Scientific Forecaster Discussion
fxus61 kpbz 192355 aaa
Area forecast discussion...updated
National Weather Service Pittsburgh PA
655 PM EST Tue Nov 19 2019
drizzle or freezing drizzle may be tonight before warmer temperature
returns during the second half of the week. The highest chance for
precipitation will come late Thursday and Friday.
Near term /through Wednesday/...
no major changes to the overnight period. The threat for any freezing
drizzle will remain over the highest elevations tonight. Latest hires
model data is indicating that surface dewpoints, in areas of possible
drizzle, will only fall below 32 on the ridge tops. This will isolate
any late night freezing drizzle to these locations. Drizzle will be
very light, and non-continuous, so impacts would be minimal. Will
leave in the hwo, but will not issue any headlines.
a shortwave trough crossing this evening will support modest lift of
the saturated layer, ensuring continuous overcast and patchy drizzle
In the wake of the wave, weak nwly flow across Lake Erie will provide
orographic lift to this saturated airmass. But a lack of ice crystals
suggests any precipitation is most likely to be drizzle/freezing
drizzle, especially in nrn zones and the ridge zones, where sfc cold
air may be sufficient for modest ice development.
Dry Wednesday with slow warming.
Short term /Wednesday night through Thursday/...
dry conditions and a warming trend are expected Thu as ridging
builds sfc high pressure across the region, with forecast maxima on
Thu reaching slightly above seasonal average.
Rain onset has trended slower the last few days, with minimal morning
chances and probability increasing only slightly late Thu afternoon.
Long term /Thursday night through Tuesday/...
precipitation chances will increase markedly late Thu night in
advance of a cold front, which is expected to bring more widespread
precipitation to the region. Best chances at this time look to be
late Thu night-Fri morning, although forecasted amounts appear to be
Temperature Thu and Thu night will be comparatively mild as cloud
cover and warm advection on swly flow will limit typical diurnal
trends. Models are in fairly good agreement with frontal passage
during the day on Fri, with a return to below-average temperature.
Although medium-range details vary among ensembles/members, the
general idea of broad ern-Continental U.S. Troughing into early next week
appears consistent until ridging builds mid-week. Below-average
temperature is expected through Tue, with a potential warm-up on
Aviation /00z Wednesday through Sunday/...
low-level moisture under an upper-level trough should maintain
MVFR/IFR conditions into Wednesday. With light wind and overnight
lows falling towards the crossover temperature, fog should form at
Winds are expected to shift from the northwest early Wednesday as
the upper-level trough exits east. Cold advection over Lake Erie
will reinforce MVFR stratocu coverage for areas northeast of hlg
into the late evening; there may be brief periods of IFR for fkl/duj.
more widespread restrictions are expected with a late-week frontal