Long Range Outlook - EPAWA Weather Consulting (2024)

OVERVIEW: Precipitation departures for the month of June thus far are much drier than usual for the interior, and generally slightly below average farther south. The US drought monitor (photo toward the bottom of this outlook) has placed parts of our region in abnormally dry conditions and this is a pre-cursor to potential drought conditions if the overall dry conditions currently don't improve. Going forward, projections for the month of June were maintained this week for a below average precipitation forecast with a rather dry (overall) late two weeks of June ensemble forecast. Aside from thunderstorm activity that is relatively limited, precipitation will be a commodity for the remainder of the month. For that reason, the projection for June as a whole is for a below average (-1.0" to -2.0") precipitation departure. The presence of thunderstorms can skew monthly projections of rainfall on a hyper-local basis, and it is important to understand that the monthly projections in storm season are a composite average based on synoptic events, not mesoscale-based activity. Our July projections were maintained this week for a near to slightly above average precipitation departure (0.0" to +1.0") for the month as a whole with the current expectation that while the beginning of the month may start off drier, but may turn around with more precipitation events during the 2nd half of July.

Shorter term, pulsing-type scattered thunderstorms will be possible both Friday and Saturday, most notably north of the I-78 corridor in both PA and NJ, mainly in a 12-8pm window each day. Pulsers are a result of very limited shear, which keeps the storms moving. Slow movement leads to storms building quickly, taking full advantage of the high instability environment, but then collapse just as quickly as the rain-cooled updrafts essentially choke off the inflow to the storm due to its slow movement. A pre-frontal trough on Sunday afternoon/evening may supply a bit more lift to generate more organized storm activity, and affecting more areas. A cold front crosses the region on Monday with scattered showers/storms for mainly eastern areas closest to the front, then another cold front will move through Thursday of next week with scattered showers and thunderstorms possible along and ahead of the boundary.

Our projection for the month of June was maintained this week for a solidly below average (-1.0" to -2.0") precipitation departure due to overwhelming ensemble support of a drier than average last 10 days of the month. As temperatures and humidity increase in July, it favors more in the way of thunderstorm activity, most notably during the 2nd half of the month, and for that reason a near to slightly above average (0.0" to +1.0") precipitation departure projection for the month as a whole is currently expected. after a drier than average first half.

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

June 22nd - June 28th: Slightly below average

June 29 - July 5th: Near to slightly below average

July 6th - July 12th: Near average

July 13th - July 19th: Near average

July 20th - July 26th: Near to slightly above average

July 27th - August 2nd: Near to slightly above average

Public/free available maps will be updated when a threat is imminent for significant weather on the weather alerts page throughout the year:http://epawaweather.com/weather-alerts/

Note: Any image below is clickable for larger viewing

OVERVIEW: After a generally near average first half of June, ridging is now dominating, and will continue to dominate through the weekend. Widespread 90°F+ temps are expected to continue through Sunday, then a slight step back early next week to near average. After this point through the end of June, the pattern still leans on the warmer side of average. June as a whole will be maintained at an above average (+2.0°F to +4.0°F) projection for the month as a whole as a result of where we are currently, and how we expect to finish the month. We also maintained projections for the month of July this week for a slightly above average (+1.0°F to +3.0°F) temperature departure. The first half of the month looks to be the hottest relative to average, then leaning to the warmer side of average during the back half of July as more precipitation chances present themselves...and this pattern may continue into at least early August.

The Madden-Julian Oscillation (MJO) is currently in the Circle of Death and likely remains there through at least the middle of July. The prolonged stretch in the Circle of Death is very typical of summer pattern where the overall flow is rather weak in the Pacific subtropical regions. As we head into July as we expect a transition from ENSO neutral where we are currently, to a weak La Niña background state at some point during the month. July as a whole should be a relatively hot month overall...which means hotter than it typically is even for July, one of the hottest months of the year. Although we limit the long range outlooks purposefully at a 5-6 week lead time with accuracy in mind, our preliminary thoughts for August and September are to see a continuation of at least slightly above average temperatures.

Average high temperatures are currently in the 82-85°F range from north to south across our coverage region, which is about 2 degrees higher than at this time last week. Temperature climb will continue at that same general rate of increase throughout June of about +1-2°F per week, with that rate of increase maintaining through early July. Any above or below average stretches listed in the outlook will be relative to seasonal norms at that time, and it is important to note that cooler/warmer periods will be relative to the time of year we are talking about. For example, the above to well above average temperatures listed through this weekend generally features highs in the 92-98° range across the region, coming at a time when average highs are generally in the lower to middle 80s. Use the average highs/lows chart below that provides a point of reference for what average is for each corresponding date through early August.

Our projection for the month of June is for an above average (+2.0­°F to +4.0°F) temperature departure, and that is largely due to the current ridging in place, and still remaining slightly above average for the final week of June. July projections were maintained this week for a slightly above average (+1.0°F to +3.0°F) temperature departure expectation, using longer term climate guidance and global observation trends, and we are expecting a transition from ENSO neutral to a weak La Niña background state at some point during the month.

Note: Any image below is clickable for larger viewing`