Climate Prediction Center

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 SUMMARY

FOR 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

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