Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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206 FXUS61 KCTP 161135 AFDCTP Area Forecast Discussion National Weather Service State College PA 735 AM EDT Tue Jul 16 2024 .SYNOPSIS... The heat will peak today across the region as unseasonably warm air is directed into the state on SW winds. Another round of thunderstorms with gusty, to locally damaging wind gusts and hail will move through the Commonwealth this afternoon and evening. A cold front will push through on Wednesday with another round of strong to severe thunderstorms. High pressure will build in from the Great Lakes and control things for the rest of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Regional sat/radar loop early this morning looks quite similar to Monday morning with respect to the approach of another MCV from the Ohio Valley. Timing of the warm advection arm with the bulk of the convection headed toward our NW zones is about 2 hours faster than what we saw Monday morning, though the intensity is fairly similar and may warrant a Special Weather Statement during the mid to late morning hours. Mainly clear skies with patchy fog will start the day throughout the valleys of northern PA Temps to start the day will range from the mid 60s over the N Mtns, to the low and mid 70s across the southern half of the state, where PWAT values are the highest. Elsewhere Abundant sunshine will occur this morning into early this afternoon with the aforementioned, initial band of convection weakening during the late morning. Diurnal heating, combined with surging pwats ahead of the approaching shortwave/MCV, should yield developing tsra during the afternoon with the highest POPs across the central and northern part of the state per latest guidance. The strongest mid level flow and deep layer shear is progged over the northern part of the state and the best combination of late day instability/shear is targeted over the northeast part of the forecast area, where HREF UHEL values are highest, signifying the best potential storm organization. Line segments producing severe/damaging gusts will be the main risk into early evening. More specifically with respect to timing of the convection today, the latest HREF and its members shows the main round of storms firing up along a line from Near KELZ south to KFIG, KUNV and KAOO between 17-18Z before solidifying into a likely line of storms and plowing across the Susq Valley. A second, weaker MCS near or just to the south of the Mason Dixon line will support additional TSRA that could linger through the early evening hours southeast of the I-81 corridor. SPC`s SLGT area for today covers all of the CWA except for Central and NW Warren county. High temperatures today may be a deg or 2 higher than Monday based on progged ensemble mean 850mb temps. An approaching mid/upper level shortwave will be preceded by a dwindling area of mainly mid and high clouds across the Western Mtns this morning while the bulk of the Central Mtns and Susq Valley will stay mostly sunny into the early afternoon. Scattered afteroon showers and thunderstorms could lead to a reduction in the heat, at least over the northern part of the state this afternoon. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... Convection intensity and coverage should wane with loss of heating tonight, but the region will remain in a ribbon of anomalous pwats/instability and prone to at least a slight chance of lingering showers/tsra overnight. An upper level trough approaching from the Grt Lks will push a cold front through the region Wednesday, accompanied by a round of showers/tsra Wed afternoon into Wed evening. Cloud cover and an early arrival of the fropa should keep the threat of severe weather low over the northwest part of the forecast area. However, pre-frontal heating of the a very moist/unstable airmass, combined with a belt of relatively strong mid level flow, support a possible threat of severe weather Wed PM across the eastern counties. Cloud cover and convection should hold temps down a bit Wednesday, even across the Lower Susq Valley. However, surging dewpoints ahead of the front could still yield heat indices near 100F across the southeast counties. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Deterministic guidance converges towards a return towards fair and seasonable weather with lower humidity Friday as high pressure builds from the Great Lakes. The bulk of guidance keeps dry conditions through Saturday morning so have capped PoPs below SChc (< 15%) through this timeframe. A stalled front is expected to nudge northward into the weekend, allowing for a return to diurnally driven convection. Have capped PoPs mainly to a SChc north of the turnpike Saturday afternoon/evening with the northward extent of SChc creeping into portions of the Middle Susquehanna Valley Sunday evening where the front could continue to drift slightly north. Model guidance does outline mainly dry conditions for the majority of the day on Monday; however, diurnally driven convection cannot be ruled out in the afternoon/evening hours with the best chances mainly south of I-80. Have capped PoPs at low-end Chc (20-30%) given some uncertainty wrt boundary placement and how this will impact any potential convection. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... 16/06Z: LIFR fog/stratus at IPT will dissipate by 13Z. Showers and t-storms are expected across the airspace from late morning through the evening - a few strong/severe storms are possible with local wind gusts 45-55kt from ~270 degrees. Sub-VFR cigs are most likely (>70%) at KBFD 06-12Z Wed with better than 50/50 odds at KJST. Outlook... Wed...AM low clouds west. Another round of t-storms with CFROPA especially central and southeast airfields. Thu...AM Showers exit southeast; MVFR cigs psbl west bcmg VFR. Fri-Sat...AM valley fog. Otherwise, no sig wx/VFR. && .CLIMATE... Daily record max temp of 99F was tied at Harrisburg on 7/15. Previous record was set in 1995. && .CTP WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM EDT this evening for PAZ019-025>028- 034-035-045-046-049>053-058. Excessive Heat Warning until 8 PM EDT this evening for PAZ036- 056-057-059-063>066. Heat Advisory from 8 PM this evening to 8 PM EDT Wednesday for PAZ036-056-057-059-063>066. && $$ SYNOPSIS...Lambert/Dangelo NEAR TERM...Lambert/Fitzgerald SHORT TERM...Lambert/Fitzgerald/Dangelo LONG TERM...Fitzgerald/NPB AVIATION...Steinbugl CLIMATE...Steinbugl