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Pittsburgh/Western Pa Weather


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Reading the NWS latest discussion, they seem quite confident in the 5-8 call right now. They said we should easily reach 5-8. Here's the discussion....

NATIONAL WEATHER SERVICE PITTSBURGH PA 1047 AM EST TUE MAR 5 2013

.SYNOPSIS... A STORM MOVING INTO THE OHIO VALLEY TODAY WILL BRING INCREASING CLOUDS AND PRECIPITATION BY AFTERNOON. THE POWERFUL AND COMPLEX STORM SYSTEM WILL BRING SIGNIFICANT SNOW TO THE REGION TONIGHT AND WEDNESDAY.

&&

.NEAR TERM /THROUGH WEDNESDAY/... WHILE MUCH OF THE FIRST HALF OF THE DAY WILL REMAIN DRY AND SUNNY...CLOUDS WILL BE ON THE INCREASE AS A DEEPENING CLOSED LOW ALOFT DIVES INTO THE LOWER OHIO VALLEY...PUSHING A SURFACE LOW TOWARDS NORTHERN WEST VIRGINIA. MUCH OF THE PRECIPITATION THAT ALREADY IS BEING INDICATED ON RADAR IS NOT REACHING THE GROUND WITH LOWER LEVELS REMAINING DRY. IT WILL TAKE SOME TIME FOR THE LOWER LEVELS TO SATURATE AND WITH THIS...HAVE ADJUSTED POP TIMING BACK JUST SLIGHTLY. INCREASING CLOUD COVER AND WEAK COLD ADVECTION SHOULD HELP TO KEEP TEMPERATURES A BIT COOLER THAN CURRENT GUIDANCE SUGGESTS...SO BUMPED TEMPS DOWN A FEW DEGREES.

WHILE PRECIPITATION MAY START OFF AS A RAIN/SNOW MIX...ESPECIALLY AT POINTS SOUTH...THERE ARE A LOT OF FACTORS COMING INTO PLAY TO INDICATE THAT MUCH OF THE REGION CAN EXPECT A PERIOD OF ACCUMULATING SNOW OVERNIGHT. STRONG DIFFLUENCE AND LIFT ASSOCIATED WITH THE UPPER LEVEL JET WILL BE SITUATED OVER NORTHERN WEST VIRGINIA OVERNIGHT. IN ADDITION...ALL OF THE MODELS CONTINUE TO SUGGEST THE DEVELOPMENT OF A TROWAL AS THE ENERGY FROM THE LOW OVER WEST VIRGINIA/OHIO TRANSLATES TO THE MID-ATLANTIC COAST BY MORNING. THIS IS COINCIDENT WITH PLENTY OF OMEGA IN THE DENDRITIC GROWTH ZONE...PROVIDING FOR A PROLONGED PERIOD OF SNOW NOT ONLY IN THE HIGHER ELEVATIONS BUT ALSO TO MANY POINTS WEST.

THUS...WITH HIGHER CONFIDENCE IN ACCUMULATING SNOWFALL FOR MUCH OF THE REGION...HAVE UPGRADED MUCH OF THE ADVISORY TO A WARNING. SNOW AMOUNTS WILL CONTINUE TO BE THE HIGHEST IN THE HIGHER ELEVATIONS OF PRESTON...TUCKER...AND GARRETT COUNTIES BUT 5-8 INCHES COULD EASILY BE REALIZED FOR MUCH OF EASTERN OH...NORTHERN WV...AND SOUTHWESTERN PA. BUFKIT PROFILES SUGGEST THAT WITH RELATIVELY WARM TEMPERATURES IN THE LOWER LEVELS...SNOW RATIONS WILL REMAIN RELATIVELY LOW...CLOSER TO THE 10 TO 1 RANGE. THIS COULD CAUSE SOME ISSUES FOR THE MOUNTAINS OF WV/MD WITH HIGHER SNOW AMOUNTS EXPECTED.

AS THE COASTAL LOW BECOMES THE DOMINANT LOW WEDNESDAY MORNING...PRECIPITATION SHOULD END RELATIVELY QUICKLY FROM WEST TO EAST BY THE AFTERNOON...LINGERING LONGEST IN THE RIDGES.

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Interesting. They are the pros, and with this complicated system just looking at pretty colors on a map will not cut it so I will go with their judgement. I hope they are right. 5-8 inches would be a decent storm. Most of it is falling overnight though which is good and bad, bad in that unless you stay up all night you miss the snow, good in that there won't  be any interference from the sun on accumulations.

 

My yard was frozen solid this morning, so I don't expect we will have to overcome much temp wise for favorable accumulations.

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Interesting. They are the pros, and with this complicated system just looking at pretty colors on a map will not cut it so I will go with their judgement. I hope they are right. 5-8 inches would be a decent storm. Most of it is falling overnight though which is good and bad, bad in that unless you stay up all night you miss the snow, good in that there won't  be any interference from the sun on accumulations.

 

My yard was frozen solid this morning, so I don't expect we will have to overcome much temp wise for favorable accumulations.

My favorite this year GGEM still looks good for our area with a solid 7 hours or so of moderate snow. If it falls between 1:00 am and 8:00 am it will accumulate well. Looking at NWS map on Facebook they have 5-8 inches from the city and south and 4-6 North of that. Just draw a line through Allegheny County and that is the difference.

http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

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From what I can see--the 1800 NAM shows about 12" with a 14:1 ratio. Big jump from the previous release!. The GFS still showing around 4". I don't have a lot of faith in either of these models, a shift either way can make a hug difference!

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We're also at 15 degree dewpoints - temps are going to drop

 

 

if it starts as rain, with the dewpoint at 15, it should turn to big snow flakes very quickly.  It may take a while for any precip to reach the ground.

That's also what I noticed.

 

There should be some decent cooling as the precip arrives.

However, because of the wet bulb nature of this storm, elevation could play a significant role in accumulation.

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Agreed, temps will not be an issue. I am much more worried that the better bands / snow rates don't make it much further North than the turnpike. Its hard to believe looking at the radar most of that is going to miss us...

 

Well, NAM really pushed south a bit. Took us from like .75 QPF to .5 this run.

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Well, NAM really pushed south a bit. Took us from like .75 QPF to .5 this run.

I think those fluctuations are well within the margin of error for a model. 25 miles one way or another in most cases but like I said yesterday that cutoff exaggerates it.

 

How often when a storm is coming up from the South and we are counting on it staying South does it go further North and turn us to slop? I know this is a different setup but I can't believe this didn't nudge north, its been pretty consistent that we are between .5 and .75. I am actually NE of the city, so I am thinking I'll be lucky to hit 4 inches. I hope I am wrong and we get clocked overnight.

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I think those fluctuations are well within the margin of error for a model. 25 miles one way or another in most cases but like I said yesterday that cutoff exaggerates it.

 

How often when a storm is coming up from the South and we are counting on it staying South does it go further North and turn us to slop? I know this is a different setup but I can't believe this didn't nudge north, its been pretty consistent that we are between .5 and .75. I am actually NE of the city, so I am thinking I'll be lucky to hit 4 inches. I hope I am wrong and we get clocked overnight.

 

Oh no, I can believe it misses us south. It seems to be our luck that we need a storm to go north, it pushes south, and when we need it to go south, it always goes north lol.

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