Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 271202
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
502 AM MST THU NOV 27 2014

.SYNOPSIS...WARM DRY HIGH PRESSURE WILL PERSIST ACROSS THE GREAT
BASIN INTO SATURDAY.

&&

.SHORT TERM (THRU 00Z MON)...THE UPPER RIDGE AXIS IS CENTERED
NEAR THE UT/NV BORDER EARLY THIS MORNING. CIRRUS STREAMING
THROUGH THE RIDGE IS INCREASING ACROSS NRN UT AND WILL OVERSPREAD
THE CWA AS THE DAY GOES ON.

THE SHORT WAVE PASSING TO THE NORTH HAS KEPT ENOUGH OF A SOUTHERLY
SURFACE GRADIENT ACROSS THE CWA TO KEEP THE NWRN AND W CENTRAL
VALLEYS FAIRLY WELL MIXED WITH CURRENT TEMPS STILL IN THE 40S IN
MANY AREAS. THE AIRMASS UNDER THE RIDGE IS FORECAST TO WARM
SEVERAL DEGREES C FROM YESTERDAY AND MANY AREAS WILL STAY
SUFFICIENTLY WELL MIXED FOR THIS TO BE REFLECTED AT THE SURFACE.
THE ONLY POSSIBLE HINDRANCE WOULD BE IF HIGH CLOUDS GET THICK
ENOUGH TO BLOCK THE SUN AND I DO EXPECT THIS AT TIMES...ESPECIALLY
NORTH. SO HAVE KEPT TEMPS TODAY NEAR YESTERDAYS READINGS BUT HAVE
WARMED THE SOUTH SOMEWHAT.

EXPECT THE WELL ABOVE NORMAL TEMPS TO CONTINUE ON FRIDAY AS THE
RIDGE AXIS SHIFTS E AND SWLY FLOW INCREASES A BIT OVER THE CWA
KEEPING INVERSIONS AT BAY.

MODELS DISAGREE ON HOW THEY HANDLE THE COLD AIR INTRUSION INTO THE
PACNW AND NRN ROCKIES THIS WEEKEND MOSTLY DUE TO HOW THEY HANDLE A
CLOSED LOW IN THE ERN PAC. THE EC KEEPS THIS FEATURE FARTHER WEST
AND DIGS THE COLD AIR DOWN THE COAST INITIALLY ON SAT WHILE THE
GFS HAS THE LOW A LITTLE CLOSER SENDING THE COLD AIR S INLAND THRU
THE NRN ROCKIES. THIS SENDS A COLD FRONT THRU NRN UT ON SAT WHILE
THE EC HOLDS IT TO OUR WEST. THE EC EVENTUALLY SENDS THE COLD AIR
INTO UT BUT NOT TIL SUN WHILE THE GFS IS ALREADY PUSHING THE
BOUNDARY BACK N AS A WARM FRONT.

THIS RUN OF THE EC IS AN OUTLIER WITH THE GFS AND ENSEMBLE MEAN
SIMILAR TO EACH OTHER. HOWEVER THE EC HAS A GOOD TRACK RECORD FOR
CATCHING CHANGES EARLY SO AM NOT WILLING TO COMPLETELY DISCOUNT
IT. SO HAVE NUDGED THE FORECAST SOMEWHAT TOWARDS THAT SOLUTION BUT
CONFIDENCE IS NOT VERY HIGH.

&&

.LONG TERM (AFTER 00Z MONDAY)...GLOBAL MODELS CONTINUE TO DISAGREE
ON THE EXTENT OF COLD AIR INTRUSION INTO UTAH BY SUNDAY
EVENING...WITH ECMWF 700 MB TEMPERATURES RUNNING ABOUT 5 DEGREES C
COLDER THAN THE GFS AT THIS TIME. THIS SAID...BOTH MODELS RENDER
CONTINUED PRECIPITATION INTO SUNDAY EVENING WITH THE EC SPREADING IT
FURTHER INTO CENTRAL UTAH. HAVE THUS NUDGED GRIDS SLIGHTLY TOWARD
THE EC SOLUTION IN BOTH TEMPERATURE AND EXTENT OF POPS SUNDAY NIGHT
INTO MONDAY. CONTINUING THE IDEA OF A VALLEY RAIN/MOUNTAIN SNOW
EVENT WITH SNOW LEVELS LOWERING A NOTCH TO 6 KFT.

FURTHER MODEL DISAGREEMENT EXTENDS INTO MIDWEEK REGARDING THE
EVOLUTION OF A PACIFIC TROUGH...WITH THE GFS PITCHING AN EJECTED
SHORTWAVE INTO UTAH TUESDAY INTO WEDNESDAY. THE EC IS BEREFT OF SAID
WAVE...SOLELY SUGGESTING THE DEVELOPMENT OF A CUTOFF LOW STALLING
WEST OF 130W...LEAVING THE STATE HIGH AND DRY. HAVE THUS PRIMARILY
REDUCED MIDWEEK POPS FROM LIKELY TO CHANCE CATEGORIES...KEEPING
TREND OF VALLEY RAIN/MTN SNOW THROUGHOUT.

&&

.AVIATION...SOUTHERLY WINDS WILL CONTINUE AT THE SLC TERMINAL
THROUGH THIS MORNING. WINDS MAY BECOME LIGHT AND VARIABLE BETWEEN
19-22Z...WITH A 30 PERCENT CHANCE OF DEVELOPING A NORTHEASTERLY
FLOW. NO SIGNIFICANT ISSUES WITH PREVAILING VFR CONDITIONS UNDER
PATCHY HIGH CLOUDS.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.

&&

$$

SHORT TERM...WILENSKY
LONG TERM/AVIATION...VERZELLA

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)

FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)


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