Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
244 PM EDT Thu Mar 29 2018


Prelim Day 1 QPF Discussion
Valid Mar 30/0000 UTC thru Mar 31/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

Central Gulf Coast into northern Florida

Lead frontal system associated with the ongoing convection moving
through the central Gulf states has picked up momentum since
yesterday and will lift northeastward this evening and overnight.
Upper dynamics have been waning but lingering inflow from the Gulf
will maintain precipitable water values 1.25-1.50" (about +1.5 to
+2 sigma) ahead of the front. This supports 0.5-1" QPF along and
north of I-10 (local max perhaps twice that) from about Mobile
eastward after 00Z. Upper jet elongates and strengthens to the
northeast, stretching out the precip overnight into tomorrow. Tail
end right entrance region may support another area of heavier rain
into north central Florida tomorrow afternoon as the front
approaches. Slight risk of excessive rainfall was maintained over
southeastern Louisiana eastward to the western Florida panhandle
overnight with embedded heavier convection, especially affecting
urban areas.

Ohio valley into the eastern Great Lakes

Boundary atop the front in the southeast will consolidate into one
entity with the front to the south by tomorrow as the surface low
lifts northeastward through the upper Ohio valley and into the
northeast by tomorrow morning. Comma head/deformation
precipitation will continue northeastward into the eastern Great
Lakes this evening and across northern NY state into northern New
England tonight/early Friday. Models still differ on timing of the
front eastward to the mid-Atlantic coast and how quickly the
precipitation shield moves along with it, but generally favored
the HREF mean for placement with adjustments on amounts per the
other guidance. Precip amounts were generally in the .50-1" range
across these regions with the most coverage across northern New
England.

Northern Rockies into the Northern Plains

Cold front pushing through the Dakotas/Minnesota will support a
lead area of light snow tonight while the more significant area
lags behind with an approaching surface low. Left exit region
upper jet will help expand snow across eastern MT through ND into
MN tomorrow with mix/light rain to the south. North-south
differences were still unresolved in the guidance, but a middle
ground seemed plausible given the split in the hi-res and global
guidance with amounts held to just under 0.5" through 00Z/31.

Pacific Northwest/southwest Canada

Mid-level shortwave will push into southern BC as a surface cold
front pushes into western Washington early Friday. Heaviest precip
totals likely to the north of the U.S./Canadian border as the jet
streak slides into northern ID and northwestern MT but .1-.25"
totals will affect the western Olympic peninsula/Olympic range and
.5-1"+ in the Cascades liquid equivalent. HREF mean offered a good
starting point.


Fracasso