Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
228 AM EDT Fri Apr 12 2019
Valid 12Z Mon Apr 15 2019 - 12Z Fri Apr 19 2019
...Active pattern to continue through next week for much of the
lower 48...
...Overview...
Upper ridging pushed out of the northeastern Pacific will surge
back toward the west coast of North America which favors renewed
downstream troughing in the central/eastern states late next week.
A lead system out of the short range will exit through New England
Monday as a couple more push through the west. By midweek, low
pressure will deepen out of the southern Plains and lift toward
the Great Lakes/southern Canada with another round of rain,
convection, and some wintry weather on the colder northwest side.
...Guidance Preferences and Predictability Assessment...
Models/ensembles align with the longwave pattern through next
week, but differ mostly on timing/depth/track of especially the
late-week system. At the start of the period, models have struggle
with the quick flow south of the Gulf of Alaska between southern
ridging and northern troughing, so a consensus position in both
depth and speed was preferred as run-to-run changes will continue.
Trend has been for a bit weaker/flatter flow but northern flow
across the U.S./Canadian border was unclear as well. By 12Z Wed,
split in the guidance was evident (and mostly mimicked in their
parent ensemble systems)--GFS/UKMET were slower than the
ECMWF/Canadian/FV3-GFS as the trough digs through the Great
Basin/Four Corners region. ECMWF has trended quicker while the GFS
trended slower, away from a common solution 24 hrs ago, but the
ensembles overlapping most just a bit slower than the 12Z ECMWF.
As the low lifts northeastward, 12Z GFS/ECMWF offered reasonable
clustering near the 12Z NAEFS mean which was not as quick as the
ECMWF ensemble mean but not as slow as the 18Z GEFS mean. This
paired well with continuity which was preferred until another
cycle or two of runs can be reviewed for short term changes that
may influence the late week system's exit speed (i.e., upstream
kicker and northern stream affects).
...Weather Highlights/Hazards...
Precipitation will again increase by Wednesday into Thursday
across the Mississippi/Missouri Valleys into the Great Lakes as
low pressure strengthens over Oklahoma/Kansas. Multi-inch rainfall
totals are probable (enhanced in embedded convection) in some
locations of the warm sector and perhaps to the north/northeast of
the low with additional northern stream support. Temperatures to
the north/northwest of the low may only be marginally cold enough
for snow (and perhaps only at night) depending on the amount of
cooler air behind a weakening Canadian cold front Wednesday.
Temperatures will largely be within 10 degrees of average values
for mid-April but with a slower moderation over parts of the
Dakotas/Minnesota owing to the near-term snow cover that will take
at least several days to melt.
Fracasso
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