####018006603#### FXUS02 KWBC 031900 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Fri May 3 2024 Valid 12Z Mon May 06 2024 - 12Z Fri May 10 2024 ...Northern Plains to Midwest Heavy Rain Threat early next week... ...Possible heavy rain across the interior South later next week... ...Overview... Models and ensemble means continue to indicate a synoptic pattern that swings upper-level troughs/lows onshore across the western U.S. that would favor cyclogenesis over the mid-section of the country followed by gradual lifting of the troughs toward New England. The beginning of the medium-range period (Monday morning) will likely feature one such cyclogenesis over the central to northern High Plains. This will support cooler than normal temperatures, gusty winds, and precipitation including higher elevation snow in the West early in the week. Rain that could be locally heavy shifts into the northern Plains and downstream through the Midwest. Meanwhile farther south, mean upper ridging will lead to warming pre-frontal temperatures for much of the central and eastern U.S. that could yield some record values. Upstream, Pacific upper trough energy will work inland over an unsettled West and to the south- central U.S.. This may interact with a wavy and stalling lead front and combine with pooling moisture and instability to fuel rain and thunderstorms over the south-central states/Mid-South and onward into later next week, still also under some influence from the lead upper low/trough. ...Guidance/Predictability Assessment... Model and ensemble solutions overall seem reasonably clustered for Monday-Wednesday and generally in step with National Blend of Models (NBM) guidance. This bolsters forecast confidence in a composite GFS/ECMWF/Canadian model blend to provide maximum system detail as consistent with feature predictability. Opted to edge toward the ECMWF and EC mean by Days 6 and 7 in favor of the more southern placement of the heavier rainfall across the interior South for next Thursday and Friday. WPC product continuity is decently maintained in this manner. The WPC forecast package was based on 40% blend of the 00Z ECMWF/EC mean, 40% from the 06Z GFS/GEFS, and 20% from the 00Z Canadian/GEM mean, increasing to 55% from the EC solutions by Day 7. ...Weather/Hazards Highlights... As a main/closed upper low tracks out of the West with additional energies reaching the West Coast, widespread precipitation will include some enhanced snow potential given cooled temperatures. The higher elevations of the Great Basin into the Intermountain West/Rockies will see May snow as the medium-range period begins Monday morning. Vigorous troughing aloft in conjunction with a potent cold front will lead to windy conditions and a threat of high winds from much of the Rockies to High Plains as the cyclogenesis should be well under way across the northern High Plains into Tuesday. Precipitation is forecast to be ahead of the system as it spreads across the northern Plains to Midwest Monday and Tuesday with some timing differences among models (faster with the ECMWF). Rainfall on the west side of the strong surface low could be heavy across eastern Montana into the Dakotas given strong upper- level support for lift with a gradual slowdown of the storm track. However, this region is not particularly sensitive to flooding concerns, and instability should be limited wrapping around the low. A WPC Excessive Rainfall Outlook (ERO) Marginal Risk area remains in place in the Day 4/Monday and into Day 5/Tuesday for this area given the potential for protracted heavy rain, but likely without widespread significant flooding impacts. The Marginal Risk extends southeast into the Upper/Mid- Mississippi Valley, where more instability will be in place for higher rain rates, but storms will likely be faster-moving. The Storm Prediction Center also has portions of the Plains delineated with potential for severe weather on Monday. Convective rainfall is forecast to shift east into the Great Lakes and Ohio Valley Tuesday into Wednesday with system progression and intercepting return flow. The Marginal Risk ERO was maintained farther east into the Great Lakes, Ohio Valley and down toward the mid-Mississippi Valley for Day 5 as the fronts push farther toward the east and northeast. Upstream, aforementioned Pacific upper trough energy will work inland over an unsettled West and over the south-central U.S. into later next week, riding under the base of the lingering main upper low/trough. These will interact with wavy and stalling fronts and combine with pooling moisture and instability to fuel a favorable pattern for rain and thunderstorms across the south-central states/Mid-South and onward to the East where downstream energy track may support moderate late next week coastal low development. Much cooler than average maximum temperatures will slowly moderate while spreading next week from the West to the northern Plains as the closed upper low ejects eastward. But farther southeast, mean upper ridging will meanwhile spread quite warm pre-frontal temperatures from the South through the Appalachians/Mid-Atlantic to threaten record seasonal values. 90s are forecast to become more widespread across the southern tier, with temperatures over 100F (and even higher heat indices) into south Texas and the possibility for the first excessive heat days of the year. 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 $$ ####018012746#### FXUS06 KWBC 031903 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EDT Fri May 03 2024 6-10 DAY OUTLOOK FOR MAY 09 - 13 2024 The ECENS, GEFS, and Canadian ensemble mean predicted 500-hPa heights are in good agreement with each other for much more robust mid-level trough to develop across the eastern contiguous U.S. (CONUS) today. This is a pattern change that some of the ensemble members have been predicting for the past several model cycles but there is more agreement in the model tools today for a pattern shift across the CONUS. The consolidation of the negative anomalies over the eastern CONUS results in several changes in the temperature and precipitation forecasts across the CONUS. Over the West, mid-level ridging looks likely to dominate much of the Pacific Northwest during the period. Some near-normal heights remain forecast for the southwestern CONUS. Weakly below-normal 500-hPa heights are forecast for Alaska. Near-normal heights are forecast for Hawaii. During the 6-10 day period, a cold front is forecast to be progressing across the eastern CONUS. This will introduce much colder temperatures to regions that in prior forecasts were forecast to see above-normal temperatures. Therefore, the above-normal temperature chances are confined to the immediate Gulf of Mexico Coast and the Atlantic states. Behind this frontal system colder temperatures are likely to prevail and below-normal is favored for much of the central CONUS. While along the West Coast, beneath the strongly positive 500-hPa height anomalies forecast today, above-normal temperatures are favored with the strongest probabilities in the Pacific Northwest. Reforecast, raw, and analog tools run on the manual 500-hPa height blend all support this forecast across the CONUS despite there being large changes from yesterday. In Alaska, continued weakly below-normal 500-hPa height anomalies leads to continued chances for below-normal temperatures across the state. In Hawaii, near- to below-normal temperatures are forecast consistent with the consolidation of tools. The 6-10 day precipitation forecast also sees fairly large changes relative to prior forecasts with generally low confidence across most of the country. In the Pacific Northwest, below-normal precipitation is likely with chances exceeding 50% beneath the strong positive 500-hPa height anomalies. The below-normal chances overspread the northern Rockies and into the Central Plains and Middle Mississippi Valley as the eastern trough strengthens. Along the southern and eastern edge of the trough above-normal precipitation is slightly favored as a surface frontal boundary is likely to become established that may help to focus precipitation along the East Coast and Gulf Coast. Areas of surface low-pressure may develop in the southern Rockies that may bring precipitation to the region. In Alaska, above-normal precipitation is forecast along the Gulf of Alaska Coast and the eastern interior as weak troughing may bring weak onshore flow. In Hawaii, near to above-normal precipitation is favored. The official 6-10 day 500-hPa height blend consists of 20% of Today's 0z GFS Ensemble Mean centered on Day 8, 20% of Today's 6z GFS Ensemble Mean centered on Day 8, 40% 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: Below-Average, 2 out of 5, Good agreement in some of the model tools offset by a progressive pattern with major changes relative to yesterday. 8-14 DAY OUTLOOK FOR MAY 11 - 17 2024 The dynamical models continue to have weak mean mid-level height anomalies for the week-2 period leading to increased uncertainty across much of the country. However, the tools generally agree on a mid-level ridge across the western CONUS with a mid-level trough across the East. This is a more amplified signal than in prior forecasts leading to changes for the temperature and precipitation forecasts for the CONUS. In Alaska, weak troughing continues to be forecast with above-normal 500-hPa heights over the Aleutians and near-normal anomalies across the Mainland. In Hawaii, near-normal heights are forecast. Below-normal temperatures chances are stronger and more pervasive across the eastern CONUS today relative to yesterday with a more amplified trough developing over the East. This leads to below-normal temperature favored for most of the eastern CONUS excluding parts of the Florida peninsula which is likely to remain south of the a frontal feature. Along the immediate Gulf Coast, near-normal temperatures are favored as a frontal boundary pushes through the region early in week-2. Across the West, above-normal temperatures are favored beneath a strong mid-level ridge. While in Alaska, below-normal temperatures are slightly favored with continued weak troughing impacting the state. Hawaii is forecasted to see below-normal temperatures. Below-normal precipitation is favored for the Pacific Northwest and parts of northern California with ridging over the region. Below-normal precipitation chances extend eastward through the northern Rockies into the Plains, and the Mississippi, Ohio and Tennessee Valleys. These eastern regions are likely to be beneath an amplified mid-level trough that will focus precipitation south and east into parts of the Northeast, Florida, and Southern Plains where above-normal precipitation is slightly favored. In parts of the southern Rockies and Great Basin, some energy may undercut the mid-level ridge over the Northwest that may bring chances for precipitation in climatologically fairly dry regions. Any precipitation in these areas may bring 7 day totals above the 67th climatological percentile. In Alaska, above-normal precipitation is generally favored across the state with unsettled weather beneath a mid-level trough continuing. Meanwhile, near to above-normal precipitation is slightly favored for Hawaii consistent with the consolidation of tools. The official 8-14 day 500-hPa height blend consists of: 10% of Today's 0z GFS Ensemble Mean centered on Day 11, 30% of Today's 6z 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: Below-Average, 2 out of 5, Good agreement in the model tools offset by a progressive pattern with major changes relative to yesterday. FORECASTER: Ryan Bolt 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: 19850423 - 19790413 - 19750429 - 20030517 - 19640503 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: 19750429 - 19640503 - 19790412 - 19980516 - 19850422 6-10 DAY OUTLOOK TABLE Outlook for May 09 - 13 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A B OREGON A B NRN CALIF A B SRN CALIF N N IDAHO N B NEVADA N N W MONTANA N B E MONTANA N B WYOMING B N UTAH N N ARIZONA N N COLORADO B A NEW MEXICO B A N DAKOTA N B S DAKOTA B B NEBRASKA B B KANSAS B N OKLAHOMA B N N TEXAS N A S TEXAS A N W TEXAS B A MINNESOTA B B IOWA B B MISSOURI B B ARKANSAS N N LOUISIANA A A WISCONSIN N B ILLINOIS N B MISSISSIPPI A A MICHIGAN N N INDIANA N N OHIO N N KENTUCKY N N TENNESSEE N N ALABAMA A A NEW YORK A A VERMONT A A NEW HAMP A A MAINE N A MASS A A CONN A A RHODE IS A A PENN A N NEW JERSEY A A W VIRGINIA A N MARYLAND A A DELAWARE A A VIRGINIA A N N CAROLINA A A S CAROLINA A A GEORGIA A A FL PNHDL A A FL PENIN A N AK N SLOPE B N AK ALEUTIAN B N AK WESTERN B N AK INT BSN B N AK S INT B A AK SO COAST B A AK PNHDL B A 8-14 DAY OUTLOOK TABLE Outlook for May 11 - 17 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A B OREGON A B NRN CALIF A N SRN CALIF A N IDAHO A N NEVADA A N W MONTANA A B E MONTANA A B WYOMING N N UTAH A A ARIZONA N N COLORADO N A NEW MEXICO B A N DAKOTA N B S DAKOTA B B NEBRASKA B N KANSAS B N OKLAHOMA B N N TEXAS B A S TEXAS N A W TEXAS B A MINNESOTA B B IOWA B N MISSOURI B N ARKANSAS B N LOUISIANA B N WISCONSIN B B ILLINOIS B B MISSISSIPPI B N MICHIGAN B B INDIANA B N OHIO B B KENTUCKY B N TENNESSEE B N ALABAMA B N NEW YORK B A VERMONT B A NEW HAMP B A MAINE B A MASS B A CONN B A RHODE IS B A PENN B N NEW JERSEY B A W VIRGINIA B N MARYLAND B N DELAWARE B N VIRGINIA B N N CAROLINA B N S CAROLINA B N GEORGIA B N FL PNHDL N N FL PENIN A A AK N SLOPE B N AK ALEUTIAN B N AK WESTERN B N AK INT BSN B A AK S INT B A AK SO COAST B A AK PNHDL B 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. $$