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Mesoscale Discussion 5
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   MESOSCALE DISCUSSION 0005
   NWS STORM PREDICTION CENTER NORMAN OK
   1107 AM CST SUN JAN 05 2014

   AREAS AFFECTED...ERN PA...NRN MD...FAR NWRN NJ

   CONCERNING...FREEZING RAIN 

   VALID 051707Z - 052300Z

   SUMMARY...PRECIPITATION IS EXPECTED TO INCREASE OVER THE NEXT
   SEVERAL HOURS ACROSS ERN PA...NRN MD...AND FAR NWRN NJ. THERMAL
   PROFILES WILL BE FAVORABLE FOR FREEZING RAIN. FZRA RATES EXCEEDING
   0.05 INCH/HR APPEAR POSSIBLE...PARTICULARLY AFTER 20Z WHEN THE
   POTENTIAL FOR CONVECTIVE ELEMENTS INCREASES.

   DISCUSSION...SURFACE OBSERVATIONS REVEAL A WEDGE OF COLD AIR /WITH
   TEMPERATURES GENERALLY IN THE MID 20S AT 17Z/ FROM ERN PA NEWD INTO
   UPSTATE NY. AS IS TYPICAL...THE WEDGE OF COLD AIR HAS BEEN WARMING
   MUCH SLOWER THAN MODEL GUIDANCE INDICATES...WITH GUIDANCE ALREADY 5
   TO 7 DEG F ABOVE OBSERVATIONS. 

   REGIONAL RADAR OBSERVATIONS SHOW A BAND OF LIGHT PRECIPITATION FROM
   NWRN MD ENEWD TOWARDS LONG ISLAND. TEMPERATURES ARE COLD ENOUGH
   ALONG PORTIONS OF THIS LINE /PARTICULARLY FAR SERN PA...NRN NJ...AND
   NEW YORK CITY METRO/ FOR VERY LIGHT FREEZING RAIN. THIS
   PRECIPITATION BAND IS EXPECTED TO CONTINUE NWWD AND EXPAND DURING
   THE NEXT SEVERAL HOURS AS A LLJ STRENGTHENS AND ASSOCIATED WAA
   INCREASES. THIS INCREASED LIFT/WAA WILL ADVECT A HIGHER THETA-E
   AIRMASS FROM THE MID-ATLANTIC /850 MB DEWPOINTS ABOVE 4 DEG C THIS
   MORNING/ ATOP THE COLD AIR ALREADY IN PLACE.

   GIVEN THE ANTICIPATED PERSISTENCE OF THE COLD AIR...FREEZING RAIN
   WILL LIKELY DEVELOP WITHIN THE NEXT HOUR OR TWO ACROSS SERN PA /AND
   ADJACENT AREAS/ AND SPREAD NWWD. MODEL GUIDANCE INDICATES
   TEMPERATURES ALOFT MAYBE COLD ENOUGH ATOP THE HIGHER THETA-E AIR TO
   SUPPORT EMBEDDED CONVECTIVE ELEMENTS...PARTICULARLY AFTER 20Z.
   LOCALIZED FREEZING RAIN RATES OVER 0.05 INCH/HR ARE POSSIBLE.

   ..MOSIER.. 01/05/2014


   ATTN...WFO...PHI...BGM...CTP...LWX...

   LAT...LON   39627882 40017880 40947802 41447704 41617616 41467515
               41267477 41057477 40637498 40197520 39777559 39497654
               39377800 39417853 39627882 

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Page last modified: March 20, 2014
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