US HAZARDS ASSESSMENT
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300
PM EST JANUARY 16 2009
SYNOPSIS: THE FLOW PATTERN RESPONSIBLE FOR
TRANSPORTING ARCTIC AIR TO THE EASTERN PORTION OF THE NATION IS FORECAST TO
RELAX NEXT THURSDAY, ALLOWING MILDER AIR TO COVER THE EAST. ABNORMAL COLD WILL
PERSIST UNTIL THAT TIME, AND A COUPLE OF LOW PRESSURE AREAS WILL SPREAD SNOW
ACROSS THE MIDWEST AND NORTHEAST. STRONG UPPER-LEVEL HIGH PRESSURE OVER THE
WEST WILL CONTINUE TO MAINTAIN ABNORMALLY MILD AIR OVER THE WEST AND HIGH
PLAINS UNTIL THE RIDGE BEGINS TO BREAK DOWN AROUND THURSDAY, WHEN ANOTHER COLD
HIGH PRESSURE SYSTEM IS FORECAST TO DROP SOUTHWARD FROM CANADA AND INVADE THE
PLAINS STATES. THE HIGH AND ASSOCIATED COLD AIR WILL PROGRESS EASTWARD,
RETURNING BELOW-NORMAL TEMPERATURES TO THE MIDWEST AND EAST FOLLOWING THE BRIEF
RESPITE FROM THE ARCTIC CHILL.
HAZARDS - MUCH BELOW-NORMAL
TEMPERATURES OVER THE EASTERN THIRD OF THE NATION JANUARY 19-21.
- IMPROVING DROUGHT CONDITIONS IN THE SOUTHERN APPALACHIANS, BUT CONTINUING
DROUGHT IN NORTHERN WISCONSIN, THE SOUTHERN PLAINS, AND PARTS OF THE WEST.
- MUCH BELOW-NORMAL TEMPERATURES OVER THE MIDWEST AND NORTHEAST JANUARY
22-25.
DETAILED SUMMARYFOR MONDAY
JANUARY 19 - WEDNESDAY JANUARY 21: THE HIGHLY AMPLIFIED UPPER-AIR
CIRCULATION PATTERN CONTINUES OVER NORTH AMERICA, WITH A SHARP RIDGE IN THE
WEST AND A DEEP TROUGH DOMINATING THE EAST. THE ALBERTA CLIPPER THAT IS
FORECAST TO REACH THE EAST COAST BY MONDAY IS LIKELY TO INTENSIFY. MODELS
DIFFER ON THE TIMING AND LOCATION OF DEVELOPMENT, WITH THE LATEST GFS (12Z,
FRIDAY) SHOWING A NOR'EASTER TRACKING NORTHWARD FROM SOUTHEAST VIRGINIA TOWARD
MAINE DURING MONDAY. THE LATEST EUROPEAN MODEL(12Z) DEVELOPS A LOW LATE TUESDAY
WELL OFF THE VIRGINIA COAST AND TAKES THE STORM NORTHWARD. THE GFS SOLUTION
WOULD BRING SEVERAL INCHES OR MORE OF SNOW TO THE I-95 CORRIDOR, WHILE THE
EUROPEAN MODEL WOULD RESULT IN MOST OF THE SNOW FALLING ON COASTAL AREAS, WITH
LITTLE ACCUMULATION ON THE POPULATION CENTERS. AT THIS TIME, THE CONSENSUS OF
THE MODELS SUGGESTS THE GFS MAY BE OVERSTATING THE THREAT OF HEAVY SNOW, AND A
SIGNIFICANT SNOW EVENT IS NOT INDICATED.
TEMPERATURES WILL REMAIN WELL BELOW NORMAL OVER THE EAST INTO WEDNESDAY
REGARDLESS OF THE EVOLUTION OF THE COASTAL LOW. THE COLDEST AIR WILL LIFT OUT
TOWARD THE NORTHEAST ON WEDNESDAY AS THE UPPER-LEVEL TROUGH SHIFTS TOWARD
SOUTHEAST CANADA.
HIGH PRESSURE MAINTAINS A TRANQUIL WEATHER PATTERN OVER THE WEST, WHILE
ABOVE-NORMAL TEMPERATURES DOMINATE THE WEST AND HIGH PLAINS. THE PRESSURE
GRADIENT BETWEEN THE GREAT BASIN AND THE CALIFORNIA COAST WILL CONTINUE TO
DIMINISH, LESSENING THE ODDS FOR DAMAGING WINDS.
IN ALASKA, THE STRONG SOUTHERLY FLOW OF MOIST AIR RESPONSIBLE FOR HEAVY
PRECIPITATION AND HIGH WINDS WILL WEAKEN BY MONDAY, AND HAZARDS ARE NO LONGER
DEPICTED. NEVERTHELESS, LOW PRESSURE WEST OF ALASKA WILL BRING POWERFUL
SOUTHERLY WINDS TO THE ALEUTIANS ON MONDAY-WEDNESDAY. MODEL FORECASTS STILL
INDICATE A PERIOD OF COLDER WEATHER FOR ALASKA OVER THE INTERIOR, BUT THE
INTENSITY AND EXTENT OF THE COLD NO LONGER WARRANT DEPICTION ON THE MAP.
NO RELIEF IS ON TAP FOR THE INTENSIFYING DROUGHT ACROSS THE SOUTHERN
PLAINS.
FOR THURSDAY JANUARY 22 - MONDAY
JANUARY 26: THE INTENSE UPPER-LEVEL TROUGH OVER THE EASTERN SEABOARD WILL
FINALLY LIFT OUT BY THURSDAY. AS UPPER-LEVEL RIDGING PUSHES EASTWARD, MILDER
AIR SHOULD DOMINATE THE EASTERN HALF OF THE NATION BY THURSDAY. THE RESPITE
FROM THE COLD MAY BE SHORT-LIVED, AS MODELS FORECAST AN UPPER-LEVEL TROUGH
PUSHING SOUTHWARD TOWARD THE CENTRAL STATES ON THURSDAY. THIS WILL TRANSPORT A
FRESH BATCH OF COLD AIR FROM WESTERN CANADA INTO THE PLAINS. THE ASSOCIATED
COLD HIGH PRESSURE AREA WILL EDGE SOUTHWARD AND EASTWARD DURING THE FOLLOWING
DAYS.
MODEL DIFFERENCES MAKE THE EVOLUTION OF THE NEXT COLD OUTBREAK LESS
CONFIDENT THAN YESTERDAY, THE EUROPEAN MODEL BRINGING THE ARCTIC HIGH INTO THE
CENTRAL STATES FASTER THAN THE GFS. THE LATTER MODEL TRACKS A LARGE LOW
PRESSURE SYSTEM NORTHEASTWARD ACROSS THE OHIO VALLEY ON FRIDAY-SATURDAY AHEAD
OF THE COLD AIR.
THE CONSENSUS OF THE MODELS RESULTS IN A DISPLACEMENT EASTWARD OF THE COLD
WEATHER HAZARD, NOW EXPECTED TO SPAN THE AREA FROM EASTERN NORTH DAKOTA TO THE
NORTHEAST STATES DURING JANUARY 22-25. BLIZZARD CONDITIONS REMAIN A POSSIBLITY
AHEAD OF THE ARCTIC AIR MASS AROUND THURSDAY-FRIDAY OVER THE NORTH-CENTRAL
STATES.
THE COLD FRONT AHEAD OF THE CANADIAN HIGH SHOULD BRING MORE RAIN FOR THE
LINGERING DROUGHT AREA IN THE APPALACHIANS. LOW PRESSURE OVER THE SOUTHWEST
MOVING EASTWARD IS FORECAST TO BRING SOME RAIN TO TEXAS, BUT MOST OF THE
MOISTURE SHOULD MISS THE MAIN DROUGHT AREA. THE CALIFORNIA DROUGHT AREA IS
LIKELY TO SEE SOME PRECIPITATION AS THE WEAKENING WESTERN RIDGE ALLOWS PACIFIC
MOISTURE TO MAKE ITS WAY EASTWARD.
FOR TUESDAY JANUARY 27 - FRIDAY
JANUARY 30: MODELS SUGGEST CONTINUED COLD AIR OVER THE NORTHERN STATES THIS
PERIOD, MAINLY OVER THE NORTHEAST. THERE ARE SOME INDICATIONS THAT ABNORMALLY
COLD AIR WILL RETURN TO ALASKA DURING THIS PERIOD, BUT THE SEVERITY OF THE COLD
IS UNCERTAIN AT THIS TIME.
FORECASTER: DOUG LECOMTE
$$