Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 PM EST Fri Feb 23 2024 Valid 12Z Mon Feb 26 2024 - 12Z Fri Mar 01 2024 ...Overview... An upper ridge traversing the central and eastern U.S. for the first half of next week will spread much above normal temperatures to the Plains and Midwest and then the East. Meanwhile, northern and weaker southern-stream troughing from the Pacific look to track into the West and bring cooler temperatures, elevation-dependent rain/snow, and windy conditions from the West Coast to the Rockies through early next week. Downstream translation may then support emerging genesis of systems and precipitation pattern from the south-central U.S. to the Midwest/Great Lakes onward into midweek, along with a post-frontal/trailing southward surge of a cold Canadian high pressure system to offer some wintry potential for the northeastern quarter of the country mid to late next week but with timing uncertainty. ...Guidance/Predictability Assessment... As the forecast period begins next Monday, guidance remains in reasonably good agreement depicting an upper-level trough diving southeast along the west coast of Canada towards the Pacific Northwest. The main forecast challenge remains with how this northern stream trough will later interact with a de-amplified upper-low lifting northeast from off the coast of California by the time they reach the mid-section of the country about next Tuesday. It appears that the general eastward acceleration of the guidance consensus for this system has continued this morning, pushing what appears to be a well-defined cold front faster into the eastern U.S. by next Wednesday. The EC ensemble means appear to have performed the best so far with this system. Guidance uncertainty appears to improve across the U.S. late next week as the uncertain upper trough lifts off the Northeast and a ridge progressively builds from the Southwest into the mid-section of the country. The WPC medium-range forecast package was based on a consensus of the 06Z GFS/GEFS, 00Z EC/EC mean, and some contributions from the 00Z CMC/CMC mean. This blend provided QPF and mass fields that were very compatible to WPC continuity from 12 hours ago, although a southward shift on the QPF axis over the Midwest, due to the faster eastward progression of the low/front midweek, was noted based on the latest guidance consensus. ...Weather/Hazards Highlights... As troughing comes into the West early next week, precipitation will spread into the Pacific Northwest and northern Rockies into Monday, including snow that could be heavy over favored terrain. Precipitation may now spread through California and into the Intermountain West by Monday, then out through the Rockies Tuesday given less likely stream phasing and northern stream upper trough progression. Additional moisture ahead of additional systems upstream over the Pacific will continue precipitation chances in the Pacific Northwest then California through Wednesday-next Friday. Overall, the highest likelihood for winter-related impacts is in the Cascades, Sierra, and portions of the Northern/Central Rockies, though most of the regional higher elevation mountain ranges will at least see some snow through the period. Widespread strong, gusty winds are also expected across much of the West, particularly for higher elevations, as a couple frontal systems pass through, lingering the longest along the eastern ranges/foothills of the Rockies and immediate High Plains. Precipitation chances will begin to increase Tuesday into Wednesday across much of the eastern half to third of the country as moist southerly flow increases ahead of the approaching upper-level trough and surface low pressure/frontal system from the West. Most precipitation will be in the form of rain given anomalous lead warmth, but some snow on the backside of the low and cold front for the Upper Midwest/Great Lakes. The WPC Winter Weather Outlook has increased probabilities there given the low and post-frontal cold onset. Some rainfall amounts could be moderately heavy, particularly for the Ohio Valley, with multiple rounds of rain possible through at least midweek. In addition, the moist, unstable airmass as well as increasingly strong winds aloft with the approaching trough will bring the chance for some severe thunderstorms, with the Storm Prediction Center highlighting this threat from the Southern Plains to Middle Mississippi Valley Tuesday and into the Mid-South and Ohio/Tennessee Valleys Wednesday, with additional southward shift of the QPF axis as noted above. Later week precipitation focus across the South appears better defined this forecast cycle as the precipitation generally pushes east toward the southeastern U.S. by next Friday. The central U.S. will see quite mild to warm temperatures early next week underneath an upper ridge. Temperatures of 20-35 degrees above average will expand throughout the Plains and Mississippi Valley, putting actual temperatures into the 80s and even 90s in Texas by Monday-Tuesday while 60s reach as far north as South Dakota and Iowa, with potential for widespread records. The upper trough and cold front pressing eastward should cool temperatures down closer to normal or a few degrees below in the central U.S. by midweek, but temperatures could already start to rebound by Thursday. The well above normal to possibly record-breaking temperatures will get shunted eastward ahead of the upper trough/underneath the upper ridge into the east-central and then eastern U.S. Tuesday-Thursday. 70s should be widespread across the Southeast and could even reach as far north as the Mid-Atlantic. Meanwhile the West is forecast to see near to slightly above normal temperatures into Sunday, but cooling to below normal particularly in terms of highs by Monday-Tuesday as upper troughing comes in. 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, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages are at: 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