996 FXUS06 KWBC 192016 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EST Fri December 19 2025 6-10 DAY OUTLOOK FOR DEC 25 - 29 2025 A highly amplified pattern is forecast for the 6-10 day period across North America and adjacent areas. A strong mid-level ridge is forecast to be centered across the Aleutian Islands and North Pacific. Downstream, negative 500-hPa height anomalies and mid-level troughing are forecast from Southeast Alaska southward offshore of the western contiguous U.S. (CONUS). This set-up favors continuing episodes of strong Pacific flow and storminess into the western CONUS during the period. An expansive area of positive 500-hPa height anomalies is forecast to be centered near the central CONUS, and another amplified positive mean 500-hPa anomaly is expected over the northeastern Atlantic, with some mid-level troughing in between these two features, in the northwestern Atlantic. In the manual blend, the locations of the most anomalous mean 500-hPa heights in this highly amplified pattern are essentially unchanged from yesterday, and even a bit more amplified (+390 m centered over the westernmost Aleutians and +330 m east of Iceland). The negative anomalies maximized over the Alaskan Panhandle are also slightly more amplified than yesterday (-210 m) while the pattern over and adjacent to the CONUS is a bit less amplified than yesterday, with mean anomalies ranging from -60 m west of California to +120 m over the central CONUS. By the end of the period, ensemble means diverge in their solutions over northwestern North America and the northeastern Pacific. The European ensemble (ECENS) mean is considerably more positively-tilted with the trough extending southward from southeastern Alaska, depicting a trough axis reaching toward the central North Pacific. This allows above-normal 500-hPa heights to build into the western CONUS. The GEFS mean places the trough axis from southeastern Alaska into the northeastern North Pacific, placing subnormal 500-hPa in the Pacific Northwest and relegating above-normal 500-hPa heights farther east. The Canadian ensemble (CNENS) mean solution is a compromise of the other two, and is the favored solution at this time as it reflects the model consensus. The eventual placement of mid-level features in this region could have a significant impact on sensible weather, as the ECENS mean featuring above-normal 500-hPa heights over the western CONUS would reduce the strength of the Pacific air flow into the western CONUS, resulting in somewhat lower precipitation totals. Farther south, a weak 500-hPa ridge over Hawaii early in the period is expected to drift eastward as below-normal 500-hPa heights encroach on the state from the west. Across the CONUS, broadly positive 500-hPa height anomalies and enhanced mild Pacific flow should result in above normal temperatures across most of the CONUS. Probabilities for above normal temperatures exceed 90% over most of the southern Plains, and some enhancement in the odds for above-normal temperatures covers almost the entire CONUS, excepting the western and northeastern fringes. The Northeast may average closer to normal under near-normal 500-hPa heights and moderate mid-level troughing in the adjacent Atlantic, while persistent precipitation over the western CONUS should limit the diurnal range and keep average temperatures from straying too far from normal. In contrast to the CONUS, below normal temperatures are favored almost regionwide across Alaska. Only the western Aleutians are an exception, with warmer than normal temperatures expected in association with large positive 500-hPa height anomalies. In Hawaii, above-normal temperatures remain favored, consistent with the consolidation forecast. The persistent mid-level trough axis just off the West Coast favors continuing episodes of storminess and atmospheric river activity in the western CONUS, and thus above-normal precipitation. The enhancement of the odds for above-normal precipitation are slightly lower than yesterday, reflecting the possibility that the mid-level trough axis may reload farther west over the central North Pacific later in the period (per the ECENS mean), which would relax the Pacific inflow and reduce precipitation totals. The highest chances for above normal precipitation (over 70 percent) extend across much of California, and odds exceeding 50 percent extend westward through the Great Basin and into the central and southern Rockies. Above-normal precipitation chances also exceed 50 percent in much of Washington as 500-hPa heights rebound over the lower western CONUS later in the period, pushing atmospheric river activity back to the north. The expected heavy precipitation and potentially windy conditions will likely result in hazardous travel conditions at times during the holiday season across parts of the West. In contrast, below normal precipitation is favored over much of the north-central and southeastern CONUS with mid-level ridging limiting precipitation potential across much of the region. Near to above normal precipitation is favored over the interior northeastern CONUS where an active storm track could set up. In Alaska, near normal precipitation is favored for the central and northern Mainland while drier than normal weather is more likely farther south downstream from the strong mid-level ridge and upstream from the Southeast Alaska negative height anomaly center. A slight tilt towards above-normal precipitation is noted for parts of the Alaskan Panhandle near or downstream from the axis of the strong mean mid-level trough, where surface storm development would be favored. Farther south, odds for surplus precipitation increase from east to west across Hawaii in concert with the encroachment of below-normal 500-hPa heights from the west. Chances for unusually wet weather exceed 40 percent over most of the western islands of Kauai and Niihau. The official 6-10 day 500-hPa height blend consists of 25% of Today's 6z GFS Ensemble Mean centered on Day 8, 25% of Today's 0z European Ensemble Mean centered on Day 8, 20% of Today's operational 0z ECMWF 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 agreement and excellent model consistency over the past several days, maintaining a stable, amplified mid-level pattern over the northern Western Hemisphere. 8-14 DAY OUTLOOK FOR DEC 27, 2025 - JAN 02, 2026 The week-2 500-hPa mean height forecast remains consistent with the 6-10 day period and with yesterday's forecast. An amplified mean mid-level ridge remains likely over the North Pacific and Aleutian Islands. Downstream mean mid-level troughing is forecast to persist over and near Southeast Alaska while the moderately-strong flat mid-level ridge remains roughly in place over much of the CONUS. A fairly weak mean trough is still anticipated off the East Coast, leading into a second strong mid-level ridge with the largest positive 500-hPa height anomalies anticipated near Iceland. The primary change from yesterday is the increased potential for mean 500-hPa heights to average closer to normal over at least part of the western CONUS, which could reduce the impact of Pacific onshore flow and atmospheric river activity, especially over central and southern portions of the West Coast. The deterministic European model and a minority of the ECENS members form a cut-off 500-hPa low for at least one or two days during week-2 near Southeast Alaska, which allows 500-hPa heights to build over the western CONUS and squelch the strong atmospheric river activity that has persistently impacted the region. This is a minority solution among the models at this time and thus not the favored solution, but the possibility results in somewhat lower likelihoods of heavy precipitation in the West, especially in the Southwest. The bottom line, however, is that the broadly persistent, amplified mean pattern is strongly favored to continue, but how individual features may cause the 500-hPa anomaly centers and mid-level ridge/trough axes to meander and/or vary in amplitude is uncertain, leading to some uncertainty in the forecast. To the south, Hawaii will likely remain downstream from a region of subnormal 500-hPa heights, keeping cyclonically-curved mid-level flow across the island chain. In concert with the 500-hPa height forecast, the temperature forecast for week-2 is quite consistent with yesterday and with the 6-10 day period. Above normal temperatures are favored for nearly all of the CONUS with the strongest chances exceeding 80% over much of the southern Great Plains. Near normal temperatures are favored for much of the immediate West Coast tied to onshore flow bringing in clouds and precipitation, and for New England under 500-hPa heights closer to normal just upstream from a moderate mean mid-level trough axis. At higher latitudes, the amplified ridge/trough couplet from the north-central Pacific into Alaska and western Canada should keep below-normal temperatures entrenched across most of Alaska, although the magnitude and expanse of the cold air will wax and wane over the course of the period. Above-normal temperatures are favored for Hawaii, with somewhat higher odds than for the 6-10 day period over central and eastern parts of the island chain.. Above-normal precipitation remains likely for the West Coast with continued chances for atmospheric river activity to impact the region throughout week-2. The potential for a period of increased 500-hPa heights reduces the odds slightly, especially over the southern half of the western CONUS, but the mean pattern favoring surplus precipitation will remain in place, focused on the Northwest during week-2. Beneath the 500-hPa ridge over the central and eastern CONUS, below-normal precipitation is generally favored for the Southeast, the immediate Eastern Seaboard, the Lower Mississippi Valley, and portions of the adjacent Plains. Otherwise, near normal precipitation is favored for most areas east of the Rockies as pieces of shortwave energy from the Pacific may induce surface storm systems and frontal complexes that bring relatively brief episodes of moderate to heavy precipitation. Near normal precipitation is favored over much of Mainland Alaska, with subnormal totals again favored across the southern tier of the Mainland, similar to the 6-10 day period. Chances for above-normal precipitation continue to increase across Hawaii, which should remain downstream from a moderate mid-level trough under near- or below-normal 500-hPa heights. The strongest probabilities for above-normal precipitation (50 to 60 percent) remain across the western islands, closer to the 500-hPa trough axis. The official 8-14 day 500-hPa height blend consists of: 29% of Today's 6z GFS Ensemble Mean centered on Day 11, 13% of Today's operational 6z GFS centered on Day 11, 29% of Today's 0z European Ensemble Mean centered on Day 11, and 29% 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 on the persistence of the amplified, stable mid-level height pattern, tempered somewhat by uncertainties in the day-to-day variance brought about as individual features move through the longwave pattern, especially along the West Coast. FORECASTER: Rich Tinker 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 (gray, "N") normal. 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 (gray, "N") normal. 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 January 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: 19951201 - 20101211 - 20121201 - 19980101 - 20211203 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: 19951130 - 20101211 - 20121130 - 19980101 - 20121205 6-10 DAY OUTLOOK TABLE Outlook for Dec 25 - 29 2025 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A A OREGON A A NRN CALIF N 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 A NEW MEXICO A A N DAKOTA A B S DAKOTA A B NEBRASKA A B KANSAS A B OKLAHOMA A N N TEXAS A N S TEXAS A A W TEXAS A N MINNESOTA A B IOWA A B MISSOURI A N ARKANSAS A N LOUISIANA A B WISCONSIN A N ILLINOIS A N MISSISSIPPI A B MICHIGAN A A INDIANA A N OHIO A A KENTUCKY A N TENNESSEE A N ALABAMA A B NEW YORK A A VERMONT A A NEW HAMP A A MAINE N A MASS A A CONN A N RHODE IS A N PENN A A NEW JERSEY A N W VIRGINIA A N MARYLAND A N DELAWARE A B VIRGINIA A B N CAROLINA A B S CAROLINA A B GEORGIA A B FL PNHDL A B FL PENIN A B AK N SLOPE B N AK ALEUTIAN B B AK WESTERN B N AK INT BSN B N AK S INT B B AK SO COAST B B AK PNHDL B A 8-14 DAY OUTLOOK TABLE Outlook for Dec 27, 2025 - Jan 02, 2026 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON N A OREGON A A NRN CALIF N A SRN CALIF A 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 N S DAKOTA A B NEBRASKA A B KANSAS A N OKLAHOMA A A N TEXAS A A S TEXAS A A W TEXAS A A MINNESOTA A B IOWA A B MISSOURI A N ARKANSAS A N LOUISIANA A B WISCONSIN A B 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 N VERMONT N B NEW HAMP N B MAINE N B MASS N B CONN N B RHODE IS N B PENN A N NEW JERSEY A B W VIRGINIA A N MARYLAND A B DELAWARE A B VIRGINIA A B N CAROLINA A B S CAROLINA A B GEORGIA A B FL PNHDL A B FL PENIN A B AK N SLOPE B N AK ALEUTIAN B B AK WESTERN B N AK INT BSN B N AK S INT B B AK SO COAST B B AK PNHDL B 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. $$