Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 211039
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
439 AM MDT SUN SEP 21 2014

.SYNOPSIS...AN UPPER LOW WILL LIFT NORTHEAST ACROSS THE GREAT
BASIN TODAY THROUGH TONIGHT THEN MOVE OFF TO THE NORTHEAST
MONDAY. HIGH PRESSURE WILL FOLLOW FOR MID WEEK.

&&

.DISCUSSION...A CLOSED LOW REMAINS CENTERED OVER CENTRAL CA EARLY
THIS MORNING WITH A MOIST SOUTHERLY FLOW OVER THE CWA. RAIN
SHOWERS HAVE BECOME FAIRLY WIDESPREAD ACROSS THE SRN 2/3 OF THE
CWA BUT OVERNIGHT RAINFALL TOTALS HAVE MOSTLY BEEN AROUND 1/3 INCH
OR LESS.

THE LOW WILL LIFT NORTHEAST TODAY AND IS FORECAST TO BE CENTERED
OVER NERN NV BY THIS EVE. EXPECT THE SHOWERS TO LIFT ACROSS THE
REMAINDER OF THE CWA BY MIDDAY AS THE LOW ADVANCES AND THEY SHOULD
CONTINUE ACROSS PRETTY MUCH THE ENTIRE AREA INTO THE AFTERNOON.

THE BEST FORCING WILL BE ACROSS SRN UT THIS MORNING THEN LIFTS
INTO NRN UT THIS AFTN. STRONGER DISCRETE CELLS HAVE BEEN STAYING
JUST TO OUR WEST SO FAR OVERNIGHT BUT SHOULD SHIFT INTO SRN UT
THRU MID MORNING BRINGING A THREAT OF HEAVIER RAINFALL AND THE
POTENTIAL FOR ISOLATED FLASH FLOODING. ALTHO CONVECTION BECOMES
MORE SCATTERED ACROSS THE SOUTH FROM ABOUT NOON ONWARD PARTIAL
CLEARING WILL ALLOW DAYTIME HEATING TO PRODUCE STRONGER STORMS
WITH THE THREAT OF HEAVY RAIN CONTINUING THRU THE AFTN.

EXPECT THE HEAVY RAINFALL THREAT TO BE LOWER ACROSS THE NORTH AS
EXTENSIVE CLOUD COVER WILL ACCOMPANY THE BEST FORCING THIS AFTN.

THE RAIN SHOULD TAPER OFF FROM THE SOUTHWEST TONIGHT BUT MORE
STRATIFORM PRECIP COULD LINGER IN WESTERLY FLOW ACROSS THE NORTH
INTO MONDAY AS THE LOW LIFTS INTO SRN ID AND TRACKS EAST THRU THE
MORNING. EXPECT PRECIP TO TAPER OFF IN THE AFTN BUT CLOUDS COULD
BE SLOWER TO CLEAR OVER THE CWA NORTH OF ABOUT SLC.

RIDGE CONDITIONS RETURN ON TUE AND CONTINUE THRU WED ALTHO THE
RIDGE AXIS SHIFTS EAST OF THE CWA BY 00Z THU. SOUTHERLY FLOW PICKS
UP ACROSS THE WRN CWA ON THU AS A DEEP LOW APPROACHES THE WEST
COAST.

THE EC AND GFS CONTINUE TO DISAGREE ON HOW FAST THIS SYSTEM
PROGRESSES INLAND AND WHERE THE CLOSED LOW THAT FORMS ENDS UP. THE
00Z EC RETURNED TO THE SOLUTION FROM THE LAST 00Z RUN WITH A
CLOSED LOW OVER CA JUST WEST OF RENO NV WHILE THE GFS HAS THE
CLOSED LOW OVER SRN ID AT THIS SAME TIME. BOTH MODELS DO BRING AN
INCREASING CHANCE OF PRECIP TO THE CWA HEADING INTO THE WEEKEND
BUT THE GFS GENERATES IT OVER MAINLY THE NWRN CWA OUT OF THE COLD
CORE OF THE LOW WHILE THE EC TAPS A SIGNIFICANT AMOUNT OF TROPICAL
MOISTURE AND SPREADS THIS ACROSS MORE OF THE CWA ON SAT INTO SUN.
LEANED TOWARDS THE EC AND KEPT POPS ABOVE CLIMO AREA-WIDE STARTING
SAT AND CONTINUING SUN. ALSO KEPT TEMP TRENDS CLOSER TO EC.

&&

.AVIATION...VFR CONDITIONS ARE EXPECTED THROUGH THE VALID TAF
PERIOD...THOUGH CEILINGS BELOW 7000 FT ARE EXPECTED FROM LATE
THIS MORNING INTO EARLY AFTERNOON IN ASSOCIATION WITH SHOWERS.
THERE IS A 20 PERCENT CHANCE FOR A THUNDERSTORM TODAY AS WELL.
LIGHT SOUTHEAST OR LIGHT AND VARIABLE WINDS WILL SHIFT TO A MORE
SOUTHERLY FLOW BY LATE MORNING.

&&

.FIRE WEATHER...A MOIST AIR MASS WILL CONTINUE TO SURGE NORTHWARD
TODAY AS A LOW PRESSURE SYSTEM OVER CENTRAL CALIFORNIA LIFTS TO THE
NORTHEAST. WITH THE MOISTURE SURGE...WETTING RAINS CAN BE
EXPECTED OVER MUCH OF THE REGION TODAY. WITH AIR MASS
DESTABILIZATION...THUNDERSTORMS WILL BE POSSIBLE...ESPECIALLY
THIS AFTERNOON AND EVENING. LINGERING SHOWERS CAN BE EXPECTED ON
MONDAY...PRIMARILY OVER NORTHERN AND EASTERN UTAH.

A RIDGE OF HIGH PRESSURE WILL BUILD OVER THE REGION TUESDAY AND
WEDNESDAY...PROVIDING DRY WEATHER CONDITIONS.

THERE REMAINS CONSIDERABLE UNCERTAINTY REGARDING THE TIMING OF A
VIGOROUS STORM SYSTEM THAT WILL IMPACT THE REGION LATE THIS WEEK.
AHEAD OF THIS SYSTEM...STRONG SOUTHERLY WINDS AND LOW RELATIVE
HUMIDITIES WILL DEVELOP. EVENTUALLY...THIS SYSTEM IS EXPECTED TO
DRAW MOISTURE NORTHWARD WITH ANOTHER ROUND OF WETTING RAINS
POSSIBLE NEXT WEEKEND.

&&

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

$$

PUBLIC...WILENSKY
FIRE WEATHER/AVIATION...BARJENBRUCH

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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