A trough brings cooler than average
temps through the late week period

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 snow, ice, or rain events, not publicly. To join this discussion and hear the updated thoughts from our team, visit The My Pocket Meteorologist Page by clicking HERE and select the “Premium Weather Forum” option.

Precipitation:

OVERVIEW:  The month of June thus far has seen its share of localized heavy rainfall in spots, but it is a case of the haves and have nots with precipitation departures on a local level due to the arbitrary placement of pop-up thunderstorm activity, as is typically expected in the late Spring and Summer months. The pattern going forward for much of the remainder of June is suggestive of near average precipitation, however the longer term ensembles continue to suggest a wet tail end to the month, which may carry into early July. Looking at July as a whole, ensemble forecasts suggest a near to slightly above average month, with the wettest period found in generally the opening week of the month. Beyond that, no extremes are noted in the climate guidance currently.

In the shorter term, a weak cold front crosses the region Saturday night, and scattered showers and thunderstorms will precede the frontal boundary Saturday evening. A few of those storms could produce gusty winds, especially in areas that see thunderstorm activity in the early evening hours rather than late evening. What could become Tropical Storm Claudette before landfall near the Louisiana coast will likely pass SE of our region Monday night, taking any remnant rain with it. It is not out of the question for fringe showers on the NW side of the departing low on Monday night in our far southeastern coastal locales, most notably between Ocean City, MD and Cape May and vicinity. A stronger and more organized cold front crosses the region Tuesday night, and will be preceded by scattered showers and thunderstorms. Timing will have to be watched closely, which will dictate severity of storms. This frontal boundary is on the lead of the next trough, and will end the stretch of several very warm/hot days prior to the front’s arrival Tuesday night.

The month of June we project will finish with near average (-0.5″ to +0.5″) precipitation departures for the month as a whole with moderately high confidence, with some areas finishing above average on a hyper-local level where thunderstorms have been the most active this month. Early look at the month of July we project a near to slightly above average precipitation (0.0″ to +1.0″) anomaly for the month as a whole, using long range climate guidance and global observational trends.

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

June 20th – June 26th:  Near average

June 27th – July 3rd:  Slightly above average

July 4th – July 10th:  Near to slightly above average

July 11th – July 17th:  Near average

July 18th – July 24th:  Near average

July 25th – July 31st:  Near 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 in the outlook is clickable for larger viewing  

The 3km NAM shows scattered showers and t-storms affecting mainly southern areas Saturday evening and part of the overnight ahead of a weak cold front. Stronger storms are possible Saturday evening.

The remnants of what could become Tropical Storm Claudette is expected to pass SE of the region Monday night, and will be followed by a stronger cold front Tuesday with more scattered t-storms.

Pattern:

OVERVIEW: Since the heatwave earlier in the month, there has been rather temperate conditions since, with some slightly below average temperature periods mixed within the past week. Going forward, we’ll see a spike in temperatures this weekend and early next week until the arrival of a cold front on the lead of the next trough Tuesday night. This trough will bring more slightly below average, yet refreshing temperatures midweek through next weekend. July will see its share of hotter temperature periods, favoring the middle two weeks of the month, but nothing too extreme or for extended periods of time. The Madden-Julian Oscillation (MJO) is currently in a weaker phase 2 signal, and will likely collapse into the Circle of Death (COD) for much of the remainder of the month of June. There are some longer term ensembles suggesting a migration into a weak phase 8-1 octants as we move into July. Typically during the summer months, it is common for tropical forcing to remain in or near the COD with less influence on our sensible weather as a result. As we progress through Summer, MJO waves will be monitored more closely for possible favorable periods of tropical cyclone development in the Atlantic.

Average highs and lows are continuing to slowly rise, and will reach annual climatological maximums by the 2nd week of July. Normal high temperatures are currently in the 80-83°F range from north to south across our coverage region. 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, slightly below average temperatures listed for midweek next week through the weekend are likely in a comfortable 75-80° range for highs. Use the average highs/lows chart below that provides a point of reference for what average is for each corresponding date, with the examples used for the Philadelphia region.

For the month of June, we expect near to slightly above average temperatures (+0.0°F to +2.0°F) when the dust settles June 30th with high confidence. This is a largely due to ridging in the beginning of the month setting the tone early, then generally seasonable/temperate conditions observed and forecast for much of the remainder of the month. Early look at the month of July as a whole suggests a slightly above average month (+1.0°F to +3.0°F) using long term climate models and seasonal/global observation trends.

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

After several days of slightly above to above average temperatures through Tuesday, a cold front is followed by another trough that brings cooler temps 75-80° midweek through next weekend.

Longer term ensembles like the GEFS extended (pictured) and the Euro weeklies suggest that after rather temperate conditions to end June, July will favor the slightly warmer/hotter side of average.

Outlook table last updated: Friday June 18th, 10:30 AM. Next scheduled update: Friday June 25th.

This is a weekly updated public long range guidance product from EPAWA. For daily long range updates and more detailed updates M-F, please join the EPAWA forum. More information/sign-up at: http://epawaweather.com/my-pocket-meteorologist/ 

*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.

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.

Forecaster: EPAWA Meteorologist Bobby Martrich
Discussion last updated: Friday June 18th, 10:30 AM