979
FXUS02 KWBC 091902
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
302 PM 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 rainfall threat looms for Florida...


...Guidance/Predictability Assessment...

Latest suite of guidance shows fairly good agreement on the large
scale pattern featuring shortwaves progressing through a mean Great
Lakes to Northeast trough with a building ridge behind. There is
still some key differences in the speed and amplitude of these
shortwaves late week, but a general model compromise seemed to work
as a good starting point. Meanwhile, out West, there is increasing
uncertainty on how quickly a northeast Pacific low or associated
energy progresses inland. The 00z and new 12z ECMWF remain on the
faster side of guidance pulling much of the upper low into Western
Canada next weekend, while there seems to be better consensus for
at least some energy to hang back off the British Columbia coast.

Meanwhile, the evolution of lowering heights, and highly anomalous
moisture axis, and energy over the Gulf of Mexico into Florida
continues to offer a ton of uncertainty. Per the latest forecast
out of the National Hurricane Center, tropical development with
this feature is not likely, but regardless, confidence in a heavy
to excessive rainfall threat for central and southern Florida is
increasing.


...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. The Day 4 WPC ERO
continues to show a small marginal risk area for portions of
central to northeast Texas. A multi- day period favorable for heavy
rains should develop early this week and continue through much of
the medium range period for 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 at least a moderate drought. There is increasing
confidence however that short range heavy rainfall potential may
mitigate that enough to support a slight risk introduction for
central and southern Florida on the Days 4 and 5 EROs, with a
looming threat into later week as well there and with any
activity/moisture feed emanating over the Gulf. Storm total
rainfall (including what falls before the medium range period even
starts) of 7-12 inches, with locally higher amounts, is possible.
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. and parts of the East 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.

Santorelli/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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