####018014585#### FXUS06 KWBC 081903 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EDT Wed May 08 2024 6-10 DAY OUTLOOK FOR MAY 14 - 18 2024 Today's dynamical model solutions are in fairly good agreement on the predicted 500-hPa circulation pattern across North America and surrounding regions during the 6-10 day period. The manual 500-hPa height blend is based on nearly-equal weighting of the 0z GFS, ECMWF, and Canadian ensemble means due to comparable model skill over the past two months. The resultant manual blend features moderate-to-strong anomalous ridges over the western Pacific, the eastern Pacific, and the central Atlantic. A moderately amplified mid-level trough and below-normal heights are predicted over Alaska, with the mean trough axis near the west coast of Alaska. A significant difference is apparent between today’s and yesterday’s height blends over central portions of North America. Yesterday, shortwave energy associated with the mid-level trough over Alaska was located over western Canada, which allowed a narrow channel/corridor of slightly positive height anomalies to develop ahead of it across the north-central and northeastern contiguous U.S. (CONUS). Today, this shortwave energy is forecast to shift from western Canada into the north-central CONUS, effectively severing the connection between the positive height anomalies across the West (associated with the anomalous ridge over the eastern Pacific) and the corridor of slightly positive height anomalies over the Northeast. Mid-level troughing is now expected to overspread the East with time, as was predicted by models several days ago. Over the east-central Pacific, weak troughing and near-normal 500-hPa heights are favored for the Hawaiian Islands. GEFS and European ensemble mean (ECENS) reforecast temperatures favor above-normal temperatures for most of the CONUS, the exception being the Southeast where the GEFS reforecast favors near-normal temperatures. This is generally consistent with a pattern dominated by near- to above-normal 500-hPa heights. The highest probabilities favoring above-normal temperatures exceed 70% over southern Florida and at least 60% over the vicinity of the Central Great Basin and much of northern and central California, and northern portions of New York and New England. A small sliver of below-normal temperatures is favored across northwestern Washington associated with a weak trough forecast to slide southward over the area. In Alaska, mid-level troughing and below-normal 500-hPa heights favor below-normal temperatures across much of the state. In Hawaii, near-normal temperatures are forecast, representing a compromise between auto-temperatures and the consolidation of tools. Below-normal precipitation is favored from most of the northern half of the Pacific coast eastward across Idaho and southwestern Montana, associated with mid-level ridging and near- to above-normal 500-hPa heights. This is supported by GEFS reforecast precipitation, and to a much lower extent, ECENS reforecast precipitation. For most of the remainder of the CONUS, these two reforecasts depict increased odds of above-normal precipitation, which is consistent with broad, low-amplitude cyclonic flow. The highest probabilities for above-normal precipitation, in excess of 60%, are indicated over the eastern Gulf Coast region and Southeast. This is associated with surface high pressure off the East Coast leading to increased onshore flow across the Gulf Coast states, a nearby warm front, and mid-level troughing. Weak residual troughing across the Southwest slightly elevates the probability of above-normal precipitation for much of that region, supported by GEFS and ECMWF ensemble mean reforecast precipitation guidance. In Alaska, above-normal precipitation is forecast over most of the state associated with broad onshore flow and mid-level troughing. In Hawaii, mostly above-normal precipitation is favored due to the proximity of a weak 500-hPa trough. The official 6-10 day 500-hPa height blend consists of 33% of Today's 0z GFS Ensemble Mean centered on Day 8, 34% of Today's 0z European Ensemble Mean centered on Day 8, and 33% 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 agreement among model solutions and forecast temperature and precipitation tools. 8-14 DAY OUTLOOK FOR MAY 16 - 22 2024 The two anomalous ridges predicted over the western and eastern Pacific during the earlier 6-10 day period are forecast to consolidate into one broad anomalous ridge, with maximum positive height anomalies of about +180 meters forecast south of the Aleutians. This pattern evolution suggests the eastern portion of this broad Pacific ridge is weakening, with the consolidation of maximum height anomalies farther west. The northern portion of this ridge is predicted to extend northward across the Alaska Peninsula and into southwestern Alaska. The trough over Alaska is forecast to weaken during week-2. A weak trough-ridge-trough pattern is indicated over the CONUS with heights predicted to be near- to slightly below-normal over the north-central states, and near- to slightly above-normal elsewhere. A weak trough and near-normal 500-hPa heights continues to be predicted in the vicinity of Hawaii. Above-normal temperatures are favored over most of the CONUS, consistent with today’s reforecast temperatures from the GEFS and ECENS. Odds favoring above-normal temperatures surpass 50% for most of the Four Corners region and Texas, and the Florida Peninsula. Predicted weak 500-hPa height anomalies and cooler raw surface temperature tools support near to slightly above-normal temperatures over much of the East. The presence of weak troughs in the Pacific Northwest, the northern Rockies, and the north-central states favor near- to below-normal temperatures across that region. In Alaska, below-normal temperatures continue to be favored by many of the tools south of the Brooks Range, even though the trough impacting the state is expected to weaken during week-2. In Hawaii, near-normal temperatures are favored, representing a compromise between the ERF consolidation tool, the auto temperature forecast, and predicted near-normal 500-hPa heights. Below-normal precipitation is slightly favored across sections of Washington and Oregon, due to residual mid-level ridging anticipated over the region. There is a slight tilt in the odds towards drier-than-normal conditions for southern portions of the Four Corners region, and western and southern parts of Texas. This is supported by the GEFS and especially the ECENS reforecast precipitation tools, and is consistent with observed 30-day and 90-day percent-of-normal rainfall and relatively dry soils. There is a slight tilt towards above-normal precipitation from southwestern California across southern Nevada, in advance of expected weak troughing near the California coast. Near- to above-normal precipitation is forecast over the remainder of the CONUS due to southerly return flow associated with mean surface high pressure over the Southeast and a broad mid-level trough expected to progress across the East. This is supported by most precipitation guidance, though raw precipitation guidance from the ECENS predicts widespread below-normal precipitation from the Desert Southwest eastward across the Southern Rockies, Southern Plains, and southern half of the Mississippi Valley. In Alaska, above-normal precipitation is slightly favored across the state with unsettled weather beneath a mid-level trough continuing. Meanwhile, near- to mostly above-normal precipitation is slightly favored for Hawaii consistent with the consolidation of tools and auto-precipitation forecast. The official 8-14 day 500-hPa height blend consists of: 35% of Today's 0z GFS Ensemble Mean centered on Day 11, 35% 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: Near average, 3 out of 5, with good agreement in the overall circulation pattern for the period, offset by weaker signals and some disagreement among precipitation and temperature tools. FORECASTER: Anthony A 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 May 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: 19750427 - 19750502 - 19640501 - 19980513 - 19850512 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: 19750427 - 19750502 - 19760423 - 19990509 - 19850422 6-10 DAY OUTLOOK TABLE Outlook for May 14 - 18 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A B OREGON A B NRN CALIF A B SRN CALIF A N IDAHO A B NEVADA A B W MONTANA A N E MONTANA A A WYOMING A N UTAH A N ARIZONA A N COLORADO A A NEW MEXICO A N N DAKOTA A A S DAKOTA A A NEBRASKA A A KANSAS A A OKLAHOMA N A N TEXAS A A S TEXAS A A W TEXAS A N MINNESOTA A A IOWA A A MISSOURI N A ARKANSAS N A LOUISIANA A A WISCONSIN A A ILLINOIS A A MISSISSIPPI N A MICHIGAN A A INDIANA A A OHIO A A KENTUCKY A A TENNESSEE N A ALABAMA N 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 A AK ALEUTIAN B N AK WESTERN B A AK INT BSN B A AK S INT B A AK SO COAST B A AK PNHDL B A 8-14 DAY OUTLOOK TABLE Outlook for May 16 - 22 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B N OREGON N N NRN CALIF A N SRN CALIF A A IDAHO A N NEVADA A N W MONTANA N N E MONTANA N N WYOMING A N UTAH A N ARIZONA A N COLORADO A N NEW MEXICO A N N DAKOTA N A S DAKOTA N A NEBRASKA A A KANSAS A A OKLAHOMA A A N TEXAS A N S TEXAS A N W TEXAS A N MINNESOTA N 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 N A ALABAMA N 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 A AK ALEUTIAN B N AK WESTERN B A AK INT BSN B A AK S INT B N AK SO COAST B N 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. $$