FXUS06 KWBC 251902 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EDT Fri April 25 2025 6-10 DAY OUTLOOK FOR MAY 01 - 05 2025 Model ensemble means (GEFS, ECMWF, and Canadian) are in good overall agreement with a progressive flow pattern over the Contiguous U.S. (CONUS) for the beginning of May. A mid-level 500-hPa trough is forecast to shift eastward from the Mississippi Valley through the eastern CONUS, while an amplified mid-level ridge progresses from the northwestern CONUS into the northern central CONUS. Late in the period positive 500-hPa height anomalies extend across the entire northern CONUS in the GEFS and Canadian ensemble mean forecasts while the ECMWF retains a weak trough over the East. For this 5-day period forecast, the manual 500-hPa height blend depicts positive 500-hPa height anomalies for most of the western and central CONUS and over parts of the Northeast. Weak troughs are forecast in the manual blend over the Southwest and over the Ohio and Tennessee Valleys. A trough is forecast across Alaska, extending into the Gulf of Alaska, with associated negative 500-hPa height anomalies across the state. Above-normal temperatures are likely for most of the West and for the Central and Northern Plains, under the predicted ridge. Probabilities exceed 70 or 80 percent for parts of the Northern Plains, under the center of positive 500-hPa height anomalies. Anomalous positive temperature anomalies are predicted over the southeastern CONUS for the first half of the 6-10 day forecast period. Near-normal temperatures are forecast over the Ohio Valley and northeastern areas of the CONUS, under the predicted trough that progresses over the East during the period. Near-normal temperatures are favored for parts of the Southwest and Southern Plains due to lower 500-hPa heights and increasing probabilities of precipitation. Below-normal temperatures are likely for much of western and northern Alaska, under predicted negative 500-hPa height anomalies. Near-normal temperatures are favored for most of southern Mainland Alaska and for Southeast Alaska, under southerly mid-level flow. Above-normal temperatures are likely for Hawaii, with positive surrounding sea surface temperature anomalies. Above-normal precipitation is favored across southern and interior Mainland Alaska with probabilities exceeding 50 percent for Southeast Alaska, ahead of a predicted trough and southerly flow. With a mid-level trough forecast to progress across the Southwest, above-normal precipitation is favored across most of the southwestern and southern central CONUS. Probabilities for above-normal precipitation exceed 50 percent for parts of the Southern Plains. Above-normal precipitation is favored for much of the eastern CONUS with a trough predicted to progress across the region. Near-to-below normal precipitation is favored across the northern central CONUS, under the ridge. Above-normal precipitation is favored for parts of Washington state, consistent with the precipitation consolidation. Dynamical model forecasts favor above-normal precipitation for Hawaii. The official 6-10 day 500-hPa height blend consists of 25% of Today's 0z GFS Ensemble Mean centered on Day 8, 45% of Today's 0z European Ensemble Mean centered on Day 8, and 30% 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 model agreement on the progressive circulation pattern, offset by some areas of disagreement among forecast tools. 8-14 DAY OUTLOOK FOR MAY 03 - 09 2025 Ensemble means forecast a transition in the mid-level circulation pattern during the week-2 period. A predicted ridge and positive 500-hPa height anomalies over the northern central CONUS at the start of the week-2 period are forecast to spread across the Northeast after the passage of a trough, as a ridge and positive 500-hPa height anomalies progress into the Northwest. A trough and associated negative 500-hPa height anomalies persist across Alaska and extend southward along the west coast of North America later in the period. A weak trough progresses eastward over the Southwest early in week 2. Above-normal temperatures continue to be likely across most of the West and northern central CONUS in the week-2 period, under positive 500-hPa height anomalies. Probabilities exceed 70 percent for parts of the Northern Plains as the ridge persists over this region. Above-normal temperatures are slightly favored for much of the northeastern CONUS and Mid-Atlantic coast consistent with the temperature consolidation. Near to below-normal temperatures are favored for parts of the Southwest and Southern Plains with predicted near-average mid-level heights and enhanced precipitation. Below-normal temperatures are favored for most of Alaska under negative 500-hPa height anomalies. Near-normal temperatures are favored for the south coast of Mainland Alaska, under southerly mid-level flow. Above-normal temperatures are predicted to persist across Hawaii during week-2 by dynamical models. Similar to the 6-10 day period, above-normal precipitation is favored for most of Mainland Alaska, excluding the west and north coasts, and favored for Southeast Alaska, ahead of a predicted trough. Above-normal precipitation continues to be favored for much of the southwestern CONUS into the Southern Plains, with a predicted trough progressing over the region. Above-normal precipitation is slightly favored for the Gulf and southern Atlantic coasts, supported by most dynamical model forecast tools. Near to below-normal precipitation is slightly favored over remaining areas of the northwestern and eastern CONUS, under mean positive 500-hPa height anomalies. Above-normal precipitation is favored for Hawaii during the week-2 period, consistent with the precipitation consolidation. The official 8-14 day 500-hPa height blend consists of: 25% of Today's 0z GFS Ensemble Mean centered on Day 11, 45% of Today's 0z European Ensemble Mean centered on Day 11, and 30% of Today's 0z Canadian Ensemble Mean centered on Day 11 FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: About average, 3 out of 5, due to good agreement among the mean dynamical model height forecasts and surface tools for most areas, offset by uncertainty due to an evolving pattern. FORECASTER: D Collins 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 1991-2020 base period means as reference in the climate outlooks. The next set of long-lead monthly and seasonal outlooks will be released on May 15. 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: 19540422 - 19640420 - 19810407 - 20020420 - 20020509 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: 19810408 - 19540422 - 20020417 - 19640421 - 20020422 6-10 DAY OUTLOOK TABLE Outlook for May 01 - 05 2025 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A A OREGON A N NRN CALIF A A SRN CALIF A A IDAHO A N NEVADA A A W MONTANA A B E MONTANA A B WYOMING A N UTAH A A ARIZONA A A COLORADO A A NEW MEXICO N A N DAKOTA A B S DAKOTA A B NEBRASKA A N KANSAS A A OKLAHOMA A A N TEXAS A A S TEXAS A A W TEXAS N A MINNESOTA A B IOWA A N MISSOURI A N ARKANSAS A N LOUISIANA A A WISCONSIN A N ILLINOIS N N MISSISSIPPI A A MICHIGAN N N INDIANA N A OHIO N A KENTUCKY N A TENNESSEE A A ALABAMA A A NEW YORK N A VERMONT N A NEW HAMP N A MAINE N A 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 A FL PNHDL A A FL PENIN A A AK N SLOPE B N AK ALEUTIAN B A AK WESTERN B N AK INT BSN B A AK S INT N A AK SO COAST N A AK PNHDL N A 8-14 DAY OUTLOOK TABLE Outlook for May 03 - 09 2025 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A N OREGON A B NRN CALIF A N SRN CALIF A A IDAHO A N NEVADA A A W MONTANA A B E MONTANA A N WYOMING A N UTAH A A ARIZONA A A COLORADO A A NEW MEXICO N A N DAKOTA A N S DAKOTA A N NEBRASKA A N KANSAS A A OKLAHOMA A A N TEXAS N A S TEXAS N A W TEXAS B A MINNESOTA A N IOWA A B MISSOURI A B ARKANSAS A N LOUISIANA A A WISCONSIN A B ILLINOIS A B MISSISSIPPI N N MICHIGAN A B INDIANA A B OHIO A B KENTUCKY N B TENNESSEE N B ALABAMA N N NEW YORK A B VERMONT A N NEW HAMP A N MAINE A N MASS A N CONN A N RHODE IS A N PENN A B NEW JERSEY A B W VIRGINIA A B MARYLAND A B DELAWARE A N VIRGINIA A B N CAROLINA A A S CAROLINA N A GEORGIA N A FL PNHDL N A FL PENIN N A AK N SLOPE B N AK ALEUTIAN B N AK WESTERN B N AK INT BSN B A AK S INT N A AK SO COAST N A AK PNHDL B 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. $$