3:30pm CST Winter Storm Forecast

I continue to forecast major snow and ice storm roughly in between I-70 on the north and I-20 on the south. The forecast track of the storm has moved north since yesterday. 

Note: I have comments on the meteorology behind this forecast at the bottom. 

The winter storm will begin Friday in the southern Great Plains and then spread rapidly east. 

The Ice Storm Potential

For those who have never experienced a major ice storm, they can do damage on the order of a tornado but over a larger geographic area. Power failures in major ice storms are extensive and can last for days or even weeks. 

Here is the best available forecast of freezing rain accumulation. The amounts from this system can be a little on the high side but generally they are reasonable. These amounts are more than sufficient for significant power outages!

The NWS system for judging the greatest ice storm danger is in the red area. However, I believe the risk is just as high in North Carolina and Virginia. 

If you are in the areas where more than 1/2 inch of ice is forecast to occur, I would be:

• Traveling any distance will be difficult to impossible. If you have a chain saw, fill it with fuel.
• Get prescriptions refilled.
• Fill your car's tank with petrol or electric charge. If you have a gas can (used for your lawn mower, etc.), fill it. 
• Get extra cash (ATM's and electronic checkout systems don't work without power)
• Prepare a "go-kit" in case you need to evacuate due to an extended power outage. If so, remember to close the valve where water comes into the house. 
• If you have a generator, fill it with gasoline or kerosene. Remember: if you have a portable generator, keep the generator's exhaust away from your home's air intakes. There is a carbon monoxide danger otherwise. 

Heavy Snow Forecast

Here is the snow from the beginning of the storm to 6pm CST Saturday. The snow will continue to fall after that time in most of the area, especially east of the Mississippi River. 

Fortunately, the winds are not forecast to be high or extreme with this system so the amount of drifting will not be significant. 

Here is a preliminary storm total snow forecast (includes lake effect, etc.) east of the Mississippi since the snow will fall for another 24-hours beyond the map above.

In some areas, the amounts may be conservative. Due to the cold temperatures, the snow will be fluffy. 

Here is the NWS's winter storm severity index up to noon Sunday due to snow (does not include the ice threat).

Extreme Cold Forecast

These maps depict the temperature (not wind chill) forecast at 6am each day. The brutal cold will make the effects of the ice storm and heavy snow even worse as it will take even longer to clear. Remember: in any areas where the temperature or sunlight might allow a little melting in the afternoon, these brutally cold temperatures will cause refreezing during the night -- causing slippery roads the next morning. 

Friday

Saturday

Sunday

Monday

Tuesday

Meteorology Discussion

The Pacific satellite  image shows on low southwest of San Francisco as well as a developing low pressure center (arrow) west of Baja. The southern low is the key to a successful forecast in this case. While there are no upper air balloons over the Pacific itself (there are two balloon stations in Hawaii), the morning flights to Hawaii from the West Coast cities do provide some data. This has been part of the reason for the forecast shifting to the north. 

I salute NOAA/NWS for sending out two Hurricane Hunter aircraft to drop instrument packages over both the Pacific and Atlantic Oceans the next two days. That extra data, which should make it into the midnight and, especially 6am Thursday, model runs will add confidence to the forecasts. 

This morning's precipitable water map already shows higher than average values near the Gulf Coast. 

In addition, the skies over the Gulf are filled with clouds, indicating there is plenty of moisture in place to fuel this storm. 

My confidence this will be a major storm is high; the location confidence is moderate. 

Note: this forecast took 4 hours to assemble.