Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1152 AM EDT Fri Jun 01 2018
Valid 12Z Mon Jun 04 2018 - 12Z Fri Jun 08 2018
...Heat wave to continue across portions of the Southern U.S...
Pattern overview and guidance evaluation
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Two prominent large scale features will be present throughout the
extended periods; a broad ridge across the southern CONUS and
trough over the Great Lakes and Northeast region. Shortwave
troughs will move onshore the Pacific Northwest Coast and ride
over the ridge top, which will then reinforce the trough over the
trough over the East.
For the latest run of the model guidance, the ensemble means are
actually having a better handle on the evolution of individual
fronts in terms of clustering and timing. The 00Z ECWMF run for
the first 3 days of the extended was more positively-tilted and
more progressive with the surface lows moving up the Northeast
Coast than all of the other solutions, but then slowed
significantly for the later periods. The 06Z GFS favored a more
neutral-slightly negatively tilted trough, which favored a slower
progression through the eastern third of the U.S. The ensemble
means took a middle ground approach, not only on the depth of the
lows but also the timing and track. With such a significant
difference within the operational models, the preferred blend for
the entire extended forecast comprised of equal parts of the 00Z
ECWMF/GEFS/NAEFS means.
The one of greatest interest will be a possible nor'easter
southeast of New England through early Tuesday, and there has been
a trend for this to be closer to the coast and slower to depart
the region. Farther upstream across the northern plains and
Midwest states, the models are having difficulty with the
progression of embedded shortwaves in the northern stream flow
that eventually amplify the large scale trough over the eastern
U.S. The guidance continues to agree well on the placement and
amplitude of the upper ridge over the southern plains.
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. There has been a trend for heavier rainfall from this
coastal low to affect parts of the northeast U.S., with the
possibility of a late season nor'easter affecting coastal New
England for early next week. 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/Central Plains.
Several locations across Texas, Oklahoma and into Kansas will
observe afternoon high temperatures exceeding 100 degrees- a few
locations may approach 110 degrees over western Texas. Daily
records for high temperature will likely be tied or broken in the
coming 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
Campbell/D. Hamrick