Quantitative Precipitation Forecast Discussion NWS Weather Prediction Center College Park MD 228 AM EDT Thu Mar 29 2018 Prelim Day 1 QPF Discussion Valid Mar 29/1200 UTC thru Mar 30/1200 UTC Reference AWIPS Graphics under...Precip Accum - 24hr Day 1 Central Gulf Coast The well defined southern stream trof moving across the Southern Plains early Thursday morning will be accelerating northeastward and becoming less defined with time day 1 as it pushes across the Lower MS Valley---TN Valley southern Appalachians and into the Mid Atlantic. The organized convection currently producing very heavy rains over east TX into LA is expected to weaken prior to the beginning of the new day 1 time period but still support a max precip area over the central gulf coastal region from southern LA eastward into the Florida panhandle. This activity is expected to be more progressive than current upstream activity---supporting areal average precip totals in the 1-2" range. The expected increased progression should lessen the threat of runoff issues along the central gulf coast compared to ongoing activity--however can not rule out at least a slight risk potential with any organized convection---especially affecting urban areas. OH Valley into the eastern Great Lakes Developing surface low pressure over the OH Valley Thursday will support an increasing comma head/deformation precipitation area over the OH Valley---pushing northeastward into the eastern Great Lakes Thursday evening and across northern NY state into northern New England Thursday night/early Friday. There is a lot of model run to run variations with respect to the qpf axis details across these regions and model to model differences leading to lower confidence. WPC qpf leaned toward the in house qpf mean to mitigate these fluctuations and differences---depicting moderate to heavy precip amounts in the .50-1"+ range across these regions. Northern Rockies into the Northern Plains Northwest mid to upper level flow with embedded shortwaves will persist day 1 from the Northern Rockies into the Northern Plains. Low confidence with respect to the areas of precipitation to the east of the Rockies into the Northern Plains given the model spread. However---model do agree that any precip will be on the light to locally moderate side given pw values that are near seasonal norms but still relatively low. Pacific Northwest/southwest Canada Northeast Pacific shortwave energy moving southeast across central to southern B.C. will help strengthen onshore flow into coastal WA late Thursday/early Friday. The heaviest precip totals likely to the north of the U.S./Canadian border across Vancouver Island and southwest B.C.---with .25"+ totals affecting the northern Washington Cascades and Olympic range. Oravec