Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
130 AM EST Thu Mar 08 2018


Prelim Day 1 QPF Discussion
Valid Mar 08/1200 UTC thru Mar 09/1200 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1...

...Northeast...

The heavier snowfall from the east coast storm will shift into
central and northern New England today. The area of low pressure
will get tucked back west into Maine later today...with it filling
out and weakening into tonight. Models remain in good agreement
with the handling of this evolution and for QPF through the day 1
period. WPC thus utilized a multi model blend, which keeps pretty
good continuity from our previous forecast. Highest totals should
generally be within the 0.75"-1" range across portions of central
and northern Maine.


...Northern CA/Northwest...

Satellite shows a compact area of low pressure off the Oregon
coast early this morning. This low will continue to move
northeastward...moving ashore across northwest Washington later
today. Precipitation intensity should pick up along the WA/OR
coast by 15z and linger through the day. Onshore westerly flow
will be around the climatological 99th percentile for a period
today...thus should see good orographic enhancement to
precipitation totals and see rates as high as 0.3"-0.4" in an
hour. The lack of anomalous PWATs and a quick progression of the
strongest forcing/onshore flow will limit the overall magnitude of
rainfall. However anticipate a longer duration of showery
conditions given continued mid level troughing overhead...thus
looking at amounts within the 1-3" range both along the coastal
ranges and the Cascades through 12z Friday.

Should see decent QPF further inland across the northern Rockies
as well...as the deep layer zonal west to east flow is favorable
for orographic enhancement. Thus anticipate some 1" totals in the
more favored locations.

Model agreement was pretty good across this region. Thus WPC was
able to utilize a multi model blend for QPF.

Chenard