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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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