Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
401 AM EDT Fri Aug 12 2022
Valid 12Z Fri Aug 12 2022 - 12Z Sat Aug 13 2022
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHWEST, EASTERN GREAT BASIN, AND NORTHERN ROCKIES...
...Southwest, eastern Great Basin, and northern Rockies...
Little change is expected in the upper pattern, with a strong high
remaining centered over the central High Plains as a upper
low/trough lingers along the Northwest coast. Deep southerly flow
between the two features will support an axis of anomalous
moisture extending from portions of the Southwest through the
eastern Great Basin, into parts of the northern Rockies, with PWs
2-4 standard deviations above normal across the region. This will
continue to fuel daily shower and thunderstorm development and the
potential for heavy amounts. Shortwave energy lifting north along
the western periphery of the ridge is expected to interact with
this moisture, supporting areas of organized convection and
heavier precipitation. This includes areas that have already seen
repeating days of active monsoon convection. Overall, the Slight
and Marginal Risk areas remain largely unchanged from the previous
Day 2 Outlook, with only relatively minor adjustments made to
their footprints based on trends shown by the overnight guidance.
...Gulf Coast to the eastern Carolinas...
Deep moisture ahead of cold front dropping across the Southeast
will continue to support diurnal convection and the potential for
locally heavy amounts today. Across the eastern Carolinas, an
amplifying upper trough and right-entrance region upper jet
forcing is expected to raise the threat for organized
precipitation and heavy amounts. While this area has been quite
dry recently, overnight heavy rains across portions of the area,
along with the potential for additional heavy amounts may warrant
an upgrade to Slight Risk later today. Along the Gulf Coast, deep
moisture (PWs 1-3 standard deviations above normal) and weak
steering flow will continue to support slow-moving storms, capable
of producing heavy rains. Given the wet antecedent soil
conditions that exist from southeastern Louisiana to the Florida
Panhandle, flash flooding will remain a concern across this area.
Shortwave energy moving off of the top of the ridge is expected to
initiate elevated showers and storms that are forecast to spread
southeast across portions of the region. An initial round
currently developing over eastern North Dakota is forecast to move
across central into southeastern Minnesota later this morning,
with some potential for training and locally heavy amounts. A
second round is forecast to develop tonight into Saturday morning,
impacting areas farther to the east across Wisconsin, with the
models once again showing some signal for training and the threat
for locally heavy amounts.
The Day 2 outlook will be updated by 0830Z.
The Day 3 outlook will be updated by 0830Z.
Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt