Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
207 PM EDT Sat Jul 4 2015
high pressure provides dry weather and seasonable temperatures
Sunday. Rain chances return Monday with an upper disturbance...and
continue into Wednesday with an approaching front.
Near term /through Sunday/...
morning low clouds have broken into a scattered-broken cumulus deck. Drier air
working in from the northwest has kept cumulus coverage much less across Ohio and
far northwest PA. Most of these will collapse with sunset. Still cannot
rule out a sprinkle or light rain shower along the eastern
ridges this afternoon...but these will be quite minor and brief.
Surface high pressure and weak h500 ridging will then lead to dry
weather tonight. The recent rainfall and calm winds overnight may
lead to at least patchy light fog in many areas tonight. The
eastern valleys figure to have the best chance given drier
dewpoints arriving here last...and have added some patchy fog to
the grids here.
The high slowly slides east Sunday. Most locations will enjoy a
mostly sunny day. However...southeast flow will promote a moisture
increase near the ridges in the southeast County Warning Area. Soundings show some
modest instability during the afternoon as well. Cannot rule out
an isolated diurnal rain showers here and have included this possibility
in the higher elevations of WV and Maryland.
Dropped low temperatures a couple degrees tonight given the clearing
skies...light wind...and lowering dewpoints. Readings recover
towards seasonable levels Sunday afternoon with warmer h850 air
and slightly more efficient mixing.
Short term /Sunday night through Tuesday/...
dry...and warmer weather is then expected as high pressure builds
through Sunday. Sunday night and Monday another disturbance is
now projected to bring chance of preciptiation to our southern
County Warning Area of WV and Maryland.
Will keep current forecast of increasing chance with the Tuesday
frontal system all areas and temperatures readings at or
slightly above seasonal averages.
Long term /Tuesday night through Saturday/...
general flattened upper flow is forecast through Saturday. Individual
disturbances advancing through the flow across the upper Ohio
Valley are expected to bring chances for showers and
thunderstorms. Previous forecast depiction looks good as they used
wpc ensemble based guidance to smooth out model differences...with
some adjustments to probability of precipitation and the prognosticated seasonally warm
Long term /Tuesday night through Friday/...
a deamplified...flattened upper flow is prognosticated by model
ensembles through the long term period. Individual shortwaves
advancing through the flow across the upper Ohio Valley are
expected to bring periodic chances for showers and thunderstorms.
Used wpc ensemble based guidance to smooth out model
differences...with some adjustments to probability of precipitation and the prognosticated
seasonally warm temperatures.
Aviation /18z Saturday through Thursday/...
VFR conditions through the evening with scattered-broken cumulus and northwest winds at
10 knots or less. With high pressure moving overhead tonight...and
the resulting clear skies and light winds...expect MVFR to IFR fog
to form after midnight. Locations like lbe and duj may even see
LIFR...due to wetter ground and lower dewpoint air arriving later
than areas to the west. Fog will burn off by 13-14z...leaving
mainly high clouds and few cumulus in its wake.
Outlook.../Sunday through Wednesday/...
restriction chances are expected to increase early next week with
several crossing disturbances.