Preliminary Forecasts
Issued by NWS
Issued by NWS
527 FXUS02 KWNH 090702 PREEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Thu May 9 2024 Valid 12Z Sun May 12 2024 - 12Z Thu May 16 2024 ...Excessive Rainfall/Flooding Threat for the Southern Plains, Gulf Coast and Southeast... ...Guidance/Predictability Assessment... The WPC medium range product suite was primarily derived from a composite blend of reaosnably well clustered guidance from the 18 UTC GFS and 12 UTC ECMWF/UKMET/Canadian for Sunday and Monday. This solution is broadly supported by ensembles and is generally compatible with the National Blend of Models, newer 00 UTC cycle guidance and WPC continuity in a pattern with slightly above normal predictabilty despite lingering and important local differences offset by the composite. Forecast spread growth prompted a transition day Tuesday to mostly still compatible 18 UTC GEFS and 12 UTC ECMWF ensemble mean guidance into next Wednesday and Thursday as predictabilty lowers through normal to lower values. ...Weather/Hazards Highlights... A general split flow pattern will persist over the lower 48 states into next week. This pattern will be highlighted by an amplified southern stream upper trough slated to eject slowly but steadily east- northeastward from the Southwest Sunday and through the Mid- South/South to offshore the Mid-Atlantic/East Coast next Thursday. This system and associated lead wavy front will increasingly tap and feed inland a return of deep Gulf moisture and instability under favorable upper trough and right entrance region upper jet support to fuel a potentially significant heavy rainfall and runoff/flooding period. The WPC Day 4/Sunday Excessive Rainfall Outlook (ERO) depicts a Marginal Risk area spread southeastward from southern Oklahoma and Texas to the lower Mississippi Valley. Within this, a Slight Risk area remains in place for Southeast Texas given moist soil/streamflow sensitivities from heavy recent rainfall. The Day 5 ERO introduces elongated Marginal and embedded Slight Risk areas stretching from southeast Texas through the central Gulf Coast and vicinity. Heavy rain and a threat of runoff issues is also expected to spread across the Southeast through next midweek to monitor. Meanwhile, several amplified upper troughs and surface systems are set to work over the northern tier of the nation from the Northwest and north- central U.S. through the Northeast and focus mainly modest moisture and precipitation. 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 $$