SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
347 PM EST TUE FEB 14 2012
 
VALID 00Z WED FEB 15 2012 - 00Z FRI FEB 17 2012
 
...A THREAT FOR SEVERE WEATHER WILL EXIST ON WEDNESDAY ACROSS
AREAS OF THE ARKLATEX AND LOWER MISSISSIPPI VALLEY...

...A PAIR OF UPPER LOWS ARE FORECAST TO IMPACT THE SOUTHWESTERN
U.S. DURING THE NEXT COUPLE OF DAYS...


THE UPPER PATTERN WILL CONTINUE TO BE COMPLEX AS A SPLIT IN THE
JET STREAM WILL BE PRESENT THROUGHOUT THE PERIOD. IN THIS
SETUP...A LARGE UPPER RIDGE HAS HELD IN PLACE ACROSS THE EASTERN
PACIFIC AS DISTURBANCES TRACK ABOVE THIS RIDGE TOWARD THE WESTERN
FRINGE OF NORTH AMERICA. AT THIS POINT...THE SPLIT BECOMES
APPARENT AS THE SOUTHERN BRANCH OF THE JET CONSISTS OF CLOSED LOWS
WHICH MIGRATE FROM THE PACIFIC NORTHWEST DOWN INTO THE DESERT
SOUTHWEST BEFORE PEELING OFF TOWARD THE EAST. MEANWHILE...MUCH OF
THE NORTHERN STREAM ENERGY PROJECTS INTO WESTERN CANADA BEFORE IT
EVENTUALLY DIVES INTO THE NORTHERN PLAINS/UPPER MIDWEST.

THE FIRST OF THESE CLOSED UPPER LOWS PUSHING THROUGH THE DESERT
SOUTHWEST IS FORECAST TO BECOME MORE OF AN OPEN WAVE AS IT TRACKS
EASTWARD TOWARD THE FOUR CORNERS REGION. BEFORE THIS OCCURS...MUCH
OF THE PRECIPITATION ACROSS THE SOUTHWESTERN STATES WILL BE DRIVEN
BY THE UPPER LOW ITSELF. MOISTURE IS EXPECTED TO BE LIMITED BEFORE
THE SYSTEM ENTERS THE GREAT PLAINS EARLY WEDNESDAY. THUS...ON
TUESDAY...PRECIPITATION WILL PRIMARILY CONCENTRATE UNDERNEATH THE
UPPER CYCLONE AND OVER UPSLOPE REGIONS OF THE MOUNTAINOUS TERRAIN.
BY THE NEXT DAY...AN EXPANSIVE REGION OF PRECIPITATION IS FORECAST
TO BREAKOUT AS THE DISTURBANCE ENCOUNTERS THE INCREASINGLY MOIST
AIR MASS OVER THE SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY. GIVEN
THE MILD NATURE OF THIS AIR...SNOW WILL NOT BE COMMONPLACE UNTIL
THE SYSTEM STARTS GAINING LATITUDE ON THURSDAY MORNING. UNTIL THIS
OCCURS...SHOWERS AND THUNDERSTORMS WILL BE COMMONPLACE OVER THE
ARKLATEX WITH SEVERE WEATHER ALSO BEING A POSSIBILITY WITH SOME OF
THE STRONGER CONVECTIVE CELLS. THEREAFTER...A BUILDING UPPER RIDGE
OVER THE EASTERN GULF OF MEXICO WILL FORCE THE SYSTEM TOWARD
HIGHER LATITUDES OF THE U.S. THIS WILL EVENTUALLY BRING SNOW INTO
THE FORECAST ALONG THE U.S./CANADIAN BORDER WITH THE BEST
ACCUMULATIONS EXPECTED ACROSS UPPER PORTIONS OF MICHIGAN.

FOLLOWING A SIMILAR TRACK TO THE PRECEDING CLOSED LOW...AN UPPER
DISTURBANCE IS FORECAST TO MOVE FROM COASTAL WASHINGTON DOWN INTO
NORTHERN BAJA CALIFORNIA DURING THE NEXT 48 HOURS. GIVEN ITS
INLAND TRAJECTORY...THE LOW-LEVEL WIND FIELD WILL PRIMARILY BE OUT
OF THE NORTH THEREBY KEEPING A BULK OF THE PACIFIC MOISTURE
OFFSHORE. JUST LIKE THE EARLIER UPPER LOW...THIS TOO WILL NOT BE A
BIG-TIME PRECIPITATION PRODUCER WITH THE ENERGY ALOFT BEING THE
PRIMARILY FORCING MECHANISM. THIS WILL KEEP SNOWFALL ACCUMULATIONS
ON THE LIGHT SIDE WITH ONLY A WIDESPREAD 2 TO 4 INCHES BEING
FORECAST BY THE HPC WINTER WEATHER DESK OVER THE SIERRA NEVADA AND
THE NORTHERN HALF OF NEVADA.       


RUBIN-OSTER


GRAPHICS AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV