Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jun 07 2023 08:14:59 FOUS30 KWBC 070814 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 413 AM EDT Wed Jun 07 2023 Day 1 Valid 12Z Wed Jun 07 2023 - 12Z Thu Jun 08 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE SOUTHERN HIGH PLAINS NORTHWEST INTO THE LEE OF THE CENTRAL ROCKIES AND ACROSS NORTHWEST WYOMING INTO SOUTH CENTRAL MONTANA... The blocking upper pattern across much of the nation will show only some small changes for the upcoming day 1 period, remaining characterized by a closed low moving slowly from southern CA into the Great Basin, an upper high over the Northern Plains and an upper vortex over New England. In this pattern there will continue to be an axis of above average PW values stretching from the Southern High Plains, north northwest through the Central to Northern Rockies and Northern High Plains. Models continue to show enhanced areas of upper difluence to the east and northeast of the CA/Great Basin Low and to the west and southwest of the Northern Plains upper high. This will again support another day of widespread scattered convection with locally heavy rainfall amounts likely. The latest HREF neighborhood probabilities are depicting this heavy rain potential with large area of high 1"+ probabilities from northwest TX/western OK Panhandle/northeast NM into central CO. The slight risk was drawn to fit this high 1"+ probabilities and reflected only minor changes to continuity.=20=20 Probabilities for 2"+ amounts decrease significantly in this axis and become more isolated. This fits in well with latest model qpf consensus and MRMS multi sensor precip estimates over the past 24 hours across these regions. Areas in the slight risk region have seen much above average precip over the past few weeks, resulting in saturated soils and elevated stream flow, with additional heavy rains producing additional instances of flash flooding. The previous small slight risk area across south central Montana was expanded southward into northwestern WY. This was to cover where low ffg values are overlapping with the latest high 1"+ HREF neighborhood probabilities. ....Northern Sierra/Northern California into portions of the Great Basin... The strong closed low centered over south central CA will begin to creep northward day 1 and slowly fill. However, overall favorable conditions for widespread scattered convection will continue to its north through the Sierra, northern California and into the Great Basin. PW values will again remain anomalously high to the north of this closed, generally in the .75-1"+ range, 1.5 to 2+ standard deviations above the mean. This, along with with upper difluence maxima to the north of the closed low and in this high PW axis will support additional scattered convection and isolated heavy rainfall potential of 1"+. The only change from the previous outlook across this area was to extend the marginal risk area farther to the south into the southern Sierra to cover model qpf spread and high HREF 1"+ probabilities.=20 ....South Florida... South Florida will continue to be to the east of a weak upper trof centered across the Gulf of Mexico on the south southwest edge of the expanding broader upper trof over the Northeast.=20 Strengthening west southwest low level flow east of this trof will raise PW values to 1.75-2", slightly above seasonal norms. Favorable right entrance region jet dynamics from a sub-tropical jet extending from the southeast Gulf into the Bahamas will support fairly widespread convection Wednesday afternoon across South Florida. Simulated hi res radars do show potential for training of cells in a general west to east direction. If this training occurs over more urbanized areas, especially along the southeast FL coast, isolated flash flooding is possible. HREF probabilities reflect this with high probabilities for 1 and 2"+ amounts and high probabilities in spots for hourly amounts greater than an inch. The previous outlook was trimmed on the northeast end to better match the latest model qpf maxima. Oravec Day 2 Valid 12Z Thu Jun 08 2023 - 12Z Fri Jun 09 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE NORTHERN ROCKIES INTO THE NORTHERN HIGH PLAINS... ....Northern Rockies into portions of the Northern High Plains... The slow moving closed low pushing out of central CA into southwest NV at the end of day 1 will accelerate to the north across the Great Basin and into the Northern Rockies. While the closed low does weaken, strong upper difluence continues to its northeast. Model consensus is for the heaviest precip potential to be shifting into the Northern Rockies/Northern High Plains day 2 where this strong upper difluence will coincide with strengthening low level easterly flow. This strengthening low level moisture flux will raise PW values to 2.5 to 3+ standard deviations above the mean, supporting potential for widespread heavy precipitation. The previous slight risk area was expanded slightly northward toward northern ID as per model qpf consensus and southward across the lower ffg values regions of northwest WY and corresponds with model consensus heavy rain potential region. ....Sierra/Northern CA/Great Basin into the Central Rockies... No changes made to the previous marginal risk area stretching across the Sierra, northern CA, the Great Basin and into Central Rockies. Another day of widespread scattered convection likely to the east of the Great Basin/Northern Rockies trof and west of the Northern Plains upper High. PW values will remain anomalous across much of this region with continued pockets of upper difluence enhancing uvvs and supporting additional isolated 1"+ rainfall totals. ....South FL... There are not anticipated any significant changes to the overall pattern from the Gulf of Mexico across South Florida from the day 1 to day 2 period. PW values will remain near seasonal norms 1.75-2". Continued favorable right entrance region jet dynamics from the sub-tropical jet stretching from the southeast Gulf into the Bahamas will continue to accentuate lift across South Florida. The continued moist low level west southwest flow will support potential for training of cells and isolated runoff issues from 1-2" rainfall amounts in a brief time, especially if the training occurs over urbanized regions of southeast FL. Expanded the previous marginal risk area westward from the southeast urban regions to be consistent with out day 1 outlook, although believe the greatest flash flood risk will be urbanized again day 2. Oravec 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!5NI5bRRtTXX0v2Gple3tXut6xxNE-AgZpTdtXVirKh_5= k_WSoOqGNPnJ0rbGffZa73db_0UxP2CAuUQv_WzR5s_F-P8$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5NI5bRRtTXX0v2Gple3tXut6xxNE-AgZpTdtXVirKh_5= k_WSoOqGNPnJ0rbGffZa73db_0UxP2CAuUQv_WzRFnnxFtQ$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5NI5bRRtTXX0v2Gple3tXut6xxNE-AgZpTdtXVirKh_5= k_WSoOqGNPnJ0rbGffZa73db_0UxP2CAuUQv_WzRwy1rJi8$=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) .