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January 17th-18th Winter Storm Discussion


BullCityWx

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I see the 40km NAM has really started to emphasize the relative minumum on the lee side of the mtns. I really hope that's incorrect, would suck to have snow on all sides of me

I'm concerned myself being that I'm in the Northern Foothills the models the past 24hrs have been showing the limited moisture for my area . Could just be a bias of the models but cannot discount the fact we might not get in on the action. I also can see us being in a sweet spot with upslope snows. 

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It's hard to tell by looking at the latest RAP precipitation forecast, but it shows almost .7 inches .9 inches of precipitation ......after what should be a changeover to snow.

It will be interesting to watch this all play out, and fascinating to look back and see where we missed it and where we hit it.

 

It's definitely getting juicier with each run.

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I'm concerned myself being that I'm in the Northern Foothills the models the past 24hrs have been showing the limited moisture for my area . Could just be a bias of the models but cannot discount the fact we might not get in on the action. I also can see us being in a sweet spot with upslope snows.

Yeah, I've been noticing that scary trend as well. We don't get upslope snow, we get downslope, which rarely ever happens. Most maps I've seen from our mets have us in the sweet spot, but that nasty dry area just into the foothills is really unnerving...

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They aren't issued for rarity or non-rarity. They are issued for impact on an area. This case being a heavy wet snow falling fast.

I get it and the part about rarity not being the important thing, but AL EMA is asking people not to drive and schools are letting out early unexpectedly, so its "heavy and high impact" for MS/AL and if it hits Atlanta for them too even if its not heavy compared to mountains or a northern city. But I know what you're saying.

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RAP STILL trending north. 18z run just started and just at hour ONE you can compare it to 17z and see the 500 low slightly farther north.

If you go back and compare to the 12z at the same time, the shift is pretty significant.

 

EDIT: Don't really see much difference at Hour 2, however, at least compared to 17z run -- maybe just initialization. Still, the trend from this morning is still clear.

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mcd0041.gif

 

This lines up with my thoughts at 11am this morning in this post:

 

http://www.americanwx.com/bb/index.php/topic/38874-january-17th-18th-winter-storm-observations/?p=2011660

 

g0nLM.png

 

As of 150pm, I am still not sure everything will work out per earlier thoughts down further south.    There is a significant warm nose being driven westward around the NC/SC line far back to the west.

 

DBvTI.png

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The majority might but I still feel we'll have a decent event with an inch laying around. Black ice will be our big threat overnight though.

I've been dry slotted with every snow for the last 4 years, and all you can hope for is some moisture dragging thougfh at the bitter end :)  It happens, but with warm ground there won't be enough rate to stick to more that car tops probably, unless there's bitter cold coming to flash freeze...but yeah, black ice looks like a good bet late.  But who knows...the snow is building down back in Ala. and it the de snowalizers on the border are on the fritz...maybe :)  T

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KTRI dropped to 35F the last hour. Wind advisory is now up for all of the MRX CWA.
 

 

...WIND ADVISORY IN EFFECT UNTIL 9 PM EST /8 PM CST/ THISEVENING...THE NATIONAL WEATHER SERVICE IN MORRISTOWN HAS ISSUED A WINDADVISORY...WHICH IS IN EFFECT UNTIL 9 PM EST /8 PM CST/ THISEVENING.* EVENT...WINDS INCREASING TO 15 TO 30 MPH WITH GUSTS TO 40 MPH.* TIMING...THIS AFTERNOON AND EVENING.* IMPACTS...WINDS OF THIS MAGNITUDE CAN MAKE DRIVING DIFFICULT...  ESPECIALLY FOR HIGH PROFILE VEHICLES. USE CAUTION THIS MORNING  WHEN DRIVING AROUND THE FOOTHILLS. ADDITIONALLY...THESE WINDS  COMBINED WITH HEAVY SNOW CAN REDUCE VISIBILITIES TO NEAR ZERO WITH  LITTLE WARNING.

 

WSW now includes "blowing snow" as a hazard. Good lord.

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Those North and West of the low will come out the best and the amounts will depend on the axis of the deformation band and the timing of the onset. RAP still seems to indicate the sweet spot(s) will be the mountains (of course) and the NW Piedmont inculding INT and GSO. As you move eastward from Burlinton to Raleigh, they could also be in a loolipop area depending on the factors I mentioned

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I have not been using this as a real guide for this storm, but the changeover was about an hour slower East of the mountains on the 15z 4km RPM, and the result was a significant decrease in snow totals. New run is going now....

 

Here that accum map:

post-390-0-88303700-1358449579_thumb.png

 

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I have not been using this as a real guide for this storm, but the changeover was about an hour slower East of the mountains on the 15z 4km RPM, and the result was a significant decrease in snow totals. New run is going now....

 

Here that accum map:

 

Yikes...not liking that. I'm guessing this due to the further north track?

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Yeah, the short-range model trending is clear -- upper level features inching north making it more difficult for cold air to turn over the precip to the immdieate north of ULL -- that would, unfortunately, mean the I-85/US74 corridor west of Charlotte

I have not been using this as a real guide for this storm, but the changeover was about an hour slower East of the mountains on the 15z 4km RPM, and the result was a significant decrease in snow totals. New run is going now....

 

Here that accum map:

attachicon.gifRPM snow.png

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Yeah, the short-range model trending is clear -- upper level features inching north making it more difficult for cold air to turn over the precip to the immdieate north of ULL -- that would, unfortunately, mean the I-85/US74 corridor west of Charlotte

 

Is it further north or just stronger and taking a more neutral tilt? Either way it certainly doesn't look good for my back yard as the northern part of that low goes right over CLT. I'm still on the side of just wait and see. Models are still models.

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I have not been using this as a real guide for this storm, but the changeover was about an hour slower East of the mountains on the 15z 4km RPM, and the result was a significant decrease in snow totals. New run is going now....

 

Here that accum map:

attachicon.gifhttp://www.americanwx.com/bb/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=85208'>RPM snow.png

Not bad, widespread 2-4" with pockets a little higher. Supposedly the RPM did fairly well with the NE event around New Years.

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Looks like RAH thinks everything is still on track.

 

NEAR TERM /THROUGH FRIDAY/...
AS OF 150 PM THURSDAY...

THROUGH TONIGHT: CONFIDENCE REMAINS HIGH IN THE OCCURRENCE OF
SIGNIFICANT BANDED SNOWFALL OVER NRN AND WRN PORTIONS OF NC EARLY
THIS EVENING THROUGH TONIGHT.

INTENSIFYING SURFACE LOW PRESSURE... LOCATED OVER NE GA EARLY THIS
AFTERNOON... WILL CONTINUE A STEADY ENE TRACK ALONG A FRONTAL ZONE
ACROSS SE NC. THE NAM/GFS/RAP/SREF MEAN HAVE EXHIBITED EXCELLENT
CONTINUITY THE LAST SEVERAL RUNS REGARDING TRACK AND TIMING... AND
HAVE SHOWN A VERY SMALL SOUTHWARD TREND IN THE EXTENT OF COLDER AIR
.

DYNAMIC LIFT WITH THIS SYSTEM WILL BE EXTREMELY STRONG -- ESPECIALLY
ALOFT WITH HIGH OMEGA FOCUSED IN THE CRUCIAL -12C TO -20C LAYER
ALOFT -- BUT QUICK-HITTING. AN INTENSE UPPER DIVERGENCE MAX EXPECTED
TO BE ROUGHLY OVER THE SRN NC FOOTHILLS AT 00Z WILL MOVE NE THROUGH
CENTRAL NC BEFORE EXITING NE SECTIONS OF THE CWA BY AROUND 07Z. THIS
IS IN TANDEM WITH THE PASSAGE OF STRONG Q-VECTOR CONVERGENCE... MID
LEVEL DCVA AND A RISE/FALL COUPLET OF AROUND +/- 200 METERS...
STRONG LOW LEVEL THETA-E ADVECTION... AND DEEP MOIST ISENTROPIC
UPGLIDE. THE FACT THAT THIS SYSTEM IS STRENGTHENING QUICKLY UPON
ARRIVAL IS ESPECIALLY TROUBLING IN THAT THE RESULTANT RAPID MASS
FIELD ADJUSTMENTS ARE LIABLE TO SIGNIFICANT AND QUICKLY BOLSTER
ASCENT AND HEIGHTEN THE EXTENT AND INTENSITY OF THE SNOW BANDING.
MOISTURE AVAILABILITY WILL GENERALLY NOT BE A PROBLEM WITH VERY HIGH
PW (OVER 200 PERCENT OF NORMAL) AND A STRONG MOISTURE TRANSPORT FROM
THE GULF...
ALTHOUGH THE INCOMING DRY SLOT ON THE SE SIDE OF THE LOW
WILL BE WORTH MONITORING AND MAY LIMIT WINTRY TOTALS IN THE
SOUTHEAST CWA (SEE BELOW). HOW FAST THE COLD AIR ARRIVES ESPECIALLY
ALOFT REMAINS A CONCERN... ALTHOUGH THE MODELS INITIALIZED WELL AND
ARE IN VERY GOOD AGREEMENT... BOOSTING CONFIDENCE IN THEIR TIMING OF
THE ANTICIPATED THERMAL CHANGES.

THE HEAVIEST SNOW BANDING IS LIKELY TO OCCUR OVER THE WRN AND NRN
PIEDMONT... FROM HIGH ROCK AND BADIN LAKES... ACROSS THE I-40 AND
HIGHWAY 64 CORRIDORS BETWEEN (AND INCLUDING) THE TRIAD AND THE
TRIANGLE... UP TO KERR LAKE AND LAKE GASTON... VERY ROUGHLY
FOLLOWING THE I-85 CORRIDOR TO THE NW... ALIGNED WITH THE AREA OF
STRONGEST DEFORMATION ALOFT. KEY TIMING STILL LOOKS TO BE FROM 23Z
UNTIL AROUND 07Z WITH A QUICK EXIT SOON THEREAFTER. SREF
PROBABILITIES HAVE BEEN VERY CONSISTENT IN SHOWING A 70+ PERCENT
CHANCE OF SNOWFALL RATES OVER ONE INCH PER HOUR ACROSS MUCH OF THE
PIEDMONT AND FAR NRN COASTAL PLAIN FROM MID EVENING UNTIL THE EARLY
OVERNIGHT HOURS. WITH THESE RATES AND THE TIMING OF A FEW HOURS OF
HEAVY BANDED SNOW (STARTING AS A RAIN/SNOW MIX)... STORM TOTAL
ACCUMULATIONS OF 2-4 INCHES IN THIS AREA WITH ISOLATED 5 INCH TOTALS
LOOK QUITE REASONABLE.
BORDERING THE WARNING AREA... STILL EXPECT AN
INCH OR SO OF ACCUMULATION MAINLY ON GRASSY AREAS... WITH A LITTLE
SLUSH ON ROADS POSSIBLE.

SOUTH AND EAST OF HERE... INCLUDING FAYETTEVILLE AND CLINTON... A
QUICK BURST OF MAINLY SNOW IS POSSIBLE WITH STRONG DYNAMIC COOLING
THROUGH THE COLUMN AS THE LOW ALOFT PASSES BY... BUT THE WINDOW OF
OPPORTUNITY WILL BE VERY SHORT AS AMOUNTS/DURATION WILL BE GREATLY
LIMITED BY THE MID-UPPER LEVEL DRY SLOT ARRIVAL WITH NOTABLE DRYING
ABOVE THE -5C LEVEL... SUPPRESSING CRYSTAL GROWTH ALOFT... PLUS
BOUNDARY LAYER TEMPS SHOULD HOLD ABOVE FREEZING FOR MUCH OF THIS
EVENT... NOT DROPPING TO NEAR FREEZING UNTIL PRECIP IS NEARLY GONE.
EXPECT LIGHT ACCUMULATIONS OF A DUSTING CONFINED TO GRASSY AREAS.

A SIDE NOTE: MID LEVEL LAPSE RATE PROGS ARE QUITE INTERESTING...
INCLUDING THE 12 KM NAM WHICH INDICATES 850-500 MB VALUES OF 5.5-6.0
C/KM TRAVERSING THE CWA... JUST WNW OF THE 850 MB LOW TRACK...
PRIMARILY BETWEEN 03Z AND 06Z. AND RECENT RAP RUNS TAKE THE 700-400
MB LAPSE RATES (WHICH CAPTURES THE MIXED PHASE REGION ALOFT) UP TO
7.0 C/KM OVER THE NW PIEDMONT TOWARD MIDNIGHT. CONSIDERING THIS
POSSIBILITY FOR UPRIGHT INSTABILITY COMBINED WITH VIGOROUS DYNAMIC
LIFT... A FEW LIGHTNING STRIKES WITHIN SNOW BANDS ARE CERTAINLY
POSSIBLE...
ALTHOUGH LIKELY TOO ISOLATED TO INCLUDE IN THE FORECAST
AT THIS TIME.

STRENGTHENING WINDS WILL BE AN ISSUE AS WELL WITH THE TIGHTENING
MSLP GRADIENT AS THE LOW APPROACHES. WE ARE ALREADY SEEING FREQUENT
GUSTS TO 25-40 KTS (ALTHOUGH SOME OF THIS MAY BE AUGMENTED BY A
POSSIBLE GRAVITY WAVE). EXPECT A PERIOD OF SUSTAINED WINDS OF 15-25
MPH WITH SPORADIC GUSTS TO AROUND 30 MPH FROM LATE AFTERNOON UNTIL
AROUND 1-2 AM.

TEMPS SHOULD STEADILY DROP THROUGH THE REST OF THE AFTERNOON AND
NIGHT. -GIH


 

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