Extended Forecast Discussion NWS Weather Prediction Center College Park MD 315 AM EDT Sat Mar 30 2024 Valid 12Z Tue Apr 02 2024 - 12Z Sat Apr 06 2024 ...Heavy Rain/Severe Weather Threat to the Eastern U.S. midweek... ...New England Coastal Storm with maritime hazards/high wind/coastal flooding and Interior Northeast Heavy Snow threat Tuesday-Thursday... ...Widespread Precipitation/Cooling for The West mid-later week... ...Guidance/Predictability Assessment... Model guidance has become increasingly better clustered through medium range time scales, bolstering forecast confidence in at least the mid-later scale system developments and evolutions. A favored model composite seems to mitigate smaller scale embedded system variance to provide a reasonable forecast basis with detail consistent with an anomolous and stormy early spring pattern with seemingly above normal predictability. WPC product continuity is well maintained and supported by multi-model ensembles. ...Pattern Overview and Weather/Hazards Highlights... Moisture and instability remain anomalously high into Tuesday as a organized main low/frontal system tracks into the East under favorable upper support. The heaviest rainfall will work out from the Tennessee Valley/Ohio Valleys and through the Appalachians and north-central Mid-Atlantic where a WPC Marginal Risk Excessive Rainfall Outlook (ERO) Marginal Risk threat area remains in place. The Storm Prediction Center is monitoring severe potential in the warm sector. Uncertainty with convective local focus has precluded issuance of a Slight Risk ERO area at this time despite moist Mid- Atlantic soils and some heavier model QPF signals to monitor. This system will transition to a deep/slow moving coastal storm just off New England Wednesday and Thursday. This setups a protracted period with enhanced wrap-back Atlantic moisture inflow into New England to fuel cooled heavy rainfall, with focus and duration maximized over eastern New England wet soils where a Day 5/Wednesday Slight Risk ERO has been introduced to include runoff susceptible metro areas from Providence and Boston to Portland. Meanwhile and significantly on the colder northern side of storm system, there will be a significant threat for blowing winds and heavy snows out from the Great Lakes and through the Interior Northeast Tuesday to Thursday as depicted by enhanced WPC Winter Weather Outlook probabilities. Well upstream, a strongly amplifying upper trough/closed low and leading and wavy cold front/secondary Canadian cold surge digging into the West should act to cool temperatures and spread enhanced precipitation and windy/unsettled flow to include coastal rains down through California along with a prolonged period with interior and terrain/mountain snows increasingly inland across much of the West midweek into next weekend. Depicted areas of precipitation are currently on the modest to moderate side given track/moisture, but ample upper support and favored terrain lift may lead to locally heavier focus and activity to monitor. The WPC Winter Weather Outlook shows the greatest snow probabilities over Northwest to northern Intermountain/Rockies terrain/mountains. 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