Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Graphics & Text | 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
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KPHI 222143 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 543 PM EDT Thu Mar 22 2018 .SYNOPSIS... The coastal storm that affected the area will continue to move into the Canadian Maritimes through tonight where it will linger into Friday. High pressure briefly affects the area Saturday while an area of low pressure passes to our south overnight. High pressure will then build across the northeast later Sunday, then across much of the east coast through early next week. A cold front is possible for the later half of the week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Storm over... and probably final PNS is posted. Map to post 330 PM and is our best presentation today for the reality that occurred Tue aftn-Wed night. Dual nor`easter imo performed, on a scale 1 to 5 scale, not quite what I expected which was a 5.0 for late March. It came in ~4 (winds down 5 kts from expected, CFlooding was down 1 category from expected and snowfall probably about 4" less than expected). STILL, this was a major winter storm for our area. On the map, you may want to take a close look in the rural hinterland of Sussex County NJ where elevations vary from roughly 400 ft to ~1800 ft. The elevated northwest corner was spared...less than an inch. The se part of the county up to 10 inches. The gradient between Sussex and Newton NJ...about 7 inches in 12 miles (similar elevation),a 20 minute drive at most. The gradient to elevated Highland Lakes, even greater. 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, or about 5 to 10 degrees below normal. 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 /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... Friday...A cold core mid level low (-18C at 700MB) and a 90M 12 hr 500mb HFC , 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. Most models are dry, 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 we have mentionable pops basically I78 north. Max temps 30s high terrain northwest, 40s elsewhere or about 10 to 15 degrees below normal. Northwest wind gusts 20 MPH. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... Any snow showers that affect the area during the daytime are expected to dissipate by the evening and lead to a dry forecast overnight. By Saturday, weak high pressure briefly affects the area, before an area of low pressure passes to our south overnight. It is expected that this low will pass far enough to our south that our area avoids another major snow event. However, several short wave/vorticity impulse are forecast to move across the area Saturday night through Sunday, while some enhanced low-mid level moisture and low-mid level lapse rates increase during the day as well. This could lead to some isolated snow showers overnight into Sunday, although it is a small chance at this time. Otherwise, a cool, breezy period is expected Saturday through Sunday. High pressure builds across the northeast Sunday, then begins to build down the east coast Sunday night. Dry conditions will return for late Sunday into Sunday night. By Monday, high pressure fully builds across the entire east coast, and remain in place through Tuesday. This will keep dry conditions across the area Monday and Tuesday. Temperatures remain below normal Monday and Tuesday, but a warming trend begins by Tuesday. Uncertainty begins to build as we move into Wednesday through Friday as there is the potential for a cold frontal passage, but there timing differences among long term models. The Canadian and ECMWF keep high pressure across the area and the cold front to our west, until they bring the frontal boundary through late Thursday into Friday. The GFS brings the cold front toward the area Wednesday and Wednesday night, then lifts an area of low pressure across the area with another frontal passage around Friday. Guidance has been reluctant to come to an agreement on a solution for the second half of the week. So we will keep a slight chance of showers in the forecast for Wednesday-Friday time period. Depending on the thermal profiles, precipitation would likely fall as rain for most areas, although some snow can`t be ruled out for some areas. && .AVIATION /22Z THURSDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Remainder of this afternoon...VFR cirrus. NW winds 10-15 kt with gusts up to 30kt. High confidence. Tonight...VFR with only high clouds (15000 AGL or higher) and those 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...Becoming VFR. Slight chance of isolated snow showers early. Northwest winds gust 15-20 knots.Moderate confidence. Saturday...VFR. Northwest winds may gust 15-20 knots early in the day. High confidence. Saturday night...VFR early, may lower to MVFR overnight. North winds becoming northeast overnight and may gust 15-20 knots late. Moderate confidence. Sunday...Becoming generally VFR. Slight chance of isolated snow showers which may temporarily lower conditions. Northeast to east winds gusting 15 to 20 knots. Moderate confidence. Sunday night...Generally VFR. East winds gusting 15-20 knots. High confidence. Monday-Tuesday...Generally VFR. High 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 all waters, then into tonight for the Atlc waters. Outlook... Friday night...Small Craft Advisory conditions possible. Saturday-Saturday night...Conditions expected to be below advisory levels. Sunday-Sunday night...Small Craft Advisory conditions possible. Monday-Tuesday...Conditions expected to be below advisory levels. && .CLIMATE...
-- Changed Discussion --
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. PHL: today is the 18th consecutive day of below normal temps in PHL. Looks like we could add 5 more to the string. 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 ABE Monthly 20.7 ranks #4 behind 1958 30.5 1993 21.6 1960 21.3 ACY monthly 9.2 ranks #5 behind 1969 17.6 2014 15.6 1960 13.4 1956 12.7 ILG monthly 20.3 ranks #2 behind 1958 20.3 PHL monthly 15.2 ranks #2 behind 1941 17.2 I tend to remember everything (at least vaguely) after 1950. Yearly July 1-June 30 snow year ACY 33.7 ranks # 9 well behind the record of 58.1 in 2010. 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. This 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. Finally PHL projection: March avg temp is likely to be less than Feb (41.9 which was 6.2 abv normal). For now, we`re projecting 39.6 or 3.9 BELOW the normal of 43.5. We could see that avg temp rise a degree above where we have it projected.
-- End Changed Discussion --
&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ450>452. Small Craft Advisory until 8 AM EDT Friday for ANZ431-453>455. Small Craft Advisory until 8 PM EDT this evening for ANZ430. && $$ Synopsis...Robertson Near Term...Drag Short Term...Drag Long Term...Robertson Aviation...Drag/Robertson Marine...Drag/Robertson Climate...543 is the U.S. government's official web portal to all federal, state and local government web resources and services.