Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Tue May 01 2018


Prelim Day 1 QPF Discussion
Valid May 01/1200 UTC thru May 02/1200 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1


...Lower Missouri Valley into the Upper Midwest...

Shortwave energy over the eastern Pacific will pivot southeastward
toward the base of the longwave western U.S. trough, and in doing
will further amplify the trough as height falls push southward
across Baja and northwest Mexico while a mid-upper low closes off
across the desert SW. While there continues to be consensus among
the models with respect to the longwave pattern, spatial and
timing differences continue with respect to the convectively-aided
shortwaves ejecting northeast of the trough and along the northern
periphery of the downstream upper ridge. Meanwhile, as separate
northern stream trough across western Canada begins to impinge the
the aforementioned upper ridge late in the period (Tue night)
across the upper MS Valley, the increased confluence aloft will
generate a 90-100+ kt upper level jet streak across far northern
portions of the Upper Midwest into southern Canada. All of the
models are picking up on this favorable dynamical signal for heavy
rainfall ahead of the MCVs and into the favorable right entrance
region of the aforementioned jet streak; however, the bimodal
distribution of QPF maxima from some of the models, along with the
typical latitudinal differences among the operational guidance
(especially global vs. high res) is once again making for a
low-confidence QPF.

Hurley