FXUS06 KWBC 081902 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EDT Thu August 08 2024 6-10 DAY OUTLOOK FOR AUG 14 - 18 2024 A generally amplified 500-hPa height pattern is forecast across North America during the 6-10 day period, with troughing over the Bering Sea and along the West Coast of the CONUS. Broad ridging is predicted across the central CONUS, with troughing downstream over the northeastern U.S. and northwest Atlantic. Today’s manual height blend depicts near-normal heights over most of the CONUS, with slightly above-normal heights over parts of the Northern Plains and Upper Mississippi Valley and below-normal heights over the Northeast and Mid-Atlantic. Below-normal heights are predicted across western Alaska, underneath the influence of troughing with a -150 meter negative height anomaly center over the Bering Sea. Compared to yesterday, the 0z GEFS and ECENS depict a more northward extension of the central Pacific ridge, resulting in near- to above-normal heights across eastern Alaska and above-normal heights over Hawaii. The evolving mid-level pattern favors elevated probabilities of above-normal temperatures over most of the interior CONUS during the 6-10 day period. The highest probabilities (greater than 60 percent) are forecast across the Southern Plains and Lower Mississippi Valley, with increasing concerns for excessive heat over these regions. The uncalibrated guidance from the 0z GEFS, ECENS, and CMCE support increased chances for below-normal temperatures near the West Coast and also along the Eastern Seaboard. The ECENS reforecast tool has increased its signal for below-normal temperatures in the East compared to yesterday, and is now more in line with other guidance. Anomalous troughing over the Bering Sea favors increased probabilities for below-normal temperatures over much of Alaska, excluding the northern Mainland where above-normal temperatures are favored. Above-normal temperature chances are increased over Hawaii, consistent with the reforecast consolidation tool. Shortwave impulses are forecast to propagate overtop the expanding ridge over the central CONUS. This favors increased chances for above-normal precipitation across much of the northern U.S., and extends to the Eastern Seaboard where the weakness in the mid-level flow favors increased frontal activity. Weak probabilities for below-normal precipitation are highlighted over the Great Lakes and northern New England, further displaced from the projected storm track and closer to the anomalous ridge center over Canada. Below-normal precipitation chances are also elevated over the south-central CONUS, supported mainly by the uncalibrated 0z ECENS and the analogues. Probabilities for above-normal precipitation are also increased across the Four Corners tied to increasing monsoonal moisture underneath the favorable mid-level ridge positioning over the region. Near- to below-normal precipitation is favored across the Great Basin supported by the GEFS and ECENS uncalibrated and reforecast tools. Troughing and increased onshore flow favors elevated chances for above-normal precipitation over the Aleutians and most of Mainland Alaska. Near- to below-normal precipitation probabilities are enhanced across eastern and Southeast Alaska underneath greater influence from ridging over Canada. Near- to below-normal precipitation is also forecast over Hawaii. The official 6-10 day 500-hPa height blend consists of 35% of Today's 0z GFS Ensemble Mean centered on Day 8, 5% of Today's operational 0z GFS centered on Day 8, 35% of Today's 0z European Ensemble Mean centered on Day 8, 5% 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 dynamical model agreement regarding the mid-level pattern, offset by weak signals in the precipitation tools. 8-14 DAY OUTLOOK FOR AUG 16 - 22 2024 Dynamical models continue to favor increasing 500-hPa heights across the CONUS during week-2, with a 594-dm ridge center depicted in the 0z ECENS, GEFS, and CMCE over the Four Corners Region by the second half of the period. The troughs along the East and West coasts of the CONUS are also forecast to weaken relative to the 6-10 day period, although these features are slightly more amplified in the week-2 manual height blend compared to yesterday indicating more persistence. The week-2 manual blend indicates near- to above-normal heights over most of the CONUS, with the largest positive height anomalies (greater than +30 meters) over the Northern Rockies, Northern Plains, and Upper Mississippi Valley. Troughing over the Bering Sea is forecast to lift out early in week-2 with a more zonally oriented flow pattern developing over Alaska as ridging over the central Pacific extends northward. This favors near- to above-normal heights across southern and eastern Alaska in the manual blend. Below normal heights remain forecast across the western Mainland with a -90 meter negative height anomaly center over the Bering Sea. Above-normal heights are predicted across Hawaii. Expanding ridging supports increased chances for above-normal temperatures over much of the CONUS. Probabilities exceed 60 percent over much of the Southern Plains and Lower Mississippi Valley, with excessive heat a concern over parts of these regions. Across parts of the Mid-Atlantic into southern New England, lingering weak troughing combined with saturated ground favors temperatures closer to normal, with larger positive height anomalies favoring above-normal temperatures across northern New England. The GEFS and CMCE reforecast tools have expanded the signal for below-normal temperatures on the East Coast compared to yesterday, and although the ECENS reforecast tool is still on the warmer side, the more persistent troughing pattern favors a slight tilt toward increased below-normal temperature probabilities over the coastal Mid-Atlantic. The GEFS and ECENS reforecast tools support enhanced probabilities of below-normal temperatures near the West Coast. Elevated probabilities for below-normal temperatures are forecast to persist over much of southwestern Alaska tied to troughing early in the period, with above-normal temperature probabilities increased over eastern Alaska consistent with more ridging building from the central Pacific. Above-normal temperatures are forecast across Hawaii supported by the reforecast consolidation tool. Above-normal precipitation probabilities remain elevated over much of the Northwest, Rockies, and Northern Plains throughout week-2, with near- to below-normal precipitation chances elevated over portions of the Great Basin. Forecast tools offer mixed signals across the Midwest, with the ECENS (GEFS) reforecast tool depicting higher chances for above (below) normal precipitation. The active storm track discussed in the 6-10 day period is likely to persist, although more ridging would support relatively drier conditions. Therefore, near-normal precipitation is forecast over much of the Midwest. The drier uncalibrated tools and analogues are preferred across the south-central CONUS, with below-normal precipitation probabilities increased closer to the ridge axis. Continued frontal activity in the East slightly enhances the odds for above-normal precipitation. The National Hurricane Center continues to monitor a tropical disturbance over the Main Development Region of the Atlantic. Many ensemble solutions indicate a recurving track across the western Atlantic and a more westward track could result in an enhancement of precipitation along the East Coast during week-2. Near- to above-normal precipitation probabilities are increased over much of Alaska underneath enhanced westerly mid-level flow, excluding Southeast Alaska where near- to below-normal precipitation is favored. Near- to below-normal precipitation chances remain elevated over Hawaii. The official 8-14 day 500-hPa height blend consists of: 40% of Today's 0z GFS Ensemble Mean centered on Day 11, 40% 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 model agreement regarding broadening ridging over the central CONUS, offset by continued weak signals in the precipitation tools and uncertainty in the tropics. 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 August 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: 20090728 - 19520804 - 19580821 - 19990802 - 19600805 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: 20090728 - 19530802 - 19990804 - 19880821 - 19520804 6-10 DAY OUTLOOK TABLE Outlook for Aug 14 - 18 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B A OREGON B A NRN CALIF B N SRN CALIF B N IDAHO N A NEVADA N B W MONTANA A A E MONTANA A A WYOMING A A UTAH A A ARIZONA A A COLORADO A A NEW MEXICO A N N DAKOTA A A S DAKOTA A A NEBRASKA A A KANSAS A N OKLAHOMA A B N TEXAS A B S TEXAS A B W TEXAS A B MINNESOTA A A IOWA A A MISSOURI A N ARKANSAS A B LOUISIANA A B WISCONSIN A N ILLINOIS N A MISSISSIPPI A B MICHIGAN A B INDIANA N N OHIO N N KENTUCKY N A TENNESSEE N N ALABAMA A N NEW YORK N N VERMONT A N NEW HAMP A N MAINE A N MASS N A CONN B A RHODE IS B A PENN B A NEW JERSEY B A W VIRGINIA B A MARYLAND B A DELAWARE B A VIRGINIA B A N CAROLINA B A S CAROLINA B A GEORGIA N N FL PNHDL A N FL PENIN A A AK N SLOPE A A AK ALEUTIAN B A AK WESTERN B A AK INT BSN N A AK S INT B A AK SO COAST B A AK PNHDL N N 8-14 DAY OUTLOOK TABLE Outlook for Aug 16 - 22 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A A OREGON N A NRN CALIF B N SRN CALIF B N IDAHO A A NEVADA A B W MONTANA A A E MONTANA A N WYOMING A N UTAH A N ARIZONA A N COLORADO A N NEW MEXICO A N N DAKOTA A A S DAKOTA A N NEBRASKA A N KANSAS A N OKLAHOMA A B N TEXAS A B S TEXAS A N W TEXAS A B MINNESOTA A N IOWA A N MISSOURI A N ARKANSAS A B LOUISIANA A B WISCONSIN A N ILLINOIS A N MISSISSIPPI A B MICHIGAN A N INDIANA A N OHIO A N KENTUCKY A N TENNESSEE A N ALABAMA A B NEW YORK A A VERMONT A A NEW HAMP A A MAINE A A MASS A A CONN N A RHODE IS N A PENN N N NEW JERSEY N A W VIRGINIA N A MARYLAND N A DELAWARE B A VIRGINIA N A N CAROLINA N A S CAROLINA N A GEORGIA A N FL PNHDL A N FL PENIN A A AK N SLOPE A A AK ALEUTIAN B A AK WESTERN B A AK INT BSN A A AK S INT B A AK SO COAST B A AK PNHDL N N 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. $$