Quantitative Precipitation Forecast
Issued by NWS
Issued by NWS
079 FOUS30 KWBC 011615 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1215 PM EDT Mon Jul 1 2024 Day 1 Valid 16Z Mon Jul 01 2024 - 12Z Tue Jul 02 2024 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE LOW COUNTRY OF SOUTH CAROLINA AND THE NORTH GEORGIA COAST... 16z Update: The Moderate risk from near Savannah, GA to Charleston, SC still looks in good shape. Convection should develop along the coast early this afternoon, and be capable of intense rainfall rates. Some question as to how quickly convection propagates offshore, with a quicker propagation and thus lower flash flood risk a possibility. However HREF EAS and neighborhood probabilities remain high, with localized amounts exceeding 5" still probable. These amounts and expected rainfall rates continue so support a locally considerable urban flash flood threat today. The front stalls out tonight near the coast, and it is possible we see redevelopment of convection overnight. Heavy rainfall will likely focus over portions of eastern NE into western IA after 00z this evening. While convection looks progressive overall, there may be two areas of opportunity for some training. One near the warm front and another on the southwest flank of the convection where activity may backbuild into the line. HREF data supports a widespread 1-2" of rain, with localized swaths of 3-5" probable. This is approaching MDT risk levels given wet antecedent conditions across this region. For now opted to stick with a higher end Slight risk. The overall progressiveness of the system, uncertainty on the location and extent of training convection, and some southward displacement from areas hardest hit by the June flooding...keep this below a MDT risk for now. But will continue to monitor and either way expect to see isolated to scattered flash flooding tonight over this region. Chenard ...Previous Discussion... ...Southeast US... Anomalous moisture with PWATs exceeding 2.25" along the Southeast Coast to N Florida (around 2.5 sigma above normal) is in place ahead of a slow moving cold front. Ongoing heavy thunderstorms over eastern NC and southeast VA will continue working south ahead of the cold front through today with activity lingering near the front which should stall along the GA/SC coasts this evening. Continued confidence for heavy rain with rates exceeding 3" in 3hrs (per the 00Z HREF) along the SC coast this afternoon warrants maintenance of the Moderate Risk along the coast that includes Charleston, SC and Savannah, GA. Pre-frontal thunderstorms farther south to the FL border warrants maintenance of the Slight Risk over southeast GA. ...Northern Plains to Upper Midwest... A trough over the northern Rockies early this morning shifts east over the northern Plains through tonight. Gulf-sourced moisture surging up the Plains and over a developing warm front that shifts east over the central Plains today/tonight. Increased confidence in two main swaths of rainfall, from eastern Neb through western WI including much of IA and southern MN warrants a high end Slight Risk considering ongoing main-stem flooding from heavy rains a week ago. The second areas is ahead of the upper trough in a stripe from north-central SD through northern MN. The Slight Risk here was expanded into northern SD given the 00Z consensus for 1.5" or so over areas with 3hr FFG of 2" or less. In between these areas, a corridor of less rainfall depicted in the 00Z consensus QPF warrants some removal of Slight Risk areas in north-Central MN. ...Southwest US... Monsoonal moisture lingers over the Four Corners states today to west of a ridge axis over the southern Plains and below an upper trough over the Intermountain West. PW anomalies of 2 to 3 sigma above normal will allow for diurnal development, primarily along terrain. Expanded the Marginal Risk over the central NM terrain given the isolated to widely scattered thunderstorm potential there that includes particularly sensitive areas in the Sacramento Mtns per the 00Z CAM consensus. Jackson Day 2 Valid 12Z Wed Jul 03 2024 - 12Z Thu Jul 04 2024 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE UPPER MIDWEST TO CENTRAL GREAT PLAINS... ...09Z Issuance... ...Upper Midwest through Central Great Plains... A reinforcing shortwave trough rounding the upper trough that will be over the Dakotas Tuesday morning crosses the Neb/SD border through the day. Right entrance jet streak dynamics warrants maintenance of ongoing activity over the central Plains, IA, and central WI that then drifts south/southeast through the day that spreads No big changes were made with this update. Concerns remain from the KC metro and northeast over an expansive area to western IL and up through much of WI as gulf-sourced moisture (PWs 2 to 2.5 sigma above normal) with deep layer SW flow allowing training thunderstorm concerns. A Moderate Risk may be needed somewhere between KC and Madison WI, but for now consider this a higher end Slight Risk. ...Southeast... A Marginal Risk is maintained over the Florida Panhandle and southern GA. This will be a continuation of the convection from Monday night ahead of a slow moving cold front. Rainfall still expected to be lower than on Monday, but the plentiful Gulf moisture allows for the potential for very high rainfall rates. ...Southwest... Again maintained a Marginal over eastern AZ/western NM with a suppressed Monsoonal flow day as troughing to the north shunts the ridge axis farther east to the lower Miss Valley. Elevated moisture is limited to the southern portions of those states and remnant stratus from Monday night activity may further suppress Tuesday activity. Jackson Day 3 Valid 12Z Wed Jul 03 2024 - 12Z Thu Jul 04 2024 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE CENTRAL PLAINS AND MID-MISSISSIPPI VALLEY... ...Midwest to Great Plains... A cold front from a passing trough over the northern tier of states stalls over KS/MO by Wednesday morning, providing continued focus for heavy thunderstorm development from eastern KS through southern IL where a Slight Risk is maintained. The frontal zone extends east over the rest of the Midwest to the eastern Great Lakes where a Marginal Risk is maintained with some areas of the Northeast trimmed with the 00Z QPF consensus being farther west. Over the northern Plains, the next trough axis enters the northern High Plains Wednesday night with activity over the Dakotas warranting a Marginal Risk. ...Southwest... A trough axis from the next reinforcing wave allows anomalous moisture over AZ/NM to spread northeast to the southern High Plains on Wednesday which warrants maintenance of the Marginal Risk with some trimming based on the 00Z consensus. Jackson Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt