textproduct: Burlington

WHAT HAS CHANGED

As of 223 AM EDT Sunday...

No significant changes made with this forecast package.

KEY MESSAGES

As of 223 AM EDT Sunday...

1. Cloudy with showers today, and then dry much of Monday.

2. Showers and thunderstorms likely Monday night into Tuesday.

3. A period of showery weather is expected mid to late week, with a emphasis on Wednesday night into Thursday.

DISCUSSION

As of 223 AM EDT Sunday...

KEY MESSAGE 1: A strong upper trough is diving southwards across Quebec Province, but the attendant surface low is far northeast of our area. A stretched out frontal boundary will sag southwards while a tongue of Pacific moisture rounds an upper ridge axis across the central US as we approach dawn. Southwest to west flow against the frontal boundary will produce intervals of showers, one along the international border this morning, and then more widespread activity this afternoon and evening. Convection this afternoon will likely be short. There's about 500 J/kg of CAPE, but the equilibrium levels will barely make it above -20 C. It will be tough to generate much cloud ice. So thunderstorms should be fairly scarce.

Precipitation will decline with sunset as the front pushes south and daytime heating ends. High pressure will begin to nose in with somewhat cooler air behind the front. A seasonable night of mid 40s to mid 50s is expected with dry, pleasant conditions much of Monday. Towards the end of Monday, precipitation will approach from the southwest.

KEY MESSAGE 2: Upper troughing will continue to dominate far eastern Canada, and this northwest flow will continue to prevent a surge of warm air from reaching this area. A sluggish warm front will slowly shift northeast while mid-level moisture moves northwest to southeast over the hump of a 500mb ridge axis extending into James Bay. So we'll observe precipitation grazing the region Monday night, with the highest rain chances across southern St. Lawrence County, and then these rain chances slowly eke northeast Tuesday morning into the afternoon. There remains some uncertainty with the placement of precipitation. The mid-level moisture could be the remnants of convection in the Great Lakes region, and where exactly the quasi-stationary front is located will play a large role in deciding the focus of heavier rain. Guidance is slightly farther northeast this evening, but not by much. Most atmospheric instability will be aloft Tuesday. Near surface conditions will be mostly stable, and so any storm activity will be garden variety.

KEY MESSAGE 3: During the middle and end of the week, an upper level trough will gradually shunt a ridge over the Midwest and Mid- Atlantic to the south, preventing any heat from building into the region. The last of a couple ridge runner type features will move through Wednesday night into Thursday, likely bringing an area of heavy rain with convective enhancement from elevated instability. The warm sector will not be fully established over the area so limited surface instability should limit the threat for severe weather. However, increasing PWATs and good dynamics will cause an axis of heavy rain to develop, though its exact placement is still uncertain. The flood threat looks low at this point but will continue to be watched. For any flash flooding to occur, the band on Wednesday night into Thursday would likely have to occur in the exact location as the heavier bands in the beginning of the week for a chance. NBM probabilities of 2+ inches of rain are up to around 20 percent for southern Vermont, the part of the region that has the highest probability of seeing the heaviest rain. GEFS 25th-75th percentiles range from a quarter to three quarters of an inch at this time, which does neglect localized higher amounts due to convection. However, trends still continue to prog the best moisture and forcing to our southwest. Brief high pressure will nudge in form the northwest late Thursday into Friday with seasonable conditions. Trends have begun to take more of a wet turn from previous forecasts for next weekend, with our Wed/Thu system occluding off the Canadian Maritimes, keeping cyclonic flow over and shower chances over our area.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Through 12Z Monday...Prevailing VFR conditions are expected to continue at all terminals through the next 18 hours. A cold front will sink south from Quebec with showers already across northern New York and portions of northern Vermont. Shower chances and confidence of rain over northern terminals including MSS/EFK/BTV/SLK/PBG will increase by 18Z with perhaps some brief heavier downpours that could lead to MVFR vsbys reductions. A few isolated thunderstorms will also be possible between 18Z-22Z in the vicinity of the aforementioned terminals, but confidence in terminal thunderstorms are low at this time, and thus have not included thunder in any TAF lines. Should a thunderstorm pass over a terminal, MVFR/IFR vsbys will be possible with changeable winds. Have generally only used PROB30 for rain shower vsby reductions this afternoon at this time. Winds around 10-15 knots will shift from the south to the southwest this morning and then west throughout the day as the cold front moves south. A few gusts around 15-20 MPH will be possible as the front passes through each terminal, mainly at MSS/BTV. Showers will taper off towards 00Z, with increasing confidence in patchy fog at the climo favored terminals closer to 06Z tonight. Should any terminal receive rain, especially if close to 22- 00Z, fog chances will increase.

Outlook...

Monday: VFR. NO SIG WX. Monday Night: VFR. Chance SHRA. Tuesday: Mainly VFR, with areas MVFR possible. Chance SHRA, Slight chance TSRA. Tuesday Night: Mainly MVFR, with areas VFR possible. Chance SHRA. Wednesday: MVFR. Likely SHRA, Slight chance TSRA. Wednesday Night: Mainly MVFR, with local IFR possible. Likely SHRA, Slight chance TSRA. Thursday: MVFR/IFR conditions possible. Chance SHRA.

BTV WATCHES/WARNINGS/ADVISORIES

VT...None. NY...None.