FXUS61 KALY 022004 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 404 PM EDT Fri May 2 2025 .SYNOPSIS... Warmer and more humid with clouds breaking for afternoon sun as isolated to scattered showers and thunderstorms develop mainly near and north/west of the Capital District. Showers and thunderstorms diminish this evening into tomorrow morning before a cold front slowly shifts southward which will support additional periods of afternoon showers and thunderstorms across much of the region. Periods of showers and thunderstorms continue through early next week as a cut-off low approaches. && .NEAR TERM /THROUGH SATURDAY NIGHT/... Key Message: - Isolated to scattered thunderstorms this afternoon into early evening mainly from the Capital District and areas north and west. Some storms may become strong to severe thunderstorms (5-15%) with damaging winds the primary hazard. - Isolated strong/severe thunderstorms possible (5-15%) for areas mainly south/east of Albany Saturday afternoon/evening. Discussion: Clouds will give way to increasing breaks of sun this afternoon as a warm front lifts north and east of the region. Insolation within a rather humid air mass characterized by dew points in the 50s will generate increased instability. Latest HREF guidance shows 50 - 70% chance for SB CAPE values to exceed 500 J/kg with the highest probs mainly north and west of Albany but probabilities are capped at just 20 - 40% to exceed 1000 J/kg with coverage much more limited. As an upper level shortwave and sfc low tracks through Ontario, we will enter into the warm sector and high temperatures this afternoon should reach into the 70s and even near 80 in valley areas. While the main cold front remains displaced well to our west, a sfc pressure trough from western/central NY will shift eastward and serve as the primary forcing for ascent. High res guidance suggests convection initiates initially in the southern/western Adirondacks by 17-18 UTC before shifting south and eastward heading towards I-90 this afternoon. Given broad southwest flow over the Eastern CONUS with a conveyor belt of rather strong low and mid-level winds, deep layer shear values will likely be strong enough to support organized convection, should it develop, as 0-6km shear values reach 30 - 45kts. While instability and shear are favorable enough to support organized convection, the lifting mechanism looks a bit weak and that may limit the strength of updrafts. The greatest overlap of instability and shear should be areas north of I-90 through mid and late afternoon, possibly shifting to near or just south of I-90 this evening. The Storm Prediction Center maintains its marginal risk (level 1 of 5) for much of the region for severe thunderstorms. Since linear storm mode or storm clusters are favored, damaging wind gusts is the primary hazard from any strong/severe storms. Stronger updrafts can also support marginally severe hail. Storm coverage weakens after sunset with most showers/storms diminishing before Midnight. The true sfc cold front then gradually slides south/east towards our area overnight. With most of the region remaining ahead the front tonight, most can expect muggy/mild conditions and where skies can at least partially clear may see some patchy fog develop. The southern/western Adirondacks and western Mohawk Valley should trend cooler/drier once the front pushes through towards sunrise. Heading into Saturday, the incoming boundary stalls around the I-90 corridor with a warmer/more humid air mass to the south and east with a slightly cooler and less humid air mass the north and west. The conveyor belt of rather strong southwest flow remains positioned over the eastern CONUS as a positively tilted potent shortwave over the TN/MS Valley amplifies into a cut-off low. A moisture plume with PWATS greater than 1" continues to stream from the Southeast U.S into the Northeast and becomes focused along the stalled boundary. As additional embedded shortwaves within the southwest flow track along the boundary, these will act as the necessary forcing mechanism to result in periods of rain. The first half of the morning looks mainly dry but then chances for rain increases by mid to late morning (10am - 12pm) and continues through mid-afternoon (2 - 5pm) before rain exits from west to east into New England. All in all, not a complete washout but there likely will be a 2 to 4 hour period of rain. Given the higher PWATS and breaks of early morning sun, morning insolation should aid in generating some instability but the higher dew points will be positioned in the mid-Hudson Valley and NW CT. Thus, the 12 UTC HREF shows 40-60% chance for SB CAPE values to exceed 1000 J/kg in these areas while probabilities in areas north/west of the Capital District are near 0%. SPC maintains its marginal risk for severe weather in our southern zones given sufficient surface based instability and higher 0-6km shear values 30-40kts that can support some organized convection. Some meager elevated instability values north/west of Albany could support some isolated thunderstorms but higher chance for storms remains near and south/east of Albany. Any storms could produce brief downpours given the high PWATs. The stalled front presses southward heading into the mid-Hudson Valley/NW CT by 21 - 00 UTC with areas north/west of the front trending drier as cooler/less humid fills in behind the boundary. Additional showers/embedded storms linger in these southern zones through the evening hours as the front shifts southward but as instability wanes, storm coverage should diminish. However, the approaching cut-off low amplifies Saturday night as it tracks into the Ohio Valley leading to building heights over the Northeast. This will allow the front to actually quickly lift northward late Saturday night into early Sunday resulting in additional areas of rain as southerly winds advect warm/moist air over the boundary. We trended POPs back to likely after Midnight from south to north. Otherwise, temperatures remain mild in the upper 40s to mid-50s with elevated dew points also supporting higher humidity. && .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... Key Message: - Increasing confidence for periods of rain Sunday through Tuesday as a cut-low approaches from the Ohio Valley. There is a 30 to 60% chance for rainfall amounts to exceed 1.5 inches mainly from the Capital District southward into Berkshire and Litchfield County, the mid-Hudson Valley, and eastern Catskills. - Poor drainage and urbanized flooding can occur where rainfall repeatedly impacts a given area. However, given rather dry antecedent conditions and recent green-up, widespread flooding is unlikely. WPC maintains a marginal risk for excessive rainfall during this period. Discussion: Periods of rain continue into Sunday as the cut-off low continues to shift eastward and upper level divergence out ahead of it advances into the Northeast. A 40-50kt southerly jet ahead of the cut-off low will direct a PWAT plume with values 1-1.5" towards the stalled boundary positioned near or just north of I-90 helping maintain overrunning and periods of rain focused here through much of the day. Thus, we continue to message likely and categorical POPS (60 - 90% chance of rain) through the day for these areas while the mid-Hudson Valley and NW CT should squeeze out more dry time as some mid-level dry air fills in behind the lifting front (lower POPs at 25 - 40%). Between the clouds and periods of rain, temperatures remain seasonable in the 60s with upper 50s in the southern/western Adirondacks. Warmer in the low 70s in southern zones. Elevated dew points will make it feel not as cool. The stalled boundary becomes less defined Sunday night and gradually sinks southward as high pressure builds into the Canadian Maritime. Our wet pattern continues into Monday and Tuesday as the cut- off low continues to shift eastward. This will allow stronger upper level divergence and enhanced forcing for ascent ahead of it to become better positioned overhead maintaining rounds of rain and some embedded thunderstorms. The southerly jet also continues to direct the moisture plume into the region with the NAEFS showing PWATs and IVT values ranking in the 90th percentile of the model climatological supporting confidence for this wet stretch. We therefore maintained 50 - 80% POPs for most of eastern NY and western New England for these two days with the highest POPs along and south of I-90 closer to the moisture plume. Probabilistic guidance shows 30 - 60% chance for rainfall amounts during this 48 hour period to exceed 1 inch and just 10 - 20% to exceed 2 inches again highest probabilities south of I-90. WPC maintains a marginal risk over the Northeast in its excessive rainfall outlook (ERO) for these two days but decided to hold off on any upgrades to a slight risk given this a day 5 outlook and antecedent conditions over the past few weeks have been rather dry. We will continue to evaluate model and QPF trends over the coming days and collaborate any necessary changes to the ERO. Conceptual models from past CSTAR and local research shows that cut-off low and moisture rich environments typically increase the potential for areas of moderate to heavy rain to train or repeatedly impact a given area especially when PWATs are high and the vertical shear profiles become strong/unidirectional. Such cases can easily result in poor drainage or urbanized flooding and in more extreme situations can lead to localized flash flooding. Given we are still 3-4 days away, confidence is still too low to know if such a favorable set-up will be place Monday and Tuesday but we will maintain a watchful eye in the coming days. && .LONG TERM /WEDNESDAY THROUGH THURSDAY/... Key Message: - Unsettled weather and above normal temps Wednesday give way to cooler and drier conditions Thursday. Discussion: Cutoff low should be centered near NY/PA to start the long term period, which will help keep the region in an unsettled weather pattern. Ample forcing with CVA around the low, diffluence aloft and ample moisture (PWATs around 1.00") will keep chances of showers and thunderstorms through Wednesday. Temperatures look to hold near to above normal with southerly flow remaining favored, with latest NBM keeping highs in the upper 60s to low 70s. Thankfully, relief from the rain chances will arrive Wednesday night and Thursday as the cutoff low phases with a stronger shortwave diving southeast out of Ontario into the Northeast. This will also sweep a cold front through the region, with cooler and drier air arriving for the daytime Thursday and lasting into the weekend. Highs Thursday should be back near normal, ranging from the mid 50s to upper 60s. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... Through 12z/Sat...A brief break in shower activity is expected this morning as cigs gradually return to VFR levels (KPSF likely the last to do so). Additional scattered showers and isolated thunderstorms are possible during the afternoon through tonight, mainly at KALB/KGFL (PROB30 groups included) with reduced confidence in activity at KPOU/KPSF (only VCSH). Cigs/vsbys could vary between MVFR and VFR tonight at all sites. Brief IFR conditions could occur in any thunderstorm. Wind will become south to southwesterly this morning and continue through this evening with a few gusts between 20-25 kt. Wind will trend light to calm overnight. Outlook... Saturday Night: High Operational Impact. Likely SHRA. Sunday: High Operational Impact. Definite SHRA. Sunday Night: High Operational Impact. Likely SHRA...TSRA. Monday: High Operational Impact. Likely SHRA. Monday Night: High Operational Impact. Likely SHRA. Tuesday: High Operational Impact. Definite SHRA...TSRA. Tuesday Night: High Operational Impact. Definite SHRA...TSRA. Wednesday: Moderate Operational Impact. Chance of SHRA...TSRA. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...KL/Speciale NEAR TERM...Speciale SHORT TERM...Speciale LONG TERM...Speck AVIATION...Frugis