Final July forecast:
- We are seeing overwhelming signals for increasing heat as we work into the month of July. Initially, high latitude blocking in both the Pacific and Atlantic will allow the warmest air to work into the Great Lakes and Hudson Bay areas.
- As the NAO trend positive in week 2, the hottest air will come south and setup over the Central Plains and Midwest. We’d expect this trend to continue into the week’s ¾ period.
- The AAM looks to remain very low over the next few weeks and rival years with the most persistent low AAM states on record. When we look at these years in the last 25 years (1998, 2005, 2010 and 2012), they overwhelmingly support widespread above normal temperatures especially in the Upper-Midwest and Great Lakes.
- MJO phase 2 also supports a ridge over the Midwest and the most similar MJO analogs (2019, 2012, 2005, 1998 and 1988) suggest a similar idea to the AAM.
- We also had a wave 5 pattern back in early-mid June that also supports heat waves in July. Overall, we had to trend our forecast a good bit warmer given these strong signals for heat.
- As the ridge builds this upcoming week the pattern will start to get less active. This doesn’t necessarily mean that there will be no rainfall chances and it’s not impossible that some areas still see timely rains especially north.
- However, as the strong ridge of high pressure builds, areas in the Central and Southern Plains especially will grow dry. We already note that E. KS and SW MO have been very dry the last 30 days and we think these areas can grow drier.
- The Ohio Valley will also see periods of dryness, however, the risk for NW flow and storm cluster east of the ridge as it meanders is possible and for this reason we’ve kept that area at only slightly below normal. Our severe weather analogs do support the risk of strong/severe clusters in the Upper-Midwest, Great Lakes and into the Mid-Atlantic.
- The first two weeks will be wet in the Northern Plains and this will be hard to overcome especially with storms riding north of the ridge at times in July.
- The main risk here is that any breakdown of the ridge can easily bring timely rain chances and we do have a few storm dates that prevents us from widespread much below normal rainfall, though some problems may grow in especially Kansas/Missouri/Texas with the hot/dry risks.