Preliminary Forecasts
Issued by NWS
Issued by NWS
297 FXUS02 KWNH 120701 PREEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Wed Jun 12 2024 Valid 12Z Sat Jun 15 2024 - 12Z Wed Jun 19 2024 ...Heatwave to spread from the Southwest to parts of the central and eastern U.S. during the period... ...Excessive Rainfall Threat for Florida wanes this weekend with focus shift to the central Gulf Coast into next week... ...Guidance/Predictability Assessment... Guidance mostly remains in good overall agreement into next week with respect to the overall pattern, featuring mean ridging over the West progressing eastward through the period over the central and then eastern U.S., and with mean troughing settling in over the West in the wake. Guidance indicates a southern stream shortwave over the Southwest will lift northeast rounding the building ridge with additional embedded waves translating the northern tier as the mean troughing begins to take hold back over the West. An upper-level weakness over Florida this week will slowly retrograde over the Gulf of Mexico this weekend into next week. This will shift a stormy pattern out from Florida to the Gulf and central to western Gulf Coast, with the ridge transitioning over the East also helping to funnel tropical moisture northward. Accordingly, the WPC medium range product suite was primarily derived from a composite blend of best clustered guidance of the 12 UTC ECMWF/Canadian/UKMET, the 01 UTC National Blend of Models and WPC continuity for Saturday into Monday in a pattern with average to above average predictability. Switched to a composite of the GEFS/ECMWF ensemble means and best clustered ECMWF early-mid next week amid growing forecast spread. ...Weather/Hazards Highlights... A complex excessive rainfall episode ongoing over the central and southern Florida Peninsula should wane this weekend as the main tropical moisture and system/flow focus likely shifts to both over the western Atlantic and also back across the Gulf of Mexico and the central to western Gulf Coast region. A Day4/Saturday ERO Marginal Risk remains for lingering activity over Florida. However, as the weekend progresses and into early next week, there is a growing guidance signal that moisture influx and possible heavy rainfall may refocus and increase into the central Gulf Coast and vicinity. A Day 5/Sunday Marginal Risk ERO has been introduced given the moist pattern. Uncertainty remains, particularly with the potential amount of rainfall and with westward extent into the western Gulf through early-mid next week. Elsewhere, a convective precipitation threat will shift across the central and northern Plains to the Upper Midwest/Great Lakes this weekend as southern stream troughing ejects northeastward toward the region from the Southwest to focus lift/instability. WPC ERO Marginal Risk areas have been introduced for Day4/Saturday and Day 5/Sunday given system progression and pooling moisture/instability. As for anomalous temperatures, an amplified upper ridge slated to steadily/broadly shift from the Southwest through the south- central U.S. to the East over the coming week will produce much warmer than average temperatures and the threat for some record heat. Temperatures will already be rather hot over portions of the South before the even broader region of heat expands into the Midwest/Ohio Valley then Mid-Atlantic and vicinity into next week as the upper-level ridging builds in. Highs are forecast well into the 90s, potentially low 100s, and with lows in the 70s providing little relief from the heat overnight. The Climate Prediction Center continues a heat threat into week 2. 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 $$