textproduct: Binghamton

WHAT HAS CHANGED

Rainfall was kept about the same as the previous forecast, though a heavier strip was added through the Southern Tier into CNY. Severe risk remains mainly south of the Wyoming valley but will need to be watched closely with how far north the surface warm front can get.

KEY MESSAGES

1) An area of low pressure passing through PA today will bring widespread rain to the region. Most areas will see between an half inch and an inch, with isolated areas seeing up to 1.5 inches.

2) Dry, northerly flow Tuesday and Wednesday will bring mostly sunny skies and a chance for overnight fog in deeper valleys.

3) Pattern turns more unsettled and warmer for the end of the week into the weekend as flow becomes more west to southwest with moisture returning to the region.

DISCUSSION

KEY MESSAGE 1...

The MCV that formed yesterday has become a weak area of low pressure that will move through PA today. Looking at Theta E fields, a warm front will lift into CNY today at 850 mb with fairly strong southerly flow feeding moisture into it. This will result in a wide area of stratiform rain for a good portion of the day basically for the northern Tier of PA and northward through CNY. For the Wyoming Valley and the Poconos, rainfall is looking more convective in nature. As of now looking at forecast soundings and surface temperatures in the CAMs, the warm front at the surface does not quite lift into southern NEPA. This should help mitigate potential severe surface based storms which would bring a wind and potentially a tornado threat. Trends through the day will need to be watched as it is tricky to nail down the northern extent of a warm front in a weak low pressure system like this significantly ahead of time. If the front does lift north enough into NEPA, MLCAPE could approach 700 to 1000 J/kg with 35 to 40 knots of shear, with looping hodographs, where forecast Storm Relative Helicity in right moving storms could approach 500 (or more but if the warm front lifts north, the surface winds will not be as backed) which is significant for this area. A big concern in this set up is storms that are on the warm side, and just cross into the cooler side where there is higher helicity and quickly spin up a tornado before it gets too far into the stable air mass. Hail does not look too likely with mid level lapse rates not too terribly steep, but there is strong winds near the EL that could help strengthen updrafts if they can get deep enough.

KEY MESSAGE 2...

Once the low is through the region Monday night, north to northwest flow behind the low brings in dry air and high pressure Tuesday and Wednesday. Day time will see mostly sunny skies with dry air mixing its way to the surface lowering humidity through peak heating. At night, with the expected rain, greater evaporation in the afternoon and evening will help increase the low level moisture enough for some valley fog development.

KEY MESSAGE 3...

For Thursday into next weekend, the flow aloft becomes more zonal with a westerly to slightly southwesterly flow. While timing of shortwaves are all over the place this far out, there is high confidence that there will be multiple waves late week and into the weekend to move through that could trigger showers and thunderstorms. The Bermuda high also is meandering back west, towards Bermuda, which will help with advecting in warmer air aloft as well as open up the region to better moisture from the Gulf and Atlantic. There is looking to be at least some severe thunderstorm risk as well, with the 500 mb wind speeds remaining between 35 and 60 knots Thursday into Saturday so that will supply some shear with the shortwave passages.

AVIATION /06Z MONDAY THROUGH FRIDAY/

VFR conditions expected thru the overnight hours as light rain showers begin to move in from the west. Restrictions should not start popping up until mid-morning, with MVFR vis and ceilings developing as rain continues to be steady. Models are showing a period of heavier rain moving in during the late morning into mid afternoon hours, where IFR restrictions could occur at AVP/BGM/ITH/ELM. Most guidance wants to crash ceilings to IFR and lower by late morning, but given the time of year and conditions upstream near the current low pressure system, confidence was not high enough to have prevailing IFR restrictions until late in the afternoon for BGM/ELM/ITH. IFR should remain thru the end of the TAF period.

SYR and RME should miss most of the IFR, but ceilings are expected to fall by the evening at SYR. Guidance is less clear on RME, with IFR chances too uncertain to include in the TAF at this time.

Outlook:

Monday night...IFR Restrictions possible as center of low moves over the region.

Tuesday through Wednesday...Mainly VFR.

Thursday through Friday...Additional restrictions possible as a short wave moves through the region with showers.

BGM WATCHES/WARNINGS/ADVISORIES

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