Hot, muggy, and unsettled to start the
week, then seasonable temps to end it 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.

Technical discussion below will feature two (2) subcategories: Precipitation, and Pattern Discussion. Storm possibilities will be discussed exclusively in the Premium Forum with intense model analysis leading up to any major rain or severe events, not publicly. To join this discussion and hear our updated thoughts from our team, visit The My Pocket Meteorologist Page by clicking HERE and select the “Premium Weather Forum” option.

Precipitation:

Mainly dry weather has been in place for the last couple of weeks, but that does look like it will change to a somewhat wetter pattern overall as we head into the 2nd half of July and first week of August. The most notable above average precipitation periods suggested by the ensemble guidance centers around the last week of July and first week of August. During this time, we expect a June-esque pattern to develop that will keep the wetter look in place.

Aside from isolated thunderstorms in spots over the weekend, the next organized activity will occur on Tuesday afternoon and evening along and ahead of a cold front advancing toward the region. Scattered thunderstorms will likely affect the entire area from W to E during that time frame, and there could be some severe weather associated with it if the timing is right. Any threat will be updated in the shorter term in local forecasts and weather alerts, as needed as we get closer to the event.

The next chance for organized activity will come toward the end of the week, and modeled timing differences exist at this range on whether this a Friday or Saturday threat, or both. A chance for scattered showers and thunderstorms is possible during this time frame, but exact specifics regarding timing and impacts are speculative at this range, and will be handled on a shorter-term basis with local forecasts beginning next week.

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

July 16th-July 22nd: Near to slightly above average

July 23rd-July 29th: Near to slightly above average

July 30th-August 5th: Slightly above average

August 6th-August 12th: Near average

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

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

The 3km NAM for Saturday evening at 8:00pm shows a line of storms crossing into northern PA from southern NY, but these will begin to die off after sunset as they push farther SE. More isolated activity is possible Sunday afternoon.

The GFS shows a cold front advancing toward the region on Tuesday, and scattered showers and thunderstorms are likely region-wide during the afternoon and evening hours. The cold front itself will clear the region overnight.

Pattern:

The Madden-Julian Oscillation (MJO): The Madden-Julian Oscillation is currently phase 5, and has been in that octant for about a week. In the coming week, eastward propagation into phase 6 is forecast. Typically these phases combined with a +AAM will yield cooler than average temperatures for the northern Plains and Midwest, but the onset has been delayed due to the track of Typhoon Maria in the Pacific, which made landfall in eastern China within the past two days. This typhoon halfway across the globe affected the jet stream enough to allow for the cooler periods to be delayed a bit longer. Eventually, phase 6 cooler anomalies will win out toward the end of July and early August.

Another warmer than average period is expected this weekend into early next week, before a cold front and associated trough ends the heat on Tuesday. Behind the front, more seasonable weather is expected for several days, with slight moderation possible the following weekend. Cooler risks begin to show up in the late July and early August time frame as the MJO reaches phase 6, but at present time, nothing looks overwhelmingly cool – mostly near to slightly below average as the core of the cooler anomalies remain in the northern Plains and Midwest, and to some extent, the Ohio Valley region.

July is projected to be a near to slightly above average month (+2.0°F to +4.0°F) when the dust settles at the end of the month. Warmer than average temperature departures during the first two weeks of July will likely offset any late month cooler risks. For the month of August we listed slightly below average temperatures (-1.5°F to +0.0°F) as supported by climate models and leading analogs chosen for the Summer months, and cooler risks shown on the ensemble guidance to at least begin the month.

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

The latest GEFS ensembles show the warmth in place through Tuesday, with the circled/highlighted trough with cooler air in the upper Plains expected to move southeastward into our region in the middle of next week.

The same GEFS shows a trough moving in toward the end of July that has a bit more staying power, and is not expected to be transient. It is likely that we see near to slightly below average temperatures from late July into early August.

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.

The My Pocket Meteorologist text alert program is a year-round program, and seasonal options for Spring/Summer will be available soon. Click on the image below for more information.

Forecaster: EPAWA Meteorologist Bobby Martrich
Discussion last updated:  Friday July 13th, 11:05am