Skip Navigation Links 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center



Follow the Weather Prediction Center on Facebook Follow the Weather Prediction Center on Twitter
NCEP Quarterly Newsletter
WPC Home
Analyses and Forecasts
   National High & Low
   WPC Discussions
   Surface Analysis
   Days ½-2½ CONUS
   Days 3-7 CONUS
   Days 4-8 Alaska
   Flood Outlook
   Winter Weather
   Storm Summaries
   Heat Index
   Tropical Products
   Daily Weather Map
   GIS Products
Current Watches/

Satellite and Radar Imagery
  GOES-East Satellite
  GOES-West Satellite
  National Radar
Product Archive
WPC Verification
   Medium Range
   Model Diagnostics
   Event Reviews
   Winter Weather
International Desks
Development and Training
WPC Overview
   About the WPC
   WPC History
   Other Sites
Meteorological Calculators
Contact Us
   About Our Site is the U.S. Government's official web portal to all federal, state, and local government web resources and services.
Excessive Rainfall Discussion
(Caution: Version displayed is not the latest version. - Issued 2030Z Dec 08, 2022)
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   11   12   13   14   15   16   17   18   19   20   
Abbreviations and acronyms used in this product
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
330 PM EST Thu Dec 08 2022

Day 1
Valid 16Z Thu Dec 08 2022 - 12Z Fri Dec 09 2022

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.


Day 2
Valid 12Z Fri Dec 09 2022 - 12Z Sat Dec 10 2022


...2030z Update...

Little change to the inherited Marginal Risk area, with some minor
expansion inland to reflect relatively high snow levels (rising to
5000-6000 feet) during the primary period of precipitation (00-12z
Saturday). Models remain in good agreement concerning this period
of interest, with the 12z HRRR indicating localized hourly rates
of 0.50-0.75"/hr. The occasionally repeating nature of these rates
may result in localized totals over 6-12 hours as high as 3-4
inches, which may result in isolated instances of flash flooding
(with particular vulnerability over burn scars and low-lying areas
with poor drainage).


...Previous Discussion...

There is fairly good agreement in the latest model guidance with
the amplification of the upper trof off the Pac NW coast late
Friday afternoon into the early hours of Saturday.  This will
strengthen the low level southwesterly flow into coastal sections
from northwestern California into Oregon, with 850-700 mb moisture
flux anomalies reaching 2 to 2.5+ standard deviations above the
mean from far southwest Oregon into northwestern California.  This
will support heavy precipitation during the 0000-1200 UTC Saturday
time period across the marginal risk area, with isolated hourly
rates of .50"+ possible.  The axis of anomalous onshore flow will,
however, be fairly progressive to the southeast.  This and only
slightly above average precip values over the  past week for
northwest California will keep the risk level at marginal at best.
 There were no significant changes from the previous outlook for
this period.


Day 3

The Day 3 outlook will be updated by 2030Z.

Day 1 threat area:
Day 2 threat area:
Day 3 threat area: