Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Dec 19 2022 08:08:40

FOUS30 KWBC 190808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
307 AM EST Mon Dec 19 2022

Day 1
Valid 12Z Mon Dec 19 2022 - 12Z Tue Dec 20 2022

....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE CENTRAL and WESTERN GULF COAST STATES...=20
=20
The Marginal Risk area was largely maintained from continuity.=20
Overlapping low- to mid-level frontogenesis along with
precipitable water values of 1-1.5" within an area with 1000-500
hPa thickness values in the mid to upper 550s decameters (a
saturated atmosphere), convergent south to southwest low-level
inflow of 25-35 kts with effective bulk shear to match, and
500-1000 J/kg of MU CAPE across portions of TX, LA, and MS is
expected to lead to heavy rainfall from potentially organized
convection across and inland of the western to central Gulf Coast.
 Hourly rain totals to 1.5" inland and closer to 2" near the coast
are possible in this environment, with the HREF showing the most
potential along the immediate shoreline/coastal marshes of
Louisiana.  The 00z HREF probabilities show a high chance of 3"+
across central LA and along the central LA coast, with a 20-25%
chance of 5"+ near and west of Fort Polk LA.  Narrow streaks near
and inland of the Gulf coast have seen 300%+ of their average
rainfall during the past week, making some areas more sensitive to
additional heavy rains.  However, much of where the higher amounts
near the central LA/TX border and across western LA is wooded and
show minimal overlap where heavy rains fell during the past week.=20
Urban areas would also be sensitive to such rainfall.  While small
pockets of Slight Risk-type impacts are possible, it wouldn't be a
large enough area from a probability perspective for an upgrade.

Roth


Day 2
Valid 12Z Tue Dec 20 2022 - 12Z Wed Dec 21 2022

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN AND NEAR
FLORIDA...=20
=20
Upper level support of the right entrance region of an upper level
jet over the Southeast U.S. and difluent flow aloft over the
Florida peninsula and the northeast Gulf of Mexico will support a
blossoming area of showers and thunderstorms over the northeast
Gulf of Mexico that will make its way inland on Tuesday and
Tuesday night/early Wednesday morning.  Precipitable water values
of 1.25-1.75" are expected within an increasingly saturated
atmosphere.  Overlapping low- to mid-level frontogenesis is
expected to be the biggest factor for heavy rainfall as guidance
forecasts MU CAPE to get into the 500-1000 J/kg in narrow strips,
mostly in coastal areas of the FL peninsula.  The combination of
available instability and frontogenesis could lead to hourly rain
totals up to 1.5" particularly near and south of Lake Okeechobee
and along the FL peninsula coastline, should it anchor.  Various
pieces of deterministic guidance show the potential for local
amounts in the 3-5" range but show no agreement as to where within
this broad Marginal Risk area.  Portions of central and southern
FL have received 300-600% of their average rainfall during the
past week, but since this is their dry season, this amounts to
spotty 2-4", which in the warm season would be an average day.=20
The Marginal Risk has been maintained for this area, with the
biggest potential impacts in urban areas along/near either coast.
=20
Roth/Bann


Day 3
Valid 12Z Wed Dec 21 2022 - 12Z Thu Dec 22 2022

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.=20
=20
Roth


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!5kLSHEmtVVLHiG-cyksCNzyGyg0-uQR5OXUUYNPGF15f=
SF6WVDvznHauVlVUX6uXclhTX1funH2V1wwk3GRw9mnfm8U$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!5kLSHEmtVVLHiG-cyksCNzyGyg0-uQR5OXUUYNPGF15f=
SF6WVDvznHauVlVUX6uXclhTX1funH2V1wwk3GRwMBqpVW4$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!5kLSHEmtVVLHiG-cyksCNzyGyg0-uQR5OXUUYNPGF15f=
SF6WVDvznHauVlVUX6uXclhTX1funH2V1wwk3GRwWkZM1gA$=20


$$



=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to
https://lists.illinois.edu and use the "Unsubscribe" link.  Otherwise email
Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.14-Linux
 * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

.