textproduct: Burlington

WHAT HAS CHANGED

As of 238 PM EDT Saturday...

The forecast for the weekend remains on track with continued showers and a few embedded rumbles of thunder expected. Given recent rainfall, we continue to monitor rainfall amounts and hydrological conditions closely, but outside of some possible localized ponding, widespread flooding is not anticipated at this time.

KEY MESSAGES

As of 238 PM EDT Saturday...

1. Rounds of showers will continue through Sunday. Widespread flooding is not expected, though some isolated flooding and ponding in poor drainage areas is possible.

2. A steadier soaking rain is expected to move from west to east through New England Monday into Monday night, mainly impacting our southern counties but with the potential to track further north.

3. After some mid week drier conditions, unsettled weather is favored to return by late week.

DISCUSSION

As of 238 PM EDT Saturday...

KEY MESSAGE 1: The showery and unstable weather regime will continue as an upper low slowly pivots eastward over the Canadian Maritimes. Shortwaves rounding the base of this trough today along with additional shortwave energy rippling into the area from the west will support multiple rounds of showers with some embedded thunderstorms lasting through the end of the weekend. Despite continued cloud cover, we'll see the development of 500-1000 J/kg SB CAPE this afternoon and again Sunday afternoon. Mid-level lapse rates generally will remain in the 5-6.5 degC/km range, which all together could support the development of some scattered convective showers and potentially some embedded pulse-type thunderstorms this afternoon and again Sunday afternoon. Lack of deep-layer shear will keep thunderstorms generally sub-severe, and the Storm Prediction Center accordingly only has our area outlined in the General Thunder outline for today and tomorrow.

While this means severe winds and hail are generally not expected, the primary concern remains briefly moderate to heavy rain within heavier showers or thunderstorms, capable of producing localized ponding or isolated flooding. This is especially true in areas that have seen moderate or heavy rainfall over the last 24 hours, and thus already have near saturated soils. In general, the highest precipitation amounts over the last 24-48 hours have been observed near the International Border and over the Champlain Valley and northern Green Mountains. The good news is that precipitation rates this afternoon and tomorrow are not expected to be too concerning, with precipitable water values of around an inch limiting the heavy rain threat. The one concern would be any areas where heavier showers or thunderstorms train over one area, in which case those areas will need to be watched closely. The northwest to southeast flow continues to support a non-zero potential for some training, but so far today showers have been moving fast enough to limit the concern.

Between today and tomorrow's showers and thunderstorms, we expect a general additional quarter to half inch of rain, with locally higher amounts likely in areas that experience training showers or storms. Six hour Flash Flood Guidance from the Northeast River Forecast Center is around 1.8 to 2.25 inches. Thus, additional rainfall rates for today and tomorrow are forecast to remain below these thresholds, and widespread flooding is not anticipated. We will also continue to watch area rivers closely as rivers are generally running high but are within banks. At this point, no rivers are forecast to go into flood stage over the next few days, but this could change if precipitation amounts locally exceed our current forecast.

KEY MESSAGE 2: The pattern remains active going right into the upcoming work week. The upper-level low over the Canadian Maritimes departs to the east, but will quickly be replaced by a surface low-pressure system/open upper level wave moving east/northeastward out of the Ohio River Valley. This system will bring a eastward moving wave of steady soaking rain through New England Monday, though models still diverge on the exact track of the low and the placement of the associated rain. Notably, models have shifted the track further northward and closer to/through our forecast area with today's latest runs. This results in a tricky forecast, as it initially looked like at least northern portions of our forecast area would stay north of the system and avoid the soaking rain. However, if the trend continues, portions of our area could see an additional inch or more of rainfall. The most likely scenario at this point (which is reflected in our current forecast) is that the heavier rainfall is limited to our southern counties. However, we have tweaked PoPs up slightly for much of the area for Monday, and will continue to adjust if the northward trend continues. Temperatures will remain near seasonal norms for Monday and Tuesday.

KEY MESSAGE 3: Broad longwave troughing is projected to lift a little with a flat, migratory ridge quickly moving through its base on Wednesday. This favors drier conditions for the middle of next week, but could still see some terrain showers as temperatures warm back to the upper 70s to around 80 degrees. Projections suggest dry conditions will be short-lived as a consolidated 850-500mb trough moves through the Great Lakes region likely tilting local winds out of the southwest and increasing diffluence aloft by Thursday. This would keep the warmer temperatures through Thursday, but diffluence/height falls aloft point to increasing shower potential. Models are split on timing, but low pressure could move through the region Thursday/Friday into Saturday with more widespread rain/thunderstorms possible. Depending on details of timing and how wrapped up the low gets, it's possible that we could see an active period of thunderstorms towards the end of next week.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Through 00Z Monday...Showers and thunderstorms persist across the region this evening, bringing occasional bouts of MVFR conditions to terminals, with VFR currently prevailing otherwise. Shower chances are expected to diminish over the next several hours, but not fully dissipate. More widespread MVFR ceilings are expected to develop overnight given abundant moisture, with some IFR ceilings possible at KSLK. CEilings are expected to gradually improve after 12Z to 15Z, with most terminals improve back to VFR. Shower chances will once again increase through the afternoon hours, but overall timing and confidence in location is too low to include in the forecast at this time. Winds look to trend light and terrain driven overnight, becoming more northwesterly throughout the day tomorrow.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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