####018012793#### FXUS06 KWBC 152034 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EDT Mon April 15 2024 6-10 DAY OUTLOOK FOR APR 21 - 25 2024 A transient 500-hPa height pattern is forecast across North America during the 6-10 day period. At the outset of the period, troughing is predicted across eastern Canada and extending into the Great Lakes and Northeast. A trend toward higher mid-level heights is forecast in the East later in the period as this initial troughing lifts out and ridging shifts eastward across the CONUS. The 0z ECMWF and Canadian ensembles are more amplified with this ridge compared to the 0z GEFS, with all models in agreement for more troughing to build into the western CONUS and over the Bering Sea as the period progresses. Today’s manual 500-hPa height blend depicts near-normal heights across the Eastern Seaboard, and above-normal heights across the remainder of the CONUS. Near- to below-normal (above-normal) heights are predicted across Alaska (Hawaii). Models are in good agreement regarding anomalously cold temperatures across much of the eastern half of the CONUS at the start of the period, with moderation likely by the second half of the period. Today’s forecast depicts enhanced probabilities for below-normal temperatures over much of the eastern CONUS and Southern Plains for the period as a whole, along with increased chances for above-normal temperatures across the western CONUS, Northern and Central Plains, and Upper Mississippi Valley. Although the ECMWF reforecast tool is not as robust with below-normal temperature probabilities in the East compared to the GEFS reforecast tool, there is better agreement among the uncalibrated guidance regarding cooler temperatures. Troughing is forecast to build across the Bering Sea following some weak ridging across Mainland Alaska and Southeast Alaska early in the period. This favors a trend toward cooler temperatures across the state, with the forecast being a compromise between the warmer reforecast guidance and cooler uncalibrated tools. The largest probabilities for below-normal temperatures are favored across the western Mainland and Aleutians, with near- to slightly above-normal temperatures forecast across the remainder of the Mainland and Southeast Alaska. Below-normal temperatures are predicted across the Hawaiian Islands consistent with the consolidation forecast tool. The transient pattern favors a large area of near-normal precipitation across the CONUS during the period. Surface high pressure forecast to move across the East favors elevated chances of below-normal precipitation across the Northeast. To the south, enhanced chances for above-normal precipitation are forecast along a frontal boundary extending from the Southern Plains to the Mid-Atlantic, with return flow around surface high pressure possibly leading to renewed precipitation changes across parts of the central CONUS by the end of the period. Above-normal 500-hPa heights across the West favor enhanced chances for near- to below-normal precipitation. Increased southerly flow across Alaska ahead of developing troughing over the Bering Sea favors enhanced chances for above-normal precipitation across the state. Near- to below-normal precipitation chances are elevated across Hawaii due to increasing ridging over the central Pacific. The official 6-10 day 500-hPa height blend consists of 30% of Today's 6z GFS Ensemble Mean centered on Day 8, 40% 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 generally good agreement in the tools regarding the temperature and precipitation forecast, offset by some uncertainty related to a transient pattern. 8-14 DAY OUTLOOK FOR APR 23 - 29 2024 The 500-hPa height pattern during week-2 is forecast to continue to trend toward more ridging across the eastern CONUS and weak troughing across the western CONUS and Alaska. The manual height blend depicts the highest positive height anomalies (+60 meters) across the Ohio Valley and Northeast. Near-normal heights are favored from the Rockies westward, with below-normal heights predicted across much of Alaska associated with troughing across the Bering Sea and western Mainland. Near- to above-normal heights are forecast across Hawaii. The prevailing mid-level height pattern across the CONUS favors an anomalously warm pattern across much of the CONUS east of the Rockies during late April. The highest probabilities for above-normal temperatures (greater than 60 percent) are across the Great Plains, with decreasing chances further east as there is some uncertainty related to the lingering below-normal temperatures at the start of the period. Near- to slightly below-normal temperatures are favored along the West Coast due to more troughing and supported by the uncalibrated forecast tools, and teleconnection analysis with the positive height anomaly center in the central Pacific. Across Alaska, the reforecast tools continue to depict increased chances for above-normal temperatures across much of the state. However, the forecast leans toward higher probabilities of below-normal temperatures given the forecast increase in troughing as well as increased signals for below-normal temperatures in the uncalibrated tools and teleconnection analysis. Increased chances for below-normal temperatures remain forecast across Hawaii. The trend toward relatively lower mid-level heights across the western CONUS favors increasing chances for above-normal precipitation across a large portion of the CONUS, aided in part by increased southerly return flow in the East. This pattern sets the stage for multiple episodes of precipitation as ejecting shortwave disturbances promote a favorable environment for enhanced precipitation across parts of the central CONUS. Near-normal precipitation is favored along the Eastern Seaboard, farther displaced from the forcing upstream. Probabilities for above-normal precipitation remain elevated across Alaska consistent with the reforecast tools and troughing over the region. Above-normal precipitation chances are also increased across Hawaii. The official 8-14 day 500-hPa height blend consists of: 30% of Today's 6z GFS Ensemble Mean centered on Day 11, 40% 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: Above Average, 4 out of 5, due to good model agreement regarding amplified ridging across the eastern half of the CONUS and a subsequent warmer pattern, offset by lower confidence in the precipitation forecast. 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 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 April 18. 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: 20080411 - 19770418 - 19640426 - 19550412 - 19990405 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: 20080410 - 19770419 - 19640425 - 19550412 - 19610418 6-10 DAY OUTLOOK TABLE Outlook for Apr 21 - 25 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A N OREGON A B NRN CALIF A N SRN CALIF A N IDAHO A N NEVADA A N W MONTANA A N E MONTANA A N WYOMING A N UTAH A N ARIZONA A B COLORADO A A NEW MEXICO A A N DAKOTA A N S DAKOTA A N NEBRASKA A N KANSAS N N OKLAHOMA B N N TEXAS B A S TEXAS B A W TEXAS B A MINNESOTA A N IOWA N N MISSOURI B N ARKANSAS B N LOUISIANA B A WISCONSIN N N ILLINOIS B N MISSISSIPPI B A MICHIGAN N N INDIANA B N OHIO B N KENTUCKY B N TENNESSEE B N ALABAMA B A NEW YORK B B VERMONT N B NEW HAMP N B MAINE N B MASS B B CONN B B RHODE IS B B PENN B N NEW JERSEY B N W VIRGINIA B N MARYLAND B N DELAWARE B N VIRGINIA B N N CAROLINA B A S CAROLINA B A GEORGIA B A FL PNHDL N A FL PENIN A A AK N SLOPE B A AK ALEUTIAN B A AK WESTERN N A AK INT BSN N A AK S INT N A AK SO COAST N A AK PNHDL N A 8-14 DAY OUTLOOK TABLE Outlook for Apr 23 - 29 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON N A OREGON A N NRN CALIF N A SRN CALIF B A IDAHO A A NEVADA A A W MONTANA A A E MONTANA A A WYOMING A A UTAH A A ARIZONA A A COLORADO A A NEW MEXICO A A N DAKOTA A A S DAKOTA A A NEBRASKA A A KANSAS A A OKLAHOMA A A N TEXAS A A S TEXAS A A W TEXAS A A MINNESOTA A A IOWA A A MISSOURI A A ARKANSAS A A LOUISIANA A A WISCONSIN A A ILLINOIS A A MISSISSIPPI A A MICHIGAN A A INDIANA A A OHIO A A KENTUCKY A A TENNESSEE A A ALABAMA A N NEW YORK A N VERMONT A N NEW HAMP A N MAINE A N MASS N N CONN N N RHODE IS N N PENN A N NEW JERSEY A N W VIRGINIA A A MARYLAND A N DELAWARE N N VIRGINIA A N N CAROLINA A N S CAROLINA A N GEORGIA A N FL PNHDL A N FL PENIN A N AK N SLOPE B A AK ALEUTIAN B A AK WESTERN B A AK INT BSN B A AK S INT B A AK SO COAST B 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. $$