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February 20th-21st Winter Storm OBS/Discussion


LithiaWx

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From my side of things (a little outside looking in), RAH has added snow and sleet to my forecast for Saturday (rain Sunday). They have also lowered the high for Sunday to 48; which was 58 earlier(so another below normal day). From RAH:

 

.LONG TERM /SATURDAY THROUGH THURSDAY/...
AS OF 230 PM THURSDAY...

OVERVIEW: 1035 MB ARCTIC HIGH PRESSURE CENTERED DIRECTLY OVER
CENTRAL NC LATE FRI/FRI NIGHT WILL GRADUALLY SHIFT OFFSHORE SAT/SAT
NIGHT...THOUGH A PRONOUNCED SFC RIDGE AXIS WILL CONTINUE TO EXTEND
INTO THE REGION FROM THE EAST. MEANWHILE...SHORTWAVE ENERGY DIGGING
SOUTHEAST THROUGH THE ROCKIES INTO THE GREAT PLAINS WILL INITIATE
CYCLOGENESIS ALONG A BAROCLINIC ZONE OVER THE CENTRAL PLAINS...WITH
A DEVELOPING WARM SECTOR OVER THE DEEP SOUTH/SOUTHEAST ADVECTING
NORTHWARD INTO THE CAROLINAS LATE SAT/SAT NIGHT. THE WARM SECTOR WILL BECOME FURTHER ESTABLISHED OVER THE CAROLINAS ON SUNDAY AS THE AFOREMENTIONED LOW PRESSURE SYSTEM TRACKS EASTWARD INTO THE OH
VALLEY AND MID-ATLANTIC. AN ATTENDANT COLD FRONT WILL PROGRESS
ACROSS CENTRAL NC SUNDAY...WITH ARCTIC HIGH PRESSURE BUILDING INTO
THE REGION AGAIN EARLY/MID NEXT WEEK.

SAT-SUN NIGHT: MODEL GUIDANCE IS IN GENERAL AGREEMENT ON THE
SYNOPTIC PATTERN OVER THE WEEKEND...THOUGH SUBTLE DIFFERENCES IN THE
EVOLUTION OF THE UPPER LEVEL PATTERN AND LOW-LEVEL HEIGHT/WIND
FIELDS IS RESULTING IN MAJOR DISCREPANCIES BETWEEN THE GFS/NAM/ECMWF
WITH REGARD TO PRECIPITATION COVERAGE...AMOUNTS...TIMING AND
DURATION DURING THE DAY SATURDAY. AS A RESULT...WELL BELOW NORMAL
CONFIDENCE PERSISTS WITH REGARD TO PRECIPITATION CHANCES...
TYPE(S)...AND POTENTIAL ACCUMULATION(S)...AND LITTLE CHANGE WILL BE
MADE TO THE PRIOR FORECAST FOR SAT. QUALITATIVELY...PTYPE CONCERNS
PERSIST SAT MORNING THROUGH MID/LATE SAT AFTERNOON GIVEN AN
ATYPICALLY COLD/BITTER ANTECEDENT AIRMASS IN PLACE IMMEDIATELY PRIOR
TO THE POSSIBLE ONSET OF PRECIP...AND THAT A SFC RIDGE AXIS WILL
LIKELY PERSIST ACROSS THE NORTH/NW PIEDMONT THROUGH 00Z SUN. EXPECT
THE BEST CHANCE FOR WINTRY WX (POTENTIALLY SIGNIFICANT) ALONG AND
NORTH OF I-85...ESP IN THE FAR NW PIEDMONT (I.E. FORSYTH/GUILFORD/
NORTHERN DAVIDSON COUNTIES). THERMAL PROFILES WOULD SUPPORT SNOW OR
SNOW/SLEET THROUGH NOON...THEN RAPIDLY TO PL/FZRA AND FINALLY RAIN
FROM SE-NW DURING THE AFTERNOON...WITH RAIN EVERYWHERE BY 21-00Z.
MODEL GUIDANCE IS IN GOOD AGREEMENT ON RAIN DURING THE DAY SUNDAY.

MONDAY THROUGH THURSDAY: EXPECT WELL BELOW NORMAL TEMPERATURES TO
PERSIST FOR MUCH IF NOT ALL OF NEXT WEEK...WITH ABNORMALLY LOW
CONFIDENCE IN PRECIPITATION CHANCES DUE TO ATYPICALLY LARGE
VARIABILITY IN LONG RANGE MODEL GUIDANCE. NEEDLESS TO SAY...IF
PRECIPITATION IS POSSIBLE...PTYPE CONCERNS WILL BE PRESENT. -VINCENT


 

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Obviously, the cold front itself the next day will be a warmish rain.

I don't think a significant event is likely, but I think we may have a decent shot at some light accumulations. The key will be to get precip.

 

This will be pretty amazing system......Memphis, TN point forecast is for snow/sleet on Friday with temps. in the 30's while on Saturday a high near 62 with rain/tstorms. 

 

- Buck

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Wow, this is surprisingly bullish for FFC.  You have to think that had snowmaggedon 2014 not happened we'd still probably be looking at a watch at most.  Friday rush hour is bad enough here in 75 degrees and sun.  I'll gladly take an inch or so on this one.  Again, with air and ground temps what they are, it would only take a small shift to the south to cause some problems, especially during a Friday rush hour.

 

- Buck

 

 I wonder if this advisory this means ATL schools will be announcing closings this evening.

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Just issued:

NCZ003-019-020-VAZ022>024-200430-

/O.NEW.KRNK.WS.A.0002.150221T0500Z-150222T1100Z/

/O.CON.KRNK.WC.Y.0008.000000T0000Z-150220T1500Z/

SURRY-WILKES-YADKIN-ROANOKE-BOTETOURT-ROCKBRIDGE-

INCLUDING THE CITIES OF...DOBSON...WILKESBORO...YADKINVILLE...

ROANOKE...SALEM...FINCASTLE...LEXINGTON...BUENA VISTA

324 PM EST THU FEB 19 2015

...WIND CHILL ADVISORY REMAINS IN EFFECT UNTIL 10 AM EST FRIDAY...

...WINTER STORM WATCH IN EFFECT FROM LATE FRIDAY NIGHT THROUGH

LATE SATURDAY NIGHT...

THE NATIONAL WEATHER SERVICE IN BLACKSBURG HAS ISSUED A WINTER

STORM WATCH...WHICH IS IN EFFECT FROM LATE FRIDAY NIGHT THROUGH

LATE SATURDAY NIGHT.

* ACCUMULATIONS...SIGNIFICANT ACCUMULATIONS OF SNOW AND ICE BY

SATURDAY EVENING.

* LOCATIONS...FOOTHILLS AND PIEDMONT...INCLUDING THE ROANOKE AND

SOUTHERN SHENANDOAH VALLEYS.

* HAZARD TYPES...VERY LOW WIND CHILL READINGS TONIGHT...THEN

SNOW...SLEET AND FREEZING RAIN LATE FRIDAY NIGHT THROUGH

SATURDAY NIGHT.

* WIND CHILL READINGS...5 TO 15 BELOW ZERO TONIGHT.

* TIMING...LOW WIND CHILLS INTO FRIDAY MORNING...THEN WINTRY

WEATHER LATE FRIDAY NIGHT INTO SATURDAY NIGHT.

* IMPACTS...VERY LOW WIND CHILLS COULD RESULT IN FROSTBITE AND

HYPOTHERMIA IF LEFT EXPOSED TO THE BITTERLY COLD TEMPERATURES.

SNOW AND ICE COULD PRODUCE HAZARDOUS TRAVEL AND POWER OUTAGES

BY LATER SATURDAY.

Well guess your dream may be coming true

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For once, the 4K NAM is more bullish than is the 12K NAM.  Usually, in my experience, the 12K tends to smooth things out and spread the wealth, it also tends to miss the topography of the landscape a little more with its lower resolution.  The 4K snowfall map is first, followed by the 12K snowfall map from 18Z this afternoon:

 

 

1aoi7gi.png

 

 

pGcwf2f.png

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 I wonder if this advisory this means ATL schools will be announcing closings this evening.

I'd imagine if they were to make any decisions it would just be to close schools an hour or two early. No need to take off the whole day if precip isn't going to come in until the late afternoon as currently modeled. 

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FRIDAY...MOSTLY SUNNY. HIGHS IN THE LOWER 20S. LIGHT AND
VARIABLE WINDS.
.FRIDAY NIGHT...CLOUDY WITH A 50 PERCENT CHANCE OF SNOW. LITTLE
OR NO SNOW ACCUMULATION. NOT AS COLD WITH LOWS AROUND 17. LIGHT
AND VARIABLE WINDS.
.SATURDAY...SNOW IN THE MORNING...THEN SNOW AND SLEET IN THE
AFTERNOON. HEAVY SNOW ACCUMULATION. HIGHS IN THE LOWER 30S. SOUTH
WINDS AROUND 10 MPH. CHANCE OF PRECIPITATION 90 PERCENT. WIND
CHILL VALUES AS LOW AS 9 ABOVE.
.SATURDAY NIGHT...RAIN WITH FREEZING RAIN LIKELY IN THE EVENING...
THEN RAIN AFTER MIDNIGHT. NOT AS COOL WITH LOWS IN THE LOWER 30S.
SOUTHWEST WINDS AROUND 10 MPH. CHANCE OF PRECIPITATION
80 PERCENT.
.SUNDAY...RAIN LIKELY. NOT AS COOL WITH HIGHS IN THE MID 40S.
CHANCE OF RAIN 70 PERCENT.
.SUNDAY NIGHT...MOSTLY CLOUDY. A CHANCE OF RAIN IN THE EVENING...
THEN A CHANCE OF RAIN SHOWERS AFTER MIDNIGHT. LOWS IN THE UPPER
20S. CHANCE OF RAIN 50 PERCENT.

 

 

IDK how much is Heavy?

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I understand. I had pretty much given up until some of the modeling shifted south today. One thing we do have going for us is that it would be a cold storm with temps starting off around 20 at the surface. Frankly, if we get precip I see no way the surface ever gets above freezing until the precip moves out, which could mean icing problems potentially (we saw the models try to warm the surface in GA/SC too much with this last storm).

Obviously, the cold front itself the next day will be a warmish rain.

I don't think a significant event is likely, but I think we may have a decent shot at some light accumulations. The key will be to get precip.

 

totally agree.  I just have a problem with them putting "heavy accumulation possible" directly in the forecast.  People start freaking out especially when we dont even have an advisory in Forsyth.  More collaboration would be good between offices would be good.

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RAH Disco...

 

SAT-SUN NIGHT: MODEL GUIDANCE IS IN GENERAL AGREEMENT ON THE

SYNOPTIC PATTERN OVER THE WEEKEND...THOUGH SUBTLE DIFFERENCES IN THE
EVOLUTION OF THE UPPER LEVEL PATTERN AND LOW-LEVEL HEIGHT/WIND
FIELDS IS RESULTING IN MAJOR DISCREPANCIES BETWEEN THE GFS/NAM/ECMWF
WITH REGARD TO PRECIPITATION COVERAGE...AMOUNTS...TIMING AND
DURATION DURING THE DAY SATURDAY. AS A RESULT...WELL BELOW NORMAL
CONFIDENCE PERSISTS WITH REGARD TO PRECIPITATION CHANCES...
TYPE(S)...AND POTENTIAL ACCUMULATION(S)...AND LITTLE CHANGE WILL BE
MADE TO THE PRIOR FORECAST FOR SAT. QUALITATIVELY...PTYPE CONCERNS
PERSIST SAT MORNING THROUGH MID/LATE SAT AFTERNOON GIVEN AN
ATYPICALLY COLD/BITTER ANTECEDENT AIRMASS IN PLACE IMMEDIATELY PRIOR
TO THE POSSIBLE ONSET OF PRECIP...AND THAT A SFC RIDGE AXIS WILL
LIKELY PERSIST ACROSS THE NORTH/NW PIEDMONT THROUGH 00Z SUN. EXPECT
THE BEST CHANCE FOR WINTRY
WX (POTENTIALLY SIGNIFICANT) ALONG AND
NORTH OF I-85...
ESP IN THE FAR NW PIEDMONT (I.E. FORSYTH/GUILFORD/
NORTHERN DAVIDSON COUNTIES).
THERMAL PROFILES WOULD SUPPORT SNOW OR
SNOW/SLEET THROUGH NOON...THEN RAPIDLY TO
PL/FZRA AND FINALLY RAIN
FROM SE-NW DURING THE AFTERNOON
...WITH RAIN EVERYWHERE BY 21-00Z.
MODEL GUIDANCE IS IN GOOD AGREEMENT ON RAIN DURING THE DAY SUNDAY.

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THE BEST CHANCE FOR WINTRY WX (POTENTIALLY SIGNIFICANT) ALONG AND

NORTH OF I-85...ESP IN THE FAR NW PIEDMONT (I.E. FORSYTH/GUILFORD/

NORTHERN DAVIDSON COUNTIES). THERMAL PROFILES WOULD SUPPORT SNOW OR

SNOW/SLEET THROUGH NOON...THEN RAPIDLY TO PL/FZRA AND FINALLY RAIN

FROM SE-NW DURING THE AFTERNOON...WITH RAIN EVERYWHERE BY 21-00Z.

MODEL GUIDANCE IS IN GOOD AGREEMENT ON RAIN DURING THE DAY SUNDAY.

 

Well, thank God I live a few miles NW of I-85. ;)

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I'm not sure I'm following FFC's logic on this one. All the models want to bring the precip to far north GA, leaving ATL and AHN high and dry; even the Canadian has trended north. I have a strong feeling that 1/28/14 and Monday's event led them to issue a WWA down here as a safety mechanism, while an SPS would have been just fine.

 

I'd imagine if they were to make any decisions it would just be to close schools an hour or two early. No need to take off the whole day if precip isn't going to come in until the late afternoon as currently modeled. 

 

If you believe the Census Bureau and its definition of "metro Atlanta", one county already has: Haralson (three hours early).

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 I wonder if this advisory this means ATL schools will be announcing closings this evening.

I guess since some closed a day in advance of rain. Neither closings nor the FFC forecast look justified dont ya thinl? But what do I know lol. Maybe models become more bullish overnight, but I am in yawn mode for ATL.

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I'm not sure I'm following FFC's logic on this one. All the models want to bring the precip to far north GA, leaving ATL and AHN high and dry; even the Canadian has trended north. I have a strong feeling that 1/28/14 and Monday's event led them to issue a WWA down here as a safety mechanism, while an SPS would have been just fine.

If you believe the Census Bureau and its definition of "metro Atlanta", one county already has: Haralson (three hours early).

so what you are saying is that areas south of I-20 that are currently under an advisory shouldn't be? FFC is showing about 1/4" of snow here and some sleet and ice as well. I wonder if this storm will bust to and we end up with no precipitation until it's warmed up. nah, there's no way we could get screwed again. We are due this time.
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