EXTENDED FORECAST DISCUSSION...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1159 AM EDT WED MAR 12 2014

VALID 12Z SAT MAR 15 2014 - 12Z WED MAR 19 2014

...OVERVIEW...
COLD UPPER-LEVEL TROUGH REMAINS A FIXTURE OVER EASTERN CANADA AND
THE NORTHEAST THIS FORECAST PACKAGE...WITH A CONTINUED INFLUX OF
CANADIAN AIR MIGRATING THROUGH THE PLAINS...GREAT LAKES AND INTO
THE SOUTHEAST NEXT WEEKEND.

IN THE WEST...A PROGRESSIVE FLOW PATTERN ALONG 50 NORTH LATITUDE
WITH A STRONG SHORTWAVE RIDGE SANDWICHED BETWEEN TWO PACIFIC-GULF
OF ALASKA BASED SYSTEMS TRACKS THROUGH THE PACIFIC NORTHWEST THIS
PERIOD. 

DOWNSTREAM...THE SPLIT-FLOW PATTERN WILL PREVAIL DURING THE FIRST
HALF OF THE WEEKEND...WITH SOUTHERN STREAM ENERGY MIGRATING
THROUGH THE SOUTHERN PLAINS AND ACROSS THE GULF COAST. THIS ENERGY
ENTRAINS INTO THE BASE OF THE UPPER-LEVEL TROUGH AND EXITS THE
EASTERN SEABOARD NEXT MONDAY. DURING THE LATTER HALF OF THIS
FORECAST PERIOD (MONDAY THROUGH WEDNESDAY)...A NORTHERN STREAM
SYSTEM WILL MIGRATE ACROSS THE NORTHERN ROCKIES AND DROP INTO THE
PLAINS STATES AND MIDWEST.

...GUIDANCE EVALUATION AND MODEL PREFERENCES...
CONTINUED TO FOLLOW THE FORECASTS OF THE 11/00Z & 12/00Z CYCLES OF
THE GEFS/ECENS MEANS...FOR THE MIGRATION OF SHORTWAVE ENERGY
ACROSS THE NORTHERN ROCKIES. THIS ENERGY DIGS SOUTHWARD THROUGH
THE PLAINS STATES...AND ALLOWS THE MID-LEVEL RIDGE TO
AMPLIFY---ALBEIT FOR ONLY A BRIEF SPELL---THROUGH DAY 5...BEFORE
THE NEXT PACIFIC SYSTEM DRIVES EAST-SOUTHEASTWARD THROUGH THE
ALASKA PANHANDLE...PACIFIC NORTHWEST AND NORTHERN ROCKIES.
DOWNSTREAM...THE MEANS ARE NOT PARTICULARLY STABLE AFTER DAY
5...SO MAINTAINING CONTINUITY THROUGH DAY 6...WILL BE A CHALLENGE
AS THE SYSTEM DEPARTS THE EASTERN SEABOARD AND THE AIRMASS BEHIND
IT QUICKLY 'MODIFIES' INTO A SLIGHTLY WARMER/DRIER AIRMASS.

A KEY FEATURE OF THE PATTERN...A SURFACE WAVE MIGRATION FROM THE
LOWER MS VALLEY---ACROSS THE SOUTHEAST--TO THE OUTER BANKS (DAYS
4-5). A FOUR-CYCLE TREND OF THE ECENS MEANS INDICATE A DEEPER AND
MORE 'WELL-DEFINED' SURFACE WAVE...BUT ITS NOT NECESSARILY A MORE
STABLE SOLUTION...VS THE 'WEAKER-INVERTED TROUGH' SOLUTIONS OF THE
GEFS ENSEMBLE MEAN. BUT THE PRIMARY SENSIBLE WEATHER FEATURE TO
TRACK...REGARDLESS OF THE SOLUTION OF CHOICE...WILL BE THE COLD
FRONT (M6C AT 850 MBS)...ALLOWING FOR THE TRANSITION FROM LIQUID
TO FREEZING/FROZEN PRECIPITATION ALONG THE NORTHWEST PERIPHERY OF
THE SURFACE FEATURE. AS DRAWN NOW (DAY 5)...THIS BOUNDARY IS
COMPLETELY OVERSPREADING THE NORTHEAST AND SPREADING OUT ACROSS
THE PIEDMONT. ITS MODIFIED COUNTERPART---PLUNGING INTO THE WESTERN
GULF OF MEXICO AND THROUGH SOUTH TEXAS. 

A SECOND KEY FEATURE AND CHALLENGE IN THE MEDIUM RANGE...WILL BE
IN THE NORTHERN PLAINS BEGINNING DAY 5 AND TRANSLATING DOWNSTREAM
INTO THE GREAT LAKES...CENTRAL PLAINS...TO THE MID-MS/WRN OH
VALLEYS...DAYS 6-7. THE MEANS GENERALLY SUPPORT A NORTHERN STREAM
SYSTEM AT THE SURFACE...AND THE DEVELOPMENT OF A BROAD...PACIFIC
WARM FRONT SPREADING ACROSS THE CANADIAN ROCKIES AND NORTHERN HIGH
PLAINS FROM DAY 5 INTO DAY 6. THE DETERMINISTIC RUNS AND THEIR
MEANS--ARE UNFORTUNATELY AT ODDS---WITH THE LOCATION OF SECONDARY
CYCLOGENESIS FORMING ALONG 100 W LONGITUDE. ALOFT...THE MEANS
LOOKED BETTER BUT DO NOT NECESSARILY SUPPORT THE NOTION THAT A
SECONDARY SURFACE SYSTEM WILL TRACK SOUTHEASTWARD...IN 'ALBERTA
CLIPPER' TYPE FASHION THROUGH THE MISSOURI VALLEY. WITH WARM
ADVECTION BROADENING FROM THE OZARKS INTO THE OHIO VALLEY BY NEXT
TUESDAY (DAY 6)...THE DAY 6-7 GRAPHICS DEPICT A CLOSED SURFACE
WAVE MIGRATING JUST NORTH OF DUE EAST TOWARDS THE CENTRAL GREAT
LAKES. 

...SENSIBLE WEATHER HIGHLIGHTS...

IN THE EAST...THERE WILL BE A MUCH COOLER WEATHER PATTERN WITH
EMPHASIS ON THE CANADIAN FRONTAL PASSAGES AND WAVINESS ALONG THE
FRONT MAKING FOR A TRICKY P-TYPE FORECAST ACROSS THE EAST CENTRAL
COASTAL PLAINS DAY 4-5. STAY TUNED   

THE TWO SYSTEMS MIGRATING THROUGH THE WEST SHOULD IMPACT
WASHINGTON...OREGON...THEIR CASCADE RANGES--DOWNWIND TO THE
NORTHERN DIVIDE. PERIODS OF MID-LEVEL WARM ADVECTION
MOISTURE-PRECIPITATION COULD GENERATE 1/10TH TO 1/2 INCH LIQUID
TOTALS THIS MEDIUM RANGE PERIOD. THE MID-LEVEL SHORTWAVE RIDGE
SETTLES OVER CENTRAL AND SOUTHERN CALIFORNIA AND THE LOWER HALF OF
THE COLORADO RIVER BASIN...SO THE PACIFIC 'COLD' FRONT WILL
GENERALLY BE DRY FOR SOUTHERN CALIFORNIA...BUT CARRY SOME
COOLER...BREEZY/WINDY CONDITIONS AND A FEW SHOWERS WITH THEM FOR
NORTHERN CALIFORNIA...THE NORTHERN SIERRA AND ALONG 42W TO THE
NV/ID STATE LINE. THE MID-LEVEL WARM ADVECTION PATTERN SUGGESTS
WINDY...DOWNSLOPING FLOW FOR THE DIVIDE REGION OF THE MT/WY AND
HIGH-ELEVATION PRECIPITATION/WINDS FOR UPSLOPE REGIONS OF IDAHO IN
THIS PATTERN.   

VOJTESAK