Extended Forecast Discussion NWS Weather Prediction Center College Park MD 258 AM EDT Sun Jun 9 2024 Valid 12Z Wed Jun 12 2024 - 12Z Sun Jun 16 2024 ...Heat focus shifts from the Southwest to South Texas this week as heavy convective rainfall threats shift from the south-central U.S. to the Gulf of Mexico and Florida... ...Guidance/Predictability Assessment... Recent forecast spread and continuity issues now seem somewhat less problematic in a pattern with near average predictability overall, albeit still with standard and widespread warm season variances in the details. The greatest region of uncertainty remains over the Gulf of Mexico as lower heights aloft move into the region. The details of how this interacts with an increasing moisture feed into/towards Florida remains highly uncertain. A heavy rainfall event still seems in the cards for parts of Florida, but where the rainfall axis sets up remains variable. The WPC medium range product suite was primarily derived from a blend of reasonably clustered guidance from the 06 UTC GFS and 00 UTC ECMWF/UKMET/Canadian models and their respective ensemble means through medium range time scales. Growing forecast spread seems mainly tied to smaller scale embedded system issues that are often mitigated consistent with predictabilty by a broad guidance blending process that includes a shift toward increased ensemble mean weighting into longer time frames. This approach maintains good WPC product continuity and a composite of latest 00 UTC guidance remains mostly in line for much of this forecast period. ...Weather/Hazards Highlights... A front across the south-central Plains will combine with slow moving upper system energy and instability to offer a lingering threat for local heavy rainfall into Wednesday. A WPC Excessive Rainfall Outlook (ERO) Marginal Threat area is depicted. A multi-day period favorable for heavy rains should develop across the Florida Peninsula as well above moisture pools along and south of a wavy/stalling front with aid from upper level impulses/energy back through an unsettled Gulf of Mexico. There is a lot of uncertainty in the details and much of the state is in a drought. Still, some threat for high rain rates exists, and its possible much of the threat may manifest for more susceptable urbanized areas. WPC Day 4/Wednesday and Day 5/Thursday ERO Marginal Risk areas include much of the central and southern Florida Peninsula to account for the uncertainty, with a looming threat into later week as well there and with any activity/moisture feed eminating over the Gulf. Meanwhile, an increasing precipitation threat across much of the central and northern Plains emerges late period with troughing shifting northeastward into the region from the Southwest. An amplified mean upper ridge slated to slowly shift from the West/Southwest to the south-central U.S. will continue to produce much warmer than average temperatures. The highest temperature anomalies of 10-20F above normal are forecast for the Great Basin, shifting eastward as the week progresses into the Rockies and Plains. It will be especially hot across the Desert Southwest then South Texas given elevated Heat Risk and Heat Index threat values. 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