Quantitative Precipitation Forecast
Issued by NWS
Issued by NWS
716 FOUS30 KWBC 051924 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 224 PM EST Wed Feb 5 2025 Day 1 Valid 16Z Wed Feb 05 2025 - 12Z Thu Feb 06 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE OHIO VALLEY... ...16z Update... No change to prior reasoning and outlook, other than a minor adjustment northward to account for the 12z HRRR indicating a 1.5-2.0" stripe of QPF from southwest OH into northern WV and far southwest PA. Most CAMs are lighter overall with QPF, but a brief period of embedded training convection is possible, mainly late in the period (after 06z). Churchill ...Previous Discussion... No significant changes were made to the Marginal Risk area across the Ohio Valley. Warm advection showers are expected to break out over Kentucky, that with the infusion of upper level support and increasing instability, will allow embedded convection to develop this afternoon and evening. As the moisture plume turns the front into a warm front over the Tennessee Valley this evening, expect the addition of upslope into West Virginia to resulting locally heavier rainfall in the favored areas. Any thunderstorms will be capable of rainfall rates to 1.5 inches per hour. Soils in this area remain nearly saturated and rivers are running high from the rainfall event a few days ago. Thus, the additional rainfall forecast today and tonight, even though amounts will likely be lesser, may still cause isolated flash flooding. Wegman Day 2 Valid 12Z Thu Feb 06 2025 - 12Z Fri Feb 07 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE OHIO VALLEY AND CALIFORNIA... ...OH Valley... Another round of locally heavy rain is expected Thursday across portions of KY, TN, WV and far western VA along and ahead of an approaching cold front. Showers and embedded thunderstorms will likely be ongoing at 12z and may periodically continue through the day/evening near the only slowly southward shifting front. While nothing significant, CAPE upwards of 500-1000 j/kg still seems likely along this corridor, which should be enough to support locally heavy rainfall rates. While soil conditions and streamflows are returning closer to average after the flooding several days ago, some of this region is still likely more sensitive than normal to additional heavy rainfall. The latest WPC QPF is generally 0.75"-1", with two day totals locally exceeding 1.5". Given the instability forecast, it seems reasonable that we will see isolated totals over 2". While the 00z GEM Reg and FV3LAM are probably too high with totals, they both do suggest that if convective coverage can increase enough then some 2-3" amounts can not be ruled out. Overall expect this rainfall to pose a localized flood risk. ...California... After a one day break another system is forecast to move into CA on Thursday. This is expected to be a pretty dynamic system, with a strong mid level shortwave and upper level jet. These dynamics should support a short duration period of enhanced rainfall rates...although the quick forward motion of the system will limit overall rainfall magnitudes. Recent model runs are showing some uptick in rainfall amounts with this system over northern CA, but still generally looking at totals in the 1-2" range. Given the saturated conditions and brief potential for higher rates between 00z and 06z, this may be approaching Slight risk levels. Although will hold off for now as the short duration of these higher rates may limit the magnitude/coverage of impacts just enough to keep the risk at Marginal. The Marginal risk extends southward into Santa Barbara, Ventura and Los Angeles counties as well. Less rainfall forecast here, but there is an uptick in IVT into the terrain Thursday night, and PWs do increase towards and just over 1". Larger scale forcing generally shears off to the north, but the combination of increasing PWs, IVT and upslope flow should be enough to result in a period of moderate to locally heavy rain. We are beginning to see a slow uptick in rainfall amounts in the models, and so localized flood impacts are certainly a possibility. Although given the overall weakening of the system and very little to no instability, rainfall rates will probably only be high enough to result in a minor flood risk over just the most sensitive urban areas or recent burn scar locations. Chenard 2100 UTC Update No changes made to the previous marginal risk areas across CA or from the Upper TN Valley into the Central Appalachians. Oravec Day 3 Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Oravec 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