196
FXUS02 KWNH 090659
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Sun Jun 9 2024

Valid 12Z Wed Jun 12 2024 - 12Z Sun Jun 16 2024

...Heat focus shifts from the Southwest to South Texas this week
as heavy convective rainfall threats shift from the south-central
U.S. to the Gulf of Mexico and Florida...


...Guidance/Predictability Assessment...

Recent forecast spread and continuity issues now seem somewhat
less problematic in a pattern with near average predictability
overall, albeit still with standard and widespread warm season
variances in the details. The greatest region of uncertainty
remains over the Gulf of Mexico as lower heights aloft move into
the region. The details of how this interacts with an increasing
moisture feed into/towards Florida remains highly uncertain. A
heavy rainfall event still seems in the cards for parts of
Florida, but where the rainfall axis sets up remains variable.

The WPC medium range product suite was primarily derived from a
blend of reasonably clustered guidance from the 06 UTC GFS and 00
UTC ECMWF/UKMET/Canadian models and their respective ensemble means
through medium range time scales. Growing forecast spread seems
mainly tied to smaller scale embedded system issues that are often
mitigated consistent with predictabilty by a broad guidance
blending process that includes a shift toward increased ensemble
mean weighting into longer time frames. This approach maintains
good WPC product continuity and a composite of latest 00 UTC
guidance remains mostly in line for much of this forecast period.

...Weather/Hazards Highlights...

A front across the south-central Plains will combine with slow
moving upper system energy and instability to offer a lingering
threat
for local heavy rainfall into Wednesday. A WPC Excessive Rainfall
Outlook (ERO) Marginal Threat area is depicted. A multi-day period
favorable for heavy rains should develop across the Florida
Peninsula as well above moisture pools along and south of a
wavy/stalling front with aid from upper level impulses/energy back
through an unsettled Gulf of Mexico. There is a lot of uncertainty
in the details and much of the state is in a drought. Still, some
threat for high rain rates exists, and its possible much of the
threat may manifest for more susceptable urbanized areas. WPC Day
4/Wednesday and Day 5/Thursday ERO Marginal Risk areas include
much of the central and southern Florida Peninsula to account for
the uncertainty, with a looming threat into later week as well
there and with any activity/moisture feed eminating over the Gulf.
Meanwhile, an increasing precipitation threat across much of the
central and northern Plains emerges late period with troughing
shifting northeastward into the region from the Southwest.

An amplified mean upper ridge slated to slowly shift from the
West/Southwest to the south-central U.S. will continue to produce
much warmer than average temperatures. The highest temperature
anomalies of 10-20F above normal are forecast for the Great Basin,
shifting eastward as the week progresses into the Rockies and
Plains. It will be especially hot across the Desert Southwest then
South Texas given elevated Heat Risk and Heat Index threat values.

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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