Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
251 PM EDT Fri Apr 27 2018


Prelim Day 1 QPF Discussion
Valid Apr 28/0000 UTC thru Apr 29/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

...South Florida...

The convective activity enhancing across south Florida Friday
afternoon will likely be weakening by the beginning of the
upcoming day 1 time period...0000 UTC Saturday...and pressing to
the south and east of south Florida.  Model consensus is for the
axis of the heaviest precip to be to the south of south Florida
and the Keys---with the northern edge of the precip shield
bringing moderate precip potential to south Florida. 


...Eastern New England...

The surface wave along the northern Mid-Atlantic coast this
afternoon will continue to move quickly northeastward this evening
along the New England coast and into southeast Canada. The area of
moderate to heavy rains ahead of this wave will primarily affect
coastal to eastern Maine early in the upcoming day 1
period---supporting .25-.50" areal average amounts.   

...Great Lakes into northern NY state...

In the wake of the wave affecting eastern New England---the
upstream large scale trof will continue to amplify as it pushes
southeast across the Great Lakes tonight into Saturday.   Two
distinct surface waves expected to rotate through this amplifying
trof---helping to concentrate moderate precip totals ahead of each
wave.  A lead wave will move northeast from the eastern Great
Lakes into northern NY state and southern QB...followed by a
second wave pushing southeast from the lower Great Lakes toward
the Central Appalachians.   A stripe of moderate precip totals in
the .10-.25"+ range possible from the lower to eastern Great Lakes
region into northern NY state associated with each wave.
 
...Northern California...Pacific Northwest---northern Great Basin
into the Northern Rockies...

The latest model guidance is showing good agreement with the east
northeast push of the well defined closed low off the
California/Oregon coast this afternoon into western Oregon during
Saturday.  A broad region of showery conditions likely to the east
and northeast of this closed low from northern
California---through the Pacific Northwest---northern Great Basin
and Northern Rockies region.  Model consensus for max totals
expected over northern California where the onshore southwest flow
will have the best upslope component and over Washington from the
Cascades to the coast range where a west to east oriented precip
band to the north of the closed low is expected to pivot during
Saturday. In both regions---.25-50"+ areal average amounts
depicted with heavier localized totals likely in the favored
terrain regions.

...Northeast Mexico into far South Texas

Southern stream shortwave energy expected to push across far
northeast Mexico and far south TX early Saturday.  Shower activity
ahead of these height falls expected to primarily affect far
northeast TX where the axis of much above average pw values will
persist day 1.  The northern edge of this precip may affect far
south TX with light to moderate totals---with the better chance of
any heavy rain amounts to the south of the U.S. border.


Oravec