Area Forecast Discussion
Issued by NWS -- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KPBZ 290143
Area Forecast Discussion
National Weather Service Pittsburgh PA
943 PM EDT Fri Apr 28 2017
Unsettled but warm weather is expected for the weekend with a
crossing warm front.
.NEAR TERM /THROUGH SATURDAY/...
Minimal change was needed for the mid-evening update as showers
and storms begin to invade from the west. The main area of
deeper convection now just crossing central Ohio and will be
entering the CWA shortly...exiting an hour or so after midnight.
Upstream locations where cores have passed over reporting up to
between an inch to 1.25" of rain over 6 hours...with values
generally around a quarter inch under surrounding areas of more
stratiform rain. If this continues flash flood guidance would
not be exceeded, however, localized areas of minor flooding will
be possible under stronger convection and higher rates
Previous discussion follows...
Showers and thunderstorms are expected tonight...mid to late
evening as a MCC or it`s remnant MCV currently over Indiana
crosses the forecast area. Although model runs do show this
feature weakening over the course of the night...feel this
(weakening) may be overdone as the complex should continue to
ride along the nose of strong warm air and moisture advection
and the resulting convergence allows elevated convection to
continue as unstable air aloft is tapped. Gusty winds will be
possible initially with any storms as rain falls into drier low
Later...after midnight a shortwave riding along the warm front
beginning to lift north over the forecast area will result more
showers/storms through mid-morning.
Have increased overnight QPF amounts...especially across western
zones given M-climate anomalies and model soundings showing
continuity in PWAT values well above the max moving
average...which are closer to 99th percentile values for mid to
late June. Will need to monitor observed precipitation amounts
upstream over the coming hours.
Most models push the warm front north toward the New York and
Pennsylvania border where it stalls late day Saturday. Have
trended forecast in this direction, but confidence is not
exceptionally high. SPC has maintained a marginal risk of
severe, but with better dynamics well west of region through
Saturday, for now think severe threat not high enough to
Rising dew points will help keep temperatures mild tonight,
with warming behind the front Saturday.
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
Warm front should remain near the New York border through Sunday
night as heights rise aloft. This looks to keep a cap on
thunderstorms Sunday. With mid level ridge on Sunday much
warmer and more humid conditions will develop. Ridge begins to
break down Monday as an occluded storm system in the western
Great Lakes pushes a cold front across the region, with showers
and thunderstorms with FROPA.
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
A closed low will eventually move across Southern Canada
Tuesday and Wednesday. The surface reflection will move directly
under the 500 low, keeping the chance for showers in the
forecast. A cooler and unsettled pattern will continue into
late week as a mean mid level trough remains across the ERN
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Periodic condition deterioration to MVFR/local IFR is expected
later this evening and overnight as a cluster of showers and
thunderstorms move along an approaching warm front. Low level
jet and shortwave support should result in additional
showers/thunderstorms overnight through early Saturday morning.
Scattered showers/storms are possible through the day Saturday
as the front stalls in the vicinity, though better upper support
is progged to shift N of the area. Will mention VCSH in the
TAFs for now. A period of MVFR ceilings are expected by Sat
morning also, with improvement from S-N by afternoon.
Restrictions are possible through Sun in vicinity of a surface
front. Restriction are likely with a strong cold front Sunday
night and Monday.