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february 25 rain storm


earthlight

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We are really going to kick around 12z tomorrow. The isentropic lift is through the roof--there's tons of support for heavy rain. There will probably be convection embedded within this too..and how far north the warm front goes thereafter will play a big role in determining where we can get convection to form along the warm front. If the SPC-WRF is right, we're going to have a multi-faceted threat tomorrow. The 12 hour NAM below is a great, great signal for very heavy precipitation.

post-6-0-76349600-1298607582.gif

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spc mesoscale analysis shows the synoptics well with this precipitation coming in on the nose of stronger isentropic lifting with the mid level waa. pretty good setup for synoptic moderate to heavy rain overnight. the best isentropic lift and support for heavy precipitation is 10-12z per the 00z NAM and then the convection comes through thereafter.

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Any comment on the NAM which tracks the low over western LI and never gets most of NYC in the warm sector?

I think it's a bit too far east, but this scenario needs to be considered.

i think it's definitely too far east. the euro was still tracking the surface low to the NW of NYC and the RUC has been consistently well north and west--over PA still.

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...MID-ATLANTIC...

SFC CYCLONE ATTACHED TO THE AFOREMENTIONED UPPER SYSTEM WILL TRACK

FROM THE UPPER OH VLY AT DAYBREAK TO COASTAL MA BY 21Z. TRAILING

THE LOW...A COLD FRONT WILL SWEEP SEWD FROM THE CNTRL/SRN

APPALACHIANS...MOVING OFFSHORE THE MID-ATLANTIC/CAROLINAS BY

MID-AFTERNOON WHILE SINKING SLOWLY SWD INTO SE GA/FL PANHANDLE

TONIGHT.

SHORT-TERM MODELS ARE A FEW DEGREES TOO HIGH ON SFC DEW POINTS

ADVECTING NWD E OF THE APPALACHIAN MOUNTAINS EARLY THIS MORNING.

NONETHELESS...AT LEAST 50-55F READINGS SHOULD ADVECT NWD AHEAD OF

THE APPROACHING COLD FRONT BY MID-AFTERNOON. CLOUDS/PCPN MAY

INHIBIT LOW-LEVEL DESTABILIZATION...BUT IF BREAKS IN THE CLOUDS CAN

MATERIALIZE...EVEN WEAK AMOUNTS OF BUOYANCY WILL BE SUFFICIENT FOR A

CHANCE OF DEVELOPING TSTMS ALONG/E OF THE BLUE RIDGE BY LATE

MORNING. ACTIVITY MAY DEVELOP ENE ACROSS ERN VA/EXTREME SERN PA

NEWD THROUGH SRN NJ AND PERHAPS BACKBUILD INTO NERN NC. WINDOW OF

OPPORTUNITY WILL BE SMALL AS MAJORITY OF LARGE-SCALE ASCENT PASSES

NE OF THE REGION BY 21Z. SHOULD A STORM BECOME SUSTAINED...BRIEF

LOW-TOPPED SUPERCELLS WILL BE POSSIBLE ALONG WITH BOWING LINE

SEGMENTS /ISOLATED DAMAGING WINDS/BRIEF TORNADO/ OWING TO VERY

STRONG DEEP-LAYER AND LOW-LEVEL SHEAR. GIVEN UNCERTAINTY IN

DESTABILIZATION/TIMING/EXTENT OF STORM COVERAGE...SUB-CATEGORICAL

SLIGHT RISK SVR PROBABILITIES WILL SUFFICE AT THIS TIME.

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all of the high resolution models have a small area of moderate to heavy snow behind the cold front and thunderstorms. if this materializes this could be one of the more exciting days of weather in a long time.

refd_1000m_f25.gif

There is definitely a marginal signal at 500mb for backlash snow events in the area but its just that, quite marginal...I see greater potential on LI....as I've posted before it occurs in three scenarios....a vertically stacked system like 12/25/02, an upper low or strong vort max which trails well behind the surface low like 12/19/95 or 12/10/97, or a negatively tiled 500mb open trough well behind the storm like 12/11/93 or 12/14/10 (both of these were virtually identical setups)...this one resembles the latter with the slight negative tilt at 500mb....honestly I cannot find or recall any similar storms which took a track like this...this is a somewhat rare track for a storm to take. which make its all the more harder to get an idea if anything will occur...the SPC WRF shows two rounds of possible snow behind the storm...one from 22Z-00Z and then another batch behind that...the first round might not be all snow.

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The possibility of backlash snow for coastal areas is likely to depend strongly on the track. A track too far north of NYC will bring a dryslot to NE NJ/NYC/LI with the backlash snow further north. The only models that show backlash snow for NE NJ/NYC/LI have the track over or just south of NYC/LI.

all of the high resolution models have a small area of moderate to heavy snow behind the cold front and thunderstorms. if this materializes this could be one of the more exciting days of weather in a long time.

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The possibility of backlash snow for coastal areas is likely to depend strongly on the track. A track too far north of NYC will bring a dryslot to NE NJ/NYC/LI with the backlash snow further north. The only models that show backlash snow for NE NJ/NYC/LI have the track over or just south of NYC/LI.

I've noticed the same...there is a signal in the 700mb moisture fields for some sort of deformation zone but many models are north with it.

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<br>i think it's definitely too far east. the euro was still tracking the surface low to the NW of NYC and the RUC has been consistently well north and west--over PA still.<br>
<br><br>Things are definitely tracking further southeast then thought yesterday..Just going off what's happened in the Chicago area, and my nightmare that has been forecasting for Albany the past 2 days (has trended from mostly rain to mostly snow and a lot of it).. And now SNE changes to snow today as well..Though I do agree that NYC will get into the warm sector today, so it's not gnna go that far se
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OKX Update

Near term /through tonight/... at 12z a 993 hpa surface low was near kagc-klbe...with 3 hour pressure falls approaching 7 mb to its northeast. This would take the low on a track farther northwest than any model solution...with the RUC the closest to this idea. The models are likely wrong with their surface low track due to them not having enough upstream ridging (based on comparing their 500 hpa height forecast over New York/PA/NJ to RUC analysis). If this trend holds...then temperatures and winds are likely under forecast across the area...especially across the northern interior. Will continue to monitor this...especially with implications to wind headlines...and convective potential - could be more widespread - stronger than currently forecast if trends hold. In the short term...have updated hourly wind/temperature/dewpoint grids to better reflect current conditions - winds were increased a couple of hours too soon...and NE flow across the far western sound has resulted in temperatures at LGA being held in the upper 30s...while areas near the S shore of Long Island have warmed a tad faster than expected. Otherwise current forecast on track.

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Latest form SPC

25/00Z 4-KM ARW/NMM AND SEVERAL OF THE MORE RECENT EXPERIMENTAL HRRR SIMULATED REFLECTIVITY FORECASTS SUGGEST THE DEVELOPMENT OF DISCRETE STORMS ALONG THE COLD FRONT FROM PORTIONS OF SERN PA/NJ SWD THROUGH PARTS OF ERN VA...CNTRL/ERN MD AND DE. GIVEN THE VERY STRONG SHEAR EVIDENT IN 12Z OBSERVED AND MODEL FORECAST SOUNDINGS...THE POTENTIAL WILL EXIST FOR LOW-TOPPED SUPERCELLS WITH A RISK FOR DAMAGING WIND GUSTS AND PERHAPS A TORNADO OR TWO. THE COLD FRONT AND ANY ASSOCIATED SEVERE WEATHER THREAT SHOULD MOVE OFFSHORE BY LATE AFTERNOON OR THIS EVENING.

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