Area Forecast Discussion
Issued by NWS Tulsa, OK

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FXUS64 KTSA 232050
AFDTSA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TULSA OK
250 PM CST TUE DEC 23 2014

.DISCUSSION...

AN AMPLIFIED UPPER FLOW PATTERN IS IN PLACE OVER THE CONUS TODAY.
A DEEP LONGWAVE TROUGH OVER THE CENTRAL CONUS HAS SEVERAL PIECES
OF ENERGY ROTATING THROUGH IT. A VERY NOTICEABLE PV AXIS EXISTS
FROM THE PANHANDLE TO THE GREAT LAKES REGION...ROTATING WITHIN THE
LARGER SCALE TROUGH. THIS TROUGH AXIS WILL ROTATE AROUND AND SLIDE
EAST ACROSS THE PLAINS TONIGHT INTO WEDNESDAY MORNING. THE BULK OF
THE MOISTURE IS LOCATED EAST OF THE LARGER SCALE TROUGH AND IS
EAST OF OUR AREA. THUS...LIFT FROM THE SYSTEM WILL SQUEEZE OUT
WHAT MOISTURE IS AVAILABLE TO PRODUCE LIGHT PRECIP OVER OUR
REGION. IT IS PLENTY COLD ALOFT...ACTUALLY CLEAR DOWN TO 925 OR
950MB FOR SNOW...BUT THERE IS A LACK OF COLD AIR IN THE LOWEST
LEVELS NEAR THE GROUND. TEMPS IN THIS AREA ARE EXPECTED TO REMAIN
ABOVE FREEZING THROUGH THE ENTIRE EVENT. THE MAIN EXCEPTION WILL
BE OVER THE HIGHER TERRAIN OF THE OZARK PLATEAU...WHERE TEMPS WILL
DROP TO NEAR FREEZING. SINCE SURFACE WET BULB AND THE LAYER OF
ABOVE FREEZING TEMPS IS RATHER SHALLOW...WILL CARRY A RAIN SNOW
MIX IN MOST AREAS LATER TONIGHT...CHANGING TO ALL SNOW FOR NW AR
EARLY WEDNESDAY WITH SOME LIGHT ACCUMULATIONS /LESS THAN 1 INCH/
EXPECTED MAINLY OVER IN NW AR. SINCE TEMPS WILL BE AT OR ABOVE
FREEZING THRU THIS EVENT...ROAD CONDITIONS SHOULD STAY JUST WET.

SKIES CLEAR OUT RAPIDLY DURING THE AFTERNOON AS THE UPPER TROUGH
LIFTS OUT. DOWNSLOPE FLOW WILL INCREASE AND WILL INDUCE LEE
TROUGHING OVER THE HIGH PLAINS. STRONG SOUTH WINDS AND SUNNY SKIES
WILL LEAD TO A MILD CHRISTMAS DAY. WIND GUSTS OVER NE OK MAY
APPROACH 40 MPH...SO THIS WILL NEED TO BE MONITORED FOR A POSSIBLE
WIND ADVISORY IN FUTURE FORECASTS.

THE NEXT UPPER TROUGH WILL ORGANIZE TO OUR WEST AND WILL GAIN
POSITIVE TILT WITH TIME...ALLOWING ANOTHER PUSH OF COLD AIR TO
COME SPILLING DOWN THE PLAINS. THERE ARE STILL SIGNIFICANT
DIFFERENCES AMONGST THE TWO MAIN MEDIUM RANGE DETERMINISTIC MODELS
IN HOW THE DETAILS WILL SHAKE OUT. THE ECMWF CARVES THE BASE OF
THE UPPER TROUGH CLEAR DOWN INTO NORTHERN OLD MEXICO...WHILE THE
GFS IS MORE INTO THE FOUR CORNERS. THE LACK OF AMPLIFICATION TO
OUR WEST IN THE GFS IS THE MAIN REASON THIS MODEL IS DRY BEHIND
THE COLD FRONT...WHEREAS THE ECMWF IS CONSIDERABLY WETTER. GIVEN
THE UNCERTAINTY...TOOK A BLEND OF THE CONSENSUS AND THE PREVIOUS
FORECAST...MAINTAINING CHANCE POPS OVER THE REGION ON SATURDAY. A
VERY TIGHT NW TO SE DEEP LAYER THICKNESS GRADIENT ON EITHER SIDE
OF THE 540 LINE SPELLS TROUBLE FROM A PRECIP TYPE PERSPECTIVE. IF
THE ECMWF IS CORRECT WITH THE PRECIP...A COMPLETE SUITE OF PRECIP
TYPES ARE POSSIBLE...RANGING FROM RAIN IN THE SOUTHEAST...TO
ICE...SLEET AND SNOW IN THE FAR NORTHWEST. IF YOU MUST TRAVEL THE
WEEKEND AFTER CHRISTMAS...STAY TUNED TO THE LATEST FORECAST
UPDATES IN THE COMING DAYS. HOPEFULLY THE DETAILS WILL GET IRONED
OUT BY THEN.

TODAYS SUITE OF MODEL GUIDANCE HAS BASICALLY CANCELED WINTER
WEATHER CHANCES EARLY NEXT WEEK...AS BOTH THE GFS AND ECMWF ARE
NOW STICKING WITH A DRY NW FLOW PATTERN ON THE WEST SIDE OF BROAD
CYCLONIC FLOW OVER THE CONUS. STILL LOOKS COLD THOUGH EARLY NEXT
WEEK...WITH A DECENT TAP OF COLD AIR SET UP...AS EVIDENCED BY
NORTHERLY UPPER FLOW OVER WESTERN NORTH AMERICA EMANATING FROM
NEAR THE NORTH POLE.

LACY

&&

.PRELIMINARY POINT TEMPS/POPS...
TUL   34  43  30  56 /  30  20   0   0
FSM   36  44  30  54 /  20  20   0   0
MLC   35  44  31  56 /  20  10   0   0
BVO   33  42  26  56 /  40  20   0   0
FYV   33  38  27  50 /  20  40   0   0
BYV   33  38  28  50 /  30  50   0   0
MKO   35  43  29  56 /  30  20   0   0
MIO   34  40  28  54 /  30  50   0   0
F10   34  43  30  56 /  30  10   0   0
HHW   35  46  30  56 /  20  10   0   0

&&

.TSA WATCHES/WARNINGS/ADVISORIES...
OK...NONE.
AR...NONE.
&&

$$

LONG TERM....30





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