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Feb 25-26 Discussion/pbp


Wow

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RAH DISCUSSION mentions the possibility, but also mentions that temperatures will be very mild on wednesday so it could be a rain changing to snow type deal...  

 

Would we get a lot of accumulation on grass and roads from that scenario?  Seems like they would be pretty warm.

 

 

That was written at 3:00 this morning. Long term AFD still isnt out

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HPC doing it's normal thing of compromising but that still leans a wetter/further north system.

OUTHERN PLAINS TO SOUTHEAST ON TUE...A COLD FRONT WILL BE WELL SOUTH OF THE GULF COAST AT THE SURFACEON TUE...BUT THE COLD AIR WILL BE RELATIVELY SHALLOW. THE 925-850MB REFLECTION OF THIS BOUNDARY SHOULD BE ACROSS THE GULF COASTSTATES AS THE SOUTHERN EDGE OF A BROAD UPPER LEVEL TROUGH CROSSESTHE APPALACHIANS WITH ISENTROPIC ASCENT LEADING TO SHOWERSTHROUGHOUT THE SOUTHEAST. ABOVE THE INVERSION OVER THE GULF COASTSTATES...UNIDIRECTIONAL FLOW FROM THE WEST WILL BE PRESENT ALONGWITH WEAK INSTABILITY IN THE 700-500 MB LAYER WHICH COULD ALLOW ACONVECTIVE ELEMENT TO THE SHOWERS NEAR/NORTH OF THE FLORIDAPANHANDLE. THE 12Z GFS WAS FLATTER AND ALMOST NON-EXISTENT WITHTHE 925 MB REFLECTION OF A WAVE MOVING ALONG THE GULF COAST STATESAND WAS THEREFORE A DRY OUTLIER FOR DAY 2...00Z/24-25. A 12ZNAM/00Z ECMWF BLEND WAS USED HERE GIVEN THE SIMILARITY OF THE TWOMODELS AND THEIR AGREEMENT ON THE WEAK WAVE WITH THE LATESTDETERMINISTIC MODEL SUITE....FOUR CORNERS REGION INTO THE SRN PLAINS AND GULF COAST STATESTUE-WED...A CLOSED LOW AT THE START OF THE PERIOD...00Z/24...WILL BE PRESENTOVER THE FOUR CORNERS REGION...WITH AN EXPECTED WEAKENING/OPENINGUP AS THE FEATURE TRACKS EWD THROUGH TUE. SOME TIMING ANDPLACEMENT DIFFERENCES ARE STILL PRESENT WITH THIS WAVE BUT AT THESURFACE...LOW PRESSURE SHOULD ORGANIZE IN THE GULF OF MEXICO OUTAHEAD OF THE UPPER WAVE ALONG A STRONG BAROCLINIC ZONE...WITH THESTRENGTH/TRACK OF THE LOW MAKING SIGNIFICANT DIFFERENCES FOR THESOUTHEAST. GIVEN NWD TRENDS IN MANY OF THE 12Z MODELS WITH THEVORT MAX PASSING OVER THE DEEP SOUTH ON WED...A BLEND OF THE 12ZGFS AND 12Z ECWMF WAS USED...WITH THE 12Z ECMWF SHOWING A MOREAMPLIFIED NATURE COMPARED TO ITS PREVIOUS RUN. THE GFS/ECMWF ALSOAGREE WELL WITH TIMING...WHILE THE 12Z NAM IS FASTER...12Z CMC

day 3

 

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day 1-3 total

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To me this looks like a pretty classic setup on the NAM for a northern deepsouth/southern MA snowstorm at 500mb. Cutoff/upper low over new england and cutoff stj low over tx and into the deep south. i would love to see this trend towards a cutoff longer and longer and then it could get real interesting. 

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To me this looks like a pretty classic setup on the NAM for a northern deepsouth/southern MA snowstorm at 500mb. Cutoff/upper low over new england and cutoff stj low over tx and into the deep south. i would love to see this trend towards a cutoff longer and longer and then it could get real interesting. 

 

That's what I'm crossing my fingers for.  I know from past storms, you won't see the cutoff until with 24-28 hrs on the models, so I wouldn't be surprised one bit to see the MA get in on this as well, possibly getting up to the delmarva before moving out.

 

As I said earlier, these small differences at the 500mb level can mean a big one at the surface.

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NWS ILM's latest discussion--they favor the suppressed GFS for Wednesday night-Thursday's system:

 

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 300 PM SUNDAY...LARGE...BUT NOT EXCEPTIONALLY DEEP...TROUGH
WILL PERSIST ACROSS THE EAST INTO THE UPCOMING WEEKEND MAINTAIN
COLD AND UNSETTLED CONDITIONS FOR MUCH OF THE EXTENDED.

COLD FRONT STALLED WELL SOUTH OF THE AREA WILL SERVE AS THE
BAROCLINIC GRADIENT ALONG WHICH AN ACTIVE SOUTHERN STREAM WILL SPAWN
SEVERAL WAVES OF LOW PRESSURE. WHILE NONE OF THESE WILL BE
IMPRESSIVELY STRONG...EACH ONE WILL BRING AT LEAST A CHANCE OF
PRECIP TO THE AREA. TWO QUESTIONS WILL SURROUND EACH PASSING WAVE OF
LOW PRESSURE HOWEVER...HOW MUCH PRECIP WILL EXTEND NORTH FROM THE
LOW...AND WHETHER COLD ENOUGH AIR WILL BE IN PLACE FOR MIXED P-TYPE.

THE FIRST OF THESE...WEDNESDAY NIGHT AND THURSDAY...LOOKS NOW TO BE
THE MOST SIGNIFICANT OF THE WEEK. GUIDANCE IS TRACKING THIS SURFACE
LOW A LITTLE FURTHER WEST THAN PREVIOUS RUNS...AND THUS SLINGING
MORE PRECIP INTO THE CAROLINAS. ADMITTEDLY...THE E-W ORIENTED
BAROCLINIC ZONE DOES NOT`T SUPPORT A VERY FAR WEST TRACK AND WILL LEAN
MORE ON THE DRIER GFS
...BUT WIDESPREAD CLOUDS WITH PERIODS OF PRECIP
ARE POSSIBLE WEDNESDAY NIGHT INTO THURSDAY. WITH COLD HIGH PRESSURE
IN PLACE RAIN COULD MIX WITH SOME FREEZING/FROZEN PRECIP...EVEN
THOUGH RAIN IS EXPECTED TO BE THE PRIMARY P-TYPE. THE ECMWF...WHICH
IS MORE ROBUST WITH ITS PRECIP...IS ALSO COLDER...BUT EVEN THE GFS
DEPICTS A PERIOD OF MIXED PRECIP. LOCAL TOP-DOWN METHODOLOGY
PRODUCES PRIMARILY RAIN AS EXPECTED...BUT HAVE LEFT A PERIOD OF MIX
PRECIP...RAIN AND SNOW WITH SNOW ONLY FAR NW...LATE WED NIGHT. QPF
WILL BE LIGHT AND POP IS LOW...BUT SNOWFLAKES ARE POSSIBLE WED NIGHT
BEFORE TEMPS WARM TO SUPPORT ONLY RAIN DURING THURSDAY.

A PERIOD OF DRIER WEATHER IS EXPECTED LATE THURSDAY INTO
FRIDAY...BEFORE ANOTHER LOW PRESSURE MOVES ALONG THE STALLED
BOUNDARY TO THE SOUTH. HOWEVER...EVEN DURING THIS "DRIER" PERIOD A
SCHC POP REMAINS WARRANTED DUE TO WAVES OF LOW PRESSURE ALONG THE
OFFSHORE BAROCLINIC GRADIENT - AND THERE IS LOW CONFIDENCE IN THE
TIMING/TRACK OF THESE FEATURES. THE PAST FEW DAYS...ECMWF/GFS HAD
SHOWN GOOD AGREEMENT IN BRINGING MORE SIGNIFICANT PRECIP LOCALLY
FRIDAY INTO SATURDAY...MUCH OF WHICH WOULD BE OF THE
FREEZING-TO-LIQUID TRANSITION VARIETY. TODAY...GUIDANCE HAS BACKED
OFF CONSIDERABLY...WHICH MAY MAKE SENSE DUE TO THE EXPECTED QUICK
E/NE TRACK OF SURFACE FEATURES. STILL...AM INCLINED TO MAKE ONLY
MINIMAL CHANGES TO THE FRI/SAT TIMEFRAME AS THIS REPRESENTS A NEW
SOLUTION...AND WILL LEAVE LOW MENTIONABLE POP WITH MIXED P-TYPE.

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That's what I'm crossing my fingers for.  I know from past storms, you won't see the cutoff until with 24-28 hrs on the models, so I wouldn't be surprised one bit to see the MA get in on this as well, possibly getting up to the delmarva before moving out.

Yea if that happens, i think most of north ms/al/ga/sc/tn/nc/s va would be in store for a nice snowstorm. There are a lot of analogs for a setup like this. Just hope we can get some model consistency on this the next 24 hours and i think we can reel it in.

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Decent run for SE NC with an inch or two.  Precip makes it to Raleigh with a flizzard.  Definitely a much better run the past GFS runs, though not there yet, obviously.  I would say that this definitely leads to further support of the UKMET/Euro at this point with the GFS definitely trending towards them.

 

The 18z NAM wasn't as good of a look, but the LR NAM is sketchy and basically useless, anyways.

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Decent run for SE NC with an inch or two.  Precip makes it to Raleigh with a flizzard.  Definitely a much better run the past GFS runs, though not there yet, obviously.  I would say that this definitely leads to further support of the UKMET/Euro at this point with the GFS definitely trending towards them.

 

The 18z NAM wasn't as good of a look, but the LR NAM is sketchy and basically useless, anyways.

 

NAM looked great until 72 or so, then decided to give up its energy and didn't know where to place the sfc low.  But that's the NAM.

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