Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Sat Jun 2 2018
Valid 12Z Tue Jun 5 2018 - 12Z Sat Jun 9 2018
Pattern overview and guidance evaluation
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The forecast period begins on Tuesday with an upper trough over
the West Coast, a ridge axis encompassing the central U.S., and an
amplifying trough over the eastern U.S. with a surface low off the
New England coast. This overall synoptic scale pattern is
expected to hold through much of the upcoming week, with
disturbances tracking across the northern tier of the U.S. around
the northern periphery of the upper ridge that will be building
over the southern plains.
In terms of the model guidance, the deterministic guidance has
come into better agreement compared to 24 hours ago for the
northeast states. By Wednesday, the CMC becomes faster than the
model consensus in ejecting the upper low eastward and also shows
less amplitude with the upper ridge over the central U.S. The
UKMET is closest to the coast on Tuesday with the departing
nor'easter. With the second surface low tracking across New
England, the ECMWF is farther south whereas the GFS is displaced
farther north. The models and ensemble means continue to agree
well on the amplitude and persistence of the upper level ridge
from the southern plains to the Midwest states. There is still
model uncertainty with features crossing the northern tier of the
U.S. later in the week around the ridge, and this is where
confidence is less later in the period.
The WPC forecast incorporated some of the deterministic GFS and
ECMWF through the entire forecast, with increasing use of the
ensemble means by next Friday and Saturday. Some previous WPC
continuity was also used.
Weather highlights and hazards
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Precipitation can be expected from the north-central states to New
England with the upper low and trough, along with a surface low
developing offshore. Another area of concentrated showers and
storms is expected across the Dakotas and the Upper Midwest by the
middle of next week as a disturbance crosses near the Canadian
border. Model guidance is also signaling possible mesoscale
convective systems (MCS) developing from Oklahoma and propagating
southeast in northwest flow aloft early in the week.
The ridge over the South will result in a heat wave from southern
California, the Desert Southwest and the southern plains. Many
locations across Texas, Oklahoma and into Kansas should have
afternoon high temperatures exceeding 100 degrees, with a few
locations approaching 110 degrees over western Texas. Daily
records for high temperature will likely be tied or broken during
the upcoming week. Above normal temperatures are also expected
across the Rockies and extending northward across the
north-central U.S. More pleasant temperatures can be found for
the Northeast U.S. and the Pacific Northwest, which will be under
the influence of the upper level troughs. After an unusually warm
month of May, the beginning of June appears to be below average
for temperatures next week from the mid-Atlantic and extending
northward to New England, with cooler northerly flow behind the
low pressure system offshore.
WPC medium range forecasts of 500 mb heights, surface systems,
weather grids, quantitative precipitation, and winter weather
outlook probabilities can be found at:
http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
D. Hamrick