Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1155 AM EDT Sat Jul 13 2019 Valid 12Z Tue Jul 16 2019 - 12Z Sat Jul 20 2019 ...Tropical Storm Barry expected to weaken as it tracks up the Mississippi Valley/Lower Ohio Valley but continue to produce areas of heavy rainfall... 15Z Update: By the beginning of the forecast period on Tuesday, the remnants of Barry will be tracking northeast across Missouri and then the Ohio Valley, and then becomes absorbed by the westerlies aloft. A quasi-zonal flow pattern develops across the northern half of the U.S. by the end of the week, and this is when the models begin indicating noteworthy differences. The 00Z CMC becomes flatter with the remnant trough from Barry compared to the other guidance, and the 00Z UKMET is stronger than the model consensus regarding the central U.S. upper ridge, likely having an affect on surface temperatures. By Friday, the past two runs of the GFS are more amplified with a strong upper trough near the Canadian border, owing to differences in the handling of the large upper low that will be over the Gulf of Alaska during the short range period. Teleconnections with the negative height anomaly over British Columbia by next Saturday support a broad trough over the Great Lakes region, but not to the degree indicated by the recent GFS runs. The ECMWF appeared to have better support from the ensemble means, and thus was weighted more heavily in the medium range forecast and maintains previous WPC forecast continuity. The overnight forecast discussion is appended below for reference. D. Hamrick ------------------------------------------------------------ ...Overview and Guidance/Predictability Assessment... ...Weather Highlights/Threats... The forecast track for Tropical Storm Barry, per the National Hurricane Center, has it making landfall in south-central Louisiana on Saturday. Once inland, Barry will weaken as it goes north across Arkansas and then curves eastward through Missouri and Illinois as a remnant low by the beginning of the extended period (Tuesday). Heavy rain associated with this system will spread from central Arkansas to southern Indiana by Wednesday morning. There may be a severe threat over some areas to the right of the surface low track, but with low predictability in details this far out in time. Later in the week the remnants of Barry could interact with a wavy northern stream front and produce enhanced rainfall over the Northeast, but this depends on the strength of Barry in the short term and timing in the northern stream in several days. Please consult the latest NHC products for updated information on Barry. Much of the Southwest, southern/central Rockies, and High Plains will remain mostly dry as mid/upper level ridging remains in place. Southern Canada and the northern states will have organized convection bringing up to 2 inches of rainfall through Thursday, and across the Northeast Thursday and Friday, within the low amplitude flow. Periods of excessive rainfall may be possible across the northern Plains and Upper Mississippi Valley/Upper Great Lakes as a frontal boundary stalls over the region. The pattern across the West will transition as a low approaches the Pacific Northwest toward the end of the week. This would bring a period of steadier rainfall with additional terrain enhancement between the Pacific Northwest coast and the Cascades. Consult the latest WPC Hazards chart for more information on these potential threats. A few locations will have above normal temperatures that may tie or set new daily high minimum records. Above normal temperatures with some pockets of plus 10F or greater anomalies will spread from the northern Plains to the Northeast U.S. through Wednesday, with some warmth lingering over the Northeast into Friday. The increased cloudiness from the remnants of Tropical Storm Barry will likely keep the afternoon temperatures slightly cooler over portions of the Lower Mississippi Valley (perhaps near record low max values). Once Barry passes, portions of the central Plains and Middle Mississippi Valley will reach 10 to 15F above average by the end of the forecast period. Heat indices will be around 105 to 115F, which will likely require the future issuance of heat advisories. The Pacific Northwest will trend cooler by Friday with highs 5 to 10F cooler than average. This forecast was mostly derived from the 00Z ECWMF, with lighter weighting of the GFS, CMC and ECWMF mean. Campbell Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml