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Mesoscale Discussion 23
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   MESOSCALE DISCUSSION 0023
   NWS STORM PREDICTION CENTER NORMAN OK
   1016 AM CST SUN JAN 04 2015

   AREAS AFFECTED...NORTHERN MAINE

   CONCERNING...WINTER MIXED PRECIPITATION 

   VALID 041616Z - 042215Z

   SUMMARY...WINTER MIXED PRECIPITATION WILL INCREASE IN COVERAGE AND
   INTENSITY EARLY THIS AFTERNOON...ESPECIALLY AFTER 18Z. THIS ACTIVITY
   WILL CONTINUE INTO THE LATE AFTERNOON...BEFORE DIMINISHING THIS
   EVENING.

   DISCUSSION...RECENT WATER VAPOR LOOPS INDICATE A LOW-AMPLITUDE...
   MIDLEVEL SHORTWAVE IMPULSE TRACKING NEWD ACROSS PORTIONS OF SRN
   ONTARIO. RELATED 999-MB SFC LOW PRESSURE IS ANALYZED INVOF LAKE
   ONTARIO...AND IS FORECAST TO DEVELOP NNEWD ACROSS PORTIONS OF SRN
   ONTARIO AND INTO SRN QUEBEC DURING THE NEXT SEVERAL HOURS...IN
   CONCERT WITH THE TRACK OF THE AFOREMENTIONED IMPULSE. AS THE SFC LOW
   DEEPENS...STRENGTHENING LOW-LEVEL SWLYS TO ITS E WILL RESULT IN
   INCREASING ISENTROPIC ASCENT ACROSS PORTIONS OF NRN NEW ENGLAND. THE
   LOW-LEVEL FLOW RESPONSE IS ALREADY REFLECTED IN CXX VWP DATA THAT
   INDICATE AROUND 15-20-KT INCREASE IN 1-2-KM-AGL FLOW DURING THE PAST
   FEW HOURS TO 50-60 KT. AS SUCH...UPSTREAM PRECIPITATION ACROSS SRN
   QUEBEC WILL LIKELY BE MAINTAINED AS IT CROSSES NRN MAINE THIS
   AFTERNOON...WHILE ADDITIONAL PRECIPITATION FORMS ACROSS THE
   DISCUSSION AREA.

   WITH SFC TEMPERATURES FROM THE MIDDLE TEENS TO THE MIDDLE 20S...A
   MIX OF PRECIPITATION TYPES IS EXPECTED ACROSS THE REGION. EXTREME
   NRN MAINE WILL LIKELY EXPERIENCE SNOW AT THE ONSET OF PRECIP WHERE
   THE VERTICAL TEMPERATURE PROFILE WILL INITIALLY BE ENTIRELY
   SUBFREEZING. SLEET...AND THEN FREEZING RAIN...WILL BE INCREASINGLY
   PREDOMINANT WITH SWD DISPLACEMENT ACROSS THE DISCUSSION AREA...WHERE
   RAP/NAM SOUNDINGS INDICATE SUFFICIENTLY WARM TEMPERATURES IN THE
   850-800-MB LAYER FOR PARTIAL/COMPLETE MELTING OF DESCENDING
   HYDROMETEORS. WITH TIME...WARMING ALOFT ASSOCIATED WITH ELEVATED WAA
   IS EXPECTED TO RESULT IN THE AREA OF FREEZING RAIN EXPANDING NWD
   THROUGH THE AFTERNOON. FREEZING RAIN RATES OF 0.02-0.04 INCH PER
   HOUR WILL BE POSSIBLE...ALONG WITH LOCAL SLEET ACCUMULATION RATES OF
   0.05-0.10 INCH PER HOUR AND SNOWFALL RATES TO 1 INCH PER HOUR.

   WINTER MIXED PRECIPITATION WILL LIKELY CONTINUE THROUGH THIS
   AFTERNOON. BY EARLY EVENING...THE LEADING EDGE OF A MID-LEVEL DRY
   SLOT CURRENTLY CROSSING ERN LOWER MI PER WATER VAPOR LOOPS WILL
   LIKELY EXTEND INTO NRN NEW ENGLAND. THIS WILL RESULT IN A GRADUAL
   LESSENING OF PRECIPITATION COVERAGE AND INTENSITY AFTER 00Z.

   ..COHEN.. 01/04/2015


   ATTN...WFO...CAR...GYX...

   LAT...LON   47456931 47266802 46716769 45786789 45676892 46077000
               46637014 47456931 

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Page last modified: January 04, 2015
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