Extended Forecast Discussion NWS Weather Prediction Center College Park MD 259 AM EDT Thu Jun 30 2022 Valid 12Z Sun Jul 3 2022 - 12Z Thu Jul 7 2022 ...Overview... Broad cyclonic flow aloft will be in place across the north-central U.S. for the Sunday to Monday time period as a anomalous upper low lingers over far northern Quebec. Another synoptic scale trough is expected to remain over the eastern Pacific through much of the forecast period with multiple shortwave perturbations pivoting around it. An upper level ridge is expected to build across the central High Plains in response to this trough. A quasi-stationary frontal boundary with multiple rounds of showers and storms is expected from the Dakotas to the Great Lakes through the middle of next week. ...Guidance Evaluation/Predictability Assessment... On the synoptic scale, the 00Z guidance remains in very good agreement on placement and amplitude of the West Coast trough, Plains upper ridge, and trough over eastern Canada through the majority of the forecast period. Similar to the past couple of days, there are still some mesoscale detail differences with the individual shortwaves that will govern the magnitude and extent of heavy rain across the Plains and Midwest, so the NBM and the biased corrected ensemble model for QPF served as a good starting point in the forecast process. For fronts/pressures, a multi-deterministic blend worked well for Sunday-Tuesday, followed by some of the GEFS/ECENS for Wednesday-Thursday to account for increasing mesoscale differences. ...Sensible Weather and Potential Hazards... Scattered showers and storms are expected across the Southeast this weekend with the presence of a weakening frontal boundary and weak impulses moving through the flow aloft. Farther north, a front initially oriented from the Northeast into the Ohio Valley and central Plains will push gradually eastward during the weekend and support organized areas of showers and storms along and ahead of it. Some rainfall may be locally heavy from the central Plains into the Mid-Atlantic on Sunday as moisture converges along a quasi-stationary frontal zone. This front may continue to be a focus for rainfall into early next week as well. Monsoonal moisture over the southern Rockies is also expected to lead to mainly diurnally driven showers and storms, with weak shortwaves and moisture lifting northward between upper ridging to the east and the trough near the West Coast. The West Coast trough will likely produce periods of rainfall over parts of the Northwest, and there continues to be a signal for a period of heavier rainfall near the Canadian border early next week. Some mesoscale convective systems could also extend across the northern Plains/Upper Midwest, aided by northern tier surface features and shortwaves emerging from the West. The greatest concern for temperatures will be with heat expected to build again across the central and northern Plains by early next week in response to a strengthening upper level ridge. Highs of 5-15 degrees above normal are possible over the central Plains, equating to temperatures in the mid 90s to low 100s. Southern Plains locations will see a slightly hotter trend as well, but with less extreme anomalies. Out West, below normal highs will spread gradually inland from the West Coast during the weekend into early next week due to nearby upper troughing. A few locations may see highs 10-15F below normal around Sunday-Monday. Expect a moderating trend closer to normal heading into midweek. Across the eastern U.S., a stable upper pattern of westerlies across the Northeast and ridging over the South should keep both daytime highs and overnight lows within a few degrees of climatological averages through most of the period. Hamrick 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, experimental excessive rainfall outlook, winter weather outlook probabilities and heat indices 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