should be the warmest with readings of 70-75 expected. Unfortunately, both days will be quite windy, the price you pay for 70s in November.
The best chance of obtaining record highs comes Thursday. For the record, here's what record warm highs and lows look like Wednesday, Wednesday night, and Thursday.
THE PARTY COMES TO A RESOUNDING END...
Thursday evening a blue norther rips across the area and the party ends in a hurry with temperatures dropping like a rock. After highs in the 70s Thursday afternoon, lows by Friday morning will be in the mid 20s to low 30s, as much as 50 degrees colder. With wind chills in the mid teens it will feel as much as 60 degrees colder than 18 hours earlier. Yikes! Compared to lows Thursday morning the 24 hour change in temperatures is stark.
If the cold was not enough, a few strong thunderstorms are a possibility along the cold front somewhere in Iowa Thursday. Instability will not be overly high but shear looks strong enough to kick up a line of storms. This is what we call a low cape high shear set-up. Initially, some rotating supercells are possible before storms go linear into a squall line. The speed of the front will dictate where the severe potential sets up. Recent trends are for a faster front which if verified, puts at least my western counties in eastern Iowa at risk.
If nothing else, some fast moving thunderstorms are likely as the potent front zips east. The EURO shows a lightning flash density Thursday evening indicating convection just ahead of the front. We'll have to watch how this plays out the next 24-36 hours. Any rain that fall is generally expected to be light, worst case scenario 1/3rd of an inch.
After some morning sunshine Friday, the deepening cold air will allow stratus to invade the region due to steep lapse rates. The cold air aloft will likely lead to periods of clouds into the weekend and it would not be out of the question to see some widely scattered snow showers or flurries Friday night or Saturday. Highs over the weekend should remain in the low to mid 30s.
Last but not least, if you are up early a total lunar eclipse known as the blood moon will be ongoing. Totality occurs at 4:15am. when the moon takes on a reddish hue. Some scattered clouds are possible but hopefully we get a break where the event is readily visible.
On that note, we have a wild week of weather ahead of us and that is just fine by me. Roll weather...TS
