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As of the May 19th, 2017, release, Week 3-4 outlooks precipitation outlooks are experimental, whereas the temperature outlooks are operational. Both are issued Friday between 3pm & 4pm Eastern Time.
HOME> Outlook Maps> Week 3-4 Outlooks

Week 3-4 Outlooks
Valid: 28 Jul 2018 to 10 Aug 2018
Updated: 13 Jul 2018

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Temperature Probability


Week 3-4 Outlooks - Temperature Probability
Precipitation Probability
(Experimental)


Week 3-4 Outlooks - Precipitation Probability

Click HERE for information about how to read Week 3-4 outlook maps

Prognostic Discussion for Week 3-4 Temperature and Experimental Precipitation Outlooks
NWS Climate Prediction Center College Park MD
300PM EDT Fri Jul 13 2018

Week 3-4 Forecast Discussion Valid Sat Jul 28 2018-Fri Aug 10 2018

The Week 3-4 outlook is made amidst a backdrop of anticipation of building El Nino conditions in the tropical Pacific, while the Madden-Julian Oscillation (MJO) is crossing the Maritime Continent. The current MJO event appears largely circulation driven, with influences from extratropical waves breaking towards the equator helping with the current projection. Model guidance propagates the MJO eastward to the West Pacific during the next two weeks, although some of this signal may be due to a Kelvin wave currently approaching the primary intraseasonal envelope from the west. Teleconnections are relatively weak this time of year given the lack of sharp vorticity gradients in the Northern Hemisphere, suggesting minimal impact from the tropics on the present outlook. That said, there is a weak tendency for warming temperatures focused along the Northern Rockies by Week-4 per historical MJO composites that also shows up in some statistical tools. The primary drivers of the present outlook include ensemble guidance from the CFS, ECMWF, and JMA models in addition to decadal trends. Experimental Subseasonal Experiment (SubX) models were also consulted in developing the outlook.

Forecast 500-hPa height anomalies are characteristically small, consistent with boreal summer expectations. More attention was paid to the evolution of the forecast circulation pattern relative to Week-2 than the amplitude of the pattern itself, with emphasis given to features that evolved consistently between the two different outlook periods. Operational models generally have positive height anomalies in the vicinity of Alaska and over the West, with anomalous troughing or a weakness in the height anomalies focused over the Great Lakes and Mid-Atlantic. The experimental SubX multi-model ensemble features a similar pattern, with positive anomalies focused over the Bering Sea and Pacific Northwest and stretch across the southern U.S., while near-normal height anomalies exist from the Upper Mississippi Valley through New England.

Chances for above-normal temperatures are greatest across the Desert Southwest and South Texas in the outlook, consistent with the forecast circulation and persistence from the Week-2 period. Above-normal temperatures are broadly favored from the Rockies westward, and across the southern two-thirds of the CONUS with the exception of South Florida, where a frontal boundary may be in the vicinity. Increased odds for above-normal temperatures also exist for New England, downstream of the mean 500-hPa trough. With the potential for anomalous troughing over the Great Lakes, below-normal temperatures are favored in a strip from the North-Central Great Plains through the Western Great Lakes. This area is consistent with observed soil moisture anomalies that are well above-normal, which could help keep temperatures down. For Alaska, the highest probabilities for above-normal temperatures lie across western and southern parts of the state due to anomalously warm sea surface temperatures (SSTs) in the Bering Sea and Gulf of Alaska. Above-normal temperatures are favored across the rest of the state, tapering to a 50 percent chance of above-normal for the North Slope due to near-normal sea ice content in the Beaufort Sea.

Below-normal precipitation is favored across the CONUS for most areas west of the Appalachians. Exceptions to this include the climatologically arid areas of California, Nevada, and Oregon where no precipitation is anticipated, and an area from the Central Great Basin through the Northern Plains where model precipitation signals are mixed, possibly due to the potential for upslope flow. There are lessened chances for below-normal precipitation across the Central Plains and Mississippi Valley due to a potential mean frontal zone, consistent with the temperature outlook. Also the North American Monsoon appears to be quieting down in Week-2 and may remain quiet in this outlook period as well. Though the Kelvin wave mentioned previously, however, may help kick off tropical cyclone activity in the East Pacific by Week-3 that could initiate another moisture surge into the Southwest should a system track close to the Mexican coastline. Increased chances for above-normal precipitation exist across Florida and the Southeast given potential front positioning. Since the outlook extends into mid-August, care also has to be exercised for any possible tropical cyclone development along the tail end of a front reaching into the tropics. Anomalously warm SSTs currently observed in the Gulf of Mexico appear ripe for strengthening anything that would develop. Dynamical model guidance also points to increased odds for below-normal precipitation for southeastern Alaska and northern New England.

Near Hawaii SSTs remain around one degree Celsius warmer than normal, and the consensus of dynamical model guidance indicates enhanced probabilities for above-normal temperatures. Dynamical model precipitation forecasts are mixed across the island chain, but generally favor below-median precipitation for eastern points.







Temperature Precipitation
FCST FCST
Hilo A80 B55
Kahului A80 B55
Honolulu A80 EC
Lihue A80 EC


Forecaster: Daniel Harnos

The next week 3-4 outlook will be issued on Friday, Jul 20, 2018

These outlooks are based on departures from the 1981-2010 base period

These are two category outlooks and differ from official current three category outlooks currently used for the monthly and seasonal forecasts.



The shading on the temperature map depicts the most favored category, either above-normal (A) or below-normal (B) with the solid lines giving the probability ( >50%) of this more likely category (above or below).

The shading on the precipitation map depicts the most favored category, either above-median (A) or below-median (B) with the solid lines giving the probability ( >50%) of this more likely category (above or below).

In areas where the likelihoods of 2-week mean temperatures and accumulated precipitation amounts are similar to climatological probabilities, equal chances (EC) is indicated.



As of May 19, 2017, the temperature outlook is operational, while the precipitation outlook is still experimental



An ASCII (w/ HTML markup tags) text version of the written forecast is available.

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