044
FXUS02 KWBC 070700
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Tue May 7 2024

Valid 12Z Fri May 10 2024 - 12Z Tue May 14 2024


...Guidance/Predictability Assessment...

The 12 UTC GFS/ECMWF/Canadian model solutions seem best clustered
valid for Friday and Saturday in a pattern with good 12 UTC cycle
ensemble support and near to above normal predictability and
continuity, generallly in line with the 01 UTC National Blend of
Models (NBM). A composite blend offers good system detail, with
the most forecast spread relating to moderate coastal genesis and
development up off the East Coast. 12 UTC guidance trended toward
better clustering compared to the more varied 18 UTC GFS/GEFS. The
12 UTC guidance cycle best fits latest Machine-Learning guidance.
Latest 00 UTC guidance remains in line, but the ECMWF is delayed.

Forecast spread and model cycle to cycle continuity issues
increase more significantly over the weekend into next week over
the West in developing split flow and especially with amplitude and
extent of digging of northern stream energies down into the north-
central and/or eastern U.S.. WPC products at these longer time
frames were mainly derived from more compatible guidance from the
12 UTC ECMWF/NAEFS ensemble means and the 01 UTC NBM along with
WPC applied manual edits to maintain max WPC product continuity,
albeit with less than ideal system detail given growing uncertanty.
The latest 00 UTC models remains varied with run to run issues.

...Weather/Hazards Highlights...

A main parent low and frontal system working toward the Northeast
Friday will help focus generally moderate rainfall, with activity
aided and prolonged Saturday as uncertain downstream energy
tranference leads to coastal low genesis. Additional but uncertain
upstream northern stream systems may periodically offer bouts of
mainly lighter rains from the north-central U.S. to the Great
Lakes/Northeast Sunday-next Tuesday.

Meanwhile to the south, a cooling and trailing/wavy front will
moderate lead warmth while working through the Southeast to the
Gulf of Mexico and northern Mexico. A WPC Day4/Friday Excessive
Rainfall Outlook Marginal Risk area is in place for parts of the
Southeast given lingering deep moisture/instability and favorable
upper jet/diffluence support. This slowing front and a reinforcing
front/upper impulses are expected to periodically focus
predipitation from the southern Rockies/Plains out through the Gulf
of Mexico and Florida over the weekend into next week. Guidance
remains varied at these longer time frames, but latest signal
trends suggest the main areas to monitor for any runoff issues may
be the Florida Peninsula and the western Gulf Coast.

Schichtel


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw



























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