Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Pittsburgh PA
534 PM EDT Thursday Apr 17 2014
outside of a weak system passing Friday afternoon...dry and
generally quiescent conditions will continue into next week.
Near term /until 6 am Friday morning/...
only update needed at 530pm was to hourly temperatures and
dewpoint forecasts. Previous discussion follows.
The high clouds from earlier in the day are beginning to transit
east of the region. This should yield to clear skies for the
overnight hours. However...with a relatively constant pressure
gradient driving southeasterly flow over the forecast area...winds
should stay up enough to preclude significantly diving
temperatures. Additionally...dewpoints have already started to
creep up a bit today...and as southerly flow continues...they will
likely continue to wander northward as well. As a result...lows
tonight seem poised to be a few degrees warmer. Fries
Short term /6 am Friday morning through Sunday/...
the upper level ridge that has dominated the region for the past
36-48 hours will start to transit east on Friday. Deep layer
southwesterly flow develops and opens the door to a weak short
wave trough to pass embedded in this flow. The model solutions
have all trended faster for the past several cycles with this
feature and now pass it through the forecast area centered around
Friday afternoon. With a lack of significant moisture and
significant middle-level support for ascent shearing out as it
passes...measurable rainfall is not at all a certainty in
association with it. However...a fairly decent upper jet right
entrance region transits the area. Additionally...while not full
layer saturation...layer relative humidity values generally stay at or above
70-80 percent throughout the column along the frontal band as it
passes. As a result...while anything approaching significant
rainfall is unlikely...a few sprinkles/showers will be possible
across the northern/western portions of the area. Sprinkles have
been mentioned in the forecast to cover this...but probability of precipitation were
generally kept to a minimum.
As that system shears off to the north on Saturday...temporary
cold advection drops temperatures a few degrees Saturday before
ridging seems likely to again become the dominant feature over the
region. Low level southwesterly flow again establishes itself and
850 mb temperatures again climb to north of +10c. This should
bring temperatures in the 70s back into the region by Sunday under
sunny skies. Fries
Long term /Sunday night through Thursday/...
a dry and warm pattern expected through much of the long term. A
weak cold front and associated low pressure will bring the risk
for showers Tuesday. A bit of a cool down by the end of the long
Aviation /22z Thursday through Tuesday/...
VFR conditions will continue with only periodic high clouds. Winds
from the southeast around 10 kts will weaken overnight.
Outlook.../Friday through Sunday/...
restrictions are not expected through the weekend.