####018004658#### FXUS02 KWBC 071900 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Tue May 7 2024 Valid 12Z Fri May 10 2024 - 12Z Tue May 14 2024 ...Overview with Guidance/Predictability Assessment... Model guidance this morning shows very good agreement for mean troughing to prevail over the eastern U.S. while a modest Rex block/split flow pattern will take its time to break down or de- amplify over the western U.S. through the medium-range period. A number of shortwave troughs are forecast to rotate around the mean upper trough in the East, and they presented some issues as to when and where the shortwaves may interact and/or amplify with one another. As for the Rex block in the West, models generally show a gradual flatting of the pattern with time, with emerging differences on whether a southern stream low-amplitude trough will eject out into the southern Plains or remain slow-moving over the Desert Southwest by early next week. Despite these timing differences, there appears to be good model agreement for moisture to return to the Gulf Coast region by early next perhaps as early as Monday. Overall, a general model consensus appears to offer a good starting point out through Day 7. The 06Z GFS appears too aggressive in developing a coastal storm off the New England coast on Saturday as the 12Z GFS has backed off. The general model trend has been for the mean upper trough to sag farther south down into the eastern U.S. which would tend to eject the coastal low off into the Atlantic. The WPC medium-range forecast package was based on 40% from the 06Z GFS/GEFS, 40% from the 00Z ECMWF/EC mean, and 20% from the CMC/CMC mean. This blend provided enough system details while maintaining maximum WPC product continuity. The 12 UTC ECMWF offers a faster eastward progression of the shortwaves and mean trough over the eastern U.S. together with a faster ejection of the Southwest U.S. upper trough into the central/southern Plains early next week, but not nearly as fast as the ECMWF-AIFS guidance. ...Weather/Hazards Highlights... A main parent low and frontal system working toward the Northeast Friday will help focus generally moderate rainfall, with activity aided and prolonged Saturday as downstream energy transference may lead to coastal low genesis, although a general model trend for the mean trough to sag farther south will tend to eject the coastal low offshore. Additional northern stream systems will periodically offer bouts of mainly lighter rains from the north-central U.S. to the Great Lakes/Northeast from Sunday to next Tuesday but with some uncertainty in their timings. Meanwhile to the south, a cooling and trailing/wavy front will moderate lead warmth while working through the Southeast to the Gulf of Mexico and northern Mexico. A WPC Day 4/Friday Excessive Rainfall Outlook Marginal Risk area is maintained for parts of the Southeast given possible training of thunderstorms ahead of a cold front under lingering deep moisture/instability and favorable upper jet/diffluence support. The slowing front and a reinforcing front/upper impulses are expected to periodically focus precipitation from the southern Rockies/Plains out through the Gulf of Mexico and Florida over the weekend into next week. By early next week, there appears increasing guidance support for moisture to increase along the Gulf Coast ahead of the returning warm front. Heavy rain could move farther inland later next Tuesday as the front is forecast to edge northward. Kong/Schichtel Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation forecast (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml https://www.wpc.ncep.noaa.gov/#page=ovw $$ ####018012954#### FXUS06 KWBC 071902 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EDT Tue May 07 2024 6-10 DAY OUTLOOK FOR MAY 13 - 17 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. The anomalous ridge anticipated over the eastern Pacific extends eastward across much of the western contiguous U.S. (CONUS), with a channel of slightly above-normal heights continuing eastward across the north-central states, Great Lakes region, Northeast, and Mid-Atlantic states. East of the Rocky Mountains, one trough is forecast over the eastern Great Lakes and Northeast, while another trough is forecast to extend from the Upper Mississippi Valley southwestward to the southern High Plains and southern Rockies. Weak troughing with near-normal 500-hPa heights is favored for Hawaii. Mid-level ridging and positive 500-hPa height anomalies across the western CONUS, combined with the aforementioned channel/extension of slightly above-normal 500-hPa heights across the Northern CONUS, favors above-normal temperatures for a large portion of the CONUS. The highest probabilities favoring above-normal temperatures exceed 70% over northern California, northwestern Nevada, and southeastern Oregon. Above-normal temperatures are also favored over southern Texas and Florida, with remaining portions of the southern CONUS depicted as near-normal. In Alaska, mid-level troughing and below-normal 500-hPa heights favor below-normal temperatures across the state. In Hawaii, near- to above-normal temperatures are forecast, consistent with the consolidation of tools. Below-normal precipitation is favored from Washington southward to northern California, and eastward to central Montana. This is associated with anomalous ridging and positive 500-hPa height anomalies across this region. Across most of the remainder of the CONUS, however, above-normal precipitation is favored. For approximately the northeast quarter of the CONUS, odds favoring above-normal precipitation are slightly elevated, due to shortwave energy moving through the region. Higher probabilities for above-normal precipitation are depicted across the southern CONUS. 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 the mid-level trough noted earlier over the Plains. The expected precipitation may be enhanced by the development of surface low pressure over the southern High Plains. Probabilities favoring wetter-than-normal conditions surpass 60% for east-central portions of the Gulf Coast region. Weak residual troughing across the Southwest 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 much of Alaska associated with broad onshore flow and mid-level troughing. In Hawaii, 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 15 - 21 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 that extends northward into southwestern Alaska, accompanied by above-normal 500-hPa heights. The trough anticipated over Alaska during the 6-10 day period is expected to shift westward in week-2, with below-normal 500-hPa heights remaining only over the northwestern portion of the state. A weak trough-ridge-trough pattern is indicated over the CONUS with heights slightly above-normal across the West, and near-normal across the Central and Eastern states. A weak trough with near-normal 500-hPa heights continued to be predicted in the vicinity of Hawaii. Above-normal temperatures are favored over nearly all of the CONUS, consistent with today’s reforecast temperatures from the GEFS and ECMWF ensemble means. Odds favoring above-normal temperatures are weak across the East due to conflicting signals between significantly warmer reforecast temperatures and cooler raw temperature guidance from these ensemble means. In Alaska, below-normal temperatures continue to be favored by most tools, 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 near-normal 500-hPa heights. Below-normal precipitation is favored from the Pacific Northwest and northwestern California to western Montana, due to mid-level ridging anticipated over the region. 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. In Alaska, above-normal precipitation is generally 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: 19750426 - 19980513 - 19750502 - 19640501 - 19550422 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: 19750426 - 19550422 - 19980512 - 19980517 - 19640429 6-10 DAY OUTLOOK TABLE Outlook for May 13 - 17 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A B OREGON A B NRN CALIF A B SRN CALIF A A IDAHO A B NEVADA A A W MONTANA A B E MONTANA A N WYOMING A N UTAH A A ARIZONA A A COLORADO A A NEW MEXICO N A N DAKOTA A A S DAKOTA A N NEBRASKA A A KANSAS A A OKLAHOMA A A N TEXAS A A S TEXAS A A W TEXAS N A MINNESOTA A A IOWA A A MISSOURI A A ARKANSAS A 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 N A GEORGIA N A FL PNHDL A A FL PENIN A A AK N SLOPE B 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 15 - 21 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A B OREGON A B NRN CALIF A N SRN CALIF A A IDAHO A N NEVADA A A W MONTANA A N E MONTANA A N WYOMING A N UTAH A A ARIZONA A A COLORADO A A NEW MEXICO A A N DAKOTA A N S DAKOTA A N NEBRASKA A N KANSAS A A OKLAHOMA A A N TEXAS A A S TEXAS A A W TEXAS A N MINNESOTA A N IOWA A N MISSOURI A A ARKANSAS A A LOUISIANA A A WISCONSIN A N ILLINOIS A N MISSISSIPPI A A MICHIGAN A N INDIANA A N 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 A PENN A N 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 A AK ALEUTIAN B A AK WESTERN B A AK INT BSN B A AK S INT B A AK SO COAST B A 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. $$