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Two Clipper System's Jan 11-14th Disco/OBS


dmc76

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06Z GFS is having issues with lake effect, and weirdly has the lake effect band setup inland in Branch and Hillsdale counties.  the NAM actually looks more realistic in this case, with more spread-the-wealth LES from the levels of instability. 

 

Also, once again DTX is conservative as always. Only thinks one to two even in the snow belt.

 

PERIOD AS A SECOND CLIPPER SYSTEM...RATHER IMPRESSIVE IN AND OF

ITSELF IF CURRENT MODEL SOLUTIONS HOLD...RE-ENFORCES THE UPPER

TROUGH OVER THE EASTERN CONUS WELL INTO THE UPCOMING WEEK AFTER

BRING A WIDE SWATH OF LIGHT SNOW...ON THE ORDER OF AN INCH OR

TWO...TO THE AREA MONDAY NIGHT INTO TUESDAY. TEMPERATURES IN THE

TEENS AND 20S WILL BE COMMON FOR THE REMAINDER OF THE FORECAST

 

No part of DTX is in a west wind LES belt.

 

And besides, even the bullish NAM you reference only shows ~2" tops for much of DTX's CWA.

 

Sure, it's possible a stationary LES band could develop along a convergence zone and dump higher amounts of snow in a narrow corridor, but I wouldn't base the forecast for an entire CWA on that happening. 

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AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE WILMINGTON OH

409 PM EST SUN JAN 10 2016

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...

QUIET WEATHER IS EXPECTED ON MONDAY...AS FLAT UPPER FLOW SETTLES

BRIEFLY OVER THE OHIO VALLEY...AND A SURFACE HIGH CROSSES

EASTWARD TO THE SOUTH OF THE REGION. ALTHOUGH WARM ADVECTION WILL

BE OCCURRING ON THE NORTHEASTERN PERIPHERY OF THE HIGH...THE COLD

STARTING POINTS AND EXPECTED SHALLOW MIXING WILL KEEP TEMPERATURES

FROM RISING APPRECIABLY. MAX TEMPS ARE FORECASTED TO RANGE FROM

THE LOWER 20S (NORTHERN CWA) TO AROUND 30 (SOUTHERN CWA)...WHICH

WOULD BE THE COLDEST MAX TEMPERATURES SO FAR THIS WINTER.

ANOTHER ROUND OF SNOW IS EXPECTED FROM LATE MONDAY NIGHT THROUGH

TUESDAY MORNING...WITH CHANCES FOR SNOW SHOWERS CONTINUING INTO

THE DAY ON TUESDAY. BY MONDAY EVENING...A SHORTWAVE WILL BE

MOVING EAST INTO THE SOUTHERN GREAT LAKES REGION. TO THE SOUTH OF

THE WAVE...INCREASING WARM ADVECTION (WITH 850MB SPEED CONVERGENCE

AND ISENTROPIC LIFT) WILL ALLOW FOR PRECIPITATION TO BEGIN TO

DEVELOP OVER NORTHERN INDIANA...SPREADING INTO THE ILN FORECAST

AREA OVERNIGHT. MEANWHILE...A SURFACE LOW (THOUGH NOT PARTICULARLY

STRONG) WILL MOVE INTO MICHIGAN. TRAILING FROM THIS LOW WILL BE A

POTENT ARCTIC COLD FRONT...WHICH WILL SIGNAL ANOTHER CHANGE OF AIR

MASS FOR THE MIDDLE OHIO VALLEY.

SNOW IS EXPECTED TO OVERSPREAD THE CWA BETWEEN 06Z-15Z. THIS IS

ACTUALLY A LITTLE BIT AHEAD OF THE SURFACE COLD FRONT...THOUGH

STRONG COLD ADVECTION AT AND ABOVE 875MB WILL ALREADY BE

ONGOING...AIDED BY SUPPORT FROM THE SHORTWAVE. MODEL SOUNDINGS

INDICATE THE PRESENCE OF AN INVERSION BETWEEN 800MB AND

650MB...WHICH MAY LINE UP WITH THE FAVORABLE DENDRITIC GROWTH ZONE

FOR A WHILE...DEPENDING ON HOW EXACTLY THE TEMPERATURE PROFILES

PROGRESS. THUS...THERE IS SOME POTENTIAL FOR EFFICIENT SNOW...AND

FORECAST NUMBERS HAVE BEEN INCREASED BY AROUND A HALF INCH. THE

NEW SNOWFALL FORECAST INDICATES AROUND AN INCH IN THE SOUTHWESTERN

CWA...RANGING TO ABOUT TWO AND A HALF INCHES IN THE FAR

NORTHEASTERN CWA. AS THIS EVENT REMAINS TWO DAYS AWAY...THESE

FORECAST NUMBERS SHOULD CERTAINLY BE CONSIDERED PRELIMINARY

EXPECTATIONS. THOUGH THE RESPECTABLE FORCING AND INCREASING SNOW

RATIOS ARE FAVORABLE IN THIS CASE...THERE ARE TWO LIMITING FACTORS

TO MENTION. FIRST...THE DEPTH OF SATURATION IS NOT

IMPRESSIVE...WITH MOST OF THE ATMOSPHERIC MOISTURE CONFINED BELOW

700MB. SECOND...THE TIMING OF THE COLDEST BOUNDARY-LAYER AIR

(ALONG AND BEHIND THE FRONTAL PASSAGE) MAY NOT PERFECTLY ALIGN

WITH THE EXPECTED TIMING OF HEAVIEST PRECIPITATION.

CONDITIONS WILL CHANGE MARKEDLY BEHIND THE FRONT...AS STEADIER

SNOW ENDS...BUT THE POTENTIAL FOR SNOW SHOWERS INCREASES.

FOCUSING ON QPF OUTPUT FROM LARGER-SCALE MODELS WILL NOT TELL THE

STORY...BUT MODEL SOUNDINGS CLEARLY INDICATE A STRONGLY-MIXED

BOUNDARY LAYER (WITH WEAK/SHALLOW CONVECTIVE INSTABILITY) AND

CONTINUALLY COOLING 850MB TEMPS. WEATHER GRIDS WERE EDITED TO

INCREASE THE CHANCES FOR SNOW SHOWERS BEHIND THE ARCTIC

FRONT...AND EXTEND THESE CHANCES WELL THROUGH THE DAY. THESE EARLY

INDICATIONS DO PROVIDE FOR SOME CONCERN REGARDING THE POTENTIAL

FOR REDUCED VISIBILITIES AND GUSTY CONDITIONS.

TEMPERATURES WILL AGAIN BE NON-DIURNAL ON MONDAY NIGHT. THOUGH

CONDITIONS MAY BRIEFLY COOL DURING THE EVENING...WARMING

TEMPERATURES ARE EXPECTED THROUGH THE MORNING HOURS...AHEAD OF THE

ARCTIC FRONT. ONCE THE FRONT PASSES...PERSISTENT FALLING

TEMPERATURES ARE EXPECTED THROUGH THE DAY ON TUESDAY. WITH MIN

TEMPS ON TUESDAY NIGHT EXPECTED TO BE IN THE SINGLE DIGITS FOR

MOST OF THE CWA...AND POSSIBLY CLOSE TO ZERO IN THE FAR

NORTH...WIND CHILLS WILL EASILY DROP BELOW ZERO. IN

FACT...FOR THE FAR NORTHERN CWA...WIND CHILLS ARE CURRENTLY

FORECAST AT AROUND THE ADVISORY CRITERIA OF -10 DEGREES.

 

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DTX's thoughts:

MUCH HIGHER CONFIDENCE IN DEVELOPING SNOW MONDAY EVENING/NIGHT AS

INTENSE UPPER WAVE FROM THE ARCTIC CIRCLE DROPS INTO

THE WESTERN GREAT LAKES...WITH GOOD LARGE SCALE LIFT/PV

ADVECTION...AS ACTUAL SURFACE LOW/REFLECTION TRACKS THROUGH THE

HEART OF THE STATE. MODEL SOUNDINGS INDICATING SATURATION ALL THE

WAY UP PAST 15 KFT...WITH GENEROUS QPF AMOUNTS EXCEEDING TENTH OF AN

INCH AS WE HEAD INTO TUESDAY. LOW LEVEL LAPSE RATES DURING THE DAY

ON TUESDAY LOOK TO BE VERY STEEP WITH CAPES WITHIN THE DGZ EXCEEDING

50 J/KG AND CLOUD DEPTHS STILL 10 KFT. WITH THE STRONG WESTERLY

FLOW OFF LAKE MICHIGAN AND WINDS INCREASING BETWEEN 30 TO 40

KNOTS WITHIN THE BOUNDARY LAYER...LOOKS LIKE WE WILL BE SET UP FOR

SNOW SQUALLS AND LOCALIZED WHITE OUT CONDITIONS DURING THE DAY ON

TUESDAY. TEMPERATURES IN THE LOWER 20S WILL LIMIT THE MELTING OF

SNOW AS SALT BEGINS TO LOOSE ITS EFFECTIVENESS AS TEMPS DROP

INTO THE UPPER TEENS WITHIN THE SQUALLS. BETWEEN THE WIDESPREAD SNOW

MONDAY NIGHT AND THE MORE LOCALIZED/INTENSE NATURE ON

TUESDAY...WIDESPREAD SNOWFALL ACCUMULATIONS OF 2 TO 4 INCHES APPEARS

LIKELY WITH THE FAVORABLE SNOW RATIOS...AS 925 MB SPECIFIC

HUMIDITIES SNEAK UP TO AROUND 2 G/KG EARLY TUESDAY. LOCALIZED HIGHER

AMOUNTS ARE CERTAINLY POSSIBLE WITH ANY PERSIST NARROW BAND WHICH

SETS UP DURING TUESDAY.

Much more aggressive compared to this morning's afd

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Could be some modest multiband enhancement off Lk Ontario/Erie with this one. Good delta-ts and a S/SSE flow. Wouldn't be surprised by locally 4"+ in the golden horseshoe. 

The low will also be strengthening as it approaches S On. The Euro has a <1000mb low travelling just to our north while the REG is ~994mb. Inversion heights get as high as 700mb under a SSE flow on the NAM, although winds do veer some with height.

 

An inversion that high has been very rare lately under an easterly flow. Weve seen decent Lehs with inversion heights as low as 850-900mb.

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The low will also be strengthening as it approaches S On. The Euro has a <1000mb low travelling just to our north while the REG is ~994mb. Inversion heights get as high as 700mb under a SSE flow on the NAM, although winds do veer some with height.

 

An inversion that high has been very rare lately under an easterly flow. Weve seen decent Lehs with inversion heights as low as 850-900mb.

 

Absolutely. Going to be tough to get bands to sit still given the variable flow, and not a ton of fetch so I'm not expecting monster amounts. But always nice to track mesoscale in a larger synoptic storm.

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I noticed none of the models did very well AT ALL tonight with the LES, so I think the numbers pumped out are low an inch or two, seeing how the majority of my snow on the ground right now was from this out-of-the-blue LES.

 

Sometimes the models are waaaay underdone for LES. Just depends. How much snow have you picked up from the "storm" and then this LES?

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