Extended Forecast Discussion NWS Weather Prediction Center College Park MD 302 PM 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 rainfall threat looms for Florida... ...Guidance/Predictability Assessment... Latest suite of guidance shows fairly good agreement on the large scale pattern featuring shortwaves progressing through a mean Great Lakes to Northeast trough with a building ridge behind. There is still some key differences in the speed and amplitude of these shortwaves late week, but a general model compromise seemed to work as a good starting point. Meanwhile, out West, there is increasing uncertainty on how quickly a northeast Pacific low or associated energy progresses inland. The 00z and new 12z ECMWF remain on the faster side of guidance pulling much of the upper low into Western Canada next weekend, while there seems to be better consensus for at least some energy to hang back off the British Columbia coast. Meanwhile, the evolution of lowering heights, and highly anomalous moisture axis, and energy over the Gulf of Mexico into Florida continues to offer a ton of uncertainty. Per the latest forecast out of the National Hurricane Center, tropical development with this feature is not likely, but regardless, confidence in a heavy to excessive rainfall threat for central and southern Florida is increasing. ...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. The Day 4 WPC ERO continues to show a small marginal risk area for portions of central to northeast Texas. A multi- day period favorable for heavy rains should develop early this week and continue through much of the medium range period for 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 at least a moderate drought. There is increasing confidence however that short range heavy rainfall potential may mitigate that enough to support a slight risk introduction for central and southern Florida on the Days 4 and 5 EROs, with a looming threat into later week as well there and with any activity/moisture feed emanating over the Gulf. Storm total rainfall (including what falls before the medium range period even starts) of 7-12 inches, with locally higher amounts, is possible. 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. and parts of the East 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. Santorelli/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