Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Dec 22 2022 08:30:40

FOUS30 KWBC 220830
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
329 AM EST Thu Dec 22 2022

Day 1
Valid 12Z Thu Dec 22 2022 - 12Z Fri Dec 23 2022

....A MARGINAL RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF
MIDDLE AND UPPER EASTERN SEABOARD...=20
=20
Coastal North Carolina...=20
Areas of heavy rain from the South Carolina coast into the
southern North Carolina coast are expected to linger as a surface
low pressure system tracks northward from the Southeast coast into
eastern Virginia by later this afternoon or early evening...with a
narrow warm sector east of the frontal wave. Across the Coastal
Plain, 850 mb winds increasing to 60 kt by evening will support
precipitable water values of 1.2-1.6 inches and MUCAPE of 500-1500
J/kg. While convection should achieve some level of organization
given adequate speed shear aloft, progressive cell motions and
sandy soils/marsh are limiting factors for runoff concerns but
brief training (or cell mergers). The probabilities for 2 inch per
hour rate from the 22/00Z HREF was generally under 30
percent...however 3 inch per hour ares can not be ruled out in the
short term.  Only minor adjustments were needed to the
previously-issued Marginal Risk area.
=20=20
Appalachians/Northern Mid-Atlantic into southern New England...
Deep moisture and warmer air in the lower-levels will be drawn
northward and overspread the area from the northern Mid-Atlantic
and the Appalachians into southern New England as surface low
pressure forms and move northward today and this evening.  In
doing so...it sets up the potential for heavy to excessive
rainfall...especially along the deformation zone of the surface
low through the evening and then across portions of New England
that works in tandem with +1.5 to +2.5 standardized anomalies of
precipitable water and deep layered frontogenesis to produce areas
of enhanced rainfall rates and amounts.  Increasing on-shore flow
into southern New England (a response to a rapidly deepening low
pressure system over the Great Lakes) continues the threat of
excessive rainfall there into the overnight hours. Hourly rainfall
totals to a maximum of ~1" are expected with local amounts of 2-4"
remaining possible. Cold to frozen soil temperatures and snow
cover over northeastern Pennsylvania, southern Upstate New York
and far northern New Jersey could elevate the potential for
problems with run-off.

Bann



Day 2

The Day 2 outlook will be updated by 0830Z.


Day 3

The Day 3 outlook will be updated by 0830Z.


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!-JmI-Pdzag3kFyu-8VEtNxgRWS1ggZhwMhPjiDgp5-gO=
gNUVaU7TnbUqZRO3pO46odPMoyCTEJG0ybd849z9dWsTfns$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!-JmI-Pdzag3kFyu-8VEtNxgRWS1ggZhwMhPjiDgp5-gO=
gNUVaU7TnbUqZRO3pO46odPMoyCTEJG0ybd849z96O9h-I0$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!-JmI-Pdzag3kFyu-8VEtNxgRWS1ggZhwMhPjiDgp5-gO=
gNUVaU7TnbUqZRO3pO46odPMoyCTEJG0ybd849z967VXSbc$=20


$$



=3D =3D =3D
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