972 FXUS06 KWBC 221907 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EDT Wed May 22 2019 6-10 DAY OUTLOOK FOR MAY 28 - JUN 01, 2019 The 500-hPa geopotential height pattern across the U.S. is forecast to deamplify toward the end of the 6-10 day period. How quickly it does, differs among the model guidance, with the ECMWF being quicker than the GEFS. However, both models now agree on mid level low pressure situated just south of Hudson Bay, which is characterized by negative 500-hPa height anomalies over much of southeastern Canada and extending into the Great Lakes and parts of the Northeast. The southeastern CONUS is still favored to be under ridging and positive 500-hPa height anomalies, while troughing over the West favors negative height anomalies, especially early in the period. The exception is the Pacific Northwest, where split flow is forecast as a result of ridging over the Northeast Pacific and Western Canada, favoring positive height anomalies. The transitional nature of the pattern in the 6-10 day period yields some uncertainty in the forecast. Above normal temperature probabilities are favored for much of the East due to ridging and surface high pressure. However, influence from mid-level low pressure over Ontario support more seasonable conditions developing over the Northeast, with below normal temperature probabilities increased over Northern New England and the Great Lakes. Farther to the West, troughing is favored to be the dominant feature, with some weakening late. The GEFS shows a trend toward warmer temperatures later in the period, with the ECMWF ensembles persisting below normal temperatures longer. Today's forecast maintains continuity and supports higher below normal temperature probabilities. With ridging forecast over western Canada, above normal temperatures are favored for the Pacific Northwest. Above normal 500-hPa heights forecast over much of Alaska enhance the likelihood of above normal temperatures for most of the state, except for parts of the south coast of mainland Alaska, where near normal temperature probabilities are favored due to the influence of mid-level low pressure forecast south of the mainland. Above normal precipitation probabilities remain elevated for most of the West due to forecast troughing. Ridging over western Canada favors increased below normal precipitation probabilities for some parts of the Pacific Northwest and the Alaska Panhandle. Below normal precipitation probabilities are also enhanced across most of New Mexico and west Texas. Ridging in the East, combined with surface high pressure off the East Coast, favors increased below normal precipitation probabilities over the Southeast and Gulf Coast. With troughing remaining over the West, southerly flow over the Plains and Mississippi Valley favors enhanced chances of above normal precipitation. Frontal activity may increase across the Middle and Upper Mississippi Valley, into the Great Lakes and Northeast due to the aforementioned mid-level low pressure over Ontario favoring increased chances of above normal precipitation. Mid level low pressure forecast south of the Alaskan mainland favors increased probabilities of above normal precipitation over mainland Alaska and the Aleutians. The official 6-10 day 500-hPa height blend consists of 20% of Today's 6z GFS Ensemble Mean centered on Day 8, 10% of Today's operational 6z GFS centered on Day 8, 35% of Today's 0z European Ensemble Mean centered on Day 8, 15% of Today's operational 0z ECMWF centered on Day 8, and 20% of Today's 0z Canadian Ensemble Mean centered on Day 8 FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Above average, 4 out of 5, due to good agreement between models and tools, with some uncertainty as amplification begins to weaken. 8-14 DAY OUTLOOK FOR MAY 30 - JUN 05, 2019 During the week-2 period, split flow is forecast over the West. Troughing and near to below normal heights are favored over the Southwest with ridging centered over western Canada, and subsequent positive 500-hPa height anomalies extending over the Pacific Northwest. To the east, troughing is forecast to expand across southeastern Canada due to persistent mid-level low pressure. This favors a farther southward progression of near to negative height anomalies in the East relative to the 6-10 day period. Near normal 500-hPa heights are forecast for the central CONUS, with some indication in the model guidance of a broad ridge developing late in the week-2 period. Initially, below normal temperatures are favored for much of the Rockies, Great Basin, and the Desert Southwest as troughing is forecast to have an influence. However, as troughing weakens, a trend toward warmer temperatures is favored throughout week-2, and as a result below normal temperature probabilities are reduced compared to the 6-10 day period. Above normal temperatures are favored for the Pacific Northwest and western California, underneath the aforementioned ridge. For the East, above normal temperatures remain favored for the mid-Atlantic, Southeast, and Lower Mississippi Valley, with below normal temperatures favored for much of northern New England, the Great Lakes, and the Central and Northern Plains as a result of troughing over Eastern Canada. More seasonable temperatures are favored for the mid-Atlantic in the second half of week-2 as positive height anomalies are projected to become more focused in the South. Due to the forecast above normal heights over mainland Alaska, increased above normal temperature probabilities are highlighted for northern mainland Alaska and the Aleutians, while below normal temperature probabilities are favored for the south coast of mainland Alaska due to the continued influence of mid-level low pressure. The precipitation probability forecast during the week-2 period is similar to the 6-10 day period, but with more uncertainty as the pattern evolves. Initial troughing favors above normal precipitation for much of the western CONUS, with the exception of the Pacific Northwest where below normal precipitation is forecast. Shortwave impulses, either originating from Canada or the Southwest, are forecast to track across the Central and Eastern CONUS increasing the chances of above normal precipitation. Below normal precipitation probabilities are favored for the Florida Peninsula. For the Gulf Coast, some individual ensemble members of the ECMWF and the GEFS bring up tropical moisture from the Caribbean in early June. Given the MJO is forecast to be in an 8-1 phase, which favors enhanced convection over this region, it is a plausible scenario. Although ensemble dynamical guidance maintains below normal precipitation probabilities for the Gulf Coast, today's forecast favors near normal due to the uncertainty related to this possible tropical influence. Increased above normal precipitation probabilities remain favored for Alaska, consistent with dynamical forecast tools. The official 8-14 day 500-hPa height blend consists of: 20% of Today's 6z GFS Ensemble Mean centered on Day 11, 10% of Today's operational 6z GFS centered on Day 11, 50% of Today's 0z European Ensemble Mean centered on Day 11, and 20% of Today's 0z Canadian Ensemble Mean centered on Day 11 FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Average, 3 out of 5, due to good agreement among tools early in the period, with uncertainty regarding the pattern evolution later in the period. FORECASTER: Thomas Collow Notes: Automated forecasts are issued on Saturday and Sunday. Occasionally manual intervention is necessary to address quality control and consistency issues. In these cases, forecasts are manually drawn but a full discussion is not issued. The notation for the categorical forecast indicated on the maps is the same as that in the tables: A-above N-near normal B-below The temperature map shows regions with > 33% chance of being warmer (orange, "A"), colder (blue, "B"), or close to (unshaded, "N"). Historical average values for the calendar period of the forecast (dashes, "f"). Labels on the shaded lines give the probability (> 33%) of the more likely category (B or A). Probability of N is always < 40%. The precipitation map shows regions with > 33% chance of being wetter (green, "A"), drier (tan, "B"), or close to (unshaded, "n"). Historical median values for the calendar period of the forecast (dashes, "inches"). Labels on the shaded lines give the probability (> 33%) of the more likely category (B or A). Probability of N is always < 40%. In the southwest and other climatologically dry regions - there will be a greater than 33.3% chance of no precipitation and occasionally even a normal (i.e. Median) value of zero - especially during the dry seasons. In such cases a forecast of near normal is effectively a forecast of little or no precipitation. The climate prediction center uses 1981-2010 base period means for temperature...precipitation...and 500-hpa heights as reference in the climate outlooks. The next set of long-lead monthly and seasonal outlooks will be released on June 20. Analogs to the 5 day mean observed pattern centered 3 days ago (D-3) for the region from 20N to 70N latitude and 175E to 60W longitude include the 5 day periods centered on the following dates: 19570519 - 19950510 - 19530512 - 19930603 - 19590518 Analogs to the 7 day mean observed pattern centered 4 days ago (D-4) for the region from 20N to 70N latitude and 175E to 60W longitude include the 7 day periods centered on the following dates: 19570518 - 19950510 - 19530512 - 19930604 - 19810516 6-10 DAY OUTLOOK TABLE Outlook for May 28 - Jun 01, 2019 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A B OREGON A B NRN CALIF N A SRN CALIF B A IDAHO B A NEVADA B A W MONTANA A A E MONTANA B A WYOMING B A UTAH B A ARIZONA B N COLORADO B A NEW MEXICO B N N DAKOTA B N S DAKOTA B A NEBRASKA B A KANSAS B A OKLAHOMA A A N TEXAS A A S TEXAS A N W TEXAS N N MINNESOTA B A IOWA B A MISSOURI A A ARKANSAS A A LOUISIANA A B WISCONSIN B A ILLINOIS A A MISSISSIPPI A B MICHIGAN B A INDIANA A A OHIO A A KENTUCKY A A TENNESSEE A A ALABAMA A B NEW YORK N A VERMONT N A NEW HAMP N A MAINE B A MASS N A CONN A A RHODE IS A A PENN A A NEW JERSEY A A W VIRGINIA A A MARYLAND A A DELAWARE A A VIRGINIA A N N CAROLINA A N S CAROLINA A B GEORGIA A B FL PNHDL A B FL PENIN A B AK N SLOPE A A AK ALEUTIAN A A AK WESTERN A A AK INT BSN A A AK S INT N A AK SO COAST N A AK PNHDL A A 8-14 DAY OUTLOOK TABLE Outlook for May 30 - Jun 05, 2019 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A B OREGON A B NRN CALIF A A SRN CALIF N A IDAHO A A NEVADA N A W MONTANA A N E MONTANA N N WYOMING B A UTAH B A ARIZONA N N COLORADO B A NEW MEXICO N A N DAKOTA B B S DAKOTA B N NEBRASKA B A KANSAS B A OKLAHOMA N A N TEXAS A A S TEXAS A N W TEXAS N A MINNESOTA B N IOWA B A MISSOURI N A ARKANSAS A A LOUISIANA A N WISCONSIN B A ILLINOIS B A MISSISSIPPI A N MICHIGAN B A INDIANA B A OHIO N A KENTUCKY A A TENNESSEE A A ALABAMA A N NEW YORK B A VERMONT B A NEW HAMP B A MAINE B N MASS N A CONN N A RHODE IS N A PENN N A NEW JERSEY N A W VIRGINIA A A MARYLAND A A DELAWARE A A VIRGINIA A A N CAROLINA A A S CAROLINA A A GEORGIA A N FL PNHDL A B FL PENIN A B AK N SLOPE A A AK ALEUTIAN A A AK WESTERN A A AK INT BSN A A AK S INT B A AK SO COAST B A AK PNHDL N A LEGEND TEMPS WITH RESPECT TO NORMAL PCPN WITH RESPECT TO MEDIAN A - ABOVE N - NEAR NORMAL A - ABOVE N - NEAR MEDIAN B - BELOW B - BELOW THE FORECAST CLASSES REPRESENT AVERAGES FOR EACH STATE. NORMAL VALUES - WHICH MAY VARY WIDELY ACROSS SOME STATES - ARE AVAILABLE FROM YOUR LOCAL WEATHER SERVICE FORECAST OFFICE. FOR ADDITIONAL INFORMATION SEE MESSAGE FXUS06 KWBC - ON AWIPS AS PMDMRD. $$