Extended stretch of sun is expected
thru the start of the holiday weekend 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:

We will see a continuation of the above average precipitation though Tuesday of next week, before a drier period settles in finally for the several days that follow. Latest indications are for another very wet weekend, especially on Saturday, and then some improvement later Sunday and Monday with an upper level ridge moving in temporarily.

The first system is a quasi-stationary boundary that has been plaguing the region for several days, and will continue to affect our sensible weather over the weekend with more rain, and by Sunday, thunderstorms will also be possible. This boundary now stalled south of the DelMarVa will move slowly northward on Saturday, bringing periods of rain that will taper to showers Saturday afternoon. Sunday will likely see rain/thunderstorms in the morning along a cold front, followed by a drying trend during the afternoon as the upper level ridge moves in through Monday.

The next system will bring a cold front through the region in the Tuesday afternoon through evening time frame, with more scattered showers and thunderstorms likely along and ahead of the boundary. Depending on synoptic pieces and where they are located on Tuesday, there could be some stronger storms involved, but too early to call definitively at the moment.

Early look at Memorial Day weekend: After several dry days from next Wednesday onward, the holiday weekend will likely start off dry and seasonably warm Friday and Saturday. The better chance for scattered thunderstorms exists on Sunday and Monday, but at this point it doesn’t appear to be washout variety weather, and more likely a mix of sun and clouds with the thunderstorm risks in the usual afternoon/evening time frames. We will update the Memorial Day outlook with more precision throughout the upcoming week in shorter term local forecasts here on the website.

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

May 20th-May 26th: Near average

May 27th-June 3rd: Slightly above average

June 4th-June 10th: Near to slightly above average

June 11th-June 17th: 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 GFS shows the quasi-stationary boundary draped over the region on Saturday, which will not only keep temperatures cool until it lifts off to the north, but will also bring scattered showers during the day.

The parent low pressure associated with Saturday’s showers will move into New England finally, and the cold front tied to this low will move through on Sunday morning with scattered AM showers and thunderstorms.

Pattern:

The Madden-Julian Oscillation (MJO): The Madden-Julian Oscillation is currently in phase 1, which is an active phase from a precipitation standpoint, but also presents the battleground of cooler air north, warmer air south of our region. Projections are for the MJO to propagate eastward into phase 2 over the weekend. This could lend a hand in the active precipitation pattern discontinuing next week. Beyond week 2, indications are the MJO collapses in the circle of death where it will likely have less influence on the overall pattern.

A more zonal W-E flow has taken shape and is expected to continue into the weekend. This led to less amplification of the jet stream, and with the battlezone MJO cycle of phases 1 in place, fronts were cutting through and stalling over our region at different times in the past 7-10 days. This cycle does show signs of breaking in the midrange, and likely that we have one more day to deal with the quasi-stationary boundary on Saturday that has been plaguing the region since Tuesday’s severe storms day.

It does appear that a dry stretch will be in the cards from the middle of next week through at least the first half of the Memorial Day holiday weekend, and then some precipitation risks re-enter the picture late in the holiday weekend. At this point, it doesn’t look like late next weekend will be washout-type events, but rather sun/clouds mixed and the typical late Spring scattered PM showers and thunderstorms… but we will update that information throughout the week leading up to the holiday weekend.

May is projected to be an above average month (+2.5°F  to +4.0°F) when the dust settles end of month. A very warm/hot start to the month has temperature departures from normal at well above average levels at most reporting stations within out coverage area, however an alternating cool/warm pattern over the next few weeks will likely bring the anomalies down a bit. Still, with the warm start, we expect May will finish several degrees above average at month’s end. Early look at June suggests a slightly above average month (+0.5°F to +1.5°F) as supported by climate models and leading analogs chosen for the Spring and Summer months.

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

GEFS ensembles show a brief upper level ridge settling in later Sunday through Monday, with above average temperatures expected

Once we reach midweek, a drier zonal flow ensues with temperatures near to slightly above average heading into the holiday weekend

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 May 18th, 11:05am