textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

A Marine Dense Fog Advisory has been issued for all NJ and DE Atlantic coastal waters as well as the Delaware Bay tonight into Tuesday morning.

A Dense Fog Advisory was issued for the I-95 corridor and points south and east. The coastal strip's Dense Fog Advisory begins now with inland areas beginning later tonight or early tomorrow morning. The Dense Fog Advisory goes until 10 AM Tuesday for all areas within the Advisory.

KEY MESSAGES

1. Areas of fog are expected overnight tonight into Tuesday morning near the coast, and perhaps as far inland as the I-95 corridor.

2. Increasing warmth and humidity through Wednesday with potential record high temperatures.

3. A strong cold front crosses the region Wednesday night into Thursday morning with widespread showers and potential thunderstorms.

4. More seasonable temperatures return for the end of the week and weekend. Unsettled weather possible due to a series of disturbances.

DISCUSSION

KEY MESSAGE 1...Areas of fog are expected overnight tonight into Tuesday morning near the coast, and perhaps as far inland as the I- 95 corridor. A Dense Fog Advisory is in effect for tonight and tomorrow morning for areas along and south/east the I-95 corridor.

High pressure located off the coast of the Southeast will continue to shift gradually eastward through tonight. This has allowed for continued warm and moist air advection throughout the region. Tonight, dense fog is expected to quickly develop over the Delaware Bay and Atlantic coastal waters as temperatures cool. This fog, and perhaps some low stratus, will attempt to work its way inland overnight and into early Tuesday morning. Cape May/Wildwood Airport (KWWD) is already down to a quarter mile. As a result, went ahead and issued a Dense Fog Advisory for coastal areas in New Jersey and Delaware. The primary uncertainty with this forecast is how far inland fog is able to develop, but most guidance suggests fog, some of which likely dense (1/4SM or less), gets to the I-95 corridor. Went ahead with a Dense Fog Advisory for the I-95 corridor and points south and east for tomorrow morning. The morning commute is likely to be affected by the fog and the Dense Fog Advisory goes through 10 AM.

KEY MESSAGE 2...Increasing warmth and humidity through Wednesday with potential record high temperatures.

High pressure remains anchored off the Southeast and Mid- Atlantic coasts through Wednesday.

Tuesday morning, any low clouds and fog will likely clear out fairly quickly, with temperatures rising quickly and dewpoints mixing down. Ample sunshine is expected after any fog has dissipated, allowing temperatures to climb into the mid 70s for most of the area, with slightly cooler temperatures in the southern Poconos and in proximity to the coast where ocean temperatures remain quite cool.

A warm front lifts north through the region late Tuesday night, and low level moisture will increase over the area as surface dew points rise through the 50s. Patchy fog develops once again, with locally dense fog possible as well. Cannot rule out a few showers across northern zones by early Wednesday morning with that warm front lifting north through the region. Lows Tuesday night will be in the 40s and low 50s.

Southerly flow increases on Wednesday as a strong cold front approaches from the west and the pressure gradient tightens. Winds will increase to around 15 mph with 20 to 25 mph gusts. Even warmer and more humid air spreads into the region with highs inland in the mid to upper 70s, highs along the coast still in the 50s owed to the colder ocean waters, and highs in the 60s within 10 miles or so of the coasts. See the Climate section below for the records. The latest guidance has come in several degrees warmer than the previous forecast, so will follow suit. Some spots well inland may even come close to 80. Surface dew points will climb well into the 50s and even around 60, making it fairly humid, especially for this time of the year.

KEY MESSAGE 3...A strong cold front crosses the region Wednesday night into Thursday morning with widespread showers and potential thunderstorms.

Low pressure will be over the Great Lakes on Wednesday and will track to the north and east Wednesday night. This will drag a cold front towards the region late Wednesday, but it will not cross the region until late Wednesday night or even Thursday morning. Widespread showers will develop with the passage of the front. What remains to be seen, though, is the potential for thunderstorms. What is going against the threat is that the front does not look like it will arrive until late, and there will be a loss of diurnal heating, so SBCAPE will be minimal. However, MUCAPE will be up around 500 J/kg, at least initially, lowering to around 200 J/kg as the night progresses. 0-6 km Bulk Shear will average 50 to 55 kt. This will result in the potential for at least some elevated convection. Surface dew points will also be in the 50s to around 60. Will go ahead and add slight chance for thunderstorms throughout the forecast area for most of the night.

Front does not look like it will clear the region until late Thursday morning, and then strong cold air advection develops throughout the day. It looks like the daily high temperature will occur just after midnight, and then temperatures throughout the day Thursday will fall from the 50s in the morning to the 40s by late afternoon as strong northwest winds develop behind the front.

Showers taper off from west to east through the day, and there may even be some snow mixed with the rain, especially north and west of the Fall Line, before ending. Hope you enjoyed the early taste of Spring.

KEY MESSAGE 4...More seasonable temperatures return for the end of the week and weekend. Unsettled weather possible due to a series of disturbances.

Temperatures return to normal for this time of the year on Friday with highs in the 40s to around 50. Going through the weekend, temperatures may be several degrees above normal, but nowhere near as warm as they are during the first half of the week. A series of disturbances will pass through the region, resulting in a slight chance to chance for rain, but some snow is possible north and west of the Fall Line. PoPs will generally be in the 20 to 40 percent range.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.

Tonight...VFR to start for all terminals. KRDG/KABE actually should stay VFR through the night. A challenging forecast for the remaining terminals. Fog begins to develop by 02z along the immediate coastline and gradually expands inland. Thinking VSBYs eventually at the I-95 terminals and especially South Jersey get down to IFR/LIFR, with visibility as low as 1/4SM, with highest confidence in dense fog developing around KMIV/KACY.

The window between 08z-13z (earlier at KMIV/KACY) as the highest probability for reduced visibility, with conditions improving quickly thereafter. Winds generally light and/or calm though a south/southwest direction may be favored at times. Overall, confidence is moderate in restrictions and fog developing. The uncertainty lies in the timing and how low visibilities drop.

Tuesday...Any fog is expected to dissipate quickly after 13z, and VFR conditions are expected through the rest of the day. A sea-breeze should develop and turn winds more southerly at KMIV/KACY. High confidence in prevailing VFR after fog develops, moderate confidence in timing of wind shifts with the sea- breeze.

Outlook...

Tuesday night...Sub-VFR in BR/FG/stratus.

Wednesday through Wednesday night...VFR during the day, then sub-VFR in SHRA and isolated TSRA, mainly at night. S winds may gust to 30 kt during the day.

Thursday through Thursday night...Sub-VFR early in SHRA, which taper off late, then VFR. Abrupt shift in winds from S to NW late Thursday morning. Gusts up to 30 kt in the afternoon.

Friday through Friday night...VFR during the day, then sub-VFR possible at night in RA and/or SN, mainly north and west of the I-95 terminals.

Saturday...VFR.

MARINE

A Marine Dense Fog Advisory has been issued for all NJ and DE Atlantic coastal waters as well as the Delaware Bay from 8 PM this evening until 11 AM Tuesday. Dense fog is expected to develop tonight, with widespread visibilities under 1 NM likely. In some areas, visibilities could be reduced to 1/4 NM or less.

Southwest wind 5-15 kt tonight through Tuesday, with seas generally 1-3 feet.

Outlook...

Tuesday night...Sub-SCA conditions. VSBY restrictions in fog.

Wednesday through Wednesday night...SCA conditions developing. S winds 15 to 20 kt with 25 to 30 kt gusts. Seas 2 to 4 ft, building to 6 to 8 ft at night. VSBY restrictions in fog, then showers and isolated thunderstorms at night.

Thursday through Thursday night...Abrupt shift in winds from S to NW late Thursday morning through the afternoon with gusts up to 30 kt, diminishing at night. Seas 6 to 8 ft, diminishing to 2 to 4 ft at night. VSBY restrictions in showers on Thursday.

Friday through Friday night...Sub-SCA conditions during the day, then SCA conditions likely at night.

Saturday...Sub-SCA conditions.

CLIMATE

Near record high temperatures are forecast for March 10th and 11th. Records for our climate sites are listed below:

Record High Temperatures: March 10 Site............................Record/Year Allentown (ABE).....................80/2016 AC Airport (ACY)....................81/2016 AC Marina (55N).....................68/2000 & 2016 Georgetown (GED)....................80/2006 Mount Pocono (MPO)..................69/1977 Philadelphia (PHL)..................82/2016 Reading (RDG).......................79/2016 Trenton (TTN).......................81/2016 Wilmington (ILG)....................80/2016

Record Warmest Low Temperatures: March 11 Site............................Record/Year Allentown (ABE).....................44/2006 AC Airport (ACY)....................48/1955 AC Marina (55N).....................51/2016 Georgetown (GED)....................55/1955 & 1986 Mount Pocono (MPO)..................47/1955 Philadelphia (PHL)..................54/1955 Reading (RDG).......................51/1955 Trenton (TTN).......................51/1955 Wilmington (ILG)....................48/1955

Record High Temperatures: March 11 Site............................Record/Year Allentown (ABE).....................73/2021 AC Airport (ACY)....................79/1967 AC Marina (55N).....................70/1879 Georgetown (GED)....................77/2021 Mount Pocono (MPO)..................66/1977 Philadelphia (PHL)..................74/2021 Reading (RDG).......................77/2021 Trenton (TTN).......................73/2021 Wilmington (ILG)....................74/2021

PHI WATCHES/WARNINGS/ADVISORIES

PA...Dense Fog Advisory from 2 AM to 10 AM EDT Tuesday for PAZ070- 071-106. NJ...Dense Fog Advisory from 2 AM to 10 AM EDT Tuesday for NJZ012- 015>019. Dense Fog Advisory from midnight tonight to 10 AM EDT Tuesday for NJZ013-020>022-027. Dense Fog Advisory until 10 AM EDT Tuesday for NJZ014-023>026. DE...Dense Fog Advisory from 2 AM to 10 AM EDT Tuesday for DEZ001. Dense Fog Advisory from midnight tonight to 10 AM EDT Tuesday for DEZ002-003. Dense Fog Advisory until 10 AM EDT Tuesday for DEZ004. MD...Dense Fog Advisory from 2 AM to 10 AM EDT Tuesday for MDZ012- 015-020. Dense Fog Advisory from midnight tonight to 10 AM EDT Tuesday for MDZ019. MARINE...Dense Fog Advisory until 11 AM EDT Tuesday for ANZ430-431- 450>455.