#1849 Postby somethingfunny » Fri Dec 28, 2012 4:41 pm
A widespread deluge of cold rain for New Years to help out with the drought, but snow seems unlikely. Then it gets more interesting.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
303 PM CST FRI DEC 28 2012
.DISCUSSION...
THE UPPER LEVEL SHORTWAVE TROUGH THAT WAS RESPONSIBLE FOR THE FOG
AND DRIZZLE HAS MOVED EAST OF THE AREA. IN ITS WAKE...SURFACE
PRESSURES ARE RISING AND NORTHWESTERLY WINDS ARE INCREASING WHICH
IS HELPING TO ADVECT COOLER AND MUCH DRIER AIR INTO THE REGION.
SKIES SHOULD CLEAR BY EARLY EVENING FOR MOST AREAS...BUT WINDS
SHOULD REMAIN ABOVE 5-10 MPH TONIGHT WHICH WILL LIMIT OPTIMAL
RADIATIVE HEAT LOSS. MODELS HAVE INITIALIZED TOO MUCH SNOW COVER
REMAINING ACROSS THE NORTHERN ZONES...WHEN IN FACT MUCH OF THIS
HAS ALREADY MELTED. THE RESULT IS THAT TEMPERATURES /BOTH PERFECT
PROG AND MOS GUIDANCE/ LOOK TOO COOL IN THIS AREA. WILL FORECAST
TEMPS A FEW DEGREES WARMER THAN GUIDANCE...BUT STILL A VERY COLD
NIGHT IS EXPECTED WITH LOWS IN THE 20S AREA WIDE. LOTS OF SUNSHINE
IS EXPECTED SATURDAY AND WINDS WILL LAY DOWN DURING THE DAY...BUT
HIGH TEMPS WILL REMAIN CHILLY AND IN THE 40S. GOOD RADIATIONAL
COOLING IS EXPECTED SATURDAY NIGHT WITH THE TYPICAL COLDER
LOCATIONS BOTTOMING OUT IN THE UPPER TEENS.
THE WEATHER WILL BE IN TRANSITION DURING THE DAY SUNDAY AS A
STRONG UPPER LEVEL TROUGH DIGS INTO THE DESERT SOUTHWEST AND
BEGINS TO IMPACT OUR REGION. MID-HIGH LEVEL PACIFIC MOISTURE WILL
INCREASE DURING THE DAY AND SKIES SHOULD BE CLOUDY BY SUNSET.
SATURATION WILL OCCUR FROM TOP-DOWN...AND RAIN WILL BEGIN TO
BREAK OUT SUNDAY NIGHT. WITH THE DRY/COOL AIR INITIALLY BELOW THE
PRECIPITATING LAYER...WOULD NOT BE SURPRISED TO SEE SOME SLEET
MIXED WITH THE RAIN INITIALLY. HOWEVER SURFACE TEMPS WOULD BE
SAFELY ABOVE FREEZING WHEN THIS OCCURS. AS THE UPPER LEVEL IMPULSE
MOVES ACROSS THE AREA MONDAY...ISENTROPIC LIFT WILL BE VERY STRONG
AND TAP INTO SOME UNSEASONABLY HIGH AMOUNTS OF GULF MOISTURE.
EXPECT WIDESPREAD RAIN ACROSS THE REGION MONDAY...BUT IT SHOULD
END FROM WEST TO EAST MONDAY EVENING...PERHAPS SALVAGING NEW YEARS
EVE ACTIVITIES. IN THE WAKE OF THIS IMPULSE...WINDS WILL TURN TO
THE NORTH AND REINFORCE THE CHILLY WEATHER TUESDAY AND WEDNESDAY
WITH HIGHS IN THE 40S AND LOWS NEAR FREEZING.
FORECAST REMAINS A BIT UNCERTAIN WEDNESDAY AND THURSDAY AS ALL
MODEL GUIDANCE CONTINUES TO ADVERTISE ANOTHER PIECE OF UPPER LEVEL
ENERGY AT THE BASE OF THE TROUGH IN THE DESERT SOUTHWEST MOVING
IN FROM THE WEST WEDNESDAY NIGHT. THE AIRMASS WILL BE COLD ENOUGH
FOR SOME WINTRY PRECIP AND THE LIFT WILL CERTAINLY BE STRONG
ENOUGH. THE MISSING PIECE OF THE EQUATION IS MOISTURE BELOW 700MB.
IN FACT THERE IS UNANIMOUS AGREEMENT ON SNOW OCCURRING ALOFT OVER
THE AREA...BUT MOST GUIDANCE SHOWS TOO MUCH DRY AIR AT THE SURFACE
FOR THE SNOW TO WORK THROUGH TO REACH THE GROUND. THE ISSUE THAT
IS INHIBITING SNOW IS A VERY STRONG NORTHERN STREAM SHORTWAVE
TROUGH WHICH DROPS SOUTH FROM CANADA INTO THE PLAINS TUESDAY NIGHT
AND WEDNESDAY. THIS PIECE OF ENERGY SERVES TO KEEP/INTENSIFY THE
COLD/DRY AIRMASS IN THE LOW LEVELS WITH STRONGER NORTHERLY WINDS.
TO GET PRECIP WE WILL NEED TO SEE 850MB WINDS OPTIMALLY OUT OF A
SOUTHERLY DIRECTION...OR AT THE LEAST BECOME LIGHT ENOUGH TO LIMIT
THE DRY ADVECTION. A WEAKER NORTHERN STREAM SHORTWAVE TROUGH WOULD
ALLOW THE UPPER SYSTEM TO THE WEST TO TURN 850MB WINDS TO A MORE
FAVORABLE DIRECTION AND WOULD RESULT IN A WINTER EVENT FOR AT
LEAST PART OF OUR AREA. THE PIECE OF ENERGY IN QUESTION IS STILL
ROTATING AROUND AN UPPER LOW IN THE BEARING SEA...BUT SHOULD BE
SAMPLED BY ALASKAN/CANADIAN RAOBS IN 2-3 DAYS. FOR NOW ONLY THE
CANADIAN MODEL SHOWS THIS NORTHERN TROUGH BEING WEAK AND THEREFORE
HAS A SIGNIFICANT WINTER SYSTEM WEDNESDAY AND WEDNESDAY NIGHT.
THE ECMWF OFFERS A GOOD COMPROMISE...HAVING LIGHT QPF OVER THE
SOUTHERN ZONES WHERE THE LOW LEVEL AIRMASS WONT BE QUITE AS
DEEP/DRY. WILL INCLUDE A 20 POP FOR LIGHT RAIN ACROSS THE SOUTHERN
ZONES WEDNESDAY NIGHT...AND AWAIT A LITTLE MORE MODEL AGREEMENT
BEFORE RAISING CONCERNS FOR A WINTER EVENT IN THE OFFICIAL FCST.
We'll see how the Canadian performs with that northern stream over the next few days.

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I am not a meteorologist, and any posts made by me are not official forecasts or to be interpreted as being intelligent. These posts are just my opinions and are probably silly opinions.