Skip Navigation Links weather.gov 
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
   QPF
   PQPF
   Flood Outlook
   Winter Weather
   Storm Summaries
   Heat Index
   Tropical Products
   Daily Weather Map
   GIS Products
Current Watches/
Warnings

Satellite and Radar Imagery
  GOES-East Satellite
  GOES-West Satellite
  National Radar
Product Archive
WPC Verification
   QPF
   Medium Range
   Model Diagnostics
   Event Reviews
   Winter Weather
International Desks
Development and Training
   Development
WPC Overview
   About the WPC
   Staff
   WPC History
   Other Sites
   FAQs
Meteorological Calculators
Contact Us
   About Our Site
 
USA.gov 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 2006Z Mar 28, 2024)
 
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
406 PM EDT Thu Mar 28 2024

Day 1
Valid 16Z Thu Mar 28 2024 - 12Z Fri Mar 29 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID ATLANTIC AND NORTHEAST U.S....

16Z Excessive Rainfall Discussion...

...New England...
Introduced a Slight Risk of excessive rainfall over portions of
New England through tonight. Satellite imagery showed another
region of cooling cloud tops upstream from the area as of late this
morning...so any respite from rainfall overnight and early this
morning should be short-lived. The expectation is that neither
rainfall rates nor rainfall amounts will be blockbuster in
magnitude and that most places would be handled under most
circumstances (as suggested by the 12Z HREF neighborhood
probabilities showing less than 5 percent risk of 1-/3-/6-hour QPF
exceeding respective Flash Flood Guidance). But discussions with
the National Water Center and offices in the area indicate that the
amount of water added by melting and compaction of the snowpack
may be enough for more than isolated problems with runoff in areas
of poor drainage. 12Z HREF guidance shows better coverage of
rainfall along and near the coastal regions of New England with
nearly 1.5 inches of additional rainfall.

...Eastern Carolinas...
Maintained the Slight Risk for the time being as rain continues to
call over eastern North Carolina as higher reflectivity continue
to move from south to north across the region. The entire area of
rain should be shifting off-shore during the afternoon but
localized higher rainfall rates may still occur before rain ends.

Bann


08Z Excessive Rainfall Discussion...

...Eastern North Carolina - Southeastern Virginia...
An upper trough moving over the lower Mississippi Valley and
northern Gulf will begin to assume a negative tilt as it moves into
the Southeast today. Right-entrance region upper jet forcing will
support a deepening low that will track north along the Southeast
to the southern Mid-Atlantic coast later this morning. This will
support continued southwest to northeast training showers and
thunderstorms into the afternoon, with additional heavy rainfall
amounts expected over the region. Although instability will be
limited, strong forcing interacting with sufficient moisture (PWs
1.25-1.5 inches) will be enough to support rainfall rates up 1
inch/hour and accumulations 1-3 inches. HREF neighborhood
probabilities indicate that additional totals of 2 inches or more
are likely within the Slight Risk area. These amounts on top of
wet antecedent conditions can be expected to cause additional
runoff concerns.

...New England...
As the previously noted low develops and approaches from the south,
a slow-moving front will provide the focus for deepening moisture
and soaking rains across much of coastal New England. Overall,
models have remained consistent in showing a long stripe of 1-3
inch amounts extending from eastern Connecticut to DownEast Maine.
Rainfall rates will be limited by a lack instability, likely
topping out near 0.25 inch/hour. However, given the recent rainfall
and saturated soils, there remain some runoff concerns, promoting
the continuation of a Marginal Risk.

Pereira

Day 2
Valid 12Z Fri Mar 29 2024 - 12Z Sat Mar 30 2024

....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
SOUTHERN CALIFORNIA...

20Z Excessive Rainfall Discussion...
Few changes were needed with models continuing to bring a closed
low southward along the northern California coast on Friday
night/Saturday morning. Higher rainfall rates look to approach the
central and southern coast of California late Friday night or very
early Saturday morning. The previous outlook had that covered and
only minor adjustments were made based on the 12Z suite of model
guidance and WPC QPF. Likewise...made minor adjustments to the
northern extent of the Marginal Risk area in Maine given the latest
spaghetti plots of higher QPF. In addition...there should be a
change in precipitation type from rain to snow as cold advection
sweeps across Maine which will help mitigate excessive rainfall
concerns.

Bann


08Z Excessive Rainfall Discussion...

A well-defined shortwave diving west of a closed low centered west
of Vancouver Island is expected to support the development of a
closed low further south that will drop south along the northern
California coast Friday into Saturday. Models continue to advertise
an anomalously deep system for this time of year, with 500 mb
heights dropping 1-3 standard deviations below normal across much
of California this period. Deep southwesterly flow ahead of the low
will support increasing IVTs, with the highest values dropping
south along the coast from Monterey Bay into the Transverse Ranges.
A Slight Risk was maintained over Santa Barbara and Ventura
counties, where the models continue to show a decent signal for
locally heavy amounts in the favored terrain. The consensus of the
deterministic guidance shows amounts of 1-3 inches in the region,
with locally heavier amounts possible by 12Z Saturday. There is
also some signal for locally heavy amounts further to the north
along the immediate coast, indicating the Slight Risk area may need
to be drawn further to north into central California. But for now,
maintained a broad Marginal Risk that covers much of central
California from the coast into the Sierra foothills.

....DownEast Maine...
Rain developing across the region on Day 1 is expected to carry
over into early Friday with an additional 1-2 inches of rain
expected before precipitation changes over snow and diminishes
behind of the departing low. As on Day 1, a lack of instability
will limit rainfall rates and the potential for flash flooding.
However, areal flooding will remain a concern given the saturated
soils.


Pereira

Day 3
Valid 12Z Sat Mar 30 2024 - 12Z Sun Mar 31 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
SOUTHERN CALIFORNIA..

20Z Excessive Rainfall Discussion...
Consistent model and ensemble QPF across southern California and
with WPC QPF meant little need for more than minor adjustments to
the previously issued Slight Risk across portions of southern
California and the eastward extension of the Marginal risk into
portions of southern Nevada and western Arizona.

Bann


08Z Excessive Rainfall Discussion...

As an anomalously deep low continues to drop south, excessive
rainfall concerns developing on Day 2 are expected to continue and
expand further south across portions of southern California this
period. Increasing IVTs associated with a well-defined frontal
boundary will push across southern California on Saturday, with PWs
reaching 0.75-1 inch (2-3 standard deviations above normal). A
Slight Risk remains in place from the Transverse into the
Peninsular Ranges, where areal average amounts of 1-3 inches are
expected.

Moisture spreading east of the mountains will support widespread
precipitation, with locally heavy amounts possible into the lower
Colorado Basin, where a Marginal Risk was maintained for portions
of southern Nevada and western Arizona.

Pereira


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