Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1155 AM EDT Sat Jul 13 2019
Valid 12Z Tue Jul 16 2019 - 12Z Sat Jul 20 2019
...Tropical Storm Barry expected to weaken as it tracks up the
Mississippi Valley/Lower Ohio Valley but continue to produce areas
of heavy rainfall...
15Z Update: By the beginning of the forecast period on Tuesday,
the remnants of Barry will be tracking northeast across Missouri
and then the Ohio Valley, and then becomes absorbed by the
westerlies aloft. A quasi-zonal flow pattern develops across the
northern half of the U.S. by the end of the week, and this is when
the models begin indicating noteworthy differences. The 00Z CMC
becomes flatter with the remnant trough from Barry compared to the
other guidance, and the 00Z UKMET is stronger than the model
consensus regarding the central U.S. upper ridge, likely having an
affect on surface temperatures. By Friday, the past two runs of
the GFS are more amplified with a strong upper trough near the
Canadian border, owing to differences in the handling of the large
upper low that will be over the Gulf of Alaska during the short
range period. Teleconnections with the negative height anomaly
over British Columbia by next Saturday support a broad trough over
the Great Lakes region, but not to the degree indicated by the
recent GFS runs. The ECMWF appeared to have better support from
the ensemble means, and thus was weighted more heavily in the
medium range forecast and maintains previous WPC forecast
continuity. The overnight forecast discussion is appended below
for reference.
D. Hamrick
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...Overview and Guidance/Predictability Assessment...
...Weather Highlights/Threats...
The forecast track for Tropical Storm Barry, per the National
Hurricane Center, has it making landfall in south-central
Louisiana on Saturday. Once inland, Barry will weaken as it goes
north across Arkansas and then curves eastward through Missouri
and Illinois as a remnant low by the beginning of the extended
period (Tuesday). Heavy rain associated with this system will
spread from central Arkansas to southern Indiana by Wednesday
morning. There may be a severe threat over some areas to the
right of the surface low track, but with low predictability in
details this far out in time. Later in the week the remnants of
Barry could interact with a wavy northern stream front and produce
enhanced rainfall over the Northeast, but this depends on the
strength of Barry in the short term and timing in the northern
stream in several days. Please consult the latest NHC products
for updated information on Barry.
Much of the Southwest, southern/central Rockies, and High Plains
will remain mostly dry as mid/upper level ridging remains in
place. Southern Canada and the northern states will have
organized convection bringing up to 2 inches of rainfall through
Thursday, and across the Northeast Thursday and Friday, within the
low amplitude flow. Periods of excessive rainfall may be possible
across the northern Plains and Upper Mississippi Valley/Upper
Great Lakes as a frontal boundary stalls over the region. The
pattern across the West will transition as a low approaches the
Pacific Northwest toward the end of the week. This would bring a
period of steadier rainfall with additional terrain enhancement
between the Pacific Northwest coast and the Cascades. Consult the
latest WPC Hazards chart for more information on these potential
threats.
A few locations will have above normal temperatures that may tie
or set new daily high minimum records. Above normal temperatures
with some pockets of plus 10F or greater anomalies will spread
from the northern Plains to the Northeast U.S. through Wednesday,
with some warmth lingering over the Northeast into Friday. The
increased cloudiness from the remnants of Tropical Storm Barry
will likely keep the afternoon temperatures slightly cooler over
portions of the Lower Mississippi Valley (perhaps near record low
max values). Once Barry passes, portions of the central Plains
and Middle Mississippi Valley will reach 10 to 15F above average
by the end of the forecast period. Heat indices will be around
105 to 115F, which will likely require the future issuance of heat
advisories. The Pacific Northwest will trend cooler by Friday with
highs 5 to 10F cooler than average.
This forecast was mostly derived from the 00Z ECWMF, with lighter
weighting of the GFS, CMC and ECWMF mean.
Campbell
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