128
FXUS02 KWNH 130701
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Thu Jun 13 2024

Valid 12Z Sun Jun 16 2024 - 12Z Thu Jun 20 2024


...Early season heatwave to spread from the West/Southwest out
through
the South-Central Plains to the Midwest/East Coast next week...

...Improved conditions for Florida while the central to western
Gulf becomes more active into next week...

...Multi-episode Heavy rain/convection pattern for the north-
central U.S. next week...


...General Overview and Guidance/Predictability Assessment...

The latest models and ensembles generally remain in good overall
agreement into next week with respect to the overall pattern,
featuring a strongly building upper ridge across the eastern half
of the U.S., and a developing amplified upper trough over the
West. Guidance indicates a southern stream shortwave over the
Southwest will lift northeast, and around the western periphery of
the building ridge with additional embedded waves crossing the
northern tier as the main upper trough begins to take hold over the
West. An upper-level disturbance now over Florida should slowly
work westward over the Gulf of Mexico this weekend into next week.
This will bring improving conditions for Florida, while increasing
rainfall chances for the central and western Gulf Coast and
vicinity going into Sunday and early-mid next week.

The WPC medium range product suite was primarily derived from a
composite blend of best clustered guidance of the 18 UTC
GFS/GEFS mean and 18 UTC ECMWF/ECMWF ensemble mean, the 01 UTC
National Blend of Models through medium range time scales all next
week in a pattern with near average predictability overall.

...Weather/Hazards Highlights...

A main axis of tropical moisture is forecast to shift westward
across the Gulf of Mexico and affect the central to western Gulf
Coast region next week. Day 4/Sunday and Day 5/Monday ERO Marginal
Risk areas have been introduced for the west-central Gulf Coast
given the moist pattern. Uncertainty remains, particularly with the
potential amount of rainfall and with westward extent into the
western Gulf into later next week. The 12 UTC Canadian offered an
outlier solution with tropical development and northward inland
track not supported by NHC guidance. The 00 UTC run backed off.

Elsewhere, convective precipitation event is likely across an
unstable Northern Plains and the Upper Midwest/western Great Lakes
as southern stream troughing ejects northeastward from the
Southwest as well as lagging northern stream upper trough approach.
WPC ERO Marginal Risk areas have been introduced for Day 4/5
Sunday/Monday. There is now a more consistent signal that the
subsequent
upstream march of an amplified upper trough out from the
West/Northwest will act to also support the Marginal Risk of heavy
rains over the Northern Rockies/High Plains Day5/Monday. This
focus is expected to slowly work across the north-central U.S.
Tuesday into next Thursday as aided by renewed cyclo/frontogenesis.

As for anomalous temperatures, an amplified upper ridge slated to
steadily/broadly shift from the Southwest through the south-
central U.S. to the East over the coming week will produce
widespread anomalous heat and humidity, with the potential for some
daily record highs to be established. Temperatures will already be
rather hot over portions of the South before the even broader
region of heat expands into the Midwest/Ohio Valley then Mid-
Atlantic/Northeast next week as the upper-level ridging builds in.
Highs are forecast well into the 90s and with lows in the middle
60s to middle 70s providing little overnight heat relief. Latest
guidance trends are slower to alieviate the heatwave with more
steadfast persistence of the supporting upper high/ridge.

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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