Day 2 Outlook >
WPC Day 1 Excessive Rainfall Outlook
Risk of 1 to 6 hour rainfall exceeding flash flood guidance at a point
Updated: 0825 UTC Fri Jul 30, 2021
Valid: 12 UTC Jul 30, 2021 - 12 UTC Jul 31, 2021
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
440 AM EDT Fri Jul 30 2021
Valid 12Z Fri Jul 30 2021 - 12Z Sat Jul 31 2021
...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST, GREAT BASIN AND CENTRAL ROCKIES...
...Southwest U.S. to the Northern and Central Rockies...
The threat for heavy to excessive rainfall will continue on Friday
and Friday night as the northwestward propagation of mid- to
upper-level energy across the Southwest U.S. supports another
round of convection from late morning or early afternoon into the
late evening hours. Precipitable water values in the 1.5 to 175
inch range are 2 to 3 standardized anomalies greater than
climatology across the area for this time of the year. The amount
of moisture combined with the dynamics will again result in
convection capable of supporting rainfall rates of 0.5 inch or
more anywhere from the eastern Arizona and southern Nevada into
portions of the Sierra Nevada range, the Great Basin/Intermountain
Region and in proximity to the Uinta range. The threat of flash
flooding will locally be enhanced by slow cell motion due to the
slow/weak steering flow.
Out over the other side of the Rockies, maintained the Slight Risk
area extending from Colorado into southern/southeast Wyoming as
deep-layer southeast flow will continue to tap deep moisture and
draw it upslope and to higher elevations. The anomalous moisture
and slow moving shortwave energy aloft should result in late day
and evening storms capable of producing downpours...with the
foothills and any impacted burn scar areas most vulnerable.
...Central Plains to the Mid Mississippi Valley..
Troughing across the region coupled with modest instability will
increase chances of heavy rounds of precipitation with convection
and training storms, especially Friday evening and during the
overnight hours as precipitable water values sit in the 1.75 to
2.00 inch range and MU CAPE values are still forecast to be near
2000 J/kg. The threat of excessive rainfall is mitigated a bit by
higher Flash Flood Guidance values. On the other hand, the
possibility of training or repeat convection is the main concern
with some of these storms expected to drop heavier amounts.
Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt