textproduct: Burlington

WHAT HAS CHANGED

As of 316 PM EDT Sunday...

No significant changes.

KEY MESSAGES

As of 316 PM EDT Sunday...

1. Scattered showers and thunderstorms continue this evening, then dissipate overnight.

2. Steady rainfall for southern Vermont late Monday into Monday night.

3. An approaching cold front will bring a sharp increase in shower and thunderstorm chances for the end of the week with unsettled conditions continuing into the weekend.

DISCUSSION

As of 316 PM EDT Sunday...

KEY MESSAGE 1: The overall weather pattern today into this evening remains little changed with scattered showers and some embedded thunderstorms continuing. These unsettled conditions are driven by continued cyclonic flow over eastern Canada and New England, with multiple upper low centers sending numerous shortwaves through our forecast area. Breaks in morning cloud cover have allowed 600-1200 J/kg of SBCAPE to develop as per latest RAP analysis. The building instability has supported the development of showers and thunderstorms, though weak bulk shear will keep any storms sub- severe. The Storm Prediction Center once again accordingly has our area just outlined within the General Thunder contour.

We continue to keep a close eye on hydrological conditions given fully or near saturated soils and higher flows on rivers, but at this point no flooding is anticipated. The overall environment (PW values just over 1 inch, warm cloud depths under 8kft...) does not support concerning rainfall rates, though we still can't rule out training of showers or storms over one area. If any showers/storms do end up training , we could see localized ponding in poor drainage areas. So far, rainfall rates have been generally under a quarter inch per hour, which poses no concerns, but we will be monitoring observed rainfall amounts closely.

KEY MESSAGE 2: Monday and Monday night is a tricky precipitation forecast with models still struggling to precisely converge on an exact storm track. The shortwave responsible for Monday's precipitation is currently visible on water vapor satellite imagery moving eastward over the Midwest. Of particular note on the satellite loop is the deep moisture associated with the system, with a direct Gulf connection feeding a 2+ inch PWat air mass toward the wave. As the system moves eastward over the next 24 hours, the general consensus is that the surface low will slide eastward to our south, though just how far north the low and the associated warm front (and moisture plume) track will dictate what portions of our forecast area receive the most precipitation. The deterministic GFS and ECMWF continue to keep the brunt of the rainfall to our south, but the NAM and CMC have generally been tracking the system further north... which would bring a swath of heavier rain to our forecast area. However, the latest deterministic run of the NAM (21.12Z) has notably shifted southward, and our forecast reflects a blend of this solution as well as the more consistent ECMWF and GFS. Our forecast keeps the higher PoPs (70+%) restricted to the southern Adirondacks and southern Vermont Monday afternoon/Monday evening, and then in eastern Vermont Monday night.

With regards to impacts as the system rolls through, the ingredients for moderate to heavy rain will be present...most likely over southern Vermont. However, we continue to monitor the potential that this placement may shift, and we can't discount some of the higher resolution models that maintain a swath of heavier precip as far north as central Vermont. As the previously mentioned moisture plume moves at least as far north as our southern counties, precipitable water values will climb towards 1.5 inches and warm cloud depths over 11kft. This will support heavier rainfall rates than what we have seen over the past few days, but the good news is that the system should be progressing eastward fast enough to preclude widespread hydro concerns. In addition, our southern counties (where the likeliest heaviest precip will be) have seen less precipitation recently than areas further north, thus are better able to absorb the incoming rainfall.

Rain will taper off from west to east Monday night, and outside of a few residual showers, the remainder of Tuesday should be mainly dry. Wednesday will be mainly dry with some breezy northwesterly winds around 15 mph.

KEY MESSAGE 3: Models are becoming increasingly bimodal in terms of timing for the end of week system. Blended guidance continues to bring increasing chances of showers and thunderstorms as flow tilts southwesterly and as diffluence aloft increases Thursday. However, an increasing number of deterministic models are pointing to a more delayed approach suggesting Thursday night and Friday will be the more active periods. Should the original consensus bear out, Thursday could feature some thunderstorms with temperatures being relatively warm in the upper 70s to low 80s. This could point to potential for a few stronger storms and possibly localized heavy rainfall. On the flip side, deterministic models keep temperatures warm for thursday, but drier, while Friday will be the focus for some early day thunderstorm chances. This timing would point more towards weaker thunderstorms, but not eliminate heavy rain potential. Looking at model output, flow may align more with the boundary orientation favoring a training shower/storm environment. We'll be keeping an eye on this pattern through the week given recent saturation of soils and increased runoff potential. Otherwise, cyclonic flow will likely linger behind the system keeping some shower chances in place over at least a portion of the weekend depending on how fast ridging can build back in.

AVIATION /06Z MONDAY THROUGH FRIDAY/

Through 06Z Tuesday...Recent rainfall, clear skies, and light winds early this morning is a recipe for radiational fog, and site PBG is already reporting visibilities ranging from 1 to 3 miles and occasional ceilings around 200-400 feet above ground level. We anticipate sites SLK, MPV, and EFK will join them over the next few hours, though confidence is decreased by the increasing cloud cover ahead of our next round of precipitation. However, confidence is increased at SLK by its temperature already plummeting into the 40s as of 06Z Monday. Thinking vis and cigs will go to IFR levels at these four sites on and off through 14Z Monday, and other sites may have vicinity fog approaching runways. After 12z Monday, southerly winds will increase to 5-15 knots, and rain with vis 3-6 miles and MVFR level ceilings will gradually overspread the region from the south after 18z Monday. After 00Z Tuesday, ceilings may even fall to IFR levels at RUT.

Outlook...

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

BTV WATCHES/WARNINGS/ADVISORIES

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