Extended Forecast Discussion NWS Weather Prediction Center College Park MD 314 PM EDT Tue May 31 2022 Valid 12Z Fri Jun 03 2022 - 12Z Tue Jun 07 2022 ...Heavy rain threat increasing over Florida due to tropical moisture inflow and a possibly forming tropical system... ...Overview... While the overall pattern across much of the lower 48 will remain fairly stagnant late week into early next week, with West Coast troughing and a south-central Canada upper low sending some low amplitude troughing across the central to eastern U.S. But the main notable feature to watch during the medium range period will be the possibility for a tropical cyclone to develop over the northwestern Caribbean Sea/southeastern Gulf of Mexico partially from energy from what is currently Tropical Storm Agatha over Mexico. At this time, a low track northeastward near or over the Florida Peninsula is possible, but with fairly low confidence in the track, timing, and strength of a tropical system. Regardless, heavy rain is possible late week into the weekend with substantial moisture streaming ahead of this potential system and then near its possible eventual track. ...Model Guidance Evaluation/Preferences... The latest model guidance appears to be in modest agreement as to the general synoptic pattern through the medium range period with some notable differences toward early next week. Deterministic models seem to suggest a more progressive system in the Gulf/Caribbean this weekend with the 00z CMC being an even faster outlier with the axis of precipitation. A general deterministic model blend of the 00z EC/UK/CMC and 06z GFS was applied on Friday. The 00z UK was replaced by the 00z ECE on Saturday due to better handling of the low over the Florida peninsula. The 00z CMCE was introduced on Sunday followed by a more probabilistic blend through Tuesday. The 00z EC weighting was reduced on Sunday and Monday then removed on day 7 due to the fact that it was the only bit of guidance with a closed low moving through the western Atlantic. Ensemble guidance does a good job of capturing the trough associated with the potential tropical system through next Tuesday. ...Sensible Weather/Threat Highlights... Tropical Storm Agatha has currently moved into Mexico and will weaken quickly over unfavorable terrain there. But its associated deep tropical moisture will stream into southern Florida Friday, increasing the likelihood of rain and thunderstorms becoming more frequent and widespread, first ahead of the remnant disturbance and then with the potential for a tropical low to develop (possibly partially from Agatha's remnants) and track over or near the state. Moisture aloft from the far eastern Pacific and lower level moisture from the Caribbean should lead to heavy rainfall, even if the system's timing is in question. Even in the cyclone's wake, its convergent tail appears to be stuck in the vicinity of South Florida and the Keys, keeping the threat of moderate to heavy rainfall in play into early next week. Slight Risks are in place in WPC's experimental Days 4 and 5 Excessive Rainfall Outlook. Elsewhere, rain chances are expected to increase in the Northwest late week into the weekend given the trough axis near the West Coast and onshore flow. However, the Southwest should remain dry and hot, with Death Valley expected to meet or exceed 110F high temperatures this weekend into early next week. Farther east, fronts are expected to spark rounds of showers and thunderstorms across the central and eastern U.S., with the Carolinas an area of focus on Friday and parts of the Plains and Mississippi Valley seeing convection Friday into the weekend and early next week as fronts meander there. There are increasing probabilities of an axis of heavy rainfall developing over parts of the Central Plains and Middle/Upper Mississippi Valley on Sunday. A relatively flat pattern aloft compared to the more amplified short range period should produce lesser temperature anomalies late this week into early next week. Cooler than average spots will be across the central/southern Plains Friday with rain cooled air, but should switch to above normal in Texas by 10-15F by early next week. Periodic troughing in the northern tier should lead to slightly below average temperatures by around 10F. The western U.S. could be warmer than normal by 5-10F late in the workweek but cooler temperatures are forecast by the weekend under the troughing influence and as a cold front moves through the area. Tate/Kebede 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, experimental excessive rainfall outlook, winter weather outlook probabilities and heat indices are at: 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