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.
Day 2 Outlook >
WPC Day 1 Excessive Rainfall Outlook
Risk of 1 to 6 hour rainfall exceeding flash flood guidance at a point
Updated: 1427 UTC Sat May 28, 2022
Valid: 16 UTC May 28, 2022 - 12 UTC May 29, 2022
Day 1 Excessive Rainfall Forecast
Forecast Discussion
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1043 AM EDT Sat May 28 2022
Day 1
Valid 16Z Sat May 28 2022 - 12Z Sun May 29 2022 


15Z Update...

A targeted slight risk has been added to far eastern PA, northern 
NJ, and southern Upstate NY after coordination with the affected 
WFOs. Rapidly developing thunderstorms ahead of a trough of low 
pressure will continue to expand into the aftn as MLCape rises to 
1000 J/kg and PWs remain around 1.2", above the 75th percentile 
for the date. Mid-level divergence downstream of an upper low 
combined with the RRQ of a departing upper jet streak will drive 
deep layer ascent into these favorable thermodynamics, and the 
available 12Z high-res guidance suggests convection will become 
scattered to widespread from PA into New England. Most of this 
area has been dry recently, but MRMS observations indicate 1-2.5" 
of rain has fallen across parts of eastern PA, NJ, and the Hudson 
Valley of NY in the past 24 hours leading to saturated soils and 
compromised FFG as low as 1"/3hrs. With weak mid-level winds 
driving slow storm motions, this FFG could be exceeded in a few 
areas as noted by the 06Z HREF 3-hr FFG exceedance probabilities. 
While the coverage of flash flooding instances will likely be 
limited, the slow storm motions and favorable antecedent 
hydrologic conditions support an upgrade to a SLGT risk for this 
targeted area.

Otherwise, the inherited MRGL risk was expanded only slightly to 
the north to account for coverage of thunderstorms this aftn/eve 
with 1-2"/hr rain rates. Rainfall outside of the SLGT risk area 
has been much less, so soils should mostly be able to absorb these 
rain rates. Additionally, storm motions will likely be faster as 
the upper trough and associated deep layer ascent begin to weaken 
and merge into the westerlies. This is likely to limit the 
duration of any heavy rainfall across New England, leading to only 
an isolated flash flood risk, so the MRGL risk was maintained.

...South Florida...
A washed out frontal boundary draped across the Peninsula 
interacting with daytime heating sea breeze convection should 
allow for the development of a few clusters of strong 
thunderstorms this afternoon. These cells will be capable of 
producing intense rain rates over the highly urbanized south 
Florida corridor. HREF probabilities indicate that some 2" an hour 
rains are probable, with daily totals locally exceeding 3" in 
spots. If these higher totals end up over an urban location then 
some flash flood issues could arise. Thus we will maintain the 
Marginal risk.

...Northern Plains...
A mid level impulse out ahead of the large scale troughing over 
the western U.S. will lead to convective development over the High 
Plains this afternoon. There is still a signal in most guidance 
for an axis of 1-2" of rain from eastern MT into western ND in the 
afternoon/evening hours. The lack of deeper instability and drier 
soils/streamflows should keep any flash flood risk fairly isolated 
at best. However there is some signal for amounts locally as high 
as 3" near the comma head of the developing low where increased 
convergence should support a longer rainfall duration. If amounts 
of 3" were to occur then some runoff issues seem possible, thus we 
will maintain the Marginal risk over the region.

Day 1 threat area:

NOAA/ National Weather Service
National Centers for Environmental Prediction
Weather Prediction Center
5830 University Research Court
College Park, Maryland 20740
Weather Prediction Center Web Team
Privacy Policy
About Us
Career Opportunities