Preliminary Forecasts
Issued by NWS

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FXUS02 KWNH 290522
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1222 AM EST THU JAN 29 2015

VALID 12Z SUN FEB 01 2015 - 12Z THU FEB 05 2015

...PATTERN OVERVIEW...

IT REMAINS THE CASE THAT GUIDANCE IS STILL PRETTY CONSISTENT WITH
THE IDEA OF MAINTAINING A MEAN RIDGE NEAR THE WEST COAST...WITH
ONLY BRIEF FLATTENING AROUND EARLY NEXT WEEK AS SOME PACIFIC
ENERGY FILTERS THROUGH AND HEADS INTO A BROADENING CONUS MEAN
TROUGH. THE CONUS MEAN TROUGH SEEN IN MOST SOLNS BY THE MIDDLE OF
NEXT WEEK HAS BETTER THAN AVG CONFIDENCE IN LIGHT OF UPSTREAM FLOW
AMPLITUDE. IN ADVANCE OF THIS EVOLUTION HOWEVER...MODEL/ENSEMBLE
SPREAD SUGGESTS CONTINUED LESS THAN AVG CONFIDENCE WITH THE
PARTICULARS OF SYSTEMS AFFECTING AREAS FROM THE FOUR
CORNERS/PLAINS NEWD INTO THE EAST THIS WEEKEND INTO MON AND
SUBSEQUENT SECONDARY COLD AIR SURGES DIGGING INTO THE N-CENTRAL US
FROM CANADA.

...GUIDANCE/UNCERTAINTY EVALUATION AND PREFERENCES...

AS INDICATED YESTERDAY...THERE CONTINUE TO BE VARIOUS SOURCES OF
UNCERTAINTY FOR THE SYSTEM EXPECTED TO AFFECT THE CNTRL-ERN STATES
FROM THE WEEKEND INTO THE START OF NEXT WEEK.  SUPPORTING ENERGY
AMPLIFYING INTO THE PLAINS DURING THE WEEKEND ORIGINATES FROM A
COMBINATION OF FLAT FLOW HEADING INTO BC AND SHEARED ENERGY OVER
ALASKA IN THE SHORT RANGE. THESE IMPULSES DO NOT REACH WRN CANADA
UNTIL LATE FRI SO IT MAY TAKE UNTIL AT LEAST THEN TO GET A
REASONABLE ANALYSIS OF THIS ENERGY. BEYOND THIS ISSUE IS THE
QUESTION OF NRN STREAM TROUGH AMPLITUDE OVER THE CONUS AND HOW
MUCH INTERACTION THERE IS WITH THE TROUGH OVER THE SWRN CONUS/NRN
MEXICO AND EJECTING SRN STREAM IMPLUSES.

SIGNIFICANT MODEL RUN TO RUN WAFFLING OVER THE PAST COUPLE OF DAYS
LENDS WPC PREFERENCE OF A COMPOSITE GUIDANCE SOLUTION LEANING
HEAVILY ON THE COMPARATIVELY CONSISTENT AND COMPATABLE 18 UTC GEFS
MEAN AND 12 UTC ECMWF ENSEMBLE MEAN.

...SENSIBLE WEATHER HIGHLIGHTS...

AN EXPANDING PCPN SHIELD WILL SPREAD NEWD FROM THE SRN PLAINS NEWD
THROUGH THE ERN US...MAINLY WITH THIS ROUND CLEARING THE COAST
EARLY NEXT WEEK ALONG WITH THE WAVY FRONT. GUIDANCE HAS STILL NOT
YET STABILIZED ON A PARTICULAR SOLUTION SO CONFIDENCE REMAINS MUCH
LOWER THAN DESIRED WITH PLACEMENT OF PCPN TYPES FOR THIS SYSTEM.
HOWEVER...FULLY EXPECT A SWATH OF ORGANIZED SNOWS ON THE NRN
PERIPHERY OF THE EXPANDING PCPN SHIELD WITH A MIX OF
PCPN/TRANSITION ZONE JUST S. WPC WEATHER/PRECIPIATION TYPE
GRIDS/GRAPHICS OFFER OUR BEST ESTIMATE FOR THIS THREAT AT THIS
TIME BASED FROM LATEST GUIDANCE PREFERENCES. LOCATIONS WITHIN THE
BROAD PCPN AREA MAY SEE LOCALLY HEAVY AMOUNTS. PASSAGE OF THIS
SYSTEM SHOULD SUPPORT A PERIOD OF LAKE EFFECT SNOW. SECONDARY COLD
SURGES IN THE WAKE OF THE LEAD SYSTEM WILL DIG DEEP INTO THE
CENTRAL AND  ERN US IN AMPLIFIED NRN STREAM FLOW ALONG WITH MODEST
LEAD CLIPPER LOW TO MID-ATLANTIC/NEW ENG COASTAL LOW DEVELOPMENT
TRACK AND SNOW SWATH. MEANWHILE...DRY CONDS ACROSS THE NW QUARTER
OF THE COUNTRY INLAND TO THE ROCKIES WILL TREND WETTER BY EARLY
NEXT WEEK AS ERN PAC ENERGY SLIPS THROUGH THE LONGER TERM MEAN
RIDGE ALOFT...ESPECIALLY OVER FAVORED TERRAIN.

SCHICHTEL

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