Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
064 FXUS02 KWBC 290721 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 321 AM EDT Sun Jun 29 2025 Valid 12Z Wed Jul 02 2025 - 12Z Sun Jul 06 2025 ...A protracted wet period for parts of north-central Florida... ...Southwest to southern Rockies/High Plains monsoonal flow as the tropics activate over the eastern Pacific and Bay of Campeche... ...Guidance/Predictability Assessment... Latest model guidance offers average to better flow predictability overall, but does show a bit more forecast spread than has been the case over the past few days. This is despite being reasonably well clustered with larger scale feature evolutions over the next week. The most pronounced differences remain with the handling of northern and southern stream Pacific upper trough energies moving inland and over the West, as well as with northern stream system progression and amplitude working downstream from southern Canada through the north-central to Northeast/Eastern U.S states. Guidance does provide signal for monsoon flow emergence into the Southwest with some connection to tropical activity over the eastern Pacific offshore Mexico (EP95) and from the Bay of Campeche with T.D. TWO. A favored composite blend featuring compatible 18 UTC GEFS mean and the 12 UTC ECMWF/Canadian ensemble mean should tend to address these small-mid scale differences consistent with individual system predictability. This strategy maintains good WPC product continuity as overall in line with the 01 UTC National Blend of Models, most machine learning tools and latest 00 UTC guidance. ...Weather/Hazards Highlights... Thunderstorms with deep moisture/instability will bring heavy convective downpours ahead of a upper trough and surface front into mid-late week over the far Southeast U.S. where WPC Excessive Rainfall Outlook (ERO) Marginal Risk areas exist Day 4/Wednesday and Day 5/Thursday. A focus for multi-day heavy rains slowly shifts to Gulf coastal north-central Florida where a Slight Risk area has been introduced into Day 5/Thursday given precursor rains and heavy rainfall potential seemingly reasonable given right entrance region upper jet support and anomolous Gulf moisture. Focus may shift southward over Florida late week/next weekend. Monsoonal moisture with some connection to emerging eastern Pacific (EP95) and Bay of Campeche (T.D. TWO) tropical features is likely to increase coverage and potential of rain amounts into mid- later this week into the Southwest and southern Rockies/High Plains on the western periphery of a warming central U.S. upper ridge. ERO Marginal Risk areas are planned there for Day 4/Wednesday and Day 5/Thursday so far. Areas like the Sacramento Mountains, where the steep terrain and burn scars cause the area to be particularly sensitive to rain and most vulnerable to potential flash flooding, especially with wet antecedent conditions there. Elsewhere, periodic afternoon and nocturnal strong to severe storms offer a varied guidance signal to monitor for heavy rain/runoff potential to emerge more clearly out from the northern Rockies to focus locally over the northern Plains and Upper Midwest midweek into next weekend as upper trough/impulse energies work on moisture/instability pooling near wavy passing and draping fronts. Weekend activity with upper system/frontal progressions is slated to work into the central Plains and across the Midwest/Great Lakes. 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 $$