Above Normal Rainfall Predicted for June
Figure 1. NOAA Climate Prediction Center outlook for precipitation in June. The highest likelihood of above normal precipitation is centered on Nebraska.
During the past few weeks there has been a significant increase in precipitation events across the central United States. The most widespread event occurred across Texas the third week of May as an upper air low slowly drifted from the southwestern desert region into lower Mississippi river valley. Pockets of heavy precipitation have occurred across Nebraska and Kansas, but generally have fallen outside areas reporting the most intense drought conditions.
Numerical weather models continue to indicate that Nebraska will remain within a region that is expected to see frequent precipitation events over the next couple weeks. It is entirely possible that most of Nebraska will experience normal precipitation for the month of June before we reach the middle of the month. This certainly would be welcome news for drought stricken areas from southwest through northeast Nebraska.
The US Climate Prediction Center revised their June precipitation outlook at the end of May and currently assigns the highest probability of above normal moisture for all of Nebraska (Figure 1). This is further validation that they have a high degree of confidence that current weather models are correctly forecasting active weather for the central Plains region.
While we don't expect the current drought to entirely disappear from the central Plains, it would not be unexpected to see a 1-2 category improvement for most locations north of central Kansas before the end of June. Unfortunately, we will have to endure several rounds of severe weather including widespread wind and hail events. Current weather models are projecting a few tornadoes, but not a super outbreak.
The reason for such an optimistic forecast is centered on the trend of upper air trough formation over the central and northern Rockies during June that will pull low level Gulf of Mexico moisture northward in advance of the surface lows that will form on the eastern slopes of the central Rockies. Mid-level moisture from mountain snowmelt will add additional moisture into the atmosphere over the central Plains, which will help increase precipitation output of surface lows that cross the state.
In addition to these factors for above normal moisture, a Pacific hurricane formed off the western coast of Mexico and moved northwest of the southern Baja Peninsula last week. Usually we don't see this type of hurricane track until the second half of the summer. These systems are very efficient at bringing moisture into the southwestern United States and enhance the monsoon moisture feed into the central Rockies.
We will need further confirmation that this hurricane wasn't an outlier. If additional tropical systems over the next month take a similar path, this would confirm the Climate Prediction Center forecast of an active monsoon season. An active monsoon season, coupled with a strong moisture feed into the central Rockies would be supportive of increased moisture tendencies for the western High Plains region, including Nebraska.