Mar 31 - Apr 4 Plains/MW/OV/GL Storm OBS, Please Post Last Minute Forecast and OBS Options

[jdrenken]

[ChiWxWatcher]

LOT discusses more model differences:

THE NEXT STORY WILL BE SUNDAY THROUGH EARLY NEXT WEEK AS A
SIGNIFICANT TROUGH...EMANATING FROM THE EASTERN PACIFIC...MOVES
ACROSS THE PLAINS STATES. THIS TROUGH LOOKS TO LEAD TO A AN AREA
OF LOW PRESSURE ACROSS THE PLAINS STATES BY SUNDAY. UNFORTUNATELY
I NOW HAVE SIGNIFICANT CONCERNS THAT WE WILL NOT BE AS WARM AS WE
HAVE BEEN FORECASTING PREVIOUSLY...ESPECIALLY FOR THE NEAR SHORE
AREAS. IT APPEARS THAT THE WARM FRONT...ASSOCIATED WITH THE AREA
OF LOW PRESSURE ACROSS THE PLAINS...MAY NOT GET NORTH OF THE
CHICAGO AREA ON SUNDAY. THERE IS EVEN AN INCREASING NUMBER OF
GUIDANCE MEMBERS SUGGESTING THAT A SECOND AREA OF LOW PRESSURE
ACROSS ONTARIO AND QUEBEC MAY PUSH A COLD FRONT DOWN THE LAKE.
WITH THIS IN MIND...IT APPEARS PROBABLE THAT SOME TYPE OF ONSHORE
FLOW WILL SET UP ON SUNDAY. IF THIS DOES INDEED
OCCUR...TEMPERATURES ON SUNDAY WILL BE MUCH COOLER...ESPECIALLY
ACROSS NORTHEASTERN ILLINOIS. THERE COULD EVEN BE SOME MARINE FOG
AFFECTING PORTIONS OF THE AREA. THE OTHER COMPLICATING FACTOR FOR
TEMPERATES ON SUNDAY WILL BE THE POTENTIAL FOR SOME NOCTURNAL
CONVECTION SATURDAY NIGHT INTO SUNDAY MORNING ASSOCIATED WITH THE
INCREASING AREA OF MID LEVEL WARM AIR ADVECTION NORTH OF THE WARM
FRONT. THIS MAY AFFECT TEMPERATURES INLAND AS WELL. DUE TO THE
MENTIONED CONCERNS CONFIDENCE IN SUNDAY TEMPERATURES ARE LOW AT
THIS TIME.

TEMPERATURES NEXT WEEK STILL APPEAR TO COOL OFF...ESPECIALLY BY
MID WEEK AS THE AFOREMENTIONED STORM SYSTEM PUSHES A COLD FRONT
ACROSS THE AREA. HOWEVER...MONDAY COULD POTENTIALLY END UP BEING
THE WARM DAY...DEPENDING ON THE PROGRESSION OF THE WARM FRONTAL
ZONE. IF THE FRONT IS ABLE TO LIFT NORTH OF THE AREA AND PRODUCE
OFFSHORE FLOW...THEN 80S WILL BE POSSIBLE AREA WIDE ON MONDAY.
HOWEVER...DUE TO UNCERTAINTIES WITH SUNDAY...I WAS HESITANT TO
MAKE MANY CHANGES TO MONDAY TEMPERATURES.

THERE STILL LOOKS TO BE A CHANCE OF CONVECTION SOMETIME LATE MONDAY
AND MONDAY NIGHT ASSOCIATED WITH THE COLD FRONTAL PASSAGE.
HOWEVER...SIGNIFICANT DIFFERENCE AMONGST THE LATEST MODEL GUIDANCE
AND ENSEMBLE FORECASTS SUGGEST LOW CONFIDENCE ON THE TIMING AND THE
EXACT EVOLUTION OF THIS STORM SYSTEM.

KJB

[MichelleOH]

Not very excited about tomorrow and the next few days around here.

[StormChaserCK19]

Forbes with a lot of uncertainty to his forecast, however he open with a 5 TorCon Monday for SC KS/NC OK

MON APR 2
Scattered severe thunderstorms, mainly with hail, north of the warm/stationary front in southeast MN, central and east IA, north IL. Isolated severe thunderstorms by evening in north MO, east KS, central and east OK, central TX. A cap (warm layer aloft) may limit storm coverage. TORCON - 5 north-central OK, south-central KS. Still a lot of uncertainty in this forecast.
1

[jdrenken]

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0332 AM CDT FRI MAR 30 2012

VALID 021200Z - 071200Z

...DISCUSSION...
ON MON/D4...A CUT-OFF LOW IS EXPECTED TO ENTER THE SRN PLAINS...BUT
MODELS ARE IN DISAGREEMENT WITH THE SPEED AND LOCATION OF THIS
FEATURE. THE GFS REMAINS MORE PROGRESSIVE BRINGING THE LOW EWD ALONG
THE I-40 CORRIDOR AND INTO OK BY TUE MORNING...WHILE THE ECMWF
STALLS THE SYSTEM OVER W CNTRL TX. WHILE SUBSTANTIAL BOUNDARY LAYER
MOISTURE AND INSTABILITY WILL BE IN PLACE...THE PREDICTABILITY OF
THIS SYSTEM IS TOO LOW TO DELINEATE ANY SEVERE AREAS. REGARDLESS OF
WHICH SOLUTION IS CLOSER TO REALITY...THE SEVERE EVENT DOES NOT
APPEAR TO HAVE MUCH HIGH END POTENTIAL.

FROM TUE/D5 ONWARD...THIS LOW WILL EITHER MEANDER EWD ACROSS THE
GULF COAST...OR MERGE WITH A NERN U.S. TROUGH AND PHASE ACROSS THE
TN VALLEY REGION. ONCE THIS SYSTEM EXITS...THE PATTERN SHOULD BECOME
LESS ACTIVE WITH THE POTENTIAL FOR A REX-BLOCK PATTERN TO SET UP
D7-D8.

..JEWELL.. 03/30/2012

[The Snowman]

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0328 AM CDT SAT MAR 31 2012

VALID 031200Z - 081200Z

...DISCUSSION...
AN UPPER LOW THAT IS BEING HANDLED POORLY BY THE MODELS IS FORECAST
TO BE OVER THE SRN PLAINS ON TUE/D4...AND SHOULD CONTINUE DRIFTING
EWD INTO THE LOWER OR MIDDLE MS VALLEY BY WED/D5. NUMEROUS
THUNDERSTORMS...SOME SEVERE...ARE PROBABLE...ALTHOUGH THIS SYSTEM
WILL NOT RESULT IN A SIGNIFICANT OUTBREAK. STILL...HAIL AND WIND
GUSTS WILL BE LIKELY...MAINLY FROM ERN TX INTO ERN OK...AR...AND LA
ON D4...SPREADING EWD PERHAPS INTO THE TN VALLEY AND GULF COAST
STATES ON D5. WILL DEFER TO LATER OUTLOOKS AS PREDICTABILITY
INCREASES.

THIS LOW WILL OTHERWISE BE NESTLED WITH A LARGER SCALE UPPER
RIDGE...WITH TROUGHS OVER THE NERN AND NWRN CONUS. THE NEXT WRN
TROUGH WILL LIKELY HAVE MOISTURE AND INSTABILITY TO WORK WITH AS A
COLD FRONT WITH CP AIR MASS STALLS NEAR THE GULF COAST D5/D6.
HOWEVER...MODEL DEPICTIONS ARE SIGNIFICANTLY DIFFERENT.

..JEWELL.. 03/31/2012

[The Snowman]

Relative Measure of Predictability

[MichelleOH]

Is this system still active?

[NorEaster07]

Not sure if Colorado falls under "Plains". If not maybe move this to correct thread.


CPC Heavy Snowfall Discussion

424 AM EDT MON APR 02 2012

VALID 12Z MON APR 02 2012 - 12Z THU APR 05 2012

...PAC NW (DAY 1)...

LARGE...DEEP CUTOFF LOW OFF THE BC COAST WILL CONTINUE TO IMPINGE
ON THE HIGHLY-AMPLIFIED RIDGE ACROSS THE INTERMOUNTAIN WEST TODAY.
THE STRENGTHENING GRADIENT WILL LEAD TO A 50-60 KT SSW 850-700 JET
ACROSS COASTAL WA PER THE GFS/NAM AS WELL AS THE GEFS/SREF MEANS.
IN TERMS OF 850-700 MB MOISTURE FLUX ANOMALIES...THAT EASILY
TRANSLATES TO 5-6 STD DEVS ABV NORMAL PER THE OPERATIONAL GFS/NAM
AS WELL AS THE GEFS/SREF. THE ORIENTATION OF THE FLOW (I.E. MORE
SOUTHERLY THAN WESTERLY) WILL CONFINE THE HEAVIEST PCPN ALONG THE
WA/OR COASTAL RANGES (ESP WA)...WHILE AT THE SAME TIME THE
PRE-TROUGH WAA WILL KEEP SNOW LEVELS AROUND 4500 FT BEFORE
BEGINNING TO COME DOWN TONIGHT. WHAT THIS MEANS IS GENERALLY
LIGHTER SNOWS OVER THE HIGHEST ELEVATIONS IN THE NRN WA
CASCADES...THOUGH WITH THE POTENTIAL FOR SIGNIFICANT 24 HR
ACCUMULATIONS ABV 4-4.5 KFT ACROSS THE OLYMPICS...WHICH WILL TAKE
THE BRUNT OF THE STRONG MOIST UPSLOPE FLOW AND THUS REGISTER THE
MOST IN TERMS OF LIQ EQUIV AMOUNTS (AT LEAST 2 TO 2.5 INCHES PER
HPC...SEE QPFPFD FOR MORE DETAILS). AGAIN GIVEN THE HIGH SNOW
LEVELS INITIALLY...NOT ALL OF THIS WILL FALL AS SNOW...THOUGH FEEL
AT LEAST A FOOT TO 1.5 FEET IS A GOOD BET OVER THE OLYMPIC PEAKS

...CENTRAL/SOUTHERN ROCKIES (DAYS 1 AND 2)...

WHAT WAS AN ELONGATED N-S TROUGH WILL SPLIT INTO 2 STREAMS
TODAY...WITH THE SOUTHERN PART OF THE TROF CONTINUING TO AMPLIFY
THIS MORNING...AS THE LOW DEEPENS INTO THE MID LEVELS THIS AM
ACROSS NM AND EVENTUALLY INTO THE UPPER LEVELS (300 MB) TOWARD
EVENING. THE OPERATIONAL MODELS AND ENSEMBLE MEANS ARE FAIRLY WELL
CLUSTERED WITH RESPECT TO THE TIMING AND LOCATION OF THE DEEPENING
PROCESS...THOUGH STILL NOTE DIFFERENCES WITH SOME OF THE SENSIBLE
WEATHER...MOST NOTABLY QPF. THE NAM IS MUCH WETTER FARTHER S
(ACROSS NORTH CENTRAL NM) COMPARED TO THE OTHER NON-NAM MODELS...
AS HPC FAVORED A BLEND OF THE GFS/UKMET/ECMWF AND
LOCALLY-GENERATED ENSEMBLE MEAN.

AS THE CLOSED LOW PIVOTS SLOWLY EASTWARD...THE BACKING FLOW ALOFT
WILL SPREAD A PRONOUNCED AREA OF UPPER LEVEL DIFFLUENCE/AGEOS
DIVERGENCE AND UPWARD VERTICAL MOTION ACROSS THE LOWER CENTRAL AND
SRN ROCKIES. CONTINUED WITH THE HEAVIEST ACCUMS (HIGHEST PROBS OF
8-12+ INCHES) ACROSS THE SANGRE DE CRISTO MNTNS IN THE SRN
ROCKIES... ESPECIALLY E OF THE CREST WITH THE UPSLOPE FLOW. SNOW
LEVELS INITIALLY BTWN 5-6 KFT WILL DROP TO AROUND 4 KFT BY
TONIGHT...THEN STAY THERE FOR THE DURATION OF THE EVENT (THROUGH
TUE). THEREFORE WOULD EXPECT AT LEAST SOME MINOR ACCUMS ALONG THE
FRONT RANGES...ESPECIALLY SOUTH OF THE PALMER DIVIDE

[NYCSuburbs]

Anyone know what this feature is? I thought it was a radar error at first but OBS from ground and SPC forecasts seem to be confirming this... I would've thought it was an MCS or something like that but it's different from the ones I typically see.

[jdrenken]

Not sure if Colorado falls under "Plains". If not maybe move this to correct thread.
CPC Heavy Snowfall Discussion

424 AM EDT MON APR 02 2012

VALID 12Z MON APR 02 2012 - 12Z THU APR 05 2012

...PAC NW (DAY 1)...

LARGE...DEEP CUTOFF LOW OFF THE BC COAST WILL CONTINUE TO IMPINGE
ON THE HIGHLY-AMPLIFIED RIDGE ACROSS THE INTERMOUNTAIN WEST TODAY.
THE STRENGTHENING GRADIENT WILL LEAD TO A 50-60 KT SSW 850-700 JET
ACROSS COASTAL WA PER THE GFS/NAM AS WELL AS THE GEFS/SREF MEANS.
IN TERMS OF 850-700 MB MOISTURE FLUX ANOMALIES...THAT EASILY
TRANSLATES TO 5-6 STD DEVS ABV NORMAL PER THE OPERATIONAL GFS/NAM
AS WELL AS THE GEFS/SREF. THE ORIENTATION OF THE FLOW (I.E. MORE
SOUTHERLY THAN WESTERLY) WILL CONFINE THE HEAVIEST PCPN ALONG THE
WA/OR COASTAL RANGES (ESP WA)...WHILE AT THE SAME TIME THE
PRE-TROUGH WAA WILL KEEP SNOW LEVELS AROUND 4500 FT BEFORE
BEGINNING TO COME DOWN TONIGHT. WHAT THIS MEANS IS GENERALLY
LIGHTER SNOWS OVER THE HIGHEST ELEVATIONS IN THE NRN WA
CASCADES...THOUGH WITH THE POTENTIAL FOR SIGNIFICANT 24 HR
ACCUMULATIONS ABV 4-4.5 KFT ACROSS THE OLYMPICS...WHICH WILL TAKE
THE BRUNT OF THE STRONG MOIST UPSLOPE FLOW AND THUS REGISTER THE
MOST IN TERMS OF LIQ EQUIV AMOUNTS (AT LEAST 2 TO 2.5 INCHES PER
HPC...SEE QPFPFD FOR MORE DETAILS). AGAIN GIVEN THE HIGH SNOW
LEVELS INITIALLY...NOT ALL OF THIS WILL FALL AS SNOW...THOUGH FEEL
AT LEAST A FOOT TO 1.5 FEET IS A GOOD BET OVER THE OLYMPIC PEAKS

...CENTRAL/SOUTHERN ROCKIES (DAYS 1 AND 2)...

WHAT WAS AN ELONGATED N-S TROUGH WILL SPLIT INTO 2 STREAMS
TODAY...WITH THE SOUTHERN PART OF THE TROF CONTINUING TO AMPLIFY
THIS MORNING...AS THE LOW DEEPENS INTO THE MID LEVELS THIS AM
ACROSS NM AND EVENTUALLY INTO THE UPPER LEVELS (300 MB) TOWARD
EVENING. THE OPERATIONAL MODELS AND ENSEMBLE MEANS ARE FAIRLY WELL
CLUSTERED WITH RESPECT TO THE TIMING AND LOCATION OF THE DEEPENING
PROCESS...THOUGH STILL NOTE DIFFERENCES WITH SOME OF THE SENSIBLE
WEATHER...MOST NOTABLY QPF. THE NAM IS MUCH WETTER FARTHER S
(ACROSS NORTH CENTRAL NM) COMPARED TO THE OTHER NON-NAM MODELS...
AS HPC FAVORED A BLEND OF THE GFS/UKMET/ECMWF AND
LOCALLY-GENERATED ENSEMBLE MEAN.

AS THE CLOSED LOW PIVOTS SLOWLY EASTWARD...THE BACKING FLOW ALOFT
WILL SPREAD A PRONOUNCED AREA OF UPPER LEVEL DIFFLUENCE/AGEOS
DIVERGENCE AND UPWARD VERTICAL MOTION ACROSS THE LOWER CENTRAL AND
SRN ROCKIES. CONTINUED WITH THE HEAVIEST ACCUMS (HIGHEST PROBS OF
8-12+ INCHES) ACROSS THE SANGRE DE CRISTO MNTNS IN THE SRN
ROCKIES... ESPECIALLY E OF THE CREST WITH THE UPSLOPE FLOW. SNOW
LEVELS INITIALLY BTWN 5-6 KFT WILL DROP TO AROUND 4 KFT BY
TONIGHT...THEN STAY THERE FOR THE DURATION OF THE EVENT (THROUGH
TUE). THEREFORE WOULD EXPECT AT LEAST SOME MINOR ACCUMS ALONG THE
FRONT RANGES...ESPECIALLY SOUTH OF THE PALMER DIVIDE

Those in the Rockies are "grandfathered" in since we don't have an actual region dedicated to them because of "coverage".

[Sagebrusher]

Those in the Rockies are "grandfathered" in since we don't have an actual region dedicated to them because of "coverage".

I-25 southbound closed at Raton Pass...

Here's a link to some Colorado highway webcams...

http://www.cotrip.org/device.htm



Edit: looks like it is open again

http://www.cotrip.org/roadConditions.htm



This post has been edited by Sagebrusher: Apr 3 2012, 01:12 PM