147 FXUS06 KWBC 181902 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EDT Thu September 18 2025 6-10 DAY OUTLOOK FOR SEP 24 - 28 2025 Compared to yesterday, some differences have emerged in the dynamical model guidance for the 6-10 day forecast period. Most notable is the substantially less amplified trough across the Northeast Pacific in the 0z ECENS. This is also reflected to some degree in the 0z CMCE, with the 0z GEFS maintaining the more amplified trough, and is more expansive in regards to negative 500-hPa height anomalies over the western third of the CONUS by the second half of the period. The ECENS and GEFS continue to depict anomalous ridging centered across the north-central CONUS into Canada. These models also indicate a greater degree of shortwave troughing developing over the Lower Mississippi Valley and Southeast underneath the ridge axis. Todays 6-10 day manual height blend depicts above-normal heights across the northern half of the CONUS from the Rockies to the Northeast. Near to slightly below-normal heights are now indicated across parts of the Southern Plains, Lower Mississippi Valley, and Southeast. Near- to below-normal heights are also forecast across the Northwest and extending through southeastern Alaska. Additional troughing approaching western and northern Alaska leads to near-normal heights over much of the remainder of Alaska, with the exceptions being the Aleutians and the far northeastern Mainland where above-normal heights are favored. Near- to above-normal heights are forecast across Hawaii as ridging becomes centered to the north of the islands. Increased chances for above-normal temperatures are favored across the entire CONUS supported by nearly all the forecast guidance. The highest probabilities (greater than 70 percent) are favored across the Upper Midwest, closest to the positive mid-level height anomaly maximum. Although troughing moving closer to the West Coast would support a cooling trend as the period progresses, the relatively warmer start to the period combined with weaker amplification of this trough in the ECENS and CMCE support enhanced chances for above-normal temperatures for the period as a whole, but with reduced probabilities compared to further east. The increase in troughing across the south-central CONUS favors reduced chances for above-normal temperatures, with near-normal temperatures now more likely over portions of the Central Plains and adjacent Mississippi Valley, due in part to the possibility of enhanced cloud cover and precipitation. The GEFS and ECENS reforecast tools support increased odds for above-normal temperatures across southeastern Alaska, tied to enhanced southerly flow ahead of the incoming trough. Near-normal temperatures are forecast across the remainder of Mainland Alaska, given warmer (cooler) signals in the reforecast (uncalibrated) tools. Enhanced chances of near- to below-normal temperatures are indicated across Southeast Alaska. Above-normal temperatures are likely for the Hawaiian Islands, consistent with above-normal sea surface temperatures (SSTs) in the adjacent Pacific. Troughing approaching the West Coast of the CONUS supports increasing onshore flow and above-normal precipitation. The ECENS reforecast tool continues to support elevated chances of above-normal precipitation despite the weaker trough, although probabilities have decreased in the uncalibrated ECENS compared to yesterday. As a result, probabilities for above-normal precipitation are reduced to 40-60 percent in todays forecast across much of the Northwest into northern parts of California and Nevada. Downstream, closer to the mean ridge axis, below-normal precipitation chances are slightly increased across the Upper Mississippi Valley and northern Great Lakes, with increasing Pacific flow favoring near-normal precipitation across the Northern and Central Plains. Shortwave troughing and increasing wet signals in the GEFS and ECENS reforecast tools support elevated chances for above-normal precipitation across the Southern Plains, extending northeastward through much of the eastern CONUS. The 0z ECENS depicts a cyclonic system developing across the region early in the period potentially leading to further precipitation enhancement. Above-normal precipitation chances are increased across much of western and southern Alaska ahead of incoming troughing. Below-normal precipitation chances are elevated across the northeastern Mainland. Above-normal precipitation is favored across Hawaii. The official 6-10 day 500-hPa height blend consists of 30% of Today's 0z GFS Ensemble Mean centered on Day 8, 50% of Today's 0z European Ensemble Mean 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: Average, 3 out of 5, due to decent agreement among dynamical models regarding the 500-hPa pattern evolution, offset by some uncertainty regarding the amplitude of troughing predicted along the West Coast of the CONUS. 8-14 DAY OUTLOOK FOR SEP 26 - OCT 02, 2025 During week-2, anomalous ridging remains forecast across eastern Canada, with weak troughs favored on either side of the ridge, across western North America, and over the North Atlantic. The 0z GEFS is more amplified with the trough in the West compared to the 0z ECENS and CMCE resulting in greater 500-hPa height falls across the West during the period. The 0z ECENS and to some degree the GEFS depict a greater degree of shortwave troughing across the south-central and southeastern CONUS underneath the ridge early in the period. Later in week-2, the mid-level flow across the CONUS is predicted to become more low-amplitude and zonal as the aforementioned features weaken. The week-2 manual 500-hPa height blend depicts above-normal heights across much of the Midwest, Great Lakes, and Northeast. Near-normal heights are favored across the southern half of the CONUS. Near- to slightly below-normal heights are forecast over much of Mainland and Southeast Alaska and the northwestern CONUS tied to the initial trough and a second trough forecast to move into parts of western and northern Mainland Alaska. Near-normal heights are predicted across Hawaii as ridging to the north of the islands begins to weaken. Probabilities for above-normal temperatures are increased across the CONUS from the Rockies eastward underneath ridging and supported by most forecast tools. While the GEFS supports a cooler forecast across the West due to its stronger depiction of troughing, the ECENS is comparatively warmer, resulting in a forecast of near-normal. Closer to the Pacific coast, probabilities for above-normal temperatures are increased supported by the dynamical models as well as warm SSTs. The GEFS and ECENS reforecast tools continue to support increased chances for above-normal temperatures across portions of southern Alaska and the Aleutians tied to enhanced southerly flow. Near-normal temperatures are more likely across the remainder of Mainland Alaska. Uncalibrated guidance continues to support increased chances of near- to below-normal temperatures over Southeast Alaska. Above-normal temperatures are favored for Hawaii, consistent with continued positive SST anomalies over the adjacent Pacific. Increasing Pacific flow favors broadly enhanced probabilities for above-normal precipitation across most of the CONUS. The highest chances (greater than 40 percent) are over the Northwest and Northern Plains, and over the Tennessee Valley tied to shortwave troughing and possible surface low pressure at the outset of the period. Near-normal precipitation is favored across the Great Lakes, northern Ohio Valley, and New England coinciding with increased positive 500-hPa height anomalies. Enhanced southerly flow supports increased chances of near- to above-normal precipitation across Alaska, supported by reforecast and uncalibrated tools. Weakly enhanced chances of above normal precipitation are indicated for most of Hawaii, consistent with the consolidated forecast tool. Near-normal precipitation is forecast across the Big Island. The official 8-14 day 500-hPa height blend consists of: 30% of Today's 0z GFS Ensemble Mean centered on Day 11, 50% 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: Below average, 2 out of 5, due to a similar 500-hPa pattern from the 6-10 day period, but offset due to decreasing amplification and conflicting signals in the model guidance, particularly across the western CONUS and Alaska. FORECASTER: Thomas Collow Notes: 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 October 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: 20090914 - 20090909 - 20010928 - 20090919 - 20080929 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: 20090913 - 20090908 - 20090918 - 20080929 - 20010927 6-10 DAY OUTLOOK TABLE Outlook for Sep 24 - 28 2025 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A A OREGON A A NRN CALIF A A SRN CALIF A A IDAHO A A NEVADA A A W MONTANA A A E MONTANA A N WYOMING A A UTAH A A ARIZONA A A COLORADO A N NEW MEXICO A N N DAKOTA A N S DAKOTA A N NEBRASKA A N KANSAS A A OKLAHOMA N A N TEXAS A A S TEXAS A A W TEXAS A N MINNESOTA A N IOWA A N MISSOURI A A ARKANSAS N A LOUISIANA A A WISCONSIN A B 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 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 N A AK WESTERN N A AK INT BSN N N AK S INT N A AK SO COAST A A AK PNHDL N A 8-14 DAY OUTLOOK TABLE Outlook for Sep 26 - Oct 02, 2025 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON N A OREGON N A NRN CALIF A A SRN CALIF N A IDAHO N A NEVADA N 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 N W TEXAS A N MINNESOTA A A IOWA A A MISSOURI A A ARKANSAS A A LOUISIANA A A WISCONSIN A N ILLINOIS A A MISSISSIPPI A A MICHIGAN A N INDIANA A A OHIO A N KENTUCKY A A TENNESSEE A A ALABAMA A A NEW YORK A N VERMONT A N NEW HAMP A N MAINE A N MASS A N CONN A N RHODE IS A N PENN A N 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 A AK N SLOPE N N AK ALEUTIAN A A AK WESTERN N N AK INT BSN N N AK S INT A A AK SO COAST A A AK PNHDL N 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. $$