Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 190630 AFDOKX Area Forecast Discussion National Weather Service New York NY 130 AM EST Sun Nov 19 2017 .SYNOPSIS...
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As developing low pressure passes to the north, its associated warm front will lift through the area, followed by a strong cold around daybreak. High pressure will pass to the south Monday and Tuesday, followed by a cold front on Wednesday. High pressure will build late week. Low pressure will then move across on Saturday.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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Updated the forecast, mainly due to the lack of showers east of NYC early this morning. Pre-frontal rain bands are beginning to move into areas to the west and are expected to fill in/advance eastward through the remainder of the night. PoPs have been adjusted as such. Obs indicate warm front has lifted into southern CT and extends back through KHPN-KTEB to N of KTTN. Winds to the N of the front are light and have picked up with better mixing to the south of it. Have also adjusted winds to better reflect this. Some question as to how strong the winds will get late tonight right ahead of the front as 50-60kt LLJ moves through. How much of being transported to the sfc will depend on the strength and location of the developing low level inversion. No changes to wind headlines at this time, although high wind warning may be cancelled with the 4am issuance. Instability with bands of showers overnight will be limited to the low to mid levels, with an H7 inversion limiting deeper/greater instability that would have otherwise led to thunder.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/... Cold front will be moving across in two shots, the first marking arrival of a dry slot and departure of the S-SW low level jet, the second marking the arrival of strong W-NW winds after passage of a potent, negatively-tilted shortwave trough along. There could be a brief lull in winds between these two features, but then W-NW winds likely to gust just over 45 mph with passage of the second trough (with NAM indicating narrow band of showers with the front), and then during the late morning and afternoon via a tight pressure gradient and H8 winds up to 40-45 kt. Stronger winds should hang on a few hrs longer into the daytime than model forecasts indicate, and NAM also indicates stronger H8 winds arriving in the late afternoon after another mid level shortwave passage; think winds will however start to gradually diminish by that point, so while gusty NW winds will continue into Sunday night, have not extended the advisory into Sunday night. After morning highs in the 50s, temps should gradually fall in the afternoon, back into the 40s by late afternoon, then into the 20s and 30s tonight. A few lake effect snow showers may make it into the area late Sunday night especially just NW of NYC. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Aloft, models agree early in the period as initial shortwave passes east/northeast. Downstream shortwave will then make fast eastward progress. Here is where some differences arise. Northern stream potent shortwave tracks across the Great Lakes region as it lifts northeast, with most of the energy and associated dynamics lifting well to our north Wednesday. Southern stream trough lags a bit as it moves across the Gulf states. By late Wednesday into Thursday, operational GFS seems to be a deep/strong outlier with regard to closed low around the Gulf states as the trough makes eastward progress. This upper trough weakens over the western Atlantic Thursday, with next shortwave in the northern stream moving eastward toward the northeast by next weekend. At the sfc, high pressure passes to the south Monday and Tuesday. Gusty NW flow will back around the SW as the high tracks east. Thereafter, a cold front passes Wednesday. This front is associated with northern stream shortwave. This looks like the best chance for measurable precipitation, late Tuesday night into Wednesday, chance pops. Waves of low pressure likely develop along the front well to our south in the Wednesday night/Thursday time frame. Again, GFS appears to be an outlier with wave of low pressure developing and passing close enough for measurable precip Thursday. Otherwise, model consensus suggest any precip remains to our southeast as ridge builds to the NW and waves remain far enough to the southeast. Will maintain a dry forecast as a result, leaning toward consensus. However, this will need to be watched. Dry through Friday before the next chance for precip arrives with the shortwave, clipper low Saturday. As for temperatures Monday-Saturday, followed a model/mos blend. Below normal temperatures Monday will warm to slightly above normal Tuesday as WAA occurs behind the high. Behind a cold front Wednesday, normal temps likely fall to below normal Thursday and Friday before rebounding yet again in WAA ahead of the clipper low Saturday. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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A warm front moves north of the terminals early this morning. A cold front follows around daybreak with high pressure building behind it through this evening. S flow will increase through the morning hours with gusts returning to all terminals between 06-09z. The gusts will initially be 20-30 KT, increasing to 30-40 KT towards day break. Some eastern terminals may see peak gusts 45-50 KT. LLWS is also forecast until around 12z. S-SW winds shift to the W-WNW 12z-15z with gusts frequently 35-40 KT during the day. The gusts will begin to weaken late in the afternoon and early in the evening. Mainly VFR conditions to start with conditions gradually becoming MVFR towards daybreak. There may also be some brief localized IFR. Conditions will improve to VFR 12z-15z behind the cold front. .OUTLOOK FOR 06Z MONDAY THROUGH THURSDAY... .Monday...VFR. W-NW winds G20-30KT. Gusts diminish gradually at night. .Tuesday...Mainly VFR. MVFR possible late Tuesday night in showers. SW winds G15-20KT. .Wednesday...MVFR possible with showers during the day. VFR at night. W-NW winds G15-20KT. .Thursday...VFR.
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&& .MARINE...
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No changes to headlines attm. Slight decrease in winds and seas over the waters to start with stronger winds taking a bit longer to arrive than forecast. S-SW gales develop on all waters overnight, then a strong low level jet with possibly only a weak inversion, should allow storm force gusts to occur on the eastern ocean/sound/bays, where a storm warning remains in effect. Farther west, winds should still gust to 35-45 kt, and a gale warning also remains in effect. After a cold frontal passage Sunday morning, W-NW winds should gust to 40-45 kt through the day, and fall below gale force on the non-ocean waters after midnight. Gusty NW/W flow Monday will back around the SW Monday night and Tuesday as high pressure passes to our south, then east. These SW winds eventually shift around the N/NW behind a cold front Wednesday. Northerly winds persist Wednesday night and Thursday. As for sea forecasts, rough conditions persist in the Monday and Tuesday time frame due to strong winds/tight pressure gradient. Nearshore Wave Prediction System looked quite reasonable and was followed. For Wednesday and Thursday, had to knock down sea forecasts from Wave Watch III as GFS appears to be an outlier with regard to a wave of low pressure that approaches the waters from the south/southeast.
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&& .HYDROLOGY...
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Rain with a warm frontal passage tonight, and then with bands of moderate to locally heavy showers with a strong cold frontal passage into the morning, should cause no more than local nuisance impacts. Total rainfall is expected to range between 1/2 to 1 inch, highest NW of NYC.
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&& .TIDES/COASTAL FLOODING...
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Storm surge guidance for this mornings high tide may to be on the low side given the strength of southerly winds expected ahead of a cold front this morning. But typically, S/SW winds are not conducive to building surge. However, there is a low probability of a surge of 1-2 ft. If these surge levels develop, minor coastal impacts in a strong SW/W flow would be felt mainly across eastern portions of the Great South Bay into Moriches Bay. Elsewhere any impacts would be brief and localized. Statement issued to address this potential.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...High Wind Warning until noon EST today for CTZ011-012. Wind Advisory from 7 AM this morning to 6 PM EST this evening for CTZ005-006. Wind Advisory until 6 PM EST this evening for CTZ007>010. NY...High Wind Warning until noon EST today for NYZ078>081. Wind Advisory from 7 AM this morning to 6 PM EST this evening for NYZ067>070. Wind Advisory until 6 PM EST this evening for NYZ071>075- 176>179. NJ...Wind Advisory from 7 AM this morning to 6 PM EST this evening for NJZ002-004-103>108. Wind Advisory until 6 PM EST this evening for NJZ006. MARINE...Storm Warning until noon EST today for ANZ330-340-345-350-353. Gale Warning until 6 AM EST Monday for ANZ335-338-355.
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&& $$

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