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.
WPC Met Watch

Mesoscale Precipitation Discussion: #0026
(Issued at 724 PM EST Tue Jan 11 2022 )

MPD Selection

Graphic for MPD #0026

Mesoscale Precipitation Discussion 0026
NWS Weather Prediction Center College Park MD
724 PM EST Tue Jan 11 2022

Areas affected...South Florida

Concerning...Heavy rainfall...Flash flooding possible

Valid 120024Z - 120624Z

Summary...Thunderstorms have shown the tendency to cluster and
show slow movement as of late, leading to hourly totals to 3" per
radar estimates.  With local amounts to 6" possible where activity
sits for a couple hours, flash flooding could occur within their
urban environment.

Discussion...Organized showers and thunderstorms have formed
within an unstable environment caused by cool air moving over the
Gulf Stream -- ocean effect convection.  MU CAPE values (which
seem to well describe the ongoing convective coverage) are
500-1000 J/kg.  Low-level northeast flow of 15-20 kts is being
countered by the mean 850-400 hPa wind which is from the
west-northwest at similar magnitude.  This significant change of
the wind with height is leading to effective bulk shear of 25-40
kts which is organizing the activity, with the net motion a vector
addition of the two flows -- slowly southward.  A couple of
convective areas in northeast Miami-Dade and southeast Palm Beach
have been moving slowly lately, which has ramped up hourly rain
totals to 3" per radar estimates, despite precipitable water
values just over 1.25".

The 18z HREF probabilities of heavy rainfall (0.5"+ per hour, 3"+
per 12 hours) are quite high through the overnight hours within
this area.  The 5"/12 hour probabilities were a non-trivial
20-30%.  While slow moving clusters aren't expected to persist for
more than an hour or two as activity have been constantly shifting
and reorganizing, that would lead to the potential for local 6"
amounts overnight.  The northern end of the activity is expected
to slowly shift southward through eastern Palm Beach county with
the moisture and instability fields.  The threat appears isolated,
but over urban areas, could present a meaningful though localized
flash flood risk.




LAT...LON   27068008 26928001 26687998 26258002 25828011
            25488017 25278027 25288040 25508041 25848035
            26398028 27038018

Last Updated: 724 PM EST Tue Jan 11 2022

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
Page last modified: Thursday, 12-May-2022 19:44:52 GMT