Sunday, March 15, 2015

Wintry Blast Expected to Close March, Open April

After a warmer ending to March, it is expected that a cold air mass will deliver one of the last punches of wintry weather to the country.

Tropical Tidbits
The image above shows 500mb geopotential height anomalies across the West Pacific. This forecast comes off the GFS model, valid for Wednesday, March 18th. We see a strong ridge located over Japan in this image, likely a result of the deep toughing further east in the North Pacific, as well as some more activity further west. When we apply the Typhoon Rule, stating that weather events occurring over Japan will 'come back' and 're-appear' in the US 6-10 days later, we could expect a generally warmer pattern persisting through about March 26th-ish, probably a bit longer.

Tropical Tidbits
The picture becomes much more ominous by March 23rd. By that time, the GFS model expects a rather large upper level low to drop into Japan, as shown by the deep negative anomalies over the island nation. In a nutshell, this means very cold weather is expected about 6-10 days later, likely in the very final days of March and the first week or so of April. If this happened in the middle of winter, we would likely be looking at record-breaking cold. However, due to the significant loss of snow-cover as of late, as well as climatological numbers telling us how quickly our average high and low temperatures are rising, this will likely be more of a strong cold blast, as opposed to a deep freeze.

To summarize:

- Predominantly warm weather is expected to persist through the end of March.
- The last few days of March and first week of April could see a shot of rather strong cold weather.