Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1210 PM EDT Fri Apr 12 2019
Valid 12Z Mon Apr 15 2019 - 12Z Fri Apr 19 2019
...Another major spring storm next week to bring risk of heavy
rainfall/flooding from the mid-lower Mississippi Valley/Ohio
Valley along some risk of lead severe weather south and wrapback
snows north...
...Guidance Preferences and Predictability Assessment...
A deep lead short range system will exit through New England
Monday as our weather emphasis returns to the West. Models and
ensembles overall cluster reasonably well Monday into Wednesday
and a preferred composite blend continues maintains good WPC
continuity in showcasing the track of a series of dynamic
mid-upper level shortwave troughs/height falls and associated
swaths of enhanced but progressive precipitation from the eastern
Pacific inland across the West/Rockies with a substantial heavy
mountain snow threat. Energies then emerge within another pattern
favorable for major storm genesis over the Plains into midweek.
Models and ensembles have not been as aligned with recent runs
with subsequent storm timing/details into later next week, but the
overall signal for significant storm genesis remains quite strong.
The latest GFS and ECMWF deterministic runs trended faster
overnight, but have now retreated back slower to offer better
continuity with yesterdays WPC forecast again. This is albeit with
a shift a bit more northwestaward that could portend a better
opportunity for wintery precipitation over a marginally coolded
Upper Midwest/Great Lakes into next Friday considering most
solutions do still wrap up quite a deep surface low/frontal system
and cooling northern stream frontal drape overtop. Interestingly,
the GEFS individual ensemble members uncharacteristically cluster
slower than the GFS/ECMWF while ECMWF ensemble members
uncharacteristically cluster more progressive than the GFS/ECMWF.
Overall, WPC has trended back slower versus our overnight
continuity most now in line with the deterministic GFS/ECMWF into
Thursday and next Friday.
...Weather Highlights/Hazards...
Significant 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 depending on the amount of
cooler air behind a Canadian cold front. 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
melting of near-term snow cover.
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