341
FXUS02 KWNH 110701
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Tue Jun 11 2024

Valid 12Z Fri Jun 14 2024 - 12Z Tue Jun 18 2024


...Heatwave to spread from the Southwest to parts of the central
and eastern U.S. during the period...

...Excessive Rainfall Threat for Florida through late week and
perhaps the central Gulf Coast early next week...


...Guidance/Predictability Assessment...

The WPC medium range product suite was primarily derived from a
composite blend of reasonably well clustered overall guidance from
the 18 UTC GFS and 12 UTC ECMWF/Canadian/UKMET, the 01 UTC
National Blend of Models and WPC continuity for Friday into Sunday
in a pattern with average to above average predictability. Opted
for smaller input from the models in lieu of more run to run
consistent
GEFS/ECMWF ensemble mean blending into early next week amid
growing uncertainties, including in particular continued variances
with local sensible weather/threat focus. The blending process
tends to mitigate variance by limiting detail consistent with
individual feature predictability. This also acts to maintain good
WPC product continuity that remains generally in line with a
similar blend of latest 12 UTC guidance.

...Weather/Hazards Highlights...

A protracted period favorable for heavy rains should continue
through later week for the Florida Peninsula as well above normal
tropical/Caribbean moisture pools along and south of a wavy
stalled front with aid from upper level impulses/energy back
through an unsettled Gulf of Mexico. There remains high confidence
in heavy rainfall in Florida with locally heavy rainfall rates, but
lower confidence on placement of any extreme convective amounts on
any particular day. Storm total rainfall (including what falls
before the medium range period even starts) of 7-10 inches, with
locally higher amounts to 15 inches, is forecast. WPC Excessive
Rainfall Outlook Slight Risk areas remain in place for the central
to southern Florida Peninsula into Day 4/Friday. Heavy rain may
last into Saturday across Florida where a Day 5 Marginal Risk has
been introduced via collaboration with local WFO offices for
lingering activity. However, as the weekend progresses and into
early next week, there is a growing guidance signal that moisture
influx and possible heavy rainfall may refocus and increase into
the central Gulf Coast and vicinity to monitor for runoff issues
given the favorable deeply moist pattern.

Meanwhile, leading and dynamic northern stream upper trough energy
approach and passage is expected to fire convection along/ahead of
a wavy/pooling surface front over the Northeast into Friday where
a Marginal Risk area remains in place as the parallel upper flow
and convective axis may lead to repeat cells and runoff issues.

Elsewhere, an increasing convective precipitation threat will
emerge across the central and northern Plains/Upper Midwest late
week into the weekend as well defined southern stream troughing
ejects northeastward toward the region from the Southwest to focus
lift/instability. A WPC ERO Marginal Risk area remains in place
for Day4/Friday from the southern High Plains to the central
Plains, except for the Sandhills of Nebraska that are not as
sensitive
to heavy rain. A Day5/Saturday Marginal Risk area has been
introduced from the central Plains to the Upper Midwest given
system progression and continued unstable flow.

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 will produce much warmer than average
temperatures and the threat for some record heat into next week.
The Climate Prediction Center continues a heat threat into week 2.

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







$$