####018005102#### FXUS02 KWBC 141902 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 301 PM EDT Tue May 14 2024 Valid 12Z Fri May 17 2024 - 12Z Tue May 21 2024 ...Another southern tier heavy rainfall threat during the latter half of the week... ...Overview... Downstream from a reorienting eastern Pacific upper ridge, guidance is generally suggesting flat to broadly cyclonic mean flow late this week into the weekend, followed by a tendency toward more upper troughing over the West early next week. There are still a lot of lower-predictability detail questions about flow rounding the ridge and reaching the lower 48. There is also considerable spread for the details/timing of an upper shortwave and associated surface system crossing the eastern half of the country late this week into the weekend. Continue to expect the heaviest convective emphasis to be across the southern tier late this week into the weekend, with some areas of less extreme but potentially meaningful rainfall farther north. ...Guidance/Predictability Assessment... Deterministic, Ensemble and AI models tend to be in reasonable agreement that an upper trough will push through the eastern half of the CONUS this weekend, while shortwave energy grazes the northern tier and a trough emerges over the West Coast. A general model blend favoring the 06z GFS and 00z ECMWF, but also consisting of the 00z UKMET/CMC, was used for days 3 and 4. The blend was expanded to incorporate the 00z ECE and 06z GEFS on day 5 to moderate deterministic model uncertainty with respect to the East Coast trough. The 00z CMCE replaces the 00z CMC on day 6 to help suppress what appears to be an overamplification of the East Coast trough by the deterministic model. On day 7, our blend simply consists of the 00z ECE/CMCE and 06z GEFS with the latter being favored slightly. ...Weather/Hazards Highlights... Another southern tier convective event should be in progress at the start of the period early Friday. The Day 4 Excessive Rainfall Outlook that covers the Friday-Friday night time frame continues to depict a Slight Risk area that extends from Louisiana into Alabama, with some adjustment from continuity to reflect latest guidance. This area will be sensitive to additional rainfall given wet soil conditions. Frontal/wave focus with available moisture and instability along with potential for repeat rains may enhance totals. The surrounding Marginal Risk area accounts for some potential of a convective axis hanging back even farther to the west (still most pronounced in GFS runs). Farther north, latest ECMWF/GFS/CMC/ICON runs are starting to cluster toward a potential axis of less extreme but locally heavy rainfall over the Ohio Valley in association with a front affecting the region. Short-term rainfall should lead to somewhat wetter soil than initially observed. The Day 4 ERO introduces a Marginal Risk area to account for the developing guidance cluster. By Day 5 Saturday, the only coherent area of potentially heavy rainfall is over portions of the Southeast as the southern tier surface front/waviness continue onward. A Marginal Risk provides a reasonable starting point given the guidance scatter within this region. Confidence is much lower for rainfall coverage and totals farther northward over the East. Otherwise, some rainfall could linger along parts of the East Coast into Sunday if the slower side of the envelope verifies for the system affecting the region. Some areas of rainfall may develop over portions of the northern-central Plains into the Midwest by the weekend or early next week depending on shortwave energy/surface details, with low confidence for specifics of intensity at any particular location. Portions of the West may begin to see scattered precipitation by the weekend and early next week with the tendency toward more upper troughing and arrival of the southern stream upper low. The southern two-thirds of the West will likely see above normal temperatures continue through the weekend with some areas seeing highs 10-15F or so above normal. Northern areas will already be moderating close to normal Friday-Sunday while additional lowering of heights aloft over the West early next week should bring temperatures toward normal over the remainder of the West. Some of the western warmth will extend into portions of the Plains and Mississippi Valley with plus 5-15F anomalies. The Florida Peninsula and South Texas should see several days with highs up to 5-10F above normal, in a warm pattern to the south of a couple fronts expected to focus upon reaching more northern parts of these states. Some daily records for highs/warm lows will be possible. These temperatures may bring heat indices as high as 105-110 degrees for south Florida and upwards to 115 degrees for south Texas, highlighting a threat of hazardous heat. Kebede/Rausch $$ ####018011783#### FXUS06 KWBC 141902 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 14 2024 6-10 DAY OUTLOOK FOR MAY 20 - 24 2024 Today’s model solutions have come into better agreement over the last few days and the GEFS, ECMWF, and CMCE all depict a similar synoptic picture over the 6-10 day forecast period, although differences still remain when considering the daily evolution of various features. Today’s manual blend features widespread positive height anomalies over the North Pacific, a weak subtropical ridge centered over southeastern Texas, and troughing over the northwestern and north-central CONUS. Weak troughing is also favored near the East Coast. Subtropical ridging favors above-normal temperatures for much of the southern and eastern contiguous U.S. (CONUS), with probabilities exceeding 80% for portions of South Texas. Troughing over the West Coast favors below-normal temperatures for much of the CONUS west of the Rockies, especially the northwest CONUS where probabilities exceed 50%. Portions of southern California also have enhanced chances of below-normal temperatures, consistent with most forecast tools. For Alaska, increased northwesterly flow aloft favors increased cloudiness and below-normal temperatures for the Alaskan Interior and extending southeastward through the Panhandle, while the North Slope tilts slightly towards above-normal temperatures, as indicated by the GEFS and ECMWF reforecast tools. The Hawaii ERF consolidation (CON) favors above-normal temperatures for the entire state. Troughing over both coasts and positive height anomalies centered over northern Mexico develop a stronger than normal jet stream for this time of year, favoring a more active pattern which tilts the odds toward above-normal precipitation for most of the CONUS east of the Rockies. The subtropical ridge favors below-normal precipitation for portions of the southern CONUS, especially for portions of southern New Mexico and southeastern Texas. Much of Alaska tilts towards above-normal precipitation with weak troughing favored over eastern Siberia although model solutions generally keep the enhanced potential for precipitation confined to the Mainland and below-normal precipitation is slightly favored for the southern coast and the Panhandle of Alaska. The Hawaii CON indicates above-normal precipitation for most of the state, with odds increasing from east to west, while near-normal precipitation is most likely for the Big Island. The official 6-10 day 500-hPa height blend consists of 40% of Today's 0z 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: Above average, 4 out of 5, with good run-to-run continuity among forecast models, offset by differences between models regarding strength and position of various synoptic features. 8-14 DAY OUTLOOK FOR MAY 22 - 28 2024 Ensemble mean solutions for the 8-14 day (week-2) period predict a de-amplification of the 500-hPa circulation pattern relative to the 6-10 day period across North America and the surrounding regions. Height anomalies are weaker relative to the 6-10 day period as the synoptic pattern becomes more zonal and spread among model solutions increases. During week-2, positive 500-hPa height anomalies persist over the North Pacific and the south-central and southeastern CONUS, while weak troughing continues over the coasts. This persistence of the synoptic pattern results in similar outlooks between forecast periods for both temperature and precipitation. Above-normal temperatures continue to be favored for the southern CONUS east of the Rockies. Continued troughing over both coasts favors an eastward expansion of chances for below-normal temperatures as far as the Great Lakes, while near-normal temperatures become most likely for the northeastern CONUS. Western Alaska continues to tilt towards below-normal temperatures with northwesterly flow aloft continuing, while reforecast tools continue to favor a slight tilt towards above-normal temperatures for the North Slope, and indicate a similar tilt for southeastern Alaska as well. Most of Hawaii continues to be favored for above-normal temperatures, although near-normal temperatures are now most likely for the Big Island, consistent with today’s autoblend and Hawaii CON tool. Subtropical ridging over the southern CONUS continues to favor below-normal precipitation for portions of the Four Corners, southeastern Texas, and south Florida, while the weak troughing present on both coasts results in a tilt towards above-normal precipitation for much of the CONUS, supported by the majority of forecast tools. Continued troughing over Siberia favors above-normal precipitation for much of the Alaskan Mainland, however surface flow is favored to become southeasterly over the Panhandle, resulting in a slight tilt towards below-normal precipitation. Above-normal precipitation continues to be favored for Hawaii, especially Kawai. The official 8-14 day 500-hPa height blend consists of: 33% of Today's 0z GFS Ensemble Mean centered on Day 11, 34% of Today's 0z European Ensemble Mean centered on Day 11, and 33% 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, with good run-to-run continuity among forecast models, offset by differences between models regarding strength and position of various synoptic features. FORECASTER: Daniel Barandiaran 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: 19710506 - 19730518 - 19520523 - 20060504 - 20060427 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: 19990527 - 19710505 - 19730519 - 19520521 - 20060504 6-10 DAY OUTLOOK TABLE Outlook for May 20 - 24 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B N OREGON B N NRN CALIF B N SRN CALIF B N IDAHO B A NEVADA B N W MONTANA B A E MONTANA B A WYOMING B A UTAH B A ARIZONA N N COLORADO A A NEW MEXICO A B N DAKOTA B A S DAKOTA B A NEBRASKA N A KANSAS A A OKLAHOMA A N N TEXAS A N S TEXAS A B W TEXAS A B MINNESOTA N A IOWA A A MISSOURI A A ARKANSAS A A LOUISIANA A B WISCONSIN A A ILLINOIS A A MISSISSIPPI A N MICHIGAN A A INDIANA A A OHIO A A KENTUCKY A A TENNESSEE A A ALABAMA A N NEW YORK A A VERMONT A A NEW HAMP A N MAINE A A MASS A N CONN A N RHODE IS A N PENN A A NEW JERSEY A N W VIRGINIA A A MARYLAND A N DELAWARE A N VIRGINIA A N N CAROLINA A N S CAROLINA A N GEORGIA A N FL PNHDL A N FL PENIN A N AK N SLOPE A A AK ALEUTIAN N N AK WESTERN B A AK INT BSN N A AK S INT N N AK SO COAST N N AK PNHDL B N 8-14 DAY OUTLOOK TABLE Outlook for May 22 - 28 2024 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B N OREGON B N NRN CALIF B N SRN CALIF B N IDAHO B N NEVADA B N W MONTANA B N E MONTANA B A WYOMING B A UTAH B N ARIZONA B B COLORADO B N NEW MEXICO A B N DAKOTA B A S DAKOTA B A NEBRASKA B A KANSAS N A OKLAHOMA A A N TEXAS A A S TEXAS A N W TEXAS A N MINNESOTA B A IOWA B A MISSOURI N A ARKANSAS A A LOUISIANA A N WISCONSIN B A ILLINOIS N A MISSISSIPPI A A MICHIGAN N A INDIANA N A OHIO N A KENTUCKY A A TENNESSEE A A ALABAMA A A NEW YORK N A VERMONT N N NEW HAMP N A MAINE N N MASS N A CONN N A RHODE IS N A PENN N A NEW JERSEY N A W VIRGINIA A A MARYLAND N A DELAWARE N A VIRGINIA A A N CAROLINA A A S CAROLINA A A GEORGIA A A FL PNHDL A N FL PENIN A N AK N SLOPE A A AK ALEUTIAN N N AK WESTERN B A AK INT BSN N A AK S INT N N AK SO COAST N N AK PNHDL A 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. $$