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Author Topic: Potential Presidents' Day Weekend Snow for Southern Cities  (Read 1276 times)

Offline toxictwister00

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Potential Presidents' Day Weekend Snow for Southern Cities
« on: February 15, 2013, 09:03:19 AM »
Two pieces of energy, one diving in from the north and another digging in from the south are expected to potentially phase together to develop a SLP off the SE coast. Interestingly enough, Looking at the RAP model (very short model for those who don't know) it has the southern energy digging much further south than most other mdoels do and if it that happens and it manages to phase with the northern energy developing a SLP in the Gulf, this very minor event could translate into a major event, however that's just speculation on the way the RAP seems to be heading, but we'll see.

Here's what some of the NWS offices are saying in their AFDs.

Atlanta, GA
Code: [Select]
THE NEXT ISSUE IS THE POTENTIAL FOR WINTRY PRECIP ON SATURDAY.

BOTH THE GFS AND NAM HAVE A BULLSEYE OF OVER 1 INCH SOUTH OF
CSG BY 18Z SATURDAY. 21Z SREF PROBS KEPT THE PROBABILITY OF MEASURABLE SNOW
MUCH FARTHER NORTH...BUT THE NEW 03Z RUN JUST COMING IN LENDS MUCH
MORE CREDENCE TO THE NAM AND GFS SOLUTIONS WITH A SWATH OF 60-70
PERCENT MEASURABLE SNOW BETWEEN THE NORTHEAST MOUNTAIN AND CTJ AT
12Z SATURDAY

BETWEEN ATL AND CSG AT 15Z /THOUGH THESE PROBS
ARE FOR LESS THAN 1 INCH ACCUM/. OF COURSE...THE VERY STRONG CAA
WILL BE COMPETING WITH RETREATING MOISTURE. VERY STEEP LAPSE RATES
FROM 18-21Z ON SATURDAY WILL LEAD TO A VERY CONVECTIVELY-DRIVEN
EVENT WITH WIDESPREAD COLD AIR STRATOCU OR PERHAPS EVEN COLD AIR
CU...BUT THE DEPTH OF CONVECTION WILL BE VERY DEPENDENT ON MOISTURE
AVAILABILITY AS THE UPPER TROUGH AXIS WILL BE MOVING INTO THE AREA

WITH THE EXPECTED CONVECTION...IT IS LIKELY THAT AT LEAST
SOME SNOW WILL REACH THE GROUND ACROSS MOST OF THE CWA IN A
BRIEF WINDOW WHERE INCOMING COLD TEMPS WILL LINE UP BEST WITH THE MOISTURE.
HOWEVER...IN CONVECTION...SURFACE TEMPS DO NOT HAVE TO BE QUITE AS COLD FOR
SNOW TO REACH THE GROUND...SO EXPECT THAT SNOW WILL FALL AT TEMPS IN
THE MID AND POSSIBLY UPPER 30S. THIS SAID...HAVE BROUGHT THE
RAIN/SNOW MIX DOWN TO EXTREME SOUTHWEST ZONES FOR SATURDAY
MORNING...WITH ALL SNOW AS FAR SOUTH AS A FRANKLIN TO MCDONOUGH TO
ATHENS LINE.

MOISTURE IS JUST NOT REALLY DEEP ENOUGH BUT MOISTURE TRENDS WILL
HAVE TO BE MONITORED.

- I don't know about you guys, but when I hear convection and snow in the same paragraph I get very excited! I've seen what that's capable of doing.  :D

Columbia, SC
Code: [Select]
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
THE MODELS CONTINUED TO SHOW DEEP UPPER TROUGHING DEVELOPING SATURDAY WITH
ENHANCED MOISTURE ASSOCIATED WITH A SHORTWAVE TROUGH. MOISTURE AND
INSTABILITY ASSOCIATED WITH THE TROUGH MAY SUPPORT PRECIPITATION.
THE NAM AND ESPECIALLY THE GFS HAVE TRENDED WITH HIGHER POPS.
THE NAM POPS WERE ALSO SUPPORTED BY THE SREF GUIDANCE WHERE MOST
MEMBERS INDICATED A GRADIENT OF POPS RANGING FROM NEAR 40 PERCENT IN
THE NORTHEAST SECTION TO LESS THAN 20 PERCENT IN THE CENTRAL SAVANNAH RIVER AREA.
ALL OF THE MODELS INDICATED GREATER MOISTURE AND LIFT IN THE NORTHEAST PART CLOSER
TO LOW PRESSURE THAT SHOULD DEVELOP OFF THE COAST IN RESPONSE TO
THE STRONG MID- LEVEL SHORTWAVE TROUGH. PRECIPITATION TYPE IS A
PROBLEM. THE NAM AND GFS FORECAST OF 1000-500 MB THICKNESSES AND
H85 TEMPERATURES SUPPORT SNOW. HOWEVER...THE MODEL TEMPERATURE
PROFILES INDICATE RAIN UNLESS SIGNIFICANT WET-BULB COOLING OCCURS
WHICH IS QUESTIONABLE BECAUSE OF EXPECTED LIGHT AMOUNTS. SOIL
TEMPERATURES ARE RELATIVELY WARM AND WITH MARGINAL NEAR-SURFACE
TEMPERATURES LITTLE OR NO ACCUMULATION SHOULD OCCUR. ANY
PRECIPITATION SHOULD END FROM SOUTHWEST TO NORTHEAST SATURDAY
NIGHT AS LOW PRESSURE OFF THE COAST LIFTS FARTHER AWAY FROM THE
AREA. THE GUIDANCE TEMPERATURES APPEAR TOO WARM SATURDAY BASED ON
THE COLD UPPER- LEVEL TROUGH AND EXPECTED CLOUDINESS.

Raleigh, NC
Code: [Select]
.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
AS OF 330 AM FRIDAY...

...POTENTIAL FOR WINTER WEATHER INCREASING ACROSS PORTIONS OF
CENTRAL NC SATURDAY EVENING/NIGHT...

VERY INTERESTING SETUP IN THE SHORT TERM PERIOD IN ASSOC/W A DYNAMIC
AND POTENTIALLY EXPLOSIVE PATTERN. IF UPSTREAM QPF OVER THE DEEP
SOUTH SATURDAY MORNING IS ACCURATE...THE POTENT UPPER LEVEL WAVE
DIGGING INTO THE SOUTHEAST CONUS AND ASSOCIATED COASTAL CYCLONE WILL
REMAIN PROGRESSIVE OVER THE SOUTHEAST/CAROLINAS...WITH LIGHT
PRECIPITATION AND ANY WINTER WEATHER POTENTIAL OF THE NUISANCE
VARIETY. HOWEVER...IF THE 00Z MODEL GUIDANCE IS UNDER-DONE
(ESPECIALLY WELL UNDER-DONE) WITH PRECIP AMOUNTS IN ADVANCE OF THE
AMPLIFYING UPPER LEVEL TROUGH UPSTREAM OVER THE DEEP SOUTH...WHICH
IS DEFINITELY POSSIBLE IN THIS TYPE OF SETUP...THE ASSOCIATED LATENT
HEAT RELEASE AND RESULTING DOWNSTREAM RIDGING COULD FURTHER AMPLIFY
THE UPPER LEVEL WAVE DIGGING INTO THE SOUTHEAST LATE SAT INTO SAT
NIGHT...RESULTING IN A SLOWER/STRONGER SURFACE CYCLONE THAT IS MUCH
CLOSER TO THE COAST...AND A POTENTIAL FOR SIGNIFICANT WINTER WEATHER
ACROSS PORTIONS OF THE CAROLINAS...ESPECIALLY EAST OF HIGHWAY 1.
WILL HAVE TO PAY VERY CLOSE ATTENTION TO UPSTREAM PRECIPITATION OVER
THE DEEP SOUTH SATURDAY MORNING...AND HOW WELL MODEL GUIDANCE IS
VERIFYING W/REGARD TO QPF. THE LATEST 00Z MODEL GUIDANCE HAS TRENDED
WETTER OVERALL SAT AFTERNOON INTO SAT NIGHT...WITH A GOOD 0.25" OF
LIQUID EQUIVALENT OVER CENTRAL NC (ALONG/EAST OF HWY 1) BETWEEN 18Z
SAT AFTERNOON AND 06-12Z SUN IN ASSOC/W STRONG UPPER LEVEL DYNAMICS.
FCST SOUNDINGS AND CRITICAL THICKNESSES SUGGEST PRECIP BEGINNING AS
RAIN SAT AFTERNOON...WITH A BOUNDARY LAYER (LOWEST 1-3 KFT)
INITIALLY JUST TOO WARM AND INSUFFICIENTLY DRY TO SUPPORT FROZEN
PTYPES. HOWEVER...AS THE ASSOCIATED SFC CYCLONE BEGINS TO RAPIDLY
DEEPEN OFFSHORE...THE ONSET OF STRONG LOW-LEVEL COLD ADVECTION
/NORTHERLY FLOW/ SATURDAY EVENING IS EXPECTED TO LEAD TO A RAPID
CHANGEOVER FROM RAIN-SNOW BY ~00Z. IF AND HOW MUCH SNOW ACCUMULATION
OCCURS WILL HIGHLY DEPEND ON PRECIPITATION AMOUNTS... WHICH WILL IN
TURN HIGHLY DEPEND ON THE EVOLUTION OF THE SFC CYCLONE AS OUTLINED
ABOVE. GIVEN THE PRECIP AMOUNTS CURRENTLY ANTICIPATED AND THE TIMING
OF THE CHANGEOVER...EXPECT A POTENTIAL FOR UP TO AN INCH OF
ACCUMULATION EAST OF HIGHWAY 1 SATURDAY EVENING/NIGHT... PRIMARILY
FROM THE TRIANGLE EAST TO GOLDSBORO NORTH TO ROANOKE RAPIDS. -VINCENT


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Offline TWCCraig

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Re: Potential Presidents' Day Weekend Snow for Southern Cities
« Reply #1 on: February 15, 2013, 04:55:41 PM »
Based on the 18z GFS, northern Florida might see more snow than us from this system. Crazy.
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Offline toxictwister00

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Re: Potential Presidents' Day Weekend Snow for Southern Cities
« Reply #2 on: February 15, 2013, 05:06:23 PM »
Verbatim at 850mb they might could, but 2m temps are way too warm. However if any part of FL sees a flake before I do out of this, I'm gonna pull my hair out of my head.  :P


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