066 FXUS06 KWBC 301912 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EDT Mon March 30 2020 6-10 DAY OUTLOOK FOR APR 05 - 09 2020 There is general agreement on the forecast 500-hPa circulation pattern for the 6-10 day period over North America among dynamical model forecasts. Model forecasts from the ECMWF, NCEP GEFS, and Canadian ensembles predict split flow over the North Pacific with a shortwave trough to the Northwest of Hawaii and ridging over the Aleutian Islands. A downstream trough is forecast by all models over the Pacific Coast of the CONUS, while a ridge is predicted over the eastern CONUS. There are relatively small differences among the ECMWF, NCEP GEFS, and Canadian ensemble means, while the ECMWF and Canadian models indicate greater ensemble spread and uncertainty over the CONUS than the NCEP GEFS ensemble. As a result, the GEFS ensemble mean forecast indicates a more amplified negative 500-hPa height anomaly over the western CONUS and positive 500-hPa height anomaly over the eastern CONUS. Today's manual 500-hPa height blend weights the ECMWF ensemble mean slightly greater than the NCEP GEFS and Canadian ensemble means, due to recent model skill. The arctic oscillation or AO has been positive for much of the time since the beginning of the year, and the predicted circulation pattern for the 6-10 day period projects onto the positive phase of the AO. The 6-10 day temperature outlook calls for likely below normal temperatures over much of the western CONUS along the entire Pacific Coast and across the central and northern Rocky Mountains into the parts of the northwestern Great Plains, under predicted negative 500-hPa height anomalies. Above normal temperatures are likely over the central and eastern CONUS, under a predicted ridge and positive 500-hPs height anomalies, with probabilities exceeding 80 percent for parts of the Gulf Coast region. Probabilities of above normal temperatures decrease over parts of the Northeast and New England, where there is the potential for a cold front and northerly flow of cold air. All dynamical model forecasts indicate likely below normal temperatures for southern areas of mainland Alaska and the Alaska Panhandle, under predicted anomalous northerly flow. Above normal temperatures are likely for the western Aleutians, under a predicted ridge, and for northern Alaska, where temperature trends are significant. The 6-10 day precipitation outlook calls for likely above normal precipitation over much of the CONUS, ahead of a predicted trough along the Pacific coast. Probabilities for above normal precipitation exceed 50 or 60 percent for parts of California and Nevada due to predicted onshore flow. Above normal precipitation is likely across the Central and Upper Mississippi Valley and the Great Lakes region as storm systems are predicted to move over the ridge centered over the Southeast CONUS. Near to below normal precipitation is likely over the Northeast region under anomalous northerly flow. Significant southerly surface moisture flow from the Gulf of Mexico leads to likely above normal precipitation for much of the Gulf Coast region to the Rio Grande Valley, with probabilities as high as 60 percent for southwestern areas of Texas. Near to below normal precipitation is more likely for the Florida Peninsula, as indicated by dynamical model forecasts. Above normal precipitation is likely for much of mainland Alaska ahead of predicted strong westerly flow, while near to below normal precipitation is likely for the south coast of Alaska from the Aleutian Islands to the Alaska Panhandle under a predicted ridge over the Aleutians and anomalous northerly flow over the Alaska Mainland and Panhandle. 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: Well above average, 5 out of 5, due to good model forecast and tool agreement, as well as low ensemble spread and a fairly amplified 500-hPa circulation pattern forecast. 8-14 DAY OUTLOOK FOR APR 07 - 13 2020 The predicted circulation pattern for the 8-14 day period is similar to the forecast for the 6-10 day period in all dynamical model forecasts. A ridge and above normal 500-hPa heights persist over the Aleutian Islands, while a trough is forecast along the Pacific Coast of North America. Negative 500-hPa height anomalies over the western CONUS and positive 500-hPa height anomalies over the eastern CONUS are predicted to continue into the 8-14 day period, with lower amplitude in ensemble mean forecasts in the 8-14 day period than in the 6-10 day period, as ensemble spread and uncertainty increase. The 8-14 day temperature outlook is very similar to the temperature pattern forecast for the 6-10 day period. Below normal temperatures continue to be likely for the western CONUS along the Pacific Coast and eastward across the Great Basin and Northern Rockies, under predicted negative 500-hPa height anomalies. Above normal temperatures continue to be favored over the central and eastern CONUS into the 8-14 day period, under continued positive 500-hPs height anomalies, however probabilities are decreased with a decrease in amplitude of the predicted ridge. Probabilities of above normal temperatures decrease to below 40 percent over parts of New England, with an increasing potential for a cold front over the region. Below normal temperatures continue to be likely for southern mainland Alaska and the Alaska Panhandle, under predicted anomalous northerly flow, while above normal temperatures are likely for the western Aleutians, under a predicted ridge. Above normal temperatures are also likely for northern Alaska, with strong decadal temperature trends. A pattern of likely above normal precipitation over much of the CONUS continues for the 8-14 day period, as a predicted trough along the Pacific coast persists, with the exception of likely near normal precipitation over the Northeast, parts of eastern Arizona into the Central Plains, and the Florida Peninsula. Above normal precipitation is likely for much of the Gulf Coast region with predicted surface moisture flow from the Gulf of Mexico. Above normal precipitation continues to be likely for much of mainland Alaska ahead of strong westerly flow, while near to below normal precipitation is likely for the south coast of Alaska in the 8-14 day period. 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 agreement among model circulation forecasts and good tool agreement, offset by increasing ensemble spread. 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 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 April 16. 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: 19810407 - 19630313 - 19630318 - 19670413 - 20090313 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: 19810407 - 19630316 - 19670412 - 20090312 - 19550312 6-10 DAY OUTLOOK TABLE Outlook for Apr 05 - 09 2020 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B A OREGON B A NRN CALIF B A SRN CALIF B A IDAHO B A NEVADA B A W MONTANA B A E MONTANA B A WYOMING A A UTAH N A ARIZONA N A COLORADO A N 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 A NEW YORK A N VERMONT A N NEW HAMP A B MAINE A B MASS A B CONN A N RHODE IS A B PENN A N NEW JERSEY A N W VIRGINIA A A MARYLAND A N DELAWARE A N VIRGINIA A A N CAROLINA A A S CAROLINA A A GEORGIA A A FL PNHDL A A FL PENIN A B AK N SLOPE A A AK ALEUTIAN N N AK WESTERN N A AK INT BSN N A AK S INT B A AK SO COAST B N AK PNHDL B B 8-14 DAY OUTLOOK TABLE Outlook for Apr 07 - 13 2020 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B A OREGON B A NRN CALIF B A SRN CALIF B A IDAHO B A NEVADA B A W MONTANA B A E MONTANA B A WYOMING B A UTAH B A ARIZONA N A COLORADO A N NEW MEXICO A N N DAKOTA N A S DAKOTA A A NEBRASKA A A KANSAS A N 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 A NEW YORK A A VERMONT A N NEW HAMP A N MAINE A N MASS A N CONN A N RHODE IS A N PENN A A NEW JERSEY A N 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 B AK N SLOPE A A AK ALEUTIAN A B AK WESTERN B A AK INT BSN B A AK S INT B N AK SO COAST B B AK PNHDL B B 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. $$