Warmer through the end of the week,
then a cooler trough arrives Saturday 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 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:

An upper level low remained well to the west and southwest of the region this week, which enabled this region to miss out on the heavier rains that were expected to be over our region for much of this week. At this time last week, models suggested several inches of rain and a rather wet week, but alas only a few widely scattered showers will materialize Friday and Saturday as the upper level low and its associated surface low pulls NE and offshore. As such, the already slightly below average rainfall for the month has continued, and the margin of monthly rainfall deficits have broadened. Adjustments were made to the monthly projection to finish below average by month’s end as a result of this significant shift.

The first precipitation chance within the outlook is in the near term, as the aforementioned upper level low and its associated surface low finally pulls northeast in a much more weakened state. Scattered showers Friday will move through from south to north across the region, with a shower or two possible in spots overnight. As the upper level low moves offshore Saturday, a few very widely scattered (hit or miss) showers and perhaps thunderstorms move through parts of the region mainly during the afternoon hours – ending by early evening.

The next chance for precipitation holds off until the following weekend, a strong upper air ridge builds into the region during the week. This will lead to anomalously warmer than average temperatures just as the Memorial Day holiday weekend comes to a close, and will promote another week of dry weather under the influence of a 590dm ridge. Scattered showers and thunderstorms along and ahead of the boundary will be possible later Saturday and Saturday night as the cold front approaches.

The precipitation departure from average for the month of May we project will finish slightly below average (-0.5″ to -1.5″) with very high confidence, with not much in the way of “events” to come by for the remainder of May. Looking at the month of June using a blend of ensembles, climate models, and seasonal trends suggests a near to slightly above average (+0.0″ to +0.5″) precipitation departure for the month as a whole.

Follow our social media channels for updates:

EPAWA Facebook:  https://www.facebook.com/epawawx/

Meteorologist Bobby Martrich [EPAWA] on Twitter:  https://twitter.com/epawawx

YouTube channel/daily forecast video: https://www.youtube.com/user/eastpaweather

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

May 25th-May 31st:  Slightly below average

June 1st-June 7th:  Near average

June 8th-June 14th:  Near to slightly below average

June 15th-June 21st:  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 in the outlook is clickable for larger viewing

An upper level low and its associated surface low moves offshore Saturday, but keeps the shower/t-storm threat in the forecast for some areas on mainly Saturday afternoon/evening, but not a washout anywhere.

After a mostly dry and anomalously warm week under a 590dm ridge influence, a cold front arrives with the next chance for precipitation next Saturday and Saturday evening with scattered showers and thunderstorms.

Pattern:

The Madden-Julian Oscillation (MJO): The Madden-Julian Oscillation is currently in phase 4 temporarily through this weekend, before moving quickly into phases 5 and 6 in the week ahead. During the late Spring and Summer months, phases 5/6 are generally warmer phases, and supports next week’s expected anomalous ridging and warmth. Heading into the first week of June, the MJO propagation into phases 7 and 8, both cooler phases, is expected. This coincides with the near to slightly below average temperatures period expected during the first full week of the month.

In the shorter term, the upper level low that became a cut-off low over the Tennessee Valley for much of this past week is finally weakening and moving northeast toward our region. With the expected unsettled conditions at times to start the holiday weekend, and in the wake of that system on Sunday, much of the Memorial Day holiday weekend (through Monday) remains generally near to slightly above average in the interior, with cooler anomalies found closer to the shore points and eastern/southeastern areas, especially on Sunday and Monday. In the midterm, a strong upper air ridge [projected ~590dm] will build in beginning on Tuesday, and lasts through Saturday of next week. During this time, temperatures will reach the 80s Tuesday, and will become progressively warmer than that throughout the week, culminating with mid to upper 80s for highs by Friday and Saturday. Longer term, and post-frontal passage on Saturday evening/overnight, temperatures will drop to near to slightly below average leading into the first full week of June as troughing is expected to follow the front and lingers for several days.

Although we don’t do seasonal forecasting for the much longer term, early indications are that in the July-September period, probabilities favor warmer/hotter than average conditions rather than cooler.

Breaking down the remainder of the month of May, the slightly cooler than average temperatures for the month thus far found currently for most locations will be replaced with anomalous warmth next week, which renders the month as a whole near average (-1.0°F to +1.0°F) when the dust settles May 31st with very high confidence. Looking at the month of June as a whole, we maintain projections this week of slightly above average (+1.0° to +3.0°F) temperatures, using longer range climate ensembles and global observation trends.

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

In the short term, we’ll see temperatures near to slightly above average through much of the holiday weekend, but cooler temps will be found closer to the shore points with an onshore flow, especially Sunday and Monday.

A strong ridge that peaks late week as high as 590dm will move in beginning this Tuesday, and lasts through Saturday of next week until the next trough and cold front arrives. Temps well into the 80s will be common.

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.

Spring and Summer text alerts and premium forum options are now available for advance purchase. A nominal one-time fee will bring you detailed alerts throughout the Spring and Summer between April 1st, 2020 and September 30th, 2020, and includes real-time thunderstorm alerts. Visit http://epawaweather.com/spring-summer-alerts/ for full details, or simply click on the banner below.

Forecaster: EPAWA Meteorologist Bobby Martrich
Discussion last updated: Friday May 22nd, 10:30AM