Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 221554 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1154 AM EDT Thu Mar 22 2018 .SYNOPSIS...
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High pressure in Canada will very slowly build south into the northeastern USA by Saturday. Low pressure over the southern Plains on Saturday will move off the Carolinas Sunday morning. Thereafter, it will become an intense and large storm meandering over the western Atlantic early next week, held just far enough offshore by the high pressure system to our north.
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&& .NEAR TERM /THROUGH TONIGHT/... 1030AM: going forward now. 930 AM update: No change to the public grids. will start digging into the future at 1030AM (winter not over). 845 AM: While storm over... this is a big wrapup day for NWS Mount Holly. Storm performed imo, probably on a scale 1 to 5 scale, i expected a 5.0 for late March and it came in ~4 (winds down 5 kts from expected, CFlooding was down 1 cat from expected and snowfall probably about 4" less than expected). STILL, this was a major winter storm for our area. The PNS/LSR summaries delivered between 11A and 1 PM with associated posting of storm total snow map will speak the reality. You may want to be aware, that if you had 6+ inches of wet snow along and se of I95 s of the I-195 intersection in NJ and you didn`t lose power, you`re fortunate. We see on one media source,, that at 1AM 90,000 customers were without power and at 8AM its still 80,000 customers (2.5/household=or about 200,000 directly affected without power), just there in s NJ. We know that is at least 2% of entire NJ customer base of 4 million without power. We just posted a report from a former NMC-NCEP meteorologist... hundreds of trees and poles down vicinity of Buena in Atlantic County NJ with a likely power outage last 3 days or more. Final PNS and map post around 1PM. Take a close look in the rural hinterland of Sussex County NJ where elevations vary from roughly 480 ft top 1800 ft. The elevated northwest corner was spared...less than an inch. the se part of the county up to 10 inches. Models had a sharp northern cut off...we just were never sure where it would be. While this storm produced... it was never completely organized as one mammoth storm that we sometimes see spin up just south of LI. A nice afternoon is in progress for cleaning up. Gusty northwest winds to 25 mph with variable amts of cirrus. Visible imagery shows the extent of the snowcover from ydys storm. Tonight...Cirrus early then clear late. Temperatures tonight are expected to be lower than what we saw this morning, with lows tonight forecast to be generally in the 20s across the region. As a result, any water on the roads from snow melt during the day could freeze leading to slippery conditions on area roads tonight into early Friday morning. && .SHORT TERM /FRIDAY/... Friday...A cold core mid level low (-18C at 700MB), digs quickly southeast over the region through the mid and late aftn. This will result not only in increasing low clouds, but also scattered rain and snow showers, especially along and north of the I-78 corridor through the afternoon. BTV snow squall parameters appear to be met so we`ll be on the lookout. ECMWF continues to show dry conditions this day, and moisture could be very limited with little chance for moisture advection before this event. However, lower resolution models tend to underforecast precip with these types of clipper systems, so kept PoPs close to the previous forecast. Northwest wind gusts 20 MPH. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Did not spend much time on the forecast beyond Friday to focus on wrapping up the winter storm event. From the previous discussion...Another strong vort max moves southward from eastern Canada on Saturday as a separate vort max moves west- to- east through the central U.S. and interacts with the digging perturbation. Attendant surface low in the central plains Saturday looks to be shunted southward somewhat as it tracks into the Ohio/Tennessee Valleys. Just how far south is a challenging question, with considerable disagreement among the operational guidance. The GFS looks especially suspicious, though, given its very progressive evolution of the northern- stream vort max. The 12Z CMC/ECMWF are slower and (as a result) have the track of the southern- stream system a little farther north. This may give the Delmarva Peninsula a chance for some precipitation Saturday night and Sunday. Additionally, there are some indications that as the surface low intensifies off the coast that wraparound (light) precipitation may affect the eastern CWA on Sunday (aided by the passage of the main northern-stream vort max). Cannot discount chances of rain and/or snow for much (if any) of the area during this period, so kept slight-chance PoPs in the grids. If the southward- deflection of the southern-stream system occurs later than anticipated, this may bring somewhat heavier precipitation into the area (especially Delmarva). A low- confidence forecast exists for this period, to be sure. Strong ridging develops early next week as the strong cyclonic vortex meanders eastward off the Atlantic coast. This should bring a prolonged dry period to the area along with a warming trend. A system may affect the region by mid to late week, but models have large timing differences. Generally included slight-chance to low- chance PoPs on Wednesday for now, but temperatures fortunately look more seasonal by then. && .AVIATION /16Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. This afternoon...VFR cirrus expected. NW winds 10-15 kt with gusts up to 23 kt. High confidence. Tonight...VFR conditions expected with only high clouds (15000 AGL or higher) and they clear after 09z. Northwesterly winds near or below 10 KT. High confidence. Friday...VFR to start. Potential for MVFR or low VFR CIGs and rain/snow showers, especially vcnty of ABE-TTN during the afternoon. Northwest winds 5 to 15 kts with potential for gusts to 20 kts or so. High confidence. Outlook... Friday night and Saturday: VFR with northwest winds 5 to 15 kts, potentially lighter during the night. High confidence. Saturday night and Sunday: Some potential for sub-VFR conditions with light rain and/or snow. Winds north to northeast under 10 kts Saturday night and 10 to 20 kts on Sunday. Very low confidence. && .MARINE... Today and tonight...nw winds gusty 20-30 kt this afternoon and 15-25 kt tonight. Atlantic seas will continue to slowly subside. Seas continue to run above the NWPS forecast by 2 ft. So its mainly an SCA this aftn, then into tonight for the Atlc waters. Outlook... Friday and Friday night: May see a lull in winds on Friday morning, but they should increase again by afternoon evening to advisory criteria. Saturday and Saturday night: Sub-advisory winds/seas expected. A slight chance of rain and/or snow late, especially near/south of Delaware Bay. Sunday: Advisory-level northeast winds expected, with some potential for gales (though this is low confidence). Some potential for rain and/or snow. && .CLIMATE...
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RTP water equivalent pcpn: MANY stations were set to missing as the pcpn amounts were far too low as melted by the system. What we KNOW. There were several record daily maximum snowfalls set yesterday, March 21st. This occurred at Philadelphia, Wilmington and Allentown (which smashed their daily record). Atlantic City just missed the daily snowfall record. Location Record for 3/21 Actual Snowfall 3/21/18 -------- --------------- ----------------------- PHL 4.7" (1932) 6.7" ACY 5.9" (1889) 5.7" ILG 5.4" (1964) 6.7" ABE 4.3" (1964) 13.2" ACY 1 day snowfall of 5.7" ranks as the 7th highest March, single day total. Philly did not place top 10 1 or two day. Wilmington 6.7 was the 6th highest 1 day total in the historical database and the two day 8.1 was tied for 7th highest. Allentown 13.2 was the 4th largest single day total behind the 16.7 3/13/93 16.5 3/20/58 13.8 3/3/60 What is as yet unconfirmed and may not be for several days... A new NJ state record for the month of March, may have been set this morning. Thisn is as yet unconfirmed so we`re not saying RECORD, but near record works for me...something else may turn up in the database that was overlooked. Jefferson Township 11.1 inches ydy (1.03 w.e) raised the monthly total to 44.3 inches. So far the record, as we know it, is 43.0 in 1958 Canistear Reservoir. UNOFFICIAL but as fyi... but impressive if you like snow.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ450>455. Small Craft Advisory until 6 PM EDT this evening for ANZ431. && $$ Synopsis...Johnson Near Term...Drag Short Term...Drag Long Term...CMS/Johnson Aviation...CMS/Drag Marine...CMS/Drag Climate...Kruzdlo on digging up the rankings/Drag on the commentary 1153A is the U.S. government's official web portal to all federal, state and local government web resources and services.