For many of our areas, an extended
heatwave likely continues this week Get The Forecast!

*Indications of above or below average temperatures in the table above are relative to what is considered “normal” using data collected over the long term for a particular date. This is collected and maintained by the National Climatic Data Center in conjunction with the National Weather Service actual data from previous years collected at official ASOS/climatology stations across our coverage area. Also note that as time moves forward into a different period as shown above, average temperatures for those dates will also change. See the example below using Philadelphia, PA as the climo station:

The departure from normal uses the average temperature for the date, averaging temps over 24 hours for any given location, using both high and low temperatures hourly during any particular day. This outlook determines warm vs. cool periods relative to normal temperatures.

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Precipitation:

Overall dry conditions were found most of the month of June with a few exceptions, mainly in our far southern and southeastern areas thanks to a training thunderstorms event earlier in the month. Going forward through July, the pattern will largely not change as we transition into a more typical La Niña background state. Aside from the occasional frontal passages and thunderstorms associated with them, which in many cases can be hit-or-miss, no large scale synoptic all-day rain events are on the horizon.

Albeit a relatively small chance, as ridging continues to build in next week and humidity/dewpoints increase, isolated “heat-of-the-day” diurnally driven thunderstorms will be possible on ANY day between Monday and Friday. These will generally be garden-variety and sub-severe if and where they do hit. Activity will be very limited and arbitrarily placed, coinciding with weak shortwave triggers throughout the week. Next chance for more organized thunderstorms will be over the weekend, as a cold front attempts to temporarily lower temperatures and humidity behind it. Ahead of this boundary will be the chance for scattered thunderstorms, and timing/severity of storms will be monitored and adjusted as needed throughout the week.

The precipitation departure from average for the month of July we project will finish slightly below average (-0.5″ to -1.0″) with moderately high confidence. The exception in any given individual area, as is the case in most summers, would be heavy rain associated with thunderstorms on a more hyper-local level that [locally] skews the projection. Early look at the month of August using a blend of ensembles, climate models, and seasonal trends suggests a near average (-0.5″ to +0.5″) precipitation departure for the month as a whole.

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Breakdown of precipitation departures from normal over the next several weeks:

July 4th-July 10th:  Below average

July 11th-July 17th:  Slightly below average

July 18th-July 24th:  Near average

July 25th-July 31st:  Near average

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Note:  Any image in the outlook is clickable for larger viewing

A dry pattern is expected in the week ahead as heat/ridging builds into the region. Although pop-up isolated storms are possible, the attached image shows below average precipitation departures expected through July 10th.

The next chance for more organized and scattered showers/thunderstorms will come in advance of an approaching cold front next Saturday, and timing/severity of storms will be determined throughout the week.

Pattern:

The Madden-Julian Oscillation (MJO): The Madden-Julian Oscillation is currently teetering between the circle of death (COD) and a weak phase 2 signal in the Indian Ocean, and is largely expected to remain in that general vicinity in the next few weeks. As we head into July, the Euro Weeklies suggest the MJO will remain largely in the COD or in a weak phase 2 signal like it is currently. The MJO is not as influential on the overall pattern with other factors becoming more dominant players this time of year, and weaker impulses that don’t play a role as prominently during the Summer months are common. Indian Ocean convection is more La Niña ‘ish, which fits the overall pattern.

We continue to project the month of July as a whole will be largely dominated by above average temperatures. As we transition to a more La Niña background state, typical La Niña Summer conditions will take over that features hotter than average temperatures and generally drier conditions. Several heatwaves will be possible during the month of July, the first of which is expected from late weekend through most of next week. During this time, several days of middle 90s air temperatures with high humidity and dewpoints are expected. Heat advisories from the National Weather Service may be needed almost daily next week for the urban areas especially. For what is now the 6th consecutive week since we projected ahead to the month of July, we maintain projections of above average temperatures (+3.0°F to +5.0°F) as it looks to be a toasty month.

Mostly due to the aforementioned La Niña during the summer months, we expect August will follow suit with above average temperature departures, and we have an identical (+3.0°F to +5.0°F) temperature projection for August as July. We don’t do seasonal stuff beyond a 5-6 week lead time (such as with this outlook) but early indications are that September could also follow up as a warmer than average month.

For the month of July, we expect largely above average temperatures throughout the month, and (+3.0°F to +5.0°F) when the dust settles July 31st with high confidence. Early look at the month of August suggests another above average month (+3.0° to +5.0°F) using longer range climate ensembles and global observation trends.

Note:  Any image in the outlook is clickable for larger viewing

A heatwave is expected to take shape from late weekend through most of next week. Temperatures at the peak mid-late week especially will climb into the middle 90s with higher humidity values compared to this week.

After a couple of slightly cooler days behind a cold front next weekend, strong ridging in the center of the county again expands and flexes, indicating another heatwave may be following the first one expected this week.

Images below are clickable for better viewing

Days 1-5 – confidence VERY HIGH

Days 6-10 – confidence HIGH

Days 11-15 – confidence MODERATELY HIGH

Days 16-20 – confidence MODERATE

Below is a look at the latest Soil Moisture Anomaly for the Contiguous United States. This is used by NOAA/CPC for the purpose of drought monitoring and drought outlooks.

This image will automatically update daily.

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Forecaster: EPAWA Meteorologist Bobby Martrich
Discussion last updated: Friday July 3rd, 11:40AM