Forecasters struggle again with Tues/Weds storm
Here we go again. The weather story all winter, it seems, has been one of forecasters and their computer models struggling to get a grip on a repeated pattern of complex storm systems.
This weekend seems to be no exception. Once again, the supercomputers are wrestling with a combination of a clipper-like storm moving out of the Northwest, expected to cross the country's mid-section, converge on a southern low that will cross the South and emerge off the mid-Atlantic coast early next week.
Where will these disturbances go, exactly? When will they get there? Will the systems merge in just the right spot to dump snow? Will one pass to our north or west and bring rain and sleet? Or, will they both veer away and leave us in the bubble again?
AccuWeather.com is already sounding pretty aggressive on this one, although they don't seem to have figured out the storm tracks, either. The NOAA Climate Prediction Center has us in the "Heavy Snow" zone on their forecast map. But the "Heavy Rain" zone is nearby. Foot's Forecast lays out two scenarios. Here's the official forecast from Sterling.
Today's NWS forecast discussion from Sterling contains an unusual admission of the difficulties the folks at Sterling have been having this winter. I present it below, edited only to expand abbreviations:
"MOST OF THE LONG TERM FORECAST WAS SPENT LOOKING AT THE POTENTIAL
COASTAL STORM TUES INTO WED. THIS WINTER HAS FEATURED MANY COMPLEX
STORM SYSTEMS IN THE MEDIUM RANGE THAT HAD A POTENTIAL TO IMPACT
THE AREA. OPERATIONAL MODEL GUIDANCE HAS HANDLED THESE PHASING
SYSTEMS POORLY SO FAR THIS WINTER...RESULTING IN LOWER THAN NORMAL
MODEL SKILL AND FORECAST CONFIDENCE MORE THAN A COUPLE DAYS OUT.
"THE UPCOMING TUE-WED SYSTEM WILL BE NO EXCEPTION. WHILE CONFIDENCE
IS HIGH THAT A COASTAL LOW WILL DEVELOP NEAR THE SOUTHEASTERN
COAST...THE EXACT TRACK OF THE LOW IS HIGHLY UNCERTAIN. THE TRACK
OF THE LOW /WHICH DEPENDS ON THE TIMING AND OCCURRENCE OF PHASING
BETWEEN SOUTHERN AND NORTHERN STREAM DISTURBANCES/ AND THE EASTWARD PROGRESSION OF THE SURFACE HIGH MOVING NORTHEAST OF NEW ENGLAND WILL BE CRITICAL
IN DETERMINING THE PRECIP AMOUNTS AND THE PRECIP TYPE.
"IT IS TOO EARLY AT THE MOMENT TO NAIL DOWN THE SPECIFICS AS THE PRIMARY NORTHERN STREAM ENERGY ASSOCIATED WITH THE UPCOMING STORM IS STILL NEAR THE GULF OF
ALASKA. THE MODELS HOPEFULLY WILL CAPTURE THIS ENERGY BETTER ONCE
IT MOVES INTO WESTERN CANADA TONIGHT INTO SUNDAY.
"AS STATED ABOVE...THE WIDE RANGE OF MODEL SOLUTIONS PROVIDES A WIDE
RANGE OF POSSIBLE IMPACTS FROM THIS SYSTEM. THE WESTERN-TRACK SOLUTIONS
SUCH AS THE 12Z NAM [MODEL] /TOWARD THE END OF ITS RUN/ AND GEM [MODEL] HAVE A
TRACK OF THE LOW CLOSER TO THE APPALACHIAN SPINE THAT WOULD RESULT
IN A MOSTLY RAIN EVENT.
"THE EASTERN-MOST SOLUTION THAT THE 12Z GFS [MODEL RUN] PORTRAYS HAS A TRACK WELL OFF THE COAST...SAVING THE AREA FROM A DIRECT IMPACT. THE MEAN OF THE 12Z GFS ENSEMBLE MEMBERS AND 12Z ECMWF SHOWS A SOLUTION SLIGHTLY WEST OF THE 12Z OPERATIONAL GFS RUN...WHICH WOULD LEAD TO THE BIGGEST IMPACT WITH MORE SNOW THAN
RAIN. COMPARED TO YESTERDAY...
"THERE IS A EASTWARD TREND IN THE TRACK OF THE LOW. GIVEN LATEST TRENDS AND SPREAD IN GUIDANCE...DO NOT FEEL THAT INCREASING [PRECIPITATION PROBABILITIES] IS WARRANTED. HAVE ALSO TRIED TO DETERMINE MOST LIKELY TIME PERIOD FOR PRECIP WITH THIS SYSTEM...WHICH NOW APPEARS TO BE LATE TUES INTO WED.
"WHAT HAPPENS AFTER THIS STORM PULLS AWAY FROM THE AREA WILL DEPEND
ON PRIOR EVENTS WITH THE MIDWEEK SYSTEM. IT DOES APPEAR THAT THE PACIFIC
NORTHWEST JET STREAM REMAINS ACTIVE EVEN INTO THE END OF NEXT WEEK...WITH
RIDGING OVER THE WEST COAST AND TROUGHING OVER THE EASTERN CONTINENTAL US HOLDING
FIRM. THIS PATTERN WILL FAVOR NEAR- TO BELOW-NORMAL TEMPERATURES
CONTINUING INTO THE WEEKEND."