Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1201 PM EDT Fri Apr 12 2019
Valid 12Z Mon Apr 15 2019 - 12Z Fri Apr 19 2019
...A threat for another major spring storm with a risk heavy
rainfall/flooding from the mid-lower Mississippi Valley to the
Ohio Valley starting midweek along some lead risk of severe
weather...
...Guidance Preferences and Predictability Assessment...
A deep lead system out of the short range 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, emerging with yet 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...
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.
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