Subj : HVYRAIN: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Nov 07 2022 07:39:55 FOUS30 KWBC 070739 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 239 AM EST Mon Nov 07 2022 Day 1 Valid 01Z Mon Nov 07 2022 - 12Z Mon Nov 07 2022 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS THE TRANSVERSE RANGES OF SOUTHERN CALIFORNIA... ....Central and Southern California... The deepening trough and vertically stacked low will continue propagating south down the coast from Washington State to just west of northern California on Monday. This will cause the longwave trough to amplify in a positively-tilted direction. The result will effectively be a shifting on the main onshore moisture flow southward down the California coast into central and southern California. The jet streak rounding the base of the trough will provide the best forcing as a lobe of vorticity remains well offshore. The deeper moisture plume will continue to slowly drop in latitude and focus toward the Transverse Ranges into the L.A. Basin. Integrated Vapor Transport values will be weak to modest a best with 300-400 kg/m/s values initially directed a bit south of due west, but with the deepening trof further north it is expected to back and maintain a longer duration through the afternoon into the morning overnight period on the 8th. Rates are not expected to exceed .5"/hr until this redirection/secondary surge occurs later in the overnight period (after 00z), but still remain low in the 10-20% range for Southern California. Still the shear duration of .25"/hr rates in the Transverse Ranges will support localized of 1.5-2.5", worthy enough to maintain the Marginal Risk for the region. Further north, the timing of the sharpening/approaching embedded shortwave off the NW CA coast, will support strengthening southwesterly confluent flow after 08.06z with 850mb winds increasing to 40-50kts by 12z and bring nose of .7-.8" TPW values to the Santa Cruz Mountains. IVT values increase to 400-500 kg/m/s values and Hi-Res CAMs ramp up to 1-1.75" totals between 06-12z. While this is on the edge of a large enough area for a risk area, it does dove-tail nicely with the thinking within the Day 2 ERO period and allows for some remaining uncertainty for timing given the slight trend faster over the last few cycles.=20=20=20=20 ....Arkansas through Northeast Texas... There remains a non-zero chance for thunderstorms capable of intense rainfall rates extending from a weak shortwave/low level inflection across the central AR/MS Mississippi Valley, slowly expanding westward into Northeast Texas from the start of the forecast period through the morning into early afternoon. This is response to weak FGEN forcing/convergence along the morning return warm front from the higher theta-E air streaming off the western Gulf of Mexico. Moisture flux convergence and enhanced deeper layer moisture will be consolidated near the inflection where PWat values of 1.75-1.9" are well above climatological averages close to 95th to 97th percentiles. Modest instability of 500-750 J/kg of MUCAPE will be available for these likely slower moving cells (given proximity to the weak low to mid-level wave) and as such Hi-Res CAMs support localized rates of 1.5"-1.75"/hr. Slow westward propagation as increasingly unstable air may allow for additional scattered development upstream into TX through mid/late morning with better instability given 1000-2000 J/kg of CAPE maybe available, yet this is also a factor of slightly enhanced capping relative to further east and less focused moisture convergence to support even more isolated nature to these stronger thunderstorms. HREF probabilities are not suggestive of rates over 2", though 2"/3hr totals do maximize around 12-15z in SE AR with 50% probabilities. The fact there is already ongoing convection that may have exhausted some localized pockets of enhanced instability may suggest Hi-Res CAMs supporting the HREF may be a bit too slow. While FFG values for the region have rebounded, they may have too quickly given NASA SPoRT LIS relative soil saturation values are in the 40-50s ranges across much of E AR, N LA and parts of NE TX and best heavy rainfall signal lies on the fringes of these areas. As such, a small Marginal Risk was considered across southeast AR, but probabilities are likely too low extending back toward the west into TX. Gallina Day 2 The Day 2 outlook will be updated by 0830Z. Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-kHm_VOKLmZUmtTfURmTPdqe3_5NV8zEEXR3XdK0baie= QkEsFdtMfRCfC7Y_rmuvLUJb5_djEVjBQ8fcTjwZkeEdvNg$=20=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-kHm_VOKLmZUmtTfURmTPdqe3_5NV8zEEXR3XdK0baie= QkEsFdtMfRCfC7Y_rmuvLUJb5_djEVjBQ8fcTjwZR4L_lYw$=20=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-kHm_VOKLmZUmtTfURmTPdqe3_5NV8zEEXR3XdK0baie= QkEsFdtMfRCfC7Y_rmuvLUJb5_djEVjBQ8fcTjwZ6dUc6LQ$=20=20 $$ =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .