Area Forecast Discussion
Issued by NWS State College, PA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KCTP 281427 AFDCTP Area Forecast Discussion National Weather Service State College PA 1027 AM EDT Wed Sep 28 2016 .SYNOPSIS... A multi-day heavy rain event is probable across far south-central Pennsylvania beginning later today and continuing tonight through Thursday. Flooding impacts are likely across the southern half of central PA...but impacts may be lessened to some extent by dry antecedent conditions. Unsettled weather with occasional lighter rain showers will persist into the weekend with a gradual drying trend by early next week. && .NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Increasing southeast flow aiding expansion of lower clouds from the Mason Dixon line northward into the Laurel Highlands and parts of the South Central and Central mountains and Ridge and Valley region at mid morning. Deep easterly flow with long over water fetch from the Western Atlantic is pushing low clouds westward from the Hudson River Valley into nrn NJ and the Catskills as well. Persistent showers ongoing well south of my area from areas south of DC to the Chesapeake and HRRR shows this area pivoting and lifting into the south central mountains and lower Susq by late afternoon. Earlier light showers which trekked north of the Mason Dixon line have dissipated due to dry air entrainment. Clouds will continue to increase from south to north throughout the day as southeast flow increases and boundary layer moisture deepens. Model guidance still shows the main surge in rain coverage and intensity later tonight into Thursday which corresponds with arrival of stronger dynamical forcing and strengthening E-SE upslope low level flow. Showers with locally heavy banded and orographics will increase by late evening and overnight across the southern third to half of central PA.
-- End Changed Discussion --
&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... *Flood Watch in effect for the Laurel Highlands, South Central Mountains and southern portions of the Central Mountains midnight tonight through Friday morning. *Heavy rainfall event probable over far south-central Pennsylvania on Thursday *Flooding is likely however high impacts may be mitigated by dry antecedent conditions Heavy rain event is expected to be ongoing over south-central PA on Thursday. An enhanced convergence axis/frontal zone is progged to develop on the east side of an upper low meandering over the OH/TN Valley, tapping into deep moisture/high PW air off the Atlantic Gulf Stream via anomalous east/southeast low level jet. The heavy rain axis is progged to gradually pivot to the southwest with time oriented within moderate excessive rain outlook area from southwest PA near the Laurel Highlands southeast into Northern VA/D.C. area. The strength of the upslope flow and high PW transport along with some elevated instability should provide an environment for efficient rainfall processes. WPC QPF blend again favored a slight shift in QPF to the southwest but maintained a broad area of 2-4" with localized 4-6" possible. Keep in mind these amounts are over a 36+ hour period with preceding dry conditions and near to below normal streamflows. Therefore the dry antecedent conditions may limit more significant flooding/runoff issues. Still expect flooding to result from long duration event...and have issued Areal Flood Watch for Laurel Highlands, South Central Mountains and southern portions of the Central Mountains for late tonight through Friday morning. Will continue to highlight potential flood risk in HWO elsewhere. The upper low is fcst to drift back to the west/NW into the OH Valley on Friday before slowly moving to the ENE across the Lower Great Lakes through the weekend. We should continue to see periods of showers on Friday but rainfall amounts will be much lower and less organized. && .LONG TERM /SATURDAY THROUGH TUESDAY/...
-- Changed Discussion --
Model guidance still suggests unsettled conditions over the weekend with a gradual decrease in the chance for shower. Temps still holding close to seasonal normals as we turn the calendar to October.
-- End Changed Discussion --
&& .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
Today will be the last VFR day before more showery and cloudy conditions develop later Wednesday Night into Thursday with widespread reduced conditions likely. MVFR cigs will increase by this afternoon and evening...with IFR reductions developing south to north late tonight and lasting through Friday. Outlook... Thu-Fri...Widespread showers/cig reductions. Sat...Reductions possible with a chance of showers. Sun...Improving conditions.
-- End Changed Discussion --
&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && .CTP WATCHES/WARNINGS/ADVISORIES... Flood Watch from late tonight through Friday morning for PAZ024>028-033>036-056-063>065. && $$ SYNOPSIS...Steinbugl NEAR TERM...DeVoir/Steinbugl SHORT TERM...Steinbugl LONG TERM...Steinbugl AVIATION...DeVoir/Gartner

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.