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Front stalls over our southern regions
next few days with scattered t-storms
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Long Range Outlook

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This week's long range table

ThreatsSignificanceConfidence
8/8TemperatureNear averageVery high
8/9-8/13TemperatureSlightly above to above averageVery high
8/14-8/17TemperatureNear averageHigh
8/18-8/20TemperatureNear to slightly above averageModerately high
8/21-8/27TemperatureSlightly above averageModerate
8/28-9/3TemperatureSlightly above to above averageModerate
9/4-9/10TemperatureSlightly above averageModerately low
9/11-9/17TemperatureSlightly above to above averageLow
8/12-8/13Cold frontA cold front very slowly pushes through the region Wednesday and Thursday of next week, leading to scattered PM showers/storms both days. Front pushes through late Thursday.Moderately high
8/15-8/16Scattered t-stormsThe same cold front Wed-Thurs settles south of the region on Friday and stalls there. then may push back north with low pressure moving about the boundary at times through the weekend, leading to a scattered PM showers/t-storms threat on both weekend days.Moderate
August as a wholeTemperatureSlightly above to above average (+2.0°F to +4.0°F)High
August as a wholePrecipitationAbove average (+2.0" to +6.0") but a large part of that is Isaias relatedHigh
September as a wholeTemperatureAbove average (+3.0°F to +5.0°F)Moderate
September as a wholePrecipitationNear to slightly above average (+0.0" to +1.0")Moderate

Outlook table last updated: Friday August 7th, 11:45AM. Next scheduled update: Friday August 14th.

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/ 

Climatology

*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:

DateAverage Hi/LoEPAWA projection
August 8th86°F/69°FNear average
August 15th86°F/68°FNear average
August 22nd85°F/67°FSlightly above average
August 29th84°F/66°FSlightly above to above average
September 5th82°F/64°FSlightly above average

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.

Long range analysis: Technical discussion is below for advanced readers:

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 Discussion:

Precipitation:

A very noticeable increase in precipitation to begin August was mostly centered on the extreme flooding that occurred this week as Tropical Storm Isaias impacted the region. The rain in much of the center cross-section of the region were found in most instances to be 4-7″+ as Isaias rolled through, already meeting or exceeding what is seen during the entire month of August…which is already typically/historically one of our wettest months of the year. Overall chances for rainfall will be increased this month ASIDE from what already occurred with Isaias, and will be most active over the next two weeks through the end of August week 3. Most of this activity will be due to slow-moving and stalling frontal boundaries that become the focus of scattered showers and thunderstorms.

First chance of precipitation in the outlook comes in the Wednesday-Thursday time frame of next week, with a cold approaching the region. Scattered PM showers and thunderstorms are likely Wednesday ahead of the cold front, then the front is expected to slow considerably and not push through until Thursday night. As such, scattered t-storms will again be possible along this boundary on Thursday. We have seen this same situation play out recently with boundaries slowing considerably or stalling in the absence of a stronger wind flow aloft.

The same frontal boundary heads just south of the region Friday and stalls, and then may try to creep slowly back northward over the weekend or meander in the vicinity. As shortwave impulses move about that boundary, a renewed threat for scattered showers and thunderstorms will be present both weekend days. Early indications are that the threat of storms may extend into early next week following next weekend. Active precipitation pattern looks to continue through the end of the 3rd week of August.

The month of August we project an above average precipitation month (+2.0″ to +6.0″) as a whole, thanks in large part to the heavy rain/flooding from Isaias to begin the month. We will remain wet over the next two weeks with numerous scattered thunderstorm chances as outlined above. As is the case in most summers, the caveat would be heavy rain associated with thunderstorms on a more hyper-local level that [locally] skews the projection, and any unforeseen tropical entities. Early look at the month of September using a blend of ensembles, climate models, and seasonal trends suggests a near to slightly above average (+0.0″ to +1.0″) precipitation departure for the month as a whole. Same caveats in September – thunderstorms (localized) and tropical entities can skew those projections on a hyper-local level.

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

August 8th – August 14th:  Slightly above average

August 15th – August 21st:  Slightly above average

August 22nd – August 28th:  Near to slightly above average

August 29th – September 4th:  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

A cold front approaches the region on Wednesday, which will be slowing in forward speed. Scattered showers and thunderstorms are likely Wednesday PM, but again on Thursday as the front slowly progresses through.

gfs1

Thursday’s cold front presses to the south and stalls there on Friday, and may return north or meander in the vicinity over the weekend. This could lead to a renewed threat for scattered showers and t-storms this weekend.

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Pattern Discussion:

Pattern:

The Madden-Julian Oscillation (MJO): The Madden-Julian Oscillation is currently in phase 5 in the Maritime Continent, and is expected to propagate eartward via the Circle of Death (COD) to eventually settling into phase 7/8 the following week. The MJO is typically not as influential on the overall pattern with other factors becoming more dominant players during the summer months, but with a propagation into phases 7/8 with time, that could result in a spike in Atlantic hurricane activity. For the next week or so until then, the Atlantic Basin should remain fairly quiet.

We continue to project the month of August as a whole will be largely dominated by slightly above to above average temperatures, but likely not as high above average as July was. This is largely due to an expected increase in precipitation over the next two weeks, although we will see a shorter term spike it temperatures between Sunday and Thursday of this week. Once we reach the fourth week of the month, temperature anomalies we expect will increase more consistently, and hot temperatures will be found late month heading into September. These are typical La Niña Summer conditions will continue well into September we think that features hotter than average temperatures. Additional heatwaves will still be possible late August and at least early September, and September as a whole we project will be another notably hotter than average month.

Tropics: For the next week to 10 days the Atlantic Basin should remain fairly quiet, but expect a notable increase in activity for the final third of August, especially of MJO eastward propagation reaches phases 7/8.

For the month of August, we expect largely slightly above to above average temperatures (+2.0°F to +4.0°F) when the dust settles August 31st with high confidence. Early look at the month of September suggests another above average month (+3.0° to +5.0°F) using longer range climate ensembles and global observation trends, and notably hot to begin the month.

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

We begin the period (today, Saturday) with near to slightly below average temperatures that will moderate to at least slightly above average temps Sunday through Thursday of next week until a cold front presses through.

eps

After the current trough lifts out, the upper air flow will become more zonal through the end of the 3rd week of August. No heatwaves are anticipated, and near average temps with active precipitation will continue. 

eps5

Next 3 weeks of US temperature departures

Images below are clickable for better viewing

Days 1-5 – confidence VERY HIGH

1-5

Days 6-10 – confidence HIGH

6-10

Days 11-15 – confidence MODERATELY HIGH

11-15

Days 16-20 – confidence MODERATE

16-20

Current U.S. Soil Moisture Anomaly

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.

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Forecaster: EPAWA Meteorologist Bobby Martrich
Discussion last updated: Friday August 7th, 11:45AM