textproduct: Binghamton

WHAT HAS CHANGED

Minor adjustments to bring the light rain in a few hours earlier late this evening and tonight. Temperatures were bumped up a few degrees Sunday, although it will remain cloudy and showery all day. Minor adjustments to expected rainfall totals through Sunday evening, mainly a slight lowering. Fog was removed from most locations Sunday night and Monday morning as the dry, steady northerly flow develops. Latest model guidance is trending drier for most of next week, although some uncertainty on the northern extent of clouds and/or rain showers still exists, especially Monday night into Tuesday and again toward Thursday.

KEY MESSAGES

1) A low pressure system will bring a period of steady rain and showers to the area tonight through Sunday. Rainfall amounts between a half inch to one and three quarters inch are expected.

2) The weather pattern is trending drier, with cooler, fall temperatures for much of next week. A stalled front and later a stronger low off the East Coast could keep shower chances nearby.

DISCUSSION

KEY MESSAGE 1...

Mid and high level clouds will continue to overspread the area heading into the evening hours. Low level dry air is in place, with dew points in the 40s around the region. Initially any radar returns will likely be virga (not reaching the ground) but after sunset some sprinkles and light showers will begin to spread in from the west.

The steadier rainfall looks to develop after midnight and overspread the forecast area during the predawn hours Sunday morning. Rainfall amounts by daybreak are expected to range from a quarter to half inch across Central NY and NE PA. The surface low center is forecast to track across New York state through the day on Sunday. Most of the surface based instability is progged to stay south of our area, across south-central PA. With that said, there could be a few elevated thunderstorms mainly during the day on Sunday; especially from the Twin Tiers south into NE PA. There remains discrepancies in the latest CAMs on exactly when and where the steadiest rainfall will develop. There appears to be 2-3 rounds of rain tonight through early Sunday evening , with some minor breaks of just drizzle and light showers in between. PWATs are elevated between 1.5 to 1.8 inches during this rainfall event, but as mentioned above instability looks very limited. This should keep rainfall rates down, to generally just a steady rainfall...with only a very low, marginal risk for any localized excessive rainfall. This potential is mainly confined to NE PA and the Twin Tiers, closer to the modest instability over south-central PA. Overall rainfall totals are forecast to be between 0.50 to 1.75 inches by the time the rain ends Sunday evening.

With the clouds overspreading the area tonight it will remain mild, with lows mainly in the 50s expected. Southeast winds increase between 7-15 mph with a few higher gusts possible overnight and into Sunday morning. The center of the low passes along or just south of I-90 in Central NY on Sunday. Winds will become variable as the low passes overhead, then turn northwest and increase late in the day. Just ahead of the low our area will get into a quasi-warm sector, and with dew points pushing up into the 60s it will become slightly humid. Despite overcast conditions (and rain showers) all day it does look like the warm/moist air advection will push high temperature up into the 60s across the region.

Behind the departing low, winds turn northerly overnight and gradually diminish. A very dry air mass will advect into the area from Canada late Sunday night into Monday. While there could be some patchy fog, it will most likely dissipate as drier air mixes down toward the surface. PWATs fall to under 0.50 inches for CNY by Monday morning, but could remain elevated near 1.25 inches in the Wyoming Valley. Overnight lows will be quite cool, dropping into the 40s to low 50s areawide.

KEY MESSAGE 2...

Drier air continues to advect into the area from the north (from 700mb down to the surface) through the day on Monday. However, the next shortwave will roll east along the stalled front from western PA to Central PA by late Monday. This may begin to push some additional moisture north as surface winds try to come around out of the east-northeast across the Poconos. The most likely scenario is that any rain remains south of I-80 in PA though. Clouds will be thickest and most widespread over NE PA, fading to mainly sunny conditions north along the I-90 corridor of CNY. Expect a steady northeast wind between 6 to 15 mph with a few gusts around 20 mph through the day. Temperatures will be seasonable in the 60s for highs.

The most uncertainty in the medium range forecast comes Monday night into Tuesday. The aforementioned mid level wave moves slowly east across PA and the northern Mid-Atlantic in this time period. Model differences remain in regards to the northern extent of deeper mid level moisture and potential rain. The 12z GFS remains further north and would spread steady rain across all of NE and CNY north to the US Route 20 corridor...and it doesn't shift the rain south until Tuesday evening. Meanwhile the 12z NAM brings scattered showers north to the NY/PA border area Tuesday morning, but keeps it dry further north. The ECMWF is similar to, if not slightly further south than the NAM. There will be big forecast implications depending on where this rainfall sets up; as the cool easterly flow in the low levels could lock in and keep temperatures very cool (upper 40s to mid-50s) where the rain does setup. Meanwhile to the north and east of the rain it would be partly sunny and milder with temperatures in the low to mid-60s. Considering the high amount of spread and uncertainty in the guidance, the official forecast used the blended ensemble guidance, which brings a few showers southern and western portions of the area... and allows temperatures to reach the upper 50s to mid-60s for highs.

The complex weather setup continues for mid to late week as the expansive high pressure sets up over New England and a surface low begins to take shape off the Mid-Atlantic coast. For our area, it is beginning to look like the drier air will win out, under the northeasterly flow. Wednesday and Thursday look partly sunny and a bit cool with highs in the upper 50s to mid-60s. Overnight lows will be in the low to mid 40s each night.

By Friday, uncertainty in the low track along the southern New England coast exists in the latest model guidance. As the low become vertically stacked it may stall and meander around. There is a low chance a few showers could rotate in from the east. Otherwise, partly cloudy and seasonably cool conditions continue through the end of the upcoming workweek. It will be a high amplitude narrow wavelength upper level pattern, so again, a lot of uncertainty.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Remaining VFR into this evening with lowering and thickening mid level clouds overspreading the area. MVFR CIGs and visibility develop by 04-08z as light rain develops and spreads east. IFR to perhaps occasional LIFR conditions then develop for most locations early Sunday morning and continue right through the end of this 18z TAF period. The highest probability for LIFR restrictions (CIGs) will be at BGM after about 13z Sunday. ITH and RME could also be close to LIFR at times Sunday morning. With the east-southeast winds the current thinking is that AVP, ELM and SYR will mainly see CIGs just below 1000 ft agl most of the time. Periods of rain continue through all of Sunday morning and early afternoon. MVFR visibilities are likely in the rainfall.

East-Southeast winds between 6-15 kts develop overnight and into the day on Sunday.

Outlook...

Sunday Afternoon and Evening... Rain expected for much of the period. Periods of IFR restrictions likely.

Sunday Night...Lingering restrictions as the rain moves out and skies gradually partially clear from NW to SE.

Monday...Mainly VFR expected

Monday Night and Tuesday...Possible restrictions with showers, especially NE PA and perhaps the NY Southern Tier terminals.

Wednesday and Thursday...Likely VFR most of the time.

BGM WATCHES/WARNINGS/ADVISORIES

PA...None. NY...None.