Area Forecast Discussion
Issued by NWS Mt. Holly, NJ
Issued by NWS Mt. Holly, NJ
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739 FXUS61 KPHI 272149 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 549 PM EDT Mon May 27 2024 .SYNOPSIS... A cold front crosses through our region tonight into Tuesday morning. Weak high pressure builds through the region Tuesday. Low pressure passes through Wednesday and Wednesday night. High pressure returns to close out the week. && .NEAR TERM /THROUGH TUESDAY/... Main change with the early evening update was to lower PoPs and coverage of showers and thunderstorms through the evening hours. We`re not out of the woods yet in terms of severe risk as winds just a few thousand feet aloft are above 40kt, but due to the earlier convection and cloud cover, it appears the more stable boundary layer is limiting the extent of evening thunderstorms. Very broken line of showers and storms continues to progress closer to our region from central PA and central MD. The severe thunderstorm watch continues through 9 PM EDT. That should cover the peak of the severe risk period, but may have storms and showers linger a few hours later than that. As far as hazards, wind is becoming the primary hazard. As mentioned above, we have stronger winds just above the surface, so it won`t take much to mix it down. Also have a concern for heavy rain and flooding especially in the Lehigh Valley, NW NJ, and southern Poconos where some areas have already received nearly 2 inches from earlier storms The hail threat is decreasing as convection has been relatively low topped, though can`t rule out hail around the severe threshold (1" in diameter). Low level winds are now nearly unidirectional, which further decreases the threat of tornadoes. Can`t rule any one threat out, but in general our focus now is primarily on the wind and heavy rain threat. The bulk of the activity should be east of the region around midnight, just ahead of the initial cold front. A secondary cold front will pass through later in the day on Tuesday. Temperature gradient across either front isn`t significant, so temperatures tomorrow may be close to what we are seeing today. However, the big change will be noticed in the humidity. Surface dew points drop from the upper 60s/low 70s on Monday to the upper 50s/low 60s on Tuesday. We should have mostly dry conditions tomorrow, though isolated storms are possible in the southern Poconos as a lagging mid and upper level short wave trough slides just northwest of the region. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... That upper trough will be over the Northeast/Great Lakes/Ohio Valley/Mid-Atlantic for the mid-week period. A short wave trough will dive into the base of the trough Tuesday night, and surface low pressure develops over the Appalachians. This low will the pass through the region on Wednesday and Wednesday night. Showers will become likely along with scattered thunderstorms for most of the area Wednesday. With highs generally in the mid to upper 70s and dew points mainly in the mid to upper 50s, SB CAPE looks to be minimal, generally up around 500 J/kg and highest 0-6 km Bulk Shear values will be 35-45 kt, mainly over southern New Jersey and Delmarva. So while thunderstorms are possible, there does not look to be a widespread severe weather outbreak at this time. Showers taper off Wednesday night as low pressure departs. Another shortwave trough is expected to cross on Thursday, but by then, moisture will be very limited, so only have a slight chance of showers and storms at this time. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... The Long Term period should mostly be dry as surface high pressure builds over the area. Upper trough departs over the weekend and will be replaced by mid- level ridging. Conditions should remain dry into the weekend with the next system approaching early in the new week. Cooler Friday with below normal temperatures, and then temperatures return to normal levels over the weekend. && .AVIATION /22Z MONDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas... Through Tonight...Expect periods of MVFR and even IFR during the direct impacts of the storms. The prime period for storms looks to be between 22 and 03Z. Conditions improve to VFR thereafter. S winds around 10 kt, become W after 06Z. Moderate confidence on the overall pattern, but low confidence on details. Tuesday...Mostly VFR. Westerly winds 10 to 15 kt. Moderate confidence. Outlook... Wednesday...Sub-VFR conditions Wednesday in SHRA/scattered TSRA. Thursday through Saturday...VFR. && .MARINE... Small Craft Advisory for the NJ ocean waters for this afternoon and the first half of tonight for as winds will increase to 15 to 20 kt with gusts up to 25 kt. For DE ocean waters and DE Bay, S winds will average 15 to 20 kt. Winds turn W around 10 kt late tonight. Thunderstorms will impact the waters with potentially damaging winds and large hail later today and tonight. Outlook... Tuesday through Saturday...Sub-SCA conditions expected through the week. VSBY restrictions in showers and scattered thunderstorms expected on Wednesday. Rip Currents... For Tuesday, winds will shift to more of a W to SW flow. There will continue to be a MODERATE risk for dangerous rip currents at NJ beaches and a LOW risk at DE beaches. For Wednesday, it appears that most of the region should see a LOW risk for rip currents. However, with the unique bathymetry of Altantic County, the risk there may be MODERATE. As always, rip currents can still develop, and often occur in the vicinities of jetties and piers. Utilize any guarded beaches this holiday weekend if venturing out into the water. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 1 AM EDT Tuesday for ANZ450>453. && $$ SYNOPSIS...Johnson/MPS NEAR TERM...Johnson/MPS SHORT TERM...Johnson/MPS LONG TERM...Johnson/MPS AVIATION...Johnson/MPS MARINE...Johnson/MPS