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The feb 4-5 storm (Obs/Discussions)


Ji

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Either way, the nrn edge of the snow shield should have a relatively "decent" band of precip moving across the area, and then pushing off to the se. That's where the best mid level frontogenesis and deformation will be. Tough to say where it sets up, but where ever this does end up developing, I could see this as a band of enhanced echoes in a broad area of relatively weak echoes, right on the nrn edge of the snow shield.

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Either way, the nrn edge of the snow shield should have a relatively "decent" band of precip moving across the area, and then pushing off to the se. That's where the best mid level frontogenesis and deformation will be. Tough to say where it sets up, but where ever this does end up developing, I could see this as a band of enhanced echoes in a broad area of relatively weak echoes, right on the nrn edge of the snow shield.

Over my house. :)

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Lots of banking on a near perfect phase. I guess that's to be expected at this point in our craptastic winter. I'd lean toward lighter totals still.

I was just joking around that the JMA came in drier. Euro isn't the one to hang on and I'm not saying that just because I don't like it. I've seen it enough when ull's are closed off west of the ms river. Not sure why it does what it does with closed h5 lows out west but we're not just being weenies when we refer to the euro not handling things correctly in these kind of setups.

An I agree, leaning towards higher totals is relatively safe. The entire system is going to draw a bunch of moisuture from the south into it as it traverses. It's already doing that now. I don't think a perfect phase is necessary either for a 1/2" of gpf but we def don't want the vorts to miss each other either.

Too bad the foothills outside of denver aren't within driving distance. There are going to be some 3-4' totals in areas like evergreen.

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THIS IS A LOW CONFIDENCE FORECAST. Keep that in mind.

20120205-06_MAsnowInitial.png

There is a large amount of uncertainty given the different model runs both against each other and against themselves run-to-run. Surface temperatures will be a problem with this system, only compounding the forecast headaches heading into tomorrow night. I favored some phasing of the disturbance, but did not dig the system as far south and develop as much back-end precipitation as the 12z NAM. This forecast is a blend of the 12z NAM and 12z GFS.

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I was just joking around that the JMA came in drier. Euro isn't the one to hang on and I'm not saying that just because I don't like it. I've seen it enough when ull's are closed off west of the ms river. Not sure why it does what it does with closed h5 lows out west but we're not just being weenies when we refer to the euro not handling things correctly in these kind of setups.

An I agree, leaning towards higher totals is relatively safe. The entire system is going to draw a bunch of moisuture from the south into it as it traverses. It's already doing that now. I don't think a perfect phase is necessary either for a 1/2" of gpf but we def don't want the vorts to miss each other either.

Too bad the foothills outside of denver aren't within driving distance. There are going to be some 3-4' totals in areas like evergreen.

In a complex solution it's usually safer to run toward the idea that either it won't come together as modeled or it will do so too late, in the wrong spot, etc. As was already noted the Euro was a bit dry in the last snow event but not as bad as some would lead us to believe. It could very welll be it's mishandling the 500 low... but there is plenty of rationalization in this thread that's at least somewhat questionable if not from everyone.

And I said leaning toward *lower* totals. ;)

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THIS IS A LOW CONFIDENCE FORECAST. Keep that in mind.

20120205-06_MAsnowInitial.png

There is a large amount of uncertainty given the different model runs both against each other and against themselves run-to-run. Surface temperatures will be a problem with this system, only compounding the forecast headaches heading into tomorrow night. I favored some phasing of the disturbance, but did not dig the system as far south and develop as much back-end precipitation as the 12z NAM. This forecast is a blend of the 12z NAM and 12z GFS.

I think it's a good first guess....nice map update!

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THIS IS A LOW CONFIDENCE FORECAST. Keep that in mind.

20120205-06_MAsnowInitial.png

There is a large amount of uncertainty given the different model runs both against each other and against themselves run-to-run. Surface temperatures will be a problem with this system, only compounding the forecast headaches heading into tomorrow night. I favored some phasing of the disturbance, but did not dig the system as far south and develop as much back-end precipitation as the 12z NAM. This forecast is a blend of the 12z NAM and 12z GFS.

yikes, def hurt my confidence here in the district

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In a complex solution it's usually safer to run toward the idea that either it won't come together as modeled or it will do so too late, in the wrong spot, etc. As was already noted the Euro was a bit dry in the last snow event but not as bad as some would lead us to believe. It could very welll be it's mishandling the 500 low... but there is plenty of rationalization in this thread that's at least somewhat questionable if not from everyone.

And I said leaning toward *lower* totals. ;)

Guilty as charged. E-wood's map isn't bad at all. It could easily take .4+ qpf to get 2" of snow to accumulate unless we somehow squeeze out below freezing surface temps. I have my doubts about that and I hope I'm proven way wrong.

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how? it's 2 quick moving systems, with marginal cold air, and minimal dynamics. I doubt I'll see an inch unless it's on grass.

if we end up with a situation like last winter with an ULL moving overhead, yeah, things could turn out dramatically different from Randy's prediction. but so far that's not on the table.

I think youve seen the solutions that COULD arise ala GGEM, p009 GFS....

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC

301 PM EST FRI FEB 3 2012

&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...

-- Changed Discussion --

SATURDAY...RIDGE OF HIGH PRESSURE FROM QUEBEC TO OFF THE CAROLINA COAST GETS PUSHED FARTHER EAST AS A TROUGH DROPS SOUTH ACROSS THE WESTERN GREAT LAKES...FURTHER CUTTING OFF THE CLOSED LOW OVER THE CENTRAL GREAT PLAINS. AN EAST-WEST SWATH OF LIGHT TO MODERATE RAIN WILL SPREAD EAST ALONG THE LOW LEVEL FRONT THAT DEVELOPS FRIDAY NIGHT. CHANCES OF PRECIP WILL INCREASE THROUGH THE DAY. RAISED POPS TO CATEGORICAL OVER THE POTOMAC HIGHLANDS WITH LIKELIES SPREADING EAST TO ACROSS THE BLUE RIDGE. ELEVATIONS ABOVE 3000 FT COULD SEE ALL SNOW...BUT FOR NOW WENT RAIN/SNOW FOR LOCATIONS WEST FROM THE ALLEGHENY FRONT. UNCERTAINTY COMES FROM THE PLACEMENT OF THE LOW LEVEL FRONT THAT WILL SAG SOUTH THROUGH THE DAY /SINCE COLD AIR CONTROLS FRONTS/. PRECIP WILL BE SOMEWHAT NARROW ACROSS THE FRONT...SO GREATER DETAIL CAN BE PROVIDED BY LATER SHIFTS. MAX TEMPS LIMITED DUE TO NEARLY-IF NOT COMPLETE CLOUD COVER...MID TO UPR 40S NORTH...50F DC AND SOUTH. SATURDAY NIGHT THROUGH SUNDAY NIGHT...12Z MODEL SUITE OF THE ECMWF...SREF...NAM AND GFS HAVE COME INTO BETTER AGREEMENT REGARDING THE AFOREMENTIONED STORM SYSTEM. THE UPPER TROUGH WILL HANG BACK OVER THE GREAT LAKES A BIT LONGER THAN PREVIOUSLY THOUGHT. THIS WILL ALLOW THE SURFACE LOW TO TRACK A BIT FURTHER NORTH ALONG THE FRONTAL BOUNDARY WITH BANDED PRECIPITATION CONTINUING SATURDAY NIGHT INTO SUNDAY. THE NAM AND SREF REMAIN THE COLDEST OF THE 4 SOLUTIONS WITH DECENT COLD AIR ADVECTION AND BACKING FLOW TAKING SHAPE. THIS POSES SOME CONCERN FOR HIGHER SNOWFALL ACCUMULATIONS OVER THE MOUNTAINS BUT THE NAM HAS BEEN NOTORIOUSLY COLD FOR THE PAST FEW SYSTEMS. THE GFS AND ECMWF THERMAL PROFILES ARE A BIT WARMER. SIDED TOWARD A BLEND BUT DID STAY ON THE CONSERVATIVE SIDE WITH SNOWFALL. BUFKIT SOUNDINGS DO SHOW A CHANGEOVER SATURDAY NIGHT INTO SUNDAY MORNING JUST WEST OF THE MOUNTAINS AND MIXED PRECIPITATION EAST INTO THE KIAD-KDCA-KBWI METRO. ANTECEDENT WARM TEMPERATURES WOULD LIKELY KEEP VERY MUCH FROM ACCUMULATING ON URBAN ROADWAYS BUT A DUSTING ON GRASSY SURFACES CANNOT BE RULED OUT. A GENERAL 1 TO 2 INCH ACCUMULATION APPEARS MORE LIKELY OVER THE HIGH TERRAIN WEST OF THE BLUE RIDGE WITH LOCALLY HIGHER AMOUNTS IF COLDER AIR DOES FILTER IN. CONFIDENCE IS HIGH ENOUGH TO GO WITH CATEGORICAL POPS CENTRAL AND SOUTH AND DID PUSH LIKELY POPS FURTHER NORTH TO MATCH NEIGHBORING OFFICES. WE ALSO EXTENDED POP CHANCES INTO SUNDAY AFTERNOON. THE SYSTEM WILL EXIT SUNDAY NIGHT WITH PRECIPITATION ENDING FROM WEST TO EAST DURING THE LATE AFTERNOON/EARLY EVENING.

-- End Changed Discussion --

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Guilty as charged. E-wood's map isn't bad at all. It could easily take .4+ qpf to get 2" of snow to accumulate unless we somehow squeeze out below freezing surface temps. I have my doubts about that and I hope I'm proven way wrong.

true. im not necessarily running to the euro verbatim but im leery of totally dismissing it as well in favor of finding the wettest models. as usual some middle ground is probably worthwhile.. tho in a phase or semi phase not much is set in stone around here quite often.

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