textproduct: Binghamton

WHAT HAS CHANGED

The aviation discussion has been updated.

Temperatures were lowered compared to prior forecast for central to especially eastern portions of the area again Saturday. Also, a minor lake response is now expected Sunday night into early Monday, with mixed rain-to- snow showers in Central NY.

KEY MESSAGES

1) Though generally warmer through Saturday, weak boundaries will cause temperature differences across the region and chances for scattered showers with isolated thunder.

2) A strong cold front will bring showers and thunderstorms late Saturday through Sunday morning. A few storms late Saturday could be strong to severe, and locally heavy rainfall could occur for already-sensitive areas.

3) Behind the front it will be breezy and colder, with chances of mixed rain and snow in some parts of the area late Sunday night through Tuesday.

DISCUSSION

KEY MESSAGE 1... While a warmer regime is trying to overtake the area, there are nuances that are making it more successful in some locations than others. Cool air damming from southeasterly low level flow has held temperatures cooler-than-forecast for the eastern Twin Tiers, Poconos, and Catskills. Meanwhile, downsloping of that flow in the Finger Lakes to Syracuse areas is helping them realize their full warming, with highs still reaching lower 70s there. Meanwhile, veering to southwesterly wind is finally starting to occur ahead of a weak cool front trailing from low pressure in Quebec. This will still get the rest of the area into at least the 60s this afternoon, albeit down a few degrees from prior expectations.

The weak front will dip through the area late this afternoon into evening, with little forcing and also limited moisture. Scattered showers and perhaps isolated thunder can be anticipated but by their very nature missing some locations. Severe risk is pretty doubtful, but 40-50 knot flow in the 3-6km layer could potentially lead to a few stronger wind gusts if cells can materialize in western PA-NY, perhaps edging towards Steuben County.

After that boundary passes, southeasterly low level flow gets going again with yet another setup for cool air damming. Above 850mb it is quite warm, but a strong shallow inversion is likely to hold back temperatures from their full potential and thus the lower-than-prior expectations for highs of upper 50s-mid 60s. Lower elevations of the Wyoming Valley to Bradford and Steuben Counties will be less prone to the extra clouds and cool air and thus are more likely to reach into upper 60s-lower 70s. Despite the inversion in the lower levels, there will still be waves translating with a touch of instability aloft, so isolated to scattered pre-frontal showers and thunder cannot be ruled out as the day carries on. That is correct, another front will be approaching, though this one will be stronger.

KEY MESSAGE 2... A strong cold pushes through the region Saturday night into Sunday morning. Showers and thunderstorms are expected Saturday evening through early Sunday morning. The nocturnal timing of this frontal passage is not optimal for severe thunderstorms, with a lack of surface-based instability. However, the front will be strongly-forced with at least some instability aloft, thus the marginal risk for isolated damaging wind gusts west of Interstate 81. Perhaps the more important thing to watch, given our already wet antecedent conditions, will be potential for isolated flooding issues. Areal average of one to two thirds of an inch of rainfall would ordinarily not be a problem, but there are some spots very sensitive to additional rainfall right now. Generally speaking the front will be progressive which should limit the flood risk, however things will still need to be monitored closely should locally higher amounts occur where they are least needed.

KEY MESSAGE 3... In the wake of the front, much colder air will advect across the region Sunday through Tuesday. Highs of 50s-near 60 Sunday will actually be very early, with level to falling temperatures behind the front during the daytime. 850mb temperatures will be quick to drop below freezing, initiating a post-frontal lake response Sunday evening into early Monday. There will also be a lobe of deeper moisture wrapping back around the low Monday. Thus lake-enhanced snow or mixed rain-snow showers can be anticipated, even though amounts will be light. A clipper-like system will then reinforce the chilly air Monday night into Tuesday, which could actually bring another round of snow showers to the region, before temperatures trend back up for the remainder of the workweek.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

A weak cold front will move through the region this evening veering winds from their current WSW direction to the NW and eventually light and variable as the front stalls over PA. A lot of variables will be at play for the ceilings tonight given airmass changes but overall the expectation is for MVFR to take hold with isolated IFR developing in response to moist air cooling behind the front.

Some improvement to MVFR and VFR is possible by late Saturday morning before the surface front begins returning toward northern PA and central NY as a warm front. This will reintroduce layered clouds lowering again to at least MVFR during the afternoon with visibilities also deteriorating as drizzle and showers develop.

Outlook:

Saturday Night...Flight restrictions likely in periods of showers and possible thunderstorms.

Sunday...A frontal system crosses the region with additional showers and restrictions possible, especially early in the day.

Monday and Tuesday...Mainly VFR with a low chance of rain and snow showers.

Wednesday...Mainly VFR.

BGM WATCHES/WARNINGS/ADVISORIES

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