WARNING: The chances of a significant snowstorm in April are VERY low. This post is only showing one model's output, and is made to alert people that there could be some snow in this timeframe. I do NOT expect we see these amounts verify exactly.
I'm watching the April 13-15 timeframe for what could be a strong storm system resulting in, yes, snow.
Shown above is an image depicting the most recent ECMWF model snowfall forecast for a potential April 13-15 snowstorm. The exact image showing the ECMWF snowfall output cannot be displayed for copyright purposes. In this most recent forecast, we saw a swath of 2 to 6 inches of snow stretching from northern Missouri into western Iowa and central Illinois, before moving northeast into both land masses of Michigan. Inside that accumulating snow swath, we then see a rather large area of 6 to 12 inches-plus of snow from western Iowa and northern Illinois into southeastern Wisconsin, before continuing into the northern LP of Michigan. As I mentioned above, I do not expect we see these snow amounts hitting for this timeframe; this post is merely to alert people about the potential for snow.
There is some merit to the idea that we may see a strong storm system, as the ECMWF is suggesting. Shown above was the observed 500mb height anomaly chart over the Western Pacific, where cool colors depict negative height anomalies/stormy weather, and warm colors represent quiet, warm weather. On the morning of April 6th, we saw a trough moving through Japan, possessing a pretty decent strength. This is significant, as it directly relates to what we may see in this April 13-15 timeframe .There is a rule, well explained by Joe Renken, that states a weather phenomenon in East Asia will be reciprocated in the United States 6-10 days later. This means that if there is a storm system in Japan on a certain day, we can expect a storm in the US 6-10 days after that. The same goes for high pressure and warm weather. Thus, we can expect a storm in the US on an April 12-16 period, and the April 13-15 ECMWF snowstorm falls right within this timeframe. Additionally, this trough in Japan brought along some pretty cold weather, which COULD contribute to additional chances for snow in this potential storm system.
Looking at the raw ECMWF surface pressure forecast for the morning of April 14th, we see the storm system at a pretty low minimum central pressure, likely below 1000 millibars, in the middle of Missouri. The ECMWF model may be locked on to this snowstorm idea, but its ensembles are much more uncertain.
The image above shows the projected mean surface pressure by the ECMWF ensembles, as well as the spread among all ECMWF ensemble members in the shown colors. We first observe how the ensembles are much less enthusiastic about the idea of a storm system for this timeframe, only bringing a minimum 1006 millibar swath of low pressure over an area just to the east of the ECMWF model. This sort of weaker projection is to be expected, as these ensemble means take the average of 52 ensemble members, unlike the ECMWF model, which only shows one solution. The next item we observe is the swath of oranges and yellows over the Plains and Midwest. These warmer colors indicate a higher spread in the ensembles; in other words, the ensemble members are in higher disagreement with one another over this higher spread envelope, thus indicating increased uncertainty. While this would initially disprove the idea of a storm system in this timeframe, note how the highest spread is located further west of the ensemble low pressure alignment, more in line with the ECMWF model. All in all, this means that the ensembles are seeing this idea of a storm, but aren't biting yet.
To summarize:
• A potentially major storm system is expected in the April 12-16 timeframe.
• Colder than normal weather may arrive with this storm system.
• Model guidance is hinting at a snowfall event during the April 13-15 timeframe, in conjunction with this potentially major storm system.
• There is high uncertainty with this potential event. Caution must be used.
Andrew
I'm watching the April 13-15 timeframe for what could be a strong storm system resulting in, yes, snow.
Shown above is an image depicting the most recent ECMWF model snowfall forecast for a potential April 13-15 snowstorm. The exact image showing the ECMWF snowfall output cannot be displayed for copyright purposes. In this most recent forecast, we saw a swath of 2 to 6 inches of snow stretching from northern Missouri into western Iowa and central Illinois, before moving northeast into both land masses of Michigan. Inside that accumulating snow swath, we then see a rather large area of 6 to 12 inches-plus of snow from western Iowa and northern Illinois into southeastern Wisconsin, before continuing into the northern LP of Michigan. As I mentioned above, I do not expect we see these snow amounts hitting for this timeframe; this post is merely to alert people about the potential for snow.
Tropical Tidbits |
Looking at the raw ECMWF surface pressure forecast for the morning of April 14th, we see the storm system at a pretty low minimum central pressure, likely below 1000 millibars, in the middle of Missouri. The ECMWF model may be locked on to this snowstorm idea, but its ensembles are much more uncertain.
The image above shows the projected mean surface pressure by the ECMWF ensembles, as well as the spread among all ECMWF ensemble members in the shown colors. We first observe how the ensembles are much less enthusiastic about the idea of a storm system for this timeframe, only bringing a minimum 1006 millibar swath of low pressure over an area just to the east of the ECMWF model. This sort of weaker projection is to be expected, as these ensemble means take the average of 52 ensemble members, unlike the ECMWF model, which only shows one solution. The next item we observe is the swath of oranges and yellows over the Plains and Midwest. These warmer colors indicate a higher spread in the ensembles; in other words, the ensemble members are in higher disagreement with one another over this higher spread envelope, thus indicating increased uncertainty. While this would initially disprove the idea of a storm system in this timeframe, note how the highest spread is located further west of the ensemble low pressure alignment, more in line with the ECMWF model. All in all, this means that the ensembles are seeing this idea of a storm, but aren't biting yet.
To summarize:
• A potentially major storm system is expected in the April 12-16 timeframe.
• Colder than normal weather may arrive with this storm system.
• Model guidance is hinting at a snowfall event during the April 13-15 timeframe, in conjunction with this potentially major storm system.
• There is high uncertainty with this potential event. Caution must be used.
Andrew