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  Wednesday March 4, 2015

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SPC - No watches are valid as of Wed Mar 4 15:09:01 UTC 2015

No watches are valid as of Wed Mar  4 15:09:01 UTC 2015.


SPC MD 112

MD 0112 CONCERNING WINTER MIXED PRECIPITATION FOR NORTHEAST/EAST-CENTRAL OK INTO SOUTHERN MO/FAR NORTHERN AR
MD 0112 Image


MESOSCALE DISCUSSION 0112
NWS STORM PREDICTION CENTER NORMAN OK
0640 AM CST WED MAR 04 2015

AREAS AFFECTED...NORTHEAST/EAST-CENTRAL OK INTO SOUTHERN MO/FAR
NORTHERN AR

CONCERNING...WINTER MIXED PRECIPITATION 

VALID 041240Z - 041745Z

SUMMARY...MIXED WINTER PRECIPITATION WILL BECOME INCREASINGLY COMMON
BY LATE MORNING/EARLY AFTERNOON ACROSS EAST-CENTRAL/NORTHEAST OK
INTO SOUTHERN MO/FAR NORTHERN AR AS COLDER AIR TRANSITIONS
SOUTHEASTWARD. AT LEAST SOME SLEET/LIGHT ICE ACCUMULATIONS CAN BE
EXPECTED WITHIN THIS CORRIDOR ALONG WITH SOME SNOW ACROSS PARTS OF
NORTHEAST OK AND SOUTHWEST/SOUTH-CENTRAL MO.

DISCUSSION...DOWNSTREAM OF AN UPPER LOW OVER BAJA EARLY THIS
MORNING...FORCING FOR ASCENT WILL CONTINUE TO INCREASE IN TANDEM
WITH A SHARPENING/SOUTHEASTWARD-SHIFTING FRONTAL ZONE ACROSS THE
SOUTHERN PLAINS/OZARKS. SATELLITE AND REGIONAL RADAR/SURFACE
OBSERVATIONS EARLY THIS MORNING REFLECT INCREASINGLY COLDER CLOUD
TOPS AND INCREASING PRECIPITATION FROM NORTH-CENTRAL TX AND
SOUTHERN/EASTERN OK INTO THE OZARKS.

THE SURFACE WET-BULB 32F ISOLINE...WHICH LARGELY PARALLELS I-44 FROM
OK INTO SOUTHERN MO AS OF 12Z/6 AM CST...CONTINUES TO STEADILY
PROGRESS SOUTHEASTWARD AT AROUND 15-25 MPH. AS THIS TREND
CONTINUES...PROGRESSIVELY COLDER NEAR-SURFACE AIR WILL LEAD TO A
TRANSITIONAL COMBINATION OF WINTER MIXED PRECIPITATION TYPES BY LATE
MORNING/EARLY AFTERNOON ACROSS EAST-CENTRAL/NORTHEAST OK INTO
SOUTHERN MO/FAR NORTHERN AR. 

SCATTERED/BRIEF BOUTS OF FREEZING RAIN ARE POSSIBLE...BUT A COOLING
ELEVATED WARM LAYER /ROUGHLY 825-700 MB/ SHOULD GENERALLY LEAD TO A
DOMINANT PRECIP TYPE OF SLEET ACROSS MUCH OF THIS CORRIDOR BY EARLY
AFTERNOON...WITH SOME SNOW ALSO ACROSS NORTHERN OK AND
SOUTHEAST/SOUTH-CENTRAL MO. THIS SCENARIO IS SUPPORTED BY RECENT
/12Z/ UPPER AIR OBSERVATIONS FROM SPRINGFIELD MO AND NORMAN
OK...WHERE WET-BULB TEMPERATURES WITHIN THE ELEVATED WARM LAYER WERE
OBSERVED TO BE AS MUCH AS 1 DEG C COLDER THAN 06Z NAM/RECENT HRRR
SOUNDINGS /FURTHER SUPPORTIVE OF A TREND TOWARD DOMINANT SLEET AND
SOME SNOW/.

..GUYER.. 03/04/2015

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PAH...MEG...LSX...LZK...SGF...TSA...OUN...

LAT...LON   37779041 37118941 36168979 35769333 34979536 35299665
            36669517 37779041 

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SPC Mar 4, 2015 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook
      
Day 1 Outlook Image
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0639 AM CST WED MAR 04 2015

VALID 041300Z - 051200Z

...NO SVR TSTM AREAS FORECAST...

...SUMMARY...
ISOLATED THUNDERSTORMS MAY OCCUR FROM THE SOUTHERN ROCKIES AND
SOUTHERN PLAINS TO THE TENNESSEE VALLEY AREA.

...SYNOPSIS...
MAIN FEATURE OF MID/UPPER-LEVEL SYNOPTIC-SCALE PATTERN THIS PERIOD
WILL BE TROUGHING FROM ERN CANADA TO NWRN MEX...TRAVERSED BY SEVERAL
SHORTWAVE PERTURBATIONS.  IN NRN STREAM...500-MB VORTICITY FIELD
ACCOMPANYING SHORTWAVE TROUGH NOW OVER DAKOTAS/MN IS EXPECTED TO
BECOME VERY STRETCHED/ELONGATED FROM MAINE TO LOWER MI BY 12Z.  SWRN
PART OF THAT PLUME WILL MERGE WITH INITIALLY SEPARATE PERTURBATION
NOW OVER SK/MT...AND FCST TO MOVE SEWD ACROSS NRN/CENTRAL PLAINS
THROUGH PERIOD.  SHORTWAVE TROUGH NOW OVER NRN GULF OF CA AND
CENTRAL BAJA IS FCST TO WEAKEN CONSIDERABLY AS IT EJECTS NEWD TO
CHIHUAHUA AND FAR W TX BY 00Z...THEN BECOMING ABSORBED INTO
PROGRESSIVE/NW-FLOW VORTICITY FIELD OVER OK NEAR END OF PERIOD.  BY
12Z...PRIMARY TROUGH SHOULD EXTEND FROM LM/WI SWWD ACROSS ERN
KS...TX PANHANDLE AND SONORA.

AT SFC...11Z ANALYSIS SHOWED COLD FRONT FROM NRN NY SWWD ACROSS
NRN/WRN KY...OZARKS...DFW METROPLEX...AND E-CENTRAL NM.  THIS FRONT
WILL PROCEED SWD/SEWD TO 00Z POSITION NEAR
IAD...TRI...JAN...LFK...DRT LINE.  BY 12Z FRONT SHOULD REACH NC
OUTER BANKS...NRN GA...SERN LA...NWRN GULF...AND NERN MEX S OF BRO.

...SRN PLAINS TO TN VALLEY...
BROAD SWATH OF MODEST LOW-LEVEL WAA AND MOISTURE TRANSPORT WILL
PERSIST THROUGH PERIOD...SUPPORTING EPISODIC PRECIP PLUMES AND
ISOLATED/EMBEDDED TSTMS MAINLY ALONG AND BEHIND SFC FRONT.  THIS
REGIME IS EXPECTED TO SHIFT SLOWLY EWD/SEWD BUT BECOME NARROWER
ALONG NW-SE SHORT AXIS AS DEEPER WEDGE OF POSTFRONTAL COLD AIR
PENETRATES BENEATH THIS PLUME.  RESULT SHOULD BE NET LATERAL
SHRINKAGE WITH TIME...ESPECIALLY AFTER 00Z.

WITH SUBSTANTIAL MID/UPPER-LEVEL LARGE-SCALE FORCING REMAINING
BEHIND SFC COLD FRONT...EXPECT WARM-SECTOR LAPSE RATES TO REMAIN
WEAK.  MAIN CONTRIBUTOR TO LOW-LEVEL LIFT FOR CONVECTION WILL BE
FRONTAL ZONE ITSELF...BOTH AT SFC AND FOR ELEVATED LIFTED PARCELS
FARTHER NW.  ISOLATED/SHORT-LIVED WARM-SECTOR TSTMS CANNOT BE RULED
OUT AS WELL OVER PORTIONS LOWER MS VALLEY REGION THIS AFTN INTO
EVENING...GIVEN POCKETS OF DIURNAL HEATING AMIDST WEAK CINH.  IF ANY
SUCH CONVECTION OCCURS...FCST SOUNDINGS SUGGEST AROUND 50 KT
EFFECTIVE SHEAR MAGNITUDES AND CONDITIONAL POTENTIAL FOR A SVR TSTM.
 HOWEVER...
1. RELATIVELY STABLE LAYERS AROUND 700 AND 500 MB WILL SUBSTANTIALLY
REDUCE DEEP BUOYANCY...AND
2. FOCI FOR SUSTAINED PREFRONTAL LIFT OF PARCELS OUT OF BOUNDARY
LAYER APPEAR TOO WEAK/UNCERTAIN TO DRAW UNCONDITIONAL SVR
PROBABILITIES ATTM.

...SRN ROCKIES AND VICINITY...
STEEPENING LAPSE RATES...AND RELATED POCKETS OF 100-300 J/KG MUCAPE
INTO LTG-SUITABLE ICING LAYERS...ARE POSSIBLE TODAY AS EJECTING BAJA
SHORTWAVE TROUGH AND OVERALL COOLING ALOFT WITH SYNOPTIC TROUGH
AFFECT PARTS OF THIS AREA.  LACK OF MORE ROBUST LOW-LEVEL THETAE
SHOULD KEEP TSTMS WEAK...WITH ONLY ISOLATED COVERAGE AND VERY
SPORADIC INSTEAD OF CONTINUAL OCCURRENCE.

..EDWARDS/GLEASON.. 03/04/2015

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