Area forecast discussion National Weather Service Mount Holly New Jersey 629 PM EDT Monday Mar 10 2014 Synopsis... low pressure moving across southeastern Canada trails a weak cold front into the Middle Atlantic States tonight and then stalls. Low pressure in the Central Plains Tuesday will move to Kentucky Wednesday morning, then intensify rapidly as it passes across New Jersey Wednesday evening and east of New England by early Thursday. High pressure will follow across the southeastern states by Friday morning. Low pressure in eastern Canada this weekend will send a cold front into the Middle Atlantic States by Sunday. Low pressure then develops along the southeast coast of the United States next Monday. && Near term /until 6 am Tuesday morning/... an area of low pressure will move across southeastern Canada and New England tonight, pulling a weak frontal boundary into our area. The front is not expected to have much moisture associated with it, and the strongest lift associated with the short wave will pass to our north. Therefore, we expect any precipitation to pass north of our area. Otherwise, some mainly middle to high level cloudiness will cross our County Warning Area at times. Low temperatures were a blend of the NAM/GFS MOS, with some minor tweaks made. The hourly grids were adjusted based on the latest observations, then the lamp/lav guidance was blended in. The sky cover was adjusted downward quite a bit for a time this evening as satellite imagery shows that the earlier clouds have thinned/cleared quickly thus far. Some additional middle to high level cloudiness are expected to arrive during the course of the night. && Short term /6 am Tuesday morning through 6 PM Tuesday/... the front that moves across the area overnight may get hung up across the southern half of the area on Tuesday. Again, there does not look to be much vertical moisture, nor any strong short wave/vorticity maximum during the day Tuesday, so we do not anticipate any precipitation. There will likely remain some cloud cover, mostly middle-high level clouds. With the flow becoming more zonal aloft, thicknesses will rise into Tuesday. This will allow temperatures to warm, making Tuesday one of the warmest days in quite a long time. Mav/met MOS numbers were fairly close overall, so a blend of the two was used for daytime highs, which keeps above normal temperatures everywhere. && Long term /Tuesday night through Monday/... 500mb: a sharp short wave moving southeast from the northern plains Tuesday evening evolves into a strong cold north south trough crossing the East Coast Thursday. Strong ridging follows late in the week before short waves develop a new trough in the east early next week. Temperatures: calendar day averages near or slightly above normal Wednesday as minimum temperatures occur at 1159 PM Wednesday...then well below normal Thursday and Friday with daytime maximum temperatures about 20 degrees below normal Thursday. Temperatures average near normal this weekend before probably slipping below normal early next week. Forecast basis... 12z/10 50 50 blended GFS/NAM MOS guidance Tuesday night-Wednesday night, mex MOS guidance Thursday and Thursday night then 1522z/10 wpc guidance Fri-Mon. The 12z European model (ecmwf) is received a little too late at weather forecast office level for confident adjustments to the 12z package. The 09z/10 sref 3 hour probability of precipitation and 12z/gefs 6 hour probability of precipitation for .05 were reviewed with any significant adjustments to the above forecast basis noted. The dailies below... Wednesday...mostly rain for our area except maybe several inches of snow possible at the end of the event along and north of i80 from Sussex County into the Poconos and even here...confidence for snow accumulation is below average despite the 12z/10 European model (ecmwf). Sref snow accumulate probs have dropped substantially since 03z/10. Depending on the track of the surface low...strong isallobaric gradient with associated strong pressure falls through nnj will draw cold surface air southward beneath above 32f air aloft possibly leading to a brief period of freezing rain in the Poconos late in the day Wednesday. Huge cold air advection flux with 10mb 3 hour pressure rises during the evening may permit 1 to 4 inches of snow in the Poconos in the 8pm to 1 am Thursday time frame. This is still highly uncertain. Its possible that spotty coverings of snow will extend southward to i78 but am not at all convinced since northwest flow is downslope. Low probability isolated severe Delaware-Maryland-Virginia and S New Jersey in the 3pm to 7 PM time frame Wednesday ahead of the cold front. However...ml cape is less than 200j so played it as slight chance thunder at this time. In fact...it may not rain at all prior to 6 PM Wednesday from phl south and east. Turning quite windy late Wednesday night with strong north-northwest cold air advection. Wind Advisory potential with 10mb 3 hrly rises at 03z/Thursday east PA as bl wind increases to 30 knots and cold air advection permits Transfer to about 3500 feet (42-48kt). Thursday....windy and very cold for the time of year with daytime temperatures about 20 degrees below normal. Mixed clouds and sun. Thursday night...diminishing wind and cold. Friday-Saturday...milder ahead of the next cold front and pretty much wpc grids. Not much energy expended here as the primary focus was Wednesday-Wednesday night-Thu. Sunday...a cold front passage. Wpc gridded guidance. Monday...complex and colder than normal with lots of uncertainty. The European model (ecmwf) has been off and on with a large cold storm for Monday but right now...we're talking day 7. Confidence below average. && Aviation /00z Tuesday through Saturday/... the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg, kmiv, kacy and surrounding areas. Tonight...VFR, with ceilings at times mainly at or above 15,000 feet especially from later this evening Onward. Southwesterly winds mainly 4 to 8 knots, becoming west and northwest late. Tuesday...VFR, with ceilings at times at or above 10,000 feet. West-northwest winds around 10 knots, then diminishing toward evening. Outlook... Tuesday night...VFR. High confidence. Wednesday...MVFR/IFR conds with showery rains developing in the afternoon or evening. MDT to high confidence. Slight chance of a thunderstorm Delaware-Maryland-Virginia late in the day. A gusty south-southwest wind to 25 knots developing vicinity kphl south and east during the afternoon as very strong low pressure crosses New Jersey. Wednesday night...MVFR/IFR conds in showers during the evening possibly ending as snow showers or a period of snow...mainly krdg- kabe north. Becoming very windy with northwest wind gust 28-38kt. MDT to high confidence. Thursday-Friday...VFR. Gusty northwest winds 25-35 knots Thursday. High confidence. Saturday...probably VFR. MDT confidence. && Marine... sub-advisory conditions expected overnight overnight into Tuesday. A cold front will move into the coastal waters tonight into Tuesday, which could help winds gust around 20 knots. Winds will begin out of the southwest, then become more west to northwest toward daybreak Tuesday into the day. Outlook... Tuesday night...sub-advisory conditions expected. Wednesday...increasing Small Craft Advisory conditions as low pressure approaches. Small Craft Advisory issued. Average to above average confidence Wednesday night-Thursday...gale conditions expected. Well above average confidence. Freezing spray expected for a time Thursday morning. Thursday night-Friday...Small Craft Advisory conditions. Saturday...Small Craft Advisory possible. && Hydrology... Tuesday afternoon...we'll take a closer look at quantitative precipitation forecast...anticipated runoff and any potential for any minor flooding before it all freezes up again Thursday. && Phi watches/warnings/advisories... PA...none. New Jersey...none. Delaware...none. Maryland...none. Marine...Small Craft Advisory from noon to 6 PM EDT Wednesday for anz430-431-450>455. && $$ Synopsis...drag near term...gorse/Robertson short term...Robertson long term...drag aviation...drag/gorse marine...drag/Robertson hydrology...
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