Area Forecast Discussion

WHAT HAS CHANGED

Chances of precipitation were expanded tonight into tomorrow morning, then lowered through the afternoon as very dry air advects in.

KEY MESSAGES

1) Cold air mass in place through Tuesday morning with well below average temperatures and chances of snow showers tonight.

2) A gradual warm up is expected from mid week into the start of next weekend.

DISCUSSION

KEY MESSAGE 1...

With the cold front passage this morning, temperatures cooled a a couple degrees colder than forecast so snow was a bit more widespread with several inches of accumulation at higher terrain. The sun is starting to come out from west to east as the thick cloud cover moves east with the front. The sun will likely melt all the snow that accumulated today and warm areas that see sun before 3 pm into the low 40s. With the upper level trough axis still moving in, 500 mb heights are still falling with cold air advection in aloft. The combination of solar heating warming the surface and the cooling aloft will lead to unstable conditions this afternoon and evening. Scattered rain and snow showers will develop for much of the region with the stronger showers containing graupel and potentially some lightning if the updrafts can get deep enough before losing day time heating.

Tonight, lake effect snow develops as 850 mb temperatures fall to near -10C. Boundary layer shear is not favorable for organized banding but scattered snow showers will develop for most of CNY and the Finger Lakes into the Twin Tiers of NY/PA. Accumulation of snow will likely be limited to higher terrain and elevated surfaces and likely be less than an inch.

The cold airmass remains in place tomorrow, with high temperatures struggling to climb into the 40s. Forecast soundings show very dry air advecting in aloft and as this mixes down, low level moisture mixes out so chances of precipitation were removed for tomorrow afternoon. Many CAMs are showing scattered rain/snow showers forming once again but it looks unrealistic given the dry air above the boundary layer that will mix down. The dry air, clear skies, and a surface high building in is going to lead to a very cold night Monday into Tuesday. Just for fun, the probability of lows being 25 degrees or colder on or after April 20th in any given year is around 2% for all climate sites so very anomalous for this late in the year if we do fall into the low 20s.

KEY MESSAGE 2...

After a cold morning on Tuesday, the upper level trough is on its way east with rising 500 mb heights and 850 mb temperatures warming back above freezing by the afternoon. The rest of the week into the weekend is looking mostly dry outside of a frontal passage overnight Tuesday as a weak 500 mb shortwave moves through. There is no cold air advection behind this front so a gradual warm up is expected into next weekend, with highs back into the 60s and 70s and lows back above freezing. There is hints that we could be going back into a wetter pattern next weekend as ensemble 500 mb height anomaly means show a trough trying to set up in the western US and SW flow developing over the east.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Lingering MFVR to Fuel Alt restrictions are expected to scatter out over the next few hours with VFR conditions returning. Lake effect showers are expected to stream across portions of the area this afternoon, with ITH/BGM/ELM having the best shot at seeing showers. Restrictions are not expected with these showers, but cannot be ruled out if a few of the heavier showers move over a terminal. Confidence in this is low so it was not included in the TAFs. Northwest flow with gusts under 20 knots expected this afternoon before diminishing this evening and overnight.

Outlook:

Monday morning...Occasional restrictions possible in scattered rain and snow showers.

Monday afternoon through Tuesday...Mainly VFR, then a small chance of showers and minor restrictions Tuesday night.

Wednesday...Front approaches the region with restrictions possible.

Thursday...VFR conditions possible inbetween systems.

Friday... Additional restrictions possible as another front tracks east.

BGM WATCHES / WARNINGS / ADVISORIES

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