Central/Western Summer Medium/Long Range Discussions

[Ed Lizard]

Still a little too much potential for cap bust locally (can't tell from 6 hour steps on PSU e-Wall whether IMBY gets wet pre or post frontal), farther East, crazy shear but weak lapse rates.  I picked a sounding ahead of the front in Alabama.  May not wait for TwisterData site to see if I am missing a GFS juicy spot.

 

 

ETA  Not sure why GFS seems so cool at the surface, even at DHN at 0Z.  If the wind forecast s correct but the temps are too low...  KMOB forecast skew-T only needs a few degrees bust to be a monster-scary sounding.  Anyway, a week away, I'll try not to sweat the petty stuff.

[andyhb]

Well the GFS has had the low BL temp bias since forever...as well as the tendency to saturate the mid levels unrealistically, so it becomes easy to point out. I'm more concerned currently with the area roughly encompassing Jackson's CWA.

 

I do see the problem with that ULL hanging around a bit too long and the remnant CP air mass pinching off the warm sector with eastward progression. That said, I think it's gonna have to really linger to affect things significantly as far west as the MS River.

[brettjrob]

Well the GFS has had the low BL temp bias since forever...as well as the tendency to saturate the mid levels unrealistically, so it becomes easy to point out. I'm more concerned currently with the area roughly encompassing Jackson's CWA.

 

Agreed. This looks, similar to this past weekend, like another system where the warm sector will not be able to expand particularly far northward or become too broad -- but it could be significant for areas close to the Gulf nonetheless.

[andyhb]

Agreed. This looks, similar to this past weekend, like another system where the warm sector will not be able to expand particularly far northward or become too broad -- but it could be significant for areas close to the Gulf nonetheless.

 

Seriously, if we get 65+ dews into that area...with those kinds of wind profiles, we likely have a problem on our hands, assuming mesoscale cooperation, since the synoptic setup looks very favorable with a large, low amplitude trough and strong, veering wind profiles through essentially the entire troposphere, as it is shown now.

 

GGEM would suggest the threat is a bit further west, maybe towards SHV's CWA or so.

[andyhb]

D7 issued.

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0357 AM CST FRI FEB 15 2013

VALID 181200Z - 231200Z

...DISCUSSION...
AFTER SEVERAL DAYS OF DRYING NORTHWESTERLY LOW-LEVEL FLOW...A
GRADUAL MODIFICATION OF THE BOUNDARY LAYER OVER THE GULF OF MEXICO
APPEARS LIKELY TO COMMENCE EARLY NEXT WEEK...AS A SERIES OF
SIGNIFICANT SHORT WAVE TROUGHS BEGIN TO PROGRESS ACROSS THE NATION.
AN INITIAL IMPULSE PROGRESSING EAST OF THE ROCKIES LATE THIS COMING
WEEKEND...APPEARS LIKELY TO REACH THE PLAINS/MISSISSIPPI VALLEY
REGION TOO SOON...AND TOO FAR NORTH...FOR A SUBSTANTIVE RETURN FLOW
OF MOISTURE TO DEVELOP AND CONTRIBUTE TO AN APPRECIABLE RISK FOR
SEVERE THUNDERSTORMS. HOWEVER...MEDIUM RANGE FORECAST MODELS HAVE
BEEN FAIRLY CONSISTENT FOR SEVERAL DAYS NOW...SUGGESTING THAT THE
STRONG UPSTREAM IMPULSE WILL DIG INTO THE SOUTHERN GREAT
BASIN...BEFORE LIFTING EAST NORTHEASTWARD ACROSS THE CENTRAL AND
SOUTHERN ROCKIES/PLAINS AND MIDDLE MISSISSIPPI VALLEY DURING THE
MIDDLE TO LATTER PORTION OF NEXT WEEKEND. AT THIS POINT...TIMING
INTO THE PLAINS WEDNESDAY NIGHT...AS MORE FAVORABLE INLAND MOISTURE
RETURN BEGINS TO OCCUR OFF THE WESTERN GULF OF MEXICO...DOES NOT
APPEAR OPTIMAL FOR SEVERE WEATHER POTENTIAL. BUT...BY THURSDAY...AT
LEAST ON THE SOUTHERN FRINGE OF STRONGER HIGH-LEVEL DIFLUENCE AND
MID-LEVEL HEIGHT FALLS...THERE APPEARS A GOOD LIKELIHOOD THAT
LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION AND BOUNDARY LAYER
DESTABILIZATION WILL BECOME FAVORABLY JUXTAPOSED TO SUPPORT THE RISK
FOR SEVERE STORMS...INCLUDING POTENTIAL FOR AT LEAST ISOLATED
TORNADOES.

..KERR.. 02/15/2013

[andyhb]

Lol, looking at the twister data soundings, a lot of the GFS ones are saturated up to the 150 mb level...

[thewxmann]

Wow, imagine if we had this pattern in April or May. I can't believe how many nice-looking troughs we've had just this month.

[andyhb]

Wow, imagine if we had this pattern in April or May. I can't believe how many nice-looking troughs we've had just this month.

 

This next one looks dangerous enough as is, and this is February...

[Srain]

A nice weekend is ahead for our Region with near Chamber of Commerce weather, so get out and enjoy it as change are ahead next week.

 

A very complex split zonal flow pattern develops where the cold air to the N and the return of Gulf and Pacific moisture will set the stage for a very potent Winter Storm to develop mid week across the Southern Great Basin and begin to slowly eject ENE into the Mid West later in the week. The trends overnight have been to slow the storm system down by about 24 hours and the Euro and ensembles have trend that way ~vs~ the faster North American model/ensemble (GFS/GEFS/Canadian) solution. Warm sector severe weather chances have increased with an impressive 100kt + jet streak crossing Texas on Wednesday into Thursday and the mean trough axis becomes neutral to negative tilted. Further N in the cold sector across the higher elevations of the Southern Central Rockies and Central/Northern Plains, blizzard conditions appear likely as cold air across Canadian is pulled S by the exiting early week storm complex over the NE. The mid week storm appear to be very powerful and will be very dynamic bring a wide spread storm to much of North America. It does appear another storm system will arrive later next week along the Pacific setting the stage for yet another storm event as we head into next weekend. The long range guidance continues to advertise this stormy, somewhat progressive pattern will linger into the last week of February.

Euro:

 

Euro Ensembles:

 

DAY 4-8 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   0354 AM CST SAT FEB 16 2013
  
   VALID 191200Z - 241200Z
  
   ...DISCUSSION...
   THE LATEST MEDIUM RANGE MODELS AND MODEL ENSEMBLES REMAIN FAIRLY
   CONSISTENT WITH RUNS OVER THE PAST SEVERAL DAYS...PARTICULARLY WITH
   REGARD TO A STRONG SHORT WAVE IMPULSE THAT APPEARS LIKELY TO DIG
   INTO THE CALIFORNIA COAST EARLY NEXT WEEK.  A DEEP MID-LEVEL CLOSED
   LOW MAY EVOLVE AS THE IMPULSE MIGRATES INLAND...BUT IT IS EXPECTED
   TO REMAIN PROGRESSIVE...AS ANOTHER IMPULSE EMERGES FROM THE STRONG
   UPSTREAM MID-LATITUDE PACIFIC JET...AND APPROACHES THE PACIFIC
   NORTHWEST COAST BY MID WEEK. 
  
   IN ASSOCIATION WITH THE LEAD SYSTEM...WHICH STILL APPEARS LIKELY TO
   LIFT EAST NORTHEAST OF THE SOUTHERN ROCKIES THROUGH THE CENTRAL
   PLAINS/MID MISSOURI VALLEY REGION LATE WEDNESDAY NIGHT THROUGH EARLY
   THURSDAY EVENING...SIGNIFICANT SURFACE CYCLOGENESIS APPEARS LIKELY
   ACROSS THE CENTRAL PLAINS.  THIS MAY BE ACCOMPANIED BY INCREASING
   CONVECTIVE POTENTIAL...INCLUDING AT LEAST SOME RISK FOR SEVERE
   STORMS...ACROSS PARTS OF THE CENTRAL AND SOUTHERN PLAINS LATE
   WEDNESDAY/WEDNESDAY NIGHT.  HOWEVER...IT STILL APPEARS MOST PROBABLE
   THAT SEVERE WEATHER POTENTIAL WITH THIS SYSTEM WILL BECOME MAXIMIZED
   ON THURSDAY...AS DAYTIME HEATING CONTRIBUTES TO
   DESTABILIZATION...AND RETURN FLOW CONTINUES OFF AN INCREASINGLY
   MOIST BOUNDARY LAYER OVER THE GULF OF MEXICO.
  
   AS THIS MOISTURE OVERRUNS A RESIDUAL COOL/STABLE BOUNDARY LAYER
   LINGERING OVER PARTS OF THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST
   ...THE MOIST/UNSTABLE WARM SECTOR BOUNDARY LAYER MAY NOT BECOME
   PARTICULARLY BROAD.  BUT IT IS EXPECTED TO BECOME SIZABLE ENOUGH TO
   SUPPORT A SIGNIFICANT RISK FOR SEVERE STORMS...AT LEAST ON THE
   SOUTHERN FRINGE ON THE MORE STRONGLY DIFLUENT HIGH-LEVEL FLOW... AND
   MID-LEVEL HEIGHT FALLS...ACROSS THE LOWER MISSISSIPPI VALLEY
   THURSDAY AFTERNOON AND EVENING.  THIS MAY INCLUDE THE RISK FOR
   SUPERCELLS WITH A FEW TORNADOES.
  
   ..KERR.. 02/16/2013

 

EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
153 AM EST SAT FEB 16 2013

VALID 12Z TUE FEB 19 2013 - 12Z SAT FEB 23 2013

 

...SIGNIFICANT SYSTEM POSSIBLE IN THE CENTRAL PLAINS THURSDAY...

...OVERVIEW...

 

THREE AREAS OF UPPER RIDGING SURROUNDING THE CONUS /OVER THE
NORTHEAST PACIFIC... HUDSON BAY... AND NEAR CUBA/ SHOULD HELP
BLOCK/GUIDE SEVERAL SYSTEMS NEXT WEEK. SPLIT FLOW OFF THE PACIFIC
SHOULD DIG SYSTEMS THROUGH THE WEST BEFORE EJECTING OUT ONTO THE
PLAINS AND THEN NORTHEASTWARD. COLD CANADIAN SFC HIGH PRESSURE IS
FORECAST TO REMAIN JUST NORTH OF THE HIGH PLAINS/UPPER MIDWEST.

 

...MODEL PREFERENCES...

 

THE GUIDANCE SHOWS GOOD SYNOPTIC AGREEMENT THROUGH SAT/D7. THE
MAIN DIFFERENCES SEEN BETWEEN THE GFS/GEFS AND ECMWF/ECMWF
ENSEMBLES REMAIN THE SAME... WITH THE FORMER JUST A BIT QUICKER
THAN THE LATTER OVERALL. THOUGH A WEIGHTED COMPROMISE USUALLY
PROVES BEST... THE TREND IN THE PAST 24 HRS HAS BEEN TOWARD A
SLOWER EXODUS OF THE POTENTIALLY SIGNIFICANT SFC SYSTEMS IN THE
CENTRAL/SOUTHERN PLAINS THU/D5. THUS... OPTED TO LEAN TOWARD THE
SLOWER ECMWF/ECMWF ENSEMBLE MEAN SOLUTIONS OVER THE GEFS SOLUTION.
THE UKMET/CANADIAN LARGELY SIDE WITH THE ECMWF CLUSTER AS WELL.

THE LARGEST SPREAD AMONG THE ENSEMBLES APPEARS BY SAT/D7 OVER THE
PAC NW... WHERE THE GFS/GEFS MEMBERS FORECAST ANYTHING FROM A
CLOSED LOW TO WEAK TROUGHING TO RIDGING. THE ECMWF MEMBERS SUGGEST
TROUGHING WITH DECREASED SPREAD SINCE 24 HRS AGO... BUT GIVEN ITS
ORIGIN UPSTREAM OVER THE NORTH PACIFIC /WITH A 160KT+ JET/... THIS
MAY VERY WELL CHANGE AT LEAST IN TIMING IF NOT AMPLITUDE.

 

...SENSIBLE WEATHER HIGHLIGHTS...

 

FIRST SYSTEM OVER THE GREAT LAKES TUE/D3 SHOULD EXIT STAGE RIGHT
OVER MAINE ON WED/D4... WITH LINGERING LAKE EFFECT SNOWS IN ITS
WAKE THAT SHOULD END BY THU/D5. IN THE WEST... DIGGING UPPER LOW
IS STILL FORECAST TO ROUND THE BASE OF THE TROUGH THROUGH SOUTHERN
NV/NORTHERN AZ BEFORE REFORMING OVER SE CO THU/D5. WITH COLD AIR
IN PLACE TO THE NORTHEAST... EASTERLY FLOW SHOULD SET UP A DECENT
UPSLOPE EVENT IN EASTERN COLORADO WITH HEAVY SNOW EXTENDING
EASTWARD INTO NEBRASKA. WITH PRESSURE DIFFERENCE BETWEEN THE LOW
AND HIGH TO THE NORTHEAST OVER 40MB... BLIZZARD CONDITIONS SEEM
QUITE POSSIBLE.  AS THE SFC LOW TRACKS THROUGH KANSAS... 12Z/15
ECMWF WAS A BIT SLOWER THAN ITS MEAN /AND THE GFS/ THOUGH GIVEN
THE SLOWER TREND IN THE GEFS AND ECMWF ENSEMBLE MEMBERS A
COMPROMISE BETWEEN THE TWO SEEMED REASONABLE.

 

THE GULF SHOULD BE OPEN FOR BUSINESS BY THU/D5 WITH GEFS
PROBABILITY OF PW OF AT LEAST ONE INCH OVER 50 PERCENT UP TO KY/TN
BORDER. ENSEMBLE MEANS ALREADY PUTTING OUT ABOUT 1.50IN OF QPF IN
THE FRI-SAT/D6-7 TIME FRAME WITH SOME WETTER MEMBERS OVER 3 INCHES
/GEFS/ OR EVEN 5 INCHES /ECMWF ENSEMBLES/. SEVERE WEATHER ALSO A
POSSIBILITY IN THE WARM SECTOR /SEE SPC FOR LATEST DAY 4-8
OUTLOOK/. SYSTEM SHOULD WEAKEN AS IT MOVES NORTHEAST AND THEN
POSSIBLY DEVELOPS ANOTHER MAIN SFC LOW OFFSHORE. WESTERN STATES
WILL SEE ANOTHER TROUGH DIG THROUGH THE SW FRI/D6... BUT LIKELY
NOT AS STRONG AS THE ONE PRIOR.

 

TEMPERATURES SHOULD BE COLD ACROSS THE NORTHERN PLAINS BUT MORE
VARIABLE IN THE EAST... OSCILLATING BETWEEN RELATIVELY WARMER AND
COLDER AHEAD OF AND BEHIND EACH SYSTEM... RESPECTIVELY. THE WEST
SHOULD GENERALLY STAY BELOW NORMAL WITH THE RELOADING TROUGH. THE
GULF COAST AND FLORIDA WILL BE CLOSER TO THE SUBTROPICAL RIDGE
OVER CUBA AND ARE FORECAST TO BE NEAR TO ABOVE NORMAL.

FRACASSO

[brettjrob]

Alongside the more explicit impacts, I'm very optimistic about widespread drought relief with this storm across many areas that need it badly. All the global models currently paint significant QPF across a wide swath of the Plains from N TX all the way to NE. The best part is the medium range looks relatively active with several waves potentially tracking across the Southwest.

 

On the severe side of things, it's remarkable how many similarities this bears to the 2/9-2/10 system. Would expect a noteworthy threat over a very similar area on Thursday.

[Srain]

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
140 AM EST MON FEB 18 2013

VALID 12Z THU FEB 21 2013 - 12Z MON FEB 25 2013

...SIGNIFICANT SYSTEM LIKELY IN THE CENTRAL PLAINS INTO IOWA
THURSDAY... 

...HEAVY RAIN POSSIBLE IN THE SOUTHEAST FRIDAY INTO THE WEEKEND...


 
...OVERVIEW... 

THE VERY ACTIVE PATTERN THROUGH MUCH OF THE CONUS WILL STAY IN
PLACE INTO THE START OF NEXT WEEK AS THE GRAVY TRAIN OF PACIFIC
SYSTEMS TAKES THE SCENIC ROUTE THROUGH THE COUNTRY. THESE
SPRING-LIKE SYSTEMS SHOULD BE EFFICIENT RAIN MAKERS IN THE
SOUTHERN TIER /THANKS TO THE OPEN GULF OF MEXICO/ WITH MODEST
SNOWFALL TO THE NORTH. RIDGING OVER HUDSON BAY AND CUBA/BAHAMAS
SHOULD FORCE SYSTEMS IN BETWEEN WHILE THE STRONG UPPER RIDGE
BETWEEN HAWAII AND ALASKA MAY EAST WESTWARD BY SUN-MON/D6-7.

 
...MODEL PREFERENCES... 

LITTLE SYNOPTIC SCALE CHANGE HAS BEEN SEEN IN THE MODELS/ENSEMBLES
OVER THE PAST TWO DAYS WITH RESPECT TO THE GENERAL FLOW. THE
GEFS/ECMWF ENSEMBLES HAVE NUDGED THEIR FORECASTS AROUND A COMMON
FOCI WITH EACH ITERATION... AND THE DETERMINISTIC RUNS ARE WELL
CORRELATED. A BLEND BETWEEN THE 18Z GFS AND 12Z ECMWF WAS USED AS
THE BASIS FOR THE FORECAST THROUGH DAY 7. THE UKMET WAS SOMEWHAT
IN BETWEEN THE TWO PRIMARY MODELS WHEN THEY DID DIFFER... BUT THE
CANADIAN REMAINS THE OUTLIER.

BY SUN-MON/D6-7... ANOTHER POTENT DIGGING WESTERN TROUGH OR
PERHAPS A CLOSED LOW WILL PUSH THROUGH THE ROCKIES AND OUT ONTO
THE PLAINS... IN SIMILAR FASHION TO THE START OF THE MEDIUM RANGE
ON THU/D3. MODELS HAVE BEEN LESS CONSISTENT ON THE TIMING/STRENGTH
AND THE ENSEMBLES ARE FAIRLY WEAK... BUT POTENTIAL IS THERE FOR A
MODEST SYSTEM GIVEN THE SPREAD IN SOLUTIONS. THOUGH THE 12Z ECMWF
PROBABLY ALONE FORGED A GOOD COMPROMISE POSITION... THE FASTER
ENSEMBLE CLUSTERING SUGGESTED A BIT QUICKER PROGRESSION.
 

...SENSIBLE WEATHER HIGHLIGHTS... 

VIGOROUS UPPER LOW STILL FORECAST TO EJECT OUT OF THE ROCKIES AND
SLOWLY WEAKEN AS IT HEADS NORTHEASTWARD THROUGH THE PLAINS... WITH
SFC LOW MOVING TOWARD IOWA BY FRI/D4. NEAR BLIZZARD CONDITIONS ARE
POSSIBLE WITH FORECAST SFC WINDS NEAR 30KTS AND GUSTS OVER 40KTS
ESPECIALLY FROM EASTERN NE INTO IA LATE THURSDAY. SEVERE WEATHER
STILL A THREAT IN THE LOWER MS VALLEY THU/D3 /SEE LATEST SPC
OUTLOOK/. SYSTEM HEADS EASTWARD AND WEAKENS/SHEARS WITH ENERGY
TRANSFERRING TO THE COAST. SOUTHERN END OF THE FRONT SHOULD GET
HUNG UP ACROSS SOUTHERN GEORGIA OVER THE WEEKEND... AND FLOW
AROUND THE UPPER RIDGE TO THE SOUTH SHOULD PUMP IN AMPLE GULF
MOISTURE FROM THE LOWER MS VALLEY NORTHEASTWARD. QPF PER THE
DETERMINISTIC MODELS FOR DAYS 4-7 ARE STILL IN THE 4-6 INCH RANGE
WITH INCREASING NUMBERS SEEN IN THE MEANS /OVER 2 INCHES/.

LAST SYSTEM IN THE FORECAST APPEARS TO BE A WEAKER VERSION OF THE
FIRST SYSTEM OF NOTE ON THU/D3... WITH A STRONG UPPER TROUGH OR
CLOSED LOW MOVING ONTO THE PLAINS. STILL SOME MURKY DETAILS AT
THIS FAR OUT BUT A SWATH OF SNOW TO THE NORTH... MODERATE RAINS TO
THE SOUTH... AND COLDER TEMPERATURES IN ITS WAKE ARE ALL POSSIBLE
BY EARLY IN THE WEEK IN THE CENTRAL CONUS. THOUGH ANECDOTALLY ALL
LOWS GO TO CHICAGO... 500MB CLOSED LOW CLIMATOLOGY FAVORS THIS "SW
FREEWAY" FROM THE FOUR CORNERS TO THE WESTERN LAKES... SO A
REPETITIVE TRACK MAY INDEED BE POSSIBLE.
 
 
FRACASSO

 

[Srain]

While we are watching the severe potential developing later tonight into tomorrow across Texas and Louisiana and the Winter weather across the Central Plains, there continues to be strong signals via the Global operational and ensemble guidance that a very active southern stream Winter Storm will develop to our W early next week and travel much further S than we have seen so far this winter season. As we have seen so far this season, the storm track has been that of systems developing in the Desert SW and traversing ENE into the Plains and Mid West. The upper air pattern has changed across the Northern Hemisphere to that of a strong blocking pattern over the NW Atlantic extending E into Eastern Canada. That ingredient has been missing all winter and is now firmly established. This West based –NAO regime with a –AO and  PNA pattern does bode well for a southern suppressed storm track. Another ingredient that is noteworthy is the convective activity across the Eastern Pacific that suggests a very noisy sub tropical jet. It appears that the guidance is latching on to such a scenario and agreement with the computer models lends credibility to closely monitoring the trends over the next several days. NOAA G-IV Winter Recon departed Hawaii yesterday afternoon and made several drops last night en route to Anchorage and will fly again tonight over the NE Pacific. This additional data will likely aid guidance as this progressive pattern continues as we head toward the end of February.

 

00Z Euro:

 

00Z NAEFS:

[aslkahuna]

Deep cold H5 ULL over western AZ due to swing into NM tonight. So far we've seen rain/snow in southern AZ including snow in downtown Tucson. Near blizzard to blizzard conditions with heavy snow blowing snow in Cochise County and travel is slow on I-10 from just east of TUS to NM state line. ULL expected to track throughs o TUS tonight with more snow shower activity and rapidly worsening condition in NM. Then we can expect as indicated above a major system developing in the western Plains. A significant severe weather event is likely to the east.

 

Steve

[andyhb]

 

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0342 AM CST THU FEB 21 2013

VALID 241200Z - 011200Z

...DISCUSSION...
WITHIN PERSISTENT BROADER SCALE UPPER TROUGHING...IN THE SOUTHERN
BRANCH OF A SPLIT FLOW EMERGING FROM THE PACIFIC...MEDIUM RANGE
MODELS CONTINUE TO INDICATE THE NEXT IN A SERIES OF STRONG SHORT
WAVE TROUGHS WILL DIG ACROSS THE SOUTHERN ROCKIES INTO THE SOUTHERN
PLAINS LATE THIS COMING WEEKEND. AS IT DOES...IT APPEARS LIKELY TO
GRADUALLY COME IN PHASE WITH ANOTHER STRONG JET STREAK EMERGING FROM
THE SUBTROPICAL EASTERN PACIFIC...THEN TAKE ON A NEGATIVE TILT
ACROSS THE LOWER MISSISSIPPI VALLEY...BEFORE LIFTING TOWARD THE
GREAT LAKES REGION DURING THE EARLY TO MIDDLE OF NEXT WEEK. WHILE
PRIMARY SURFACE CYCLOGENESIS APPEARS PROBABLE ACROSS THE SOUTH
CENTRAL PLAINS INTO AND THROUGH THE MIDDLE MISSISSIPPI
VALLEY...MODELS SUGGEST THAT A SIGNIFICANT SECONDARY WAVE WILL FORM
ALONG A FRONTAL ZONE ADVANCING/REDEVELOPING NORTHWARD OUT OF THE
NORTHERN GULF OF MEXICO. WHILE VARIABILITY LINGERS AMONG THE MODELS
AND MODEL ENSEMBLES...IT SEEMS PROBABLE THAT PEAK SEVERE WEATHER
POTENTIAL WITH THIS SYSTEM WILL OCCUR ON MONDAY...AS A MOIST WARM
SECTOR OVERSPREADS MUCH OF THE CENTRAL AND EASTERN GULF STATES.
DEEP LAYER AND LOW-LEVEL SHEAR SHOULD BE MORE THAN SUFFICIENT FOR
ORGANIZED SQUALL LINE AND SUPERCELL DEVELOPMENT...WITH THE RISK FOR
DAMAGING WIND AND TORNADOES.

..KERR.. 02/21/2013

[AgeeWx]

I know it's a week+ out but next Thursday appears to have kinematics that "could" be favorable for severe weather in the higher terrain of Western Kansas/Nebraska. As of now moisture is rather scarce but I have to wonder if there could be a locally maximized flux of moisture with the melting of the snow pack due to robust surface temps.

 

Thoughts?

[ZackH]

I know it's a week+ out but next Thursday appears to have kinematics that "could" be favorable for severe weather in the higher terrain of Western Kansas/Nebraska. As of now moisture is rather scarce but I have to wonder if there could be a locally maximized flux of moisture with the melting of the snow pack due to robust surface temps.

 

Thoughts?

 

Thoughts are exactly what I told you earlier today.  180+ hours out it will change a billion times.  And right on cue the 18z GFS takes your threat and laughs at it  Its a potent short wave so its worth watching, but in that area of the country this early in the year, I'd have a hard time believing the moisture or instability will be there.  Its always hard to get excited about something crazy looking when its directly after the post truncation period, ala the 12z run and last night's 00z.

[baroclinic_instability]

I know it's a week+ out but next Thursday appears to have kinematics that "could" be favorable for severe weather in the higher terrain of Western Kansas/Nebraska. As of now moisture is rather scarce but I have to wonder if there could be a locally maximized flux of moisture with the melting of the snow pack due to robust surface temps.

 

Thoughts?

 

 

Thoughts are exactly what I told you earlier today.  180+ hours out it will change a billion times.  And right on cue the 18z GFS takes your threat and laughs at it  Its a potent short wave so its worth watching, but in that area of the country this early in the year, I'd have a hard time believing the moisture or instability will be there.  Its always hard to get excited about something crazy looking when its directly after the post truncation period, ala the 12z run and last night's 00z.

 

 

I wouldn't get too excited. Classic High Plains severe needs substantial help from extreme heat to reach sufficient CAPE values...and that won't come until late spring to early summer. In rarer circumstances...long return flow with favorable easterly trajectories through the GOM can return sufficient moisture, but the GOM is absolutely closed for business here Furthermore, this trough won't have sufficient amplitude to incite long enough leeside cyclogenesis to enhance the return in the wake of the absolutely monster trough digging into the GOM then off the east coast preceding the aforementioned trough.  Melting snow alone won't sufficiently moisten the boundary layer to have any real consequence in that area of the US. 

[ZackH]

I wouldn't get too excited. Classic High Plains severe needs substantial help from extreme heat to reach sufficient CAPE values...and that won't come until late spring to early summer. In rarer circumstances...long return flow with favorable easterly trajectories through the GOM can return sufficient moisture, but the GOM is absolutely closed for business here Furthermore, this trough won't have sufficient amplitude to incite long enough leeside cyclogenesis to enhance the return in the wake of the absolutely monster trough digging into the GOM then off the east coast preceding the aforementioned trough.  Melting snow alone won't sufficiently moisten the boundary layer to have any real consequence in that area of the US. 

 

Oh trust me, I'm far from excited... just tempering Dave's expectations a bit... he was already trying to nail me down for chasing next Thursday (I don't think it would go over well either, me skipping my first presentation on my initial thesis research)... hehehe.  Just messing with you Dave.

[baroclinic_instability]

Oh trust me, I'm far from excited... just tempering Dave's expectations a bit... he was already trying to nail me down for chasing next Thursday (I don't think it would go over well either, me skipping my first presentation on my initial thesis research)... hehehe.  Just messing with you Dave.

Right, that was in response to the excitement post from David. That said, I am a natural weather pessimist, so take my pessimism with a grain of salt  

[Roger Smith]

Hello regional forums ...

 

Please note -- March temperature forecast contest deadline end of today (time penalties begin at midnight +5 min eastern time) ... new entrants welcome ... main forum, pinned thread.

[brettjrob]

Impressive week-over-week improvement on the drought monitor. Areas east of US-81 have been designated "long-term only" now. It's still going to take a few more good soakers for me to feel great about W TX and the High Plains in general, though. May have another opportunity toward the end of next week.

 

 

And the following looks more like May than February. There's still probably 0.5-1" LE remaining in snowpack throughout NW OK and the eastern Panhandle.

 

[AgeeWx]

Disclaimer: I have limited experience forecasting and way too much optimism for the field I'm in.

 

That being said, man what a difference 24 hours makes in model land huh?

 

Whoops

[Ellinwood]

Been awhile since I've posted in this sub-forum! I spent some time looking at the long range forecast for spring to try to figure out how active a tornado season we could expect. The full discussion can be found here: http://www.ustornadoes.com/2013/02/28/spring-2013-seasonal-forecast/

If you don't feel like clicking the link for the actual forecast, here's a clip from the post:

...I would expect a near average tornado season this spring (March through May), with a somewhat active early season before the longer term signals trend towards a quieter back half of spring. The warmer and drier conditions induced by the -PDO/+AMO/drought combo over the central U.S. could cut down on the tornado potential during the back half of spring and probably the summer months as well. This is a low confidence forecast due to the uncertainty in the pattern trends.

[andyhb]

Good stuff, Mark.

[baroclinic_instability]

Disclaimer: I have limited experience forecasting and way too much optimism for the field I'm in.

 

That being said, man what a difference 24 hours makes in model land huh?

 

Whoops

That optimism is much appreciated. Keep it up. 

[Srain]

Been awhile since I've posted in this sub-forum! I spent some time looking at the long range forecast for spring to try to figure out how active a tornado season we could expect. The full discussion can be found here: http://www.ustornadoes.com/2013/02/28/spring-2013-seasonal-forecast/

If you don't feel like clicking the link for the actual forecast, here's a clip from the post:

Very nice discussion Mark and I tend to agree that this severe season bodes a bit better with the increased moisture/storm track we have seen this late winter. Don't be a stranger in our sub forum and maybe Ian will give up on any snow chances for the Mid Atlantic and start spending some time around as well.

[brettjrob]

Medium range models are coming into agreement that yet another closed low will move through the Southwest into TX next weekend. If this verifies, short-term drought should be all but eliminated for a good chunk of the southern Plains. The GFS has been spitting out obscene QPF, but even cutting it in half should put us in territory comparable to the last system. Now, let's just cross our fingers that the pattern is actually progressive and the low doesn't stall out to the west.

 

Moisture return is likely to be a limiting factor for any major severe weather, but if these kind of systems keep coming into April... oh my.

[Srain]

Maybe some potential for the cold and warm sector. It's been a while since we have seen a Northern Mexico U/L.

[Indystorm]

It's way out in fantasyland, but a number of runs of the GFS have been advertising a system somewhere around the Ides of March for the southern Plains, lower MS valley, and mid South that might bear watching, especially if a western trough manages to establish itself per Euro thinking and next week's system serves to moisten things up a bit.

[Srain]

The ensembles guidance continues to advertise a deep Western trough developing as a Pacific storm moves inland along the California Coast next Thursday. While there is still some uncertainty regarding just how much return flow can become established ahead of the slow moving suppressed 5H low, it is rather clear that this will be the next major storm system for our Region with cold sector snow/ice and warm sector severe potential. The good news is that this storm will likely continue to put a big dent in the ongoing drought conditions across the Plains.

 

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
155 AM EST SAT MAR 02 2013

VALID 12Z TUE MAR 05 2013 - 12Z SAT MAR 09 2013

...POSSIBLE WINTER STORM MAY IMPACT SECTIONS OF THE MID-ATLC
SOMETIME DURING THE TUE-THU TIMEFRAME...

...A WET PATTERN IS IN STORE FOR THE WRN CONUS AS A MEAN TROF SETS
UP OVER THE REGION...


THE MID-LATITUDE PATTERN WILL BECOME A BIT MORE ACTIVE THAN THE
PRESENT SHORT RANGE PERIOD. THE INITIAL SYSTEM OF INTEREST IS AN
UPR TROF/CLOSED LOW POSITIONED INVOF THE MID MS VALLEY. AS THIS
DISTURBANCE SLIDES EWRD...IT SHOULD CONTINUE TO AMPLIFY SPREADING
HGT FALLS THRU THE SERN U.S/LWR MID-ATLC. THE GUIDANCE CONTINUES
TO DIVERGE ON EXACTLY HOW THIS WILL PLAY OUT...PARTICULARLY WITH
THE POSN OF THE UPR LOW AND HOW QUICKLY IT MOVES OFFSHORE. THE 12Z
GFS/ECMWF SUGGEST THE UPR TROF WILL BRIEFLY WRAP-UP ALONG THE
COASTAL MID-ATLC BEFORE TRACKING OFFSHORE LATE WED/EARLY THU. ON
THE CONTRARY...THE 12Z UKMET WAS MUCH QUICKER IN EJECTING THIS
SYSTEM INTO THE OFFSHORE WATERS. GIVEN THIS IDEA WAS NOT SUPPORTED
BY ANY OF THE GLOBAL ENS MEANS...THE UKMET WAS NOT UTILIZED BEYOND
DAY 4. BEFORE THIS...THE 12Z GFS/ECMWF/UKMET HAD GENERAL AGREEMENT
WITH THE SFC TRACK FROM 05/1200Z THRU 06/1200Z WITH A BLEND OF
THESE THREE PIECES OF GUIDANCE UTILIZED IN THE PRODUCTS. THE
IMPACTS FROM THIS SYSTEM WILL DEPEND ON THE TRACK AND STRENGTH BUT
THE POTENTIAL DOES HOLD FOR A WINTER STORM SOMEWHERE ACRS THE
MID-ATLC REGION. REGARDLESS...IT DOES APPEAR COLD WX WILL TAKE
HOLD FROM THE GRT PLAINS EWRD TO MUCH OF THE ERN U.S. WITH TEMP
ANOMALIES APPROACHING 15 TO 20 F BELOW CLIMO.

THE OTHER MAJOR SYSTEM IMPACTING THE CONUS WILL BE IN RESPONSE TO
A DEEP UPR LOW WHICH IS FCST TO BE JUST OFFSHORE OF THE PAC NW
EARLY TUE. AS THIS SYSTEM TRACKS INLAND...IT SHOULD SLOWLY SHEAR
OUT ACRS THE UPR INTRMTN WEST/NRN ROCKIES LATE WED INTO THU.
HOWEVER...THE MID-LEVEL IMPULSES COMBINED WITH AMPLE LOW-LEVEL
MOISTURE WILL SUPPORT PERIODS OF HEAVY PCPN ALONG THE WEST COAST
EARLY IN THE FCST PERIOD...PARTICULARLY ALONG THE FAVORED TERRAIN.
FURTHER DOWNSTREAM...BUILDING HGTS OVER THE INTRMTN WEST EWRD TO
THE GRT PLAINS WILL SUPPORT WELL ABOVE NORMAL TEMPS. THIS WILL
PREDOMINANTLY OCCUR DURING THE D4/D5 PERIOD. LOOKING BACK TO THE
WEST COAST...AS ONE SYSTEM SHEARS OUT ACR THE INTERIOR MTN
WEST...ANOTHER TROF IS FCST TO SLIDE DOWN THE WEST COAST BEFORE
CLOSING OFF ACRS CA BY EARLY FRI. DETERMINISTIC/ENS GUIDANCE
REASONABLY SHOW THIS IDEA ALTHOUGH THE 12Z CMC IS FURTHER UP THE
CA COAST. EVENTUALLY THIS MID-LEVEL ENERGY SHOULD SLOWLY PROPAGATE
TOWARD THE E REACHING NRN MX/SRN AZ BY 09/1200Z. WHILE THE
GUIDANCE DIVERGES ON THE EXACT POSN OF THIS SYSTEM ON D7...ENOUGH
552-DM SPAGHETTI MEMBERS SUGGEST THIS FCST EVOLUTION TO FEEL
REASONABLY COMFORTABLE WITH THE MODELS HERE. AS MENTIONED
EARLIER...THE 12Z GFS/ECMWF/UKMET REASONABLY AGREED TO SUPPORT
THEIR BLEND THRU D4. THEREAFTER...THE MORE PROGRESSIVE
MID-LATITUDE PATTERN THE 12Z UKMET SUGGESTS APPEARED MUCH TOO
QUICK. A COMBINATION OF THE 12Z GFS/ECMWF AND THEIR RESPECTIVE
MEANS WERE USED IN THE HPC BLEND FOR D5/D6 GIVEN INC SPREAD ACRS
THE BOARD. BY D7...ENOUGH UNCERTAINTY IN THE FCST SUGGESTED ALL
ENS MEANS...PARTICULARLY WITH THE TIMING/STRENGTH OF THE UPR
CYCLONE NEAR THE AZ/MX BORDER. ONE RAMIFICATION WITH THE POSN OF
THIS TROF IS THE ENHANCED GULF MOISTURE BEING DRAWN TOWARD THE
SRN/CNTRL PLAINS WHICH MAY BRING HEAVY RAINFALL BY LATE MAR
8/EARLY MAR 9.


RUBIN-OSTER