Area Forecast Discussion
Issued by NWS State College, PA

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038 FXUS61 KCTP 211915 AFDCTP Area Forecast Discussion National Weather Service State College PA 215 PM EST Sun Jan 21 2018 .SYNOPSIS... A warm front drifting slowly north across the region will bring some occasional light rain or drizzle into early Monday. A potent area of low pressure moving across the Great Lakes will push a trailing cold front through Pennsylvania on Tuesday. Temperatures will rise above normal today and stay there through early Tuesday, before falling back to near or slightly below normal Wednesday and Thursday. A rebound in temperatures to above normal levels will occur again for next weekend. && .NEAR TERM /THROUGH TONIGHT/... Air is still except across the wrn teerain. Advection/snow fog is making it murky/milky in many places. Expect little change to this damp period - until it rains. There is a warm front somewhere to our southwest. Best lift in the 280-285K theta layer is creating the low clouds and they are getting thicker by the hour. As shortwave ridging pumps up over the region, the mild temps aloft will help keep the mixed layer very stable and only prolong our current condition. Expect that approach of a shortwave trough later tonight and the warm front nearing at the same time will give some impetus to the atmosphere to move and create coherent showers over the western mountains around or just before sunrise. POPs will remain close to what we have, highest in the north early, then a dip later tonight before the warm front nears the west around sunrise. Mins will be a bad way to refer to the temps tonight as they will be pretty steady or even rise a little. Perhaps only the eastern valleys could drop a couple of degs overnight. && .SHORT TERM /MONDAY/... Best upper forcing will pass through in the morning and warm front should push through the south shortly after. It may just decide to hang up overhead, but will try to get into NY state. POPs drop off quite nicely after 15Z and the aftn will be dry except perhaps along the northern border if the front does not complete it`s trek across PA. Maxes will be a function of both sun and advection. Will hold the northeast the coolest, but almost everyone gets into the 50s. Southern places take a run at 60F. The winds just 1-2kft aloft start to get pretty fast (eventually 50-60kts Mon night) out of the SSW toward sunset, and help set the stage for the next forecast period. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... Another January thaw will bring a period of relatively mild weather to Central PA through early next week. Temperatures are not expected to be as warm as the previous thaw (late last week), but departures should reach +10 to +15 degrees above average for mid to late January, peaking Monday in the NW and Mon into Tues in the SE. The progressive pattern will keep the cool down during the middle/late part of next week rather brief before temperatures moderate/trend warmer into next weekend. A weak secondary low may form in the lee of the Appalachians and support a period of enhanced rainfall over the eastern 1/2 of PA Tuesday morning. At this time, the total rainfall forecast for early next week does not appear to be as heavy as Jan. 11-12. The most likely period for widespread rain is Monday night into early Tuesday along/ahead of south-southwesterly LLJ axis and cold/occluded front. Winds look rather blustery from later Tuesday into Wednesday on the backside of the low pressure system as colder air filters back in. Snow showers are likely downwind of Lake Erie into Wed night. Dry wx with moderating temperatures Thu-Fri under high pressure. Some showers may sneak into the NW Sat as weaker low pressure system lifts across the Great Lakes, with better chances for rain with another low on Sunday. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... Some improvement is occurring this aftn as heating helps to rise the cigs. But the high moisture, steep inversion and slight upslope flow into the mtns tonight will likely drop most terminals back to IFR - with DZ and FG still a problem into the morning. The best chance for organized rain showers is right before the warm fronts moves through. Timing for a line of showers is very consistent cross-models around 10-15Z. These showers will not last very long as they pass over. The highest chance for showers is over BFD and lower in JST/UNV/AOO/IPT. MDT and LNS will likely not have those showers in the morning but could still have some DZ before the warm front passes. The late morning and afternoon will hold a significant improvement across the south - VFR and even big breaks in the clouds. Everyone else will likely improve to MVFR and also dry out. An LLWS problem will develop overhead on Monday afternoon and evening as a very strong low level jet cranks up ahead of the cold front. The stable/mainly calm surface layer will be topped by a belt of 50-60kt SSWrly winds just 2-3kft aloft. Cold front moves into the west later Mon night but widespread, potentially gusty SHRA are expected and even an isold TS is possible before the cold front clears the eastern terminals mid-day Tues. Outlook... Tues PM-Wed...IFR SHSN NW. MVFR/VFR SE. Thurs-Fri...No sig wx. && .HYDROLOGY... Marietta gage /MRTP1/ pretty much steady right now. Flow is likely going to stay low enough to keep the gage itself below caution stage for the next 2 days. But, local ice effects are still possible, though. The Flood Watch for this area lasts into Monday afternoon. Due to the mild temperatures, there is a potential for ice movement, but also deterioration/thinning with time. All places along rivers and streams that have significant ice buildup should monitor water levels closely for the next several days. The anticipated rainfall totals of 0.5 to 0.8 inches over the next 48 hrs is much less than we had a few days ago, and the ice is less pervasive/extensive due to our relatively mild temps (vs the period leading up to our previous significant rainfall). && .CTP WATCHES/WARNINGS/ADVISORIES... Flood Watch through Monday afternoon for PAZ065-066. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...Lambert/RXR AVIATION...Dangelo HYDROLOGY...

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