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1/24 to 1/26 threat...


NaoPos

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Best guess for TTN:  1-3"

I dont know what I'm doing with these multiple posts.

 

If this comes to pass "as is", this might be the time for the 18z GFS to run into the office

and demand the raise. It had the clipper reinforcement that started the weakening process (as Mitch posted)

and it was the first run that took low grade warning criteria off the table.

 

C-2" NW of I-95

1"-3" near/SE of I-95

 

Based of 12z stuff, me thinks.....

 

I worry about the dry air on the NW side of the precip. field, I saw what it did up my way the other evening when I was "fringed". It ate up most of the snow.

FWIW that one was more "convective" and there were going to be hit and misses, this one is warm air advection, should not be any shut outs. Yeah I know the jumping may cast a shadow or lull near i95, but there should not be a big difference between the highest and lowest amounts with this one.

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We dismissed the first "bad" GFS run a little to quickly. As Adam posted in the other thread, the GFS has narrowed the perfomance gap with the Euro in the past year or so..

 

If this comes to pass "as is", this might be the time for the 18z GFS to run into the office

and demand the raise. It had the clipper reinforcement that started the weakening process (as Mitch posted)

and it was the first run that took low grade warning criteria off the table.

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We dismissed the first "bad" GFS run a little to quickly. As Adam posted in the other thread, the GFS has narrowed the perfomance gap with the Euro in the past year or so..

You are right, if anything the 18z GFS tends to be the wettest run of the day, so if it trends drier... every day brings a new learning lesson. The dropsonde mission looked like it helped too and that last upgrade also.

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Mount holly

 

 

 

FOR FRIDAY AND SATURDAY...WHILE A STORM IS EXPECTED TO IMPACT THEREGION, IT IS ANTICIPATED TO BE WEAK AND A QUICK MOVER. THE OVERALLPROGRESSIVE FLOW SHOULD TEND TO KEEP THE LARGE SCALE LIFT ON THEWEAKER SIDE BEFORE THE SURFACE LOW STRENGTHENS OFFSHORE AND MOVESAWAY. WHILE THERE STILL REMAINS SOME UNCERTAINTY IN THE DETAILS,THERE IS BETTER CONSENSUS THAT A LIGHT QPF EVENT MOVES ACROSS THEENTIRE CWA. THE NAM CONTINUES TO APPEAR TO QUICK AND LIES ON THEEAST SIDE OF THE MODEL SPREAD BY SATURDAY MORNING IN THE WESTERNATLANTIC. SINCE THERE IS NORTHERN AND SOME SOUTHERN STREAM ENERGYINVOLVED, THE PROGRESSIVE NATURE OF THE FLOW TENDS TO KEEP THE LARGESCALE LIFT IN CHECK FOR AWHILE. THE GENERAL IDEA OF INCREASING WAAWILL HELP TO SPREAD OUT AN AREA OF LIGHT TO PERHAPS SOME EMBEDDEDMODERATE SNOW. THE AIRMASS IS RATHER DRY TO START, BUT THE FORECASTSOUNDINGS OVERALL SUGGEST THAT THE SATURATION OCCURS FAIRLY QUICKLYDURING FRIDAY AFTERNOON. WE SHOULD LOSE SOME QPF TO EVAPORATION, BUTTHE LIGHT SNOW MAY START FAIRLY QUICKLY THEREAFTER.WE CONTINUE TO PLAY THIS IS AN OVERRUNNING EVENT FOR MOST OF THEDURATION AS THE INITIAL WAA HELPS TO TIGHTEN THE THERMAL GRADIENTALOFT, ALTHOUGH THIS IS NOT ROBUST ENOUGH TO GET MUCH IN THE WAY OFFRONTOGENETIC FORCING GOING. MODEL CROSS SECTIONS SHOW THE SNOWGROWTH REGION EDGING INTO THE LIFT AREA /SATURATION OCCURRINGTHROUGH THE DENDRITIC CRYSTAL LAYER/, HOWEVER THIS IS ON THE WEAKERSIDE. THIS ALL POINTS TO A LOW BANDING POTENTIAL UNTIL ONCE THESURFACE LOW IS OFFSHORE AND MOVING AWAY AS IT STRENGTHENS. AT LEASTONE CONCERN IS THAT AS THE MAIN SURFACE LOW STRENGTHENS OFFSHORE,DOES THIS CREATE A VOID OR MUCH WEAKER AREA OF LIFT TO ITS NORTHWESTSIDE. THIS IS A POSSIBILITY BUT FOR NOW IT IS NOT FACTORED IN AS ITAPPEARS THAT A SWATH OF MAINLY LIGHT SNOW MOVES ACROSS THE ENTIREAREA.WE SLOWED DOWN THE POPS A BIT MORE FROM WEST TO EAST DURING THE DAYFRIDAY AS THE MAIN SYSTEM LOOKS TO ARRIVE LATER IN THE AFTERNOON. IFTHE GUIDANCE CONSENSUS HOLDS, POPS CAN BE INCREASED INTO THECATEGORICAL RANGE. REGARDING PRECIPITATION TYPES, THE AIRMASS LOOKSPLENTY COLD AND GIVEN THE DRYNESS LEADING UP TO IT WE WILL MAINTAINALL SNOW THROUGHOUT. WHILE THE AIRMASS MOISTENS UP, THE FORECASTSOUNDINGS ARE STILL RATHER COLD WHICH WOULD TEND TO LEAD TOWARDHIGHER RATIOS. THE EVENT THAT TOOK PLACE THIS PAST MONDAY EVENING INPARTS OF OUR CWA HAD RATHER HIGH RATIOS /ALSO STRONG FRONTOGENETICFORCING WITH BANDING/ AND WHILE WE ARE NOT THINKING THEY WILL BETHIS HIGH FOR THIS EVENT, ABOUT 20 TO 1 IS CERTAINLY DOABLE. SINCETHERE IS WEAKER FORCING AND A LESS OF A CHC FOR BANDING, THESNOWFALL RATES ARE ANTICIPATED TO BE ON THE LIGHT SIDE. BASED ON THEQPF CONSENSUS, WE ARE LEANING TOWARD A GENERAL 1-3 INCH SNOWFALLACROSS THE AREA. WHILE THIS IS NOT A LOT, IT COULD CREATE SOMEHAZARDOUS TRAVEL FOR A TIME AS THE AIR AND GROUND IS COLD. WE WILLCONTINUE TO MENTION THIS SYSTEM IN THE HAZARDOUS WEATHER OUTLOOK.

 

 

http://forecast.weather.gov/product.php?site=NWS&issuedby=PHI&product=AFD&format=CI&version=1&glossary=1&highlight=on

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I could see a lee-Appalachian / SE PA / W NJ screw zone setting up with this one but delmarva-E NJ-SE MA getting 3+ inches easy.

 

For now, I agree about a few inches. If we could get some better frontogenesis, I would have no problem forecasting 3-6" widespread, given the cold.

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I could see a lee-Appalachian / SE PA / W NJ screw zone setting up with this one but delmarva-E NJ-SE MA getting 3+ inches easy.

For now, I agree about a few inches. If we could get some better frontogenesis, I would have no problem forecasting 3-6" widespread, given the cold.

What needs to happen to get some better frontogenesis? I would think you would need that northern stream to dig down further south and increase the ridge out west to get a low to form further south instead of just offshore
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I could see a lee-Appalachian / SE PA / W NJ screw zone setting up with this one but delmarva-E NJ-SE MA getting 3+ inches easy.

 

For now, I agree about a few inches. If we could get some better frontogenesis, I would have no problem forecasting 3-6" widespread, given the cold.

I presume you say this because of the transfer?  Being in Western Jersey (NW Jersey) I'm sensitive to that.  What I'm also sensitive to is seeing the folks on here getting some good snows after a long wait.  Up here in the 'sticks' of Jersey, we've gotten ours this year. Time to share some of the wealth. 

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What needs to happen to get some better frontogenesis? I would think you would need that northern stream to dig down further south and increase the ridge out west to get a low to form further south instead of just offshore

Basically more amplification and a faster transfer. Advection processes really ramp up just offshore and pack the gradient more. 

 

I will say this though: the profiles in the snow growth zone are really moist and they look pretty good with modest omegas around 00z FRI. Between that and the temperatures, there probably won't be a "total screw zone" of nothing. But things could reach a relative min in amounts somewhere between the two forces. This could actually end up being more east than I'm saying if the transfer is even later.

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I presume you say this because of the transfer?  Being in Western Jersey (NW Jersey) I'm sensitive to that.  What I'm also sensitive to is seeing the folks on here getting some good snows after a long wait.  Up here in the 'sticks' of Jersey, we've gotten ours this year. Time to share some of the wealth. 

Pretty much because of the transfer. I don't think we see an area of nothing because there is decent cyclonic vortex advection, cold temperatures and moist mid levels in the SNZ. The later the transfer, the more the amounts will increase for the screw zone or the earlier the transfer. But the transfer as modeled now would lead to a relative min in snow accumulation for us.

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Pretty much because of the transfer. I don't think we see an area of nothing because there is decent cyclonic vortex advection, cold temperatures and moist mid levels in the SNZ. The later the transfer, the more the amounts will increase for the screw zone or the earlier the transfer. But the transfer as modeled now would lead to a relative min in snow accumulation for us.

HM could you see the Northern Stream Vort dig even further south as we have been colder so far then forecasted could this lead to a chance that the vort digs a bit further south?

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HM could you see the Northern Stream Vort dig even further south as we have been colder so far then forecasted could this lead to a chance that the vort digs a bit further south?

 

I don't think you'll see too much more digging now from this point on. The key is the initial vort's strength and how the s/w survives the trip from the East Pacific-Rockies sector. The current temperatures will have little if any impact to how deep this s/w will get. If anything, stronger cold air advection would keep the the secondary further out to sea.

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