Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Mon Sep 16 2019
Valid 12Z Thu Sep 19 2019 - 12Z Mon Sep 23 2019
...Hurricane Humberto to track increasingly out to sea...
...Gulf of Mexico disturbance offers a Texas heavy rainfall
threat...
...Overview and Guidance Evaluation/Preferences...
The latest models and ensembles still offer a reasonably similar
and amplified larger scale pattern over the lower 48 and vicinity
for much of the upcoming medium range period. Forecast spread and
uncertainty for small-mid scale embedded features remains mostly
improved, bolstering forecast confidence.
Flow will be highlighted by an amplified and unsettling mean upper
trough to eject out from the West and sprawling/hot late summer
east-central states workweek upper ridge. The WPC medium range
product suite was primarily derived from a composite blend of the
18 UTC GFS/GEFS, 12 UTC ECMWF/ECMWF ensemble means and the
National Blend of Models.
An exception is with repsect to a current northern Gulf of Mexico
disturbance that offers an emerging Texas heavy rainfall threat
over the next few days, but mainly into Wednesday/Thursday. The
ECMWF and ECMWF ensembles and to a lesser extent the
UKMET/Canadian seem to offer a more realistic system depiction
with a slow lifting into Texas within the ridge aloft. The GFS
instead shifts the system down the Texas coast.
...Weather Highlights/Threats...
Hurricane Humberto is forecast by the NHC to track increasingly
out to sea away from the Southeast U.S. early this week.
Meanwhile, a slow moving disturbance over the northern Gulf of
Mexico may track into Texas into mid-late week. This system offers
a significant threat of locally excessive rainfall dependent on
ultimate track. Trended WPC QPF upwards over Texas and as pooled
tropical moisture lifts further inland into east-central U.S.
convection later week into the weekend in advance of an
approaching surface front, especially over the east-central Plains
and Mid-MS Valley.
As an upper trough amplifies from the Pacific Northwest expect
widespread rains (some very high elevation snow) to WA/OR
Wednesday, spreading inland/south to MT/ID and northern NV/CA on
Thursday. As the associated surface low spreads onto the northern
Plains, expect an organized convective focus with locally heavy
downpours shifts to the northern Plains Friday into Saturday
before shifting east to the Great Lakes and east-central
Plains/Mid-MS Valley/Midwest next weekend. Deepened moisture may
support some leading record high minimum temperatures.
In this pattern expect subtropical moisture out of Mexico on
southwest flow aloft over the Southwest/Four Corners states with
rain chances mainly Wed/Thu. Strong ridging downstream over the
east-central U.S. then will meanwhile favor well-above average
temperatures with some near record Deep South heat.
Schichtel
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at:
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/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml