Area Forecast Discussion

WHAT HAS CHANGED

Only minor changes made from the previous forecast, with little change to our forecast messaging. We continued with the previous forecast changes from NBM guidance including raising PoPs today, increasing wind gusts today, and going colder for low temperatures tonight.

KEY MESSAGES

1) Well below normal temperatures expected today and tonight with scattered snow/graupel showers possible today.

2) Below normal temperatures Tuesday and Wednesday trend back to near normal for the remainder of the forecast period. Aside from a few showers Tuesday night/Wednesday, mainly dry weather expected through the end of the week.

DISCUSSION

KEY MESSAGE 1...As of 1:40 AM EDT...Current sfc analysis shows a cold front tracking into our western zones early this morning. This cold front is tracking along the leading edge of a somewhat narrow albeit highly amplified upper trough easily seen approaching from the west on GOES 16 WV imagery. While skies are relatively clear now, some additional clouds and a few isolated snow showers will be possible as the front tracks through the region tonight. Lows will be mainly in the upper 20s to low 30s.

Today, the upper trough and associated cold pool aloft will be directly overhead. Sfc temps warm into the 30s(terrain) and 40s (valleys), but 500 mb temperatures will be below -30C. We are therefore expecting scattered convective snow showers to develop from late this morning through the afternoon. With steep low-level lapse rates/deep mixing, would not be surprised to see some graupel within these snow showers as well. Some rain may also mix in for the immediate river valley areas. Best chance for snow showers looks to be mainly for areas near and north of I-90, as well as over the high terrain of the Catskills/Helderbergs. Not expecting much in the way of accumulation with any of these snow showers.

Snow showers diminish this evening with the loss of daytime heating and rising heights aloft as the upper trough and associated cold pool track off to our east. Sfc high pressure builds in from the west with clearing skies and diminishing winds. This will allow for favorable radiational cooling conditions, so we went below NBM guidance for overnight lows with 10s for many high terrain areas and 20s for the valleys. Based on the current forecast, GFL and POU could get within a couple degrees of their respective daily record lows.

KEY MESSAGE 2...Tuesday, the sfc high starts off overhead, but slides off to the E/SE allowing for winds to turn more to the S/SW with temperatures climbing into the 40s (terrain) to low- mid 50s (valleys). Mainly dry weather expected with NW subsidence and NW flow aloft. An approaching warm front will likely bring some scattered showers Tuesday night into Wednesday. Some wet snow may mix in over the higher elevations, but not expecting much in the way of accumulation. Precipitation should end as we go through the day Wednesday, with temperatures continuing to moderate into the 50s for most areas, possibly to around 60 for the I-84 corridor.

Thursday and Friday, flow pattern aloft becomes more blocked, with ridging just upstream of our region and upper lows on either side of the ridge. We will therefore be in an area of persistent dry NW flow aloft and large-scale subsidence, with a ridge of sfc high pressure building over the region. Temperatures moderate back to near normal for late April with our proximity to the upper ridge, although the ridge axis and warmer temperatures should remain W/SW of our region.

Next weekend, most deterministic and ensemble guidance show the ridge pinching off aloft well to our north in Canada, with multiple rounds of upper shortwave energy tracking towards our region from the west to the south of the upper ridge. This will bring renewed chances for showers into next weekend, although details/timing remain uncertain given highly amplified and convoluted nature of the flow configuration aloft. WPC largely went with NBM temperatures (which remain near normal) for this period of the forecast.

AVIATION /06Z MONDAY THROUGH FRIDAY/

Through 06z Tuesday...VFR conditions are mainly expected to prevail through the 24 hour TAF period. The only exception is for possible brief MVFR conditions associated with scattered -SHRASN that will develop this afternoon beneath a cool pool aloft. Skies starting out mostly clear, with increasing clouds occurring this morning as the cold pool aloft approaches. Clouds will then dissipate this evening after sunset as high pressure builds in from the west. Winds will initially be westerly around 3-6 kt, becoming west-northwest and increasing to 9-13 kt with gusts of 20-25 kt developing during the morning.

Outlook...

Tuesday Night: Low Operational Impact. Slight Chance of SHRA. Wednesday: No Operational Impact. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: Low Operational Impact. Breezy. NO SIG WX. Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: Low Operational Impact. Slight Chance of SHRA. Saturday: Moderate Operational Impact. Chance of SHRA.

ALY WATCHES / WARNINGS / ADVISORIES

CT...None. NY...None. MA...None. VT...None.