####018017020#### FXUS06 KWBC 261956 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EDT Tue March 26 2024 6-10 DAY OUTLOOK FOR APR 01 - 05 2024 Dynamical model forecasts are in good agreement on the overall large-scale mean 500-hPa height pattern during the 6-10 day period, but only in fair agreement with model solutions from yesterday. At the start of the period, a strong ridge is centered near Greenland, with all ensemble means showing a closed mid-level high with 500-hPa heights of 555 to 561 dam. To the south, a strong trough is centered over or near Atlantic Canada, and the ensemble means all show either a closed 500-hPa low or a strong open wave. All ensemble means are considerably farther east with this feature than yesterday. The Canadian ensemble mean shows lower 500-hPa heights (as low as 524 dam) than the GEFS or European ensemble mean (approximately 535 dam), and has more of a closed-off circulation. These two features are representative of a strong negative phase of the North Atlantic Oscillation (NAO). The strongly negative NAO weakens with time, but is expected to remain negative through the next two weeks. In April, a negative NAO correlates with below-normal temperatures across much of the Contiguous United States (CONUS), especially west of the Mississippi River, and with above-normal precipitation in parts of the Far West, the central Great Plains, and much of the Southeast. Historically, there has been considerable variability, so these correlations aren’t hard-and-fast rules, but these temperature and precipitation patterns are generally favored in the mean during the 6-10 day and 8-14 day periods. Other features over or near North America at the start of the 6-10 day forecast period include a significant mid-level from parts of Siberia, eastward across Alaska, with negative 500-hPa anomalies covering the state. Meanwhile, a comparatively weak mid-level ridge is forecast to extend from western Canada through the Pacific Northwest and into the North Pacific, with maximum positive 500-hPa anomalies topping out at 12 to 18 dam. Somewhat above-normal 500-hPa heights are also shown by all ensemble means over the eastern CONUS, though 500-hPa anomalies are expected to remain below 12 dam. Between these two ridges, a positively-tilted mid-level trough is forecast, with its axis stretching from the central Great Plains into the Southwest. This pattern favors a surface low pressure system moving from the Great Plains into the Northeast early in the period, bringing moderate to heavy precipitation to the Ohio Valley and Northeast, while a trailing frontal system could trigger above-normal precipitation in parts of the Southeast as well. The pattern is fairly progressive over the 5-day period. 500-hPa heights are forecast to rise sharply across Alaska during the period, with positive 500-hPa height anomalies expected to cover at least the southern part of the state by the end of the period. Meanwhile, the broad ridge in the East is forecast to shift eastward into the North Atlantic and weaken early in the period as the western mid-level trough pushes into the eastern CONUS, with negative heights stretching eastward well into the North Atlantic. The European ensemble mean offers a different solution, ending the period with negative 500-hPa heights limited to the North Atlantic, and weakly above-normal 500-hPa anomalies extending southward, from the strong mid-level ridge over Greenland into the Great Lakes and northeastern CONUS. At this time, the Canadian ensemble mean and GEFS solutions are generally favored. To the west, 500-hPa heights are forecast to drop during the period, leaving some semblance of a mid-level trough in the West. Models are not consistent in their handling of this feature, with the GEFS showing a fairly deep mid-level trough while the Canadian ensemble mean is much weaker. The European ensemble mean falls between the other two, and is favored as a compromise between the stronger and weaker dynamic models. Overall, model output is slightly weaker than yesterday with features affecting North America, especially with the mid-level trough over the central and southwestern CONUS at the start of the period. The model inconsistencies result in conflicting signals in their raw and derived temperature and precipitation forecasts. Most tools are in decent agreement showing below-normal temperatures in the Southwest. Most tools also show below-normal temperatures in the northern Great Plains and across central and western Alaska, and above-normal temperatures along the South Atlantic Coast. However, there are significant inconsistencies in the interior Southeast, the Northeast, the Lower Mississippi Valley, and southeastern Alaska. Overall, the bias corrected and calibrated tools are significantly warmer than the raw ensemble output. Generally, a blend of the raw and corrected tools was favored. Significantly enhanced odds of below-normal temperatures are forecast for the Southwest, and similarly increased odds of above-normal temperatures cover the South Atlantic States, which are the two regions where guidance is in best agreement. Elsewhere, either near-normal temperatures are favored, or odds only lean slightly toward one extreme. Odds of colder than normal temperatures exceed 40 percent over the western Great Lakes, northern Great Plains, central Rockies, and a broad part of Mainland Alaska, where tools were in slightly better agreement than most other areas. Similar issues are found in the raw and reforecast precipitation output from the ensembles, with a few areas of agreement, but larger areas where signals are inconsistent, resulting in lower confidence. Guidance is fairly consistent regarding the storm and trailing cold front moving through the East early in the 6-10 day period, so odds of above-normal precipitation exceed 40 percent over this broad area. The likelihood of abnormally wet weather exceeds 50 percent in a small area centered over the Upper Ohio Valley, where guidance is most consistent in favoring wetness. There is a strong consensus showing enhanced odds of above-normal precipitation in the Southwest, although low normals this time of year means relatively light precipitation totals will verify as above normal. Odds of surplus precipitation exceed 60 percent in and near southern Arizona. Rising heights put Alaska under cyclonically-curved mid-level flow and above-normal moisture advection from the North Pacific, so odds favor wetness statewide, with the best chances in central and southwestern parts of the Mainland. Below-normal precipitation is slightly favored near the northwestern Pacific Coast region. A mid-level trough near Hawaii favors cooler and wetter than normal conditions there. The official 6-10 day 500-hPa height blend consists of 50% of Today's GFS Superensemble Mean centered on Day 8, 20% of Today's 0z European Ensemble Mean centered on Day 8, 10% of Today's operational 0z ECMWF 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: About average, 3 out of 5, due to decent agreement on the predicted circulation pattern, offset by the progressive circulation pattern and some significant differences among the forecast tools. 8-14 DAY OUTLOOK FOR APR 03 - 09 2024 The week-2 500-hPa height forecast is less certain than the 6-10 day period again today, with greater differences among the GEFS, European, and Canadian ensemble means as result of uncertainty in the eastward progression of the circulation pattern. Today’s GEFS superensemble is given the greatest weight due to its more consistent solution relative to yesterday, but forecasts from the European and Canadian ensemble means are also included in the manual height blend, reflecting the uncertainty in the evolution of the 500-hPa pattern. The manual blend of model 500-hPa height forecasts predicts a strong positive height anomaly over the Davis Strait, indicating a continuation of the negative phase of the North Atlantic Oscillation. Meanwhile, positive 500-hPa heights are expected over the North Pacific, extending into Alaska, while below-normal mid-level heights cover most of the CONUS, especially in northeastern and southwestern sections. The progressive circulation pattern and differences among the model temperature tools leads to a highly uncertain temperature outlook for the week-2 period again today. Above normal temperatures are favored for the Aleutian islands, southwestern and northeastern Mainland Alaska, Florida, and portions of the Great Lakes and Northeast, but odds of unusual warmth exceed 40 percent only in southern Florida. Meanwhile, slightly enhanced odds of subnormal temperatures cover a swath from northwestern through southeastern Alaska, the western half of the CONUS, and a band extending from the Lower Mississippi Valley to the Mid-Atlantic region. In most of these areas, the chances of below-normal temperatures are below 40 percent, but more consistency in the Southwest leads to higher probabilities of below-normal temperatures, with chances exceeding 50 percent from southeastern California through the southern Rockies. Inconsistency among the tools also keeps the precipitation forecast relatively conservative. With lower 500-hPa heights expected in the Northeast and offshore, drier than normal weather is slightly favored in parts of the Great Lakes and inner Northeast. Elsewhere, a preponderance of tools and the nature of a progressive pattern would favor above-normal precipitation, with odds exceeding 40 percent in the central Rockies, the Southwest, Florida and the adjacent Southeast, and most of Mainland Alaska, where surface low pressure and associated frontal systems appear most likely to trigger significant precipitation. Continued below-normal 500-hPa heights, representing a continuing weak mid-level trough, favor cooler and wetter than normal conditions again for week-2 across Hawaii. The official 8-14 day 500-hPa height blend consists of: 20% of Today's 6z GFS Ensemble Mean centered on Day 11, 45% of Today's GFS Superensemble Mean centered on Day 11, 25% of Today's 0z European Ensemble Mean centered on Day 11, and 10% 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, with only fair agreement among model week-2 mean 500-hPa height pattern forecasts, along with differences in the daily handling of the progressive pattern, and among model tools for precipitation and temperature. FORECASTER: Rich Tinker 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 April 18. 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: 19680405 - 19800319 - 19780311 - 19560312 - 19700328 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: 19680404 - 19730328 - 20080305 - 19520321 - 19780311 6-10 DAY OUTLOOK TABLE Outlook for Apr 01 - 05 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A N OREGON A N NRN CALIF N N SRN CALIF B A IDAHO N A NEVADA N A W MONTANA B A E MONTANA B A WYOMING B A UTAH B A ARIZONA B A COLORADO B A NEW MEXICO B A N DAKOTA B N S DAKOTA B N NEBRASKA B N KANSAS B N OKLAHOMA N N N TEXAS N N S TEXAS N N W TEXAS B A MINNESOTA B N IOWA B N MISSOURI N N ARKANSAS N N LOUISIANA N A WISCONSIN B N ILLINOIS B N MISSISSIPPI N A MICHIGAN B A INDIANA B A OHIO B A KENTUCKY N A TENNESSEE N A ALABAMA N A NEW YORK B A VERMONT B A NEW HAMP B A MAINE N A MASS B A CONN B A RHODE IS B A PENN B A NEW JERSEY B A W VIRGINIA N A MARYLAND N A DELAWARE N A VIRGINIA N 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 N A AK WESTERN B A AK INT BSN B A AK S INT B A AK SO COAST B A AK PNHDL N A 8-14 DAY OUTLOOK TABLE Outlook for Apr 03 - 09 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B N OREGON B A NRN CALIF B A SRN CALIF B A IDAHO B A NEVADA B A W MONTANA B A E MONTANA B A WYOMING B A UTAH B A ARIZONA B A COLORADO B A NEW MEXICO B A N DAKOTA N A S DAKOTA N A NEBRASKA N A KANSAS N A OKLAHOMA B A N TEXAS B N S TEXAS B N W TEXAS B N MINNESOTA N A IOWA N A MISSOURI N A ARKANSAS B A LOUISIANA B A WISCONSIN N N ILLINOIS N N MISSISSIPPI B A MICHIGAN N N INDIANA N N OHIO N N KENTUCKY B N TENNESSEE B A ALABAMA N A NEW YORK N N VERMONT A N NEW HAMP A N MAINE A N MASS N N CONN N N RHODE IS N N PENN N N NEW JERSEY N N W VIRGINIA N N MARYLAND N N DELAWARE N N VIRGINIA N N N CAROLINA N A S CAROLINA N A GEORGIA N A FL PNHDL N A FL PENIN A A AK N SLOPE B A AK ALEUTIAN A A AK WESTERN N 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. $$ ####018002478#### FXUS01 KWBC 261958 PMDSPD Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 357 PM EDT Tue Mar 26 2024 Valid 00Z Wed Mar 27 2024 - 00Z Fri Mar 29 2024 ...Severe Weather potential over parts of the Upper Great Lakes tonight... ...Heavy to Excessive Rainfall possible over portions of the Southeast and Mid-Atlantic... ...Unsettled weather returns to the Northwest on Wednesday... Heavy snow and blizzard conditions associated with a deep mid-latitude cyclone that impacted the Northern/Central Plains and Upper Midwest the past few days has ended, but some lingering mainly light snows may continue into tonight across parts of the Upper Great Lakes. Behind the associated cold front, a chilly airmass will continue to spread across the Great Plains and Midwest into Wednesday. The greatest anomalies on Wednesday will be across the Northern Plains/Upper Midwest where daytime highs 15-25 degrees below average are possible, with temperatures moderating thereafter. Widespread showers and thunderstorms are expected to accompany the above mentioned cold front through Thursday as it slowly progresses through the Midwest and East Coast states. Into this evening, the Storm Prediction Center highlights portions of southern Michigan into Indiana and Ohio within a slight risk (level 2/5) of Severe Thunderstorms. On Wednesday, the heaviest rains are expected across parts of north Florida and into the Southeast as additional moisture gets pulled northward due to a second wavy front and developing surface low where WPC has a slight risk for excessive rainfall. Showers and storms will continue across the Northeast into Thursday, though heaviest rainfall should be confined across portions of the Carolinas and the DelMarVa, and up the Northeast Coast posing a mainly localized flash flood threat. Unsettled weather will continue across the Northwest during the short range, with low elevation rain and mountain snows. Favorable upslope regions may have the greatest threat for heavy to excessive rainfall, particularly across southwest Oregon/northwest California on Wednesday. Accumulating snowfall is possible particularly across the highest elevations of the Cascades, Sierra Nevada, and into the northern Rockies. Santorelli Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php $$