861 FXUS06 KWBC 092023 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EST Mon December 09 2019 6-10 DAY OUTLOOK FOR DEC 15 - 19 2019 Today's GEFS, ECMWF, and Canadian ensemble mean solutions are in good agreement on the 500-hPa pattern over the forecast domain for the 6-10 day period. A broad trough is forecast over the Aleutian Islands. Ensemble models are consistent on a forecast of an amplified upper-level trough over northern central Canada extending across Hudson Bay with weaker troughing extending into the southwestern CONUS. The manual blend indicates negative 500-hPa height anomalies over most of North America with larger negative anomalies centered over the Gulf of Alaska and to the north of Hudson Bay with weak positive 500-hPa height anomalies over the Southeast CONUS. A predicted anomalous trough and negative 500-hPa height anomalies results in enhanced probabilities of below normal temperatures over the interior western CONUS and parts of the northern central CONUS around the upper Mississippi Valley. Southerly flow ahead of a predicted trough favors above normal temperatures for the Aleutian Islands, southern mainland Alaska, and the Alaska Panhandle, as well as for parts of the Pacific Northwest. Southerly mid-level flow ahead of troughing over the western CONUS leads to increased probabilities of above normal temperatures for parts of the Southwest region extending into the Central Plains. Near to above normal 500-hPa heights over the Southeast and southerly flow around the center of positive anomalies leads to likely above normal temperatures over the eastern CONUS. Predicted troughing over the Aleutian Islands enhances chances of above normal precipitation for the Aleutian Islands, southwestern Alaska, and the Alaska Panhandle. Above normal precipitation is likely for the Pacific Northwest, ahead of troughing over the North Pacific in model forecasts. Above normal precipitation is most likely in the 6-10 day period for a region of the central CONUS from Utah and the Four Corners region northeastward into the central Great Plains states and parts of the central Mississippi Valley. Southerly moisture flow around a predicted positive 500-hPa height anomaly over the Atlantic leads to enhanced probabilities of above normal precipitation over the eastern CONUS. Below normal precipitation is more likely over much of mainland Alaska, under anomalous easterly flow, and over parts of the northern central CONUS, under anomalous northerly flow. Near normal precipitation is indicated for regions of the Southwest, Southern Plains, and the North Slope of Alaska where climatological normal precipitation is near zero and little or no chance of precipitation is predicted. The official 6-10 day 500-hPa height blend consists of 25% of Today's 6z GFS Ensemble Mean centered on Day 8, 50% of Today's 0z European Ensemble Mean centered on Day 8, and 25% of Today's 0z Canadian Ensemble Mean centered on Day 8 FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Below average, 2 out of 5, due to good agreement on the 500-hPa pattern offset by predicted low amplitude circulation anomalies and some differences among the model forecast tools. 8-14 DAY OUTLOOK FOR DEC 17 - 23 2019 During the week-2 period, positive 500-hPa height anomalies are predicted to increase in amplitude over the eastern central CONUS centered over the central Mississippi Valley. Ensemble mean solutions show some consistency, but the ECMWF ensemble mean increases mid-level heights over the eastern CONUS earlier, which results in greater mean height anomalies over this region in week-2. The GEFS ensemble mean retains negative 500-hPa height anomalies over the Northeast region. Troughing over the North Pacific in the 6-10 day period is predicted to progress eastward towards the west coast of North America in week-2. Despite differences in the evolution of the circulation pattern between the GEFS and ECMWF ensembles, the model temperature forecasts have some similarities. Rising heights over the eastern CONUS lead to increased probabilities of above normal temperatures over the central and eastern CONUS, with probabilities exceeding 50 percent over the Central Plains and the Florida Peninsula. Enhanced probabilities of below normal temperatures persist over parts of the Great Basin, where 500-hPa height forecasts are near normal in week-2. Below normal temperatures continue to be likely for most of Alaska outside the southern coast, under predicted negative 500-hPa height anomalies, while above normal temperatures are more likely along the southern coast of Alaska, where mid-level flow is predicted to be predominantly from the south during much of week-2. The predicted trough off of the west coast of the CONUS increases the chances of above normal precipitation for much of the western CONUS in week-2. Southerly flow around surface high pressure over the eastern CONUS leads to enhanced probabilities of above normal precipitation over parts of the eastern central CONUS with the greatest probabilities over an area from East Texas into the Central Mississippi Valley. Probabilities of above normal precipitation are slightly enhanced over much of the eastern CONUS in week 2, under predominantly southerly flow in the transition from the circulation pattern predicted for the 6-10 day period. Above normal precipitation continues to be likely for the southern coast of Alaska in week-2, while below normal is likely for western mainland Alaska. The official 8-14 day 500-hPa height blend consists of: 25% of Today's 6z GFS Ensemble Mean centered on Day 11, 50% of Today's 0z European Ensemble Mean centered on Day 11, and 25% of Today's 0z Canadian Ensemble Mean centered on Day 11 FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Below average, 2 out of 5, due to only fair agreement on the 500-hPa pattern, predicted low amplitude circulation anomalies, and some differences among the model forecast tools. 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 December 19. 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: 19581125 - 19681125 - 19821124 - 19511123 - 19761213 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: 19581124 - 19821124 - 19681124 - 19761212 - 19751218 6-10 DAY OUTLOOK TABLE Outlook for Dec 15 - 19 2019 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A A OREGON N A NRN CALIF N N SRN CALIF N N IDAHO B A NEVADA B A W MONTANA N N E MONTANA N N WYOMING B A UTAH B A ARIZONA A N COLORADO N A NEW MEXICO A N N DAKOTA N B S DAKOTA N A NEBRASKA N A KANSAS A A OKLAHOMA A N N TEXAS N N S TEXAS N N W TEXAS A N MINNESOTA B B IOWA N A MISSOURI N N ARKANSAS N N LOUISIANA N A WISCONSIN N B ILLINOIS N N MISSISSIPPI N A MICHIGAN N N INDIANA N N OHIO N A KENTUCKY N A TENNESSEE A A ALABAMA A A NEW YORK A A VERMONT A A NEW HAMP A A MAINE A A MASS A 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 A N CAROLINA A A S CAROLINA A A GEORGIA A A FL PNHDL A A FL PENIN A A AK N SLOPE N N AK ALEUTIAN A N AK WESTERN N B AK INT BSN N B AK S INT A B AK SO COAST A A AK PNHDL A A 8-14 DAY OUTLOOK TABLE Outlook for Dec 17 - 23 2019 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A A OREGON A A NRN CALIF N A SRN CALIF N A IDAHO N A NEVADA B A W MONTANA N A E MONTANA A N WYOMING N B UTAH B A ARIZONA N A COLORADO A N NEW MEXICO A A N DAKOTA A N S DAKOTA A B NEBRASKA A B 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 N 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 N N MASS A 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 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 A A AK WESTERN B B AK INT BSN B B AK S INT N N AK SO COAST N N AK PNHDL A 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. $$