488
FXUS65 KSLC 232153
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
353 PM MDT SUN SEP 23 2018
SYNOPSIS
A COLD FRONT MOVING INTO NORTHWESTERN UTAH AT THIS
TIME WILL CONTINUE SOUTH AND EVENTUALLY STALL ACROSS SOUTHERN
UTAH BY MIDDAY MONDAY. AHEAD OF THE FRONT A CHANCE OF CONVECTION
REMAINS IN PLACE FOR CENTRAL PORTIONS THROUGH THIS EVENING. MUCH
COOLER TEMPERATURES WILL EXIST BEHIND THE FRONT THROUGH MIDWEEK,
BUT ANOTHER WARMING TREND IS ANTICIPATED FOR THE LATTER HALF.
SHORT TERM (THROUGH 00Z THURSDAY)
AFTERNOON WATER VAPOR LOOP
AND H5 ANALYSIS CONTINUE TO SHOW EAST-SOUTHEAST TRANSLATION OF THE
UPSTREAM TROUGH, WITH AXIS NOW DRAPED FROM NORTHWESTERN MONTANA
SOUTHWEST INTO NORTHWESTERN NEVADA. THE LEADING EDGE BAROCLINIC
ZONE IS SHOWING SIGNS OF SHARPENING PER H7 ANALYSIS TRENDS, WHILE
A SURFACE TROUGH CONTINUES TO DEEPEN OVER NORTHERN UTAH. EXPECTING
THE DEVELOPING FRONTAL BOUNDARY WILL BEGIN A SOUTHERLY SURGE ALONG
THE WASATCH FRONT OVER THE NEXT FEW HOURS, THEN CONTINUED SOUTHERN
ADVANCEMENT TO JUST SOUTH OF THE I-70 CORRIDOR BY MIDDAY MONDAY AS
THE UPPER TROUGH TRANSLATE ACROSS THE NORTHERN ROCKIES (LARGELY GRAZING
THE AREA).
PWATS CONTINUE TO TREND UP MEAGERLY SO, WITH VALUES TRENDING OVER
.50 INCHES EXTENDING NORTH THROUGH CENTRAL UTAH, AND PROGS
CONTINUE TO SUGGEST FURTHER MOISTURE ADVECTION POOLING AHEAD OF
THE FRONT OVER CENTRAL UTAH THROUGH THIS EVENING. ALTHOUGH
VERTICAL PROFILES/MOISTURE REMAIN SUB-PAR, SUBTLE INSTABILITY
IS DEVELOPING AT THE MID LEVELS (H6-H4), AND COUPLED WITH THE
MODEST FRONTAL FORCING SCATTERED SHALLOW (IN DEPTH) HIGH BASED
(AND GUSTY) CONVECTION SHOULD DEVELOP ALONG THE BOUNDARY LARGELY
BETWEEN 23-05Z THIS EVE. WEST- CENTRAL UTAH INTO SOUTHWEST WYOMING
LOOKS TO BE THE FOCUS. IT'S NOT MUCH, BUT ITS SOMETHING. SUPPORT
WILL BE LOST FOR ANY MAINTAINED CONVECTION BY EARLY MONDAY MORNING
AS MID LEVEL BAROCLINICITY WANES AND LAPSE RATES FURTHER SLACKEN.
THE MOST NOTABLE SENSIBLE CHANGE WITH THIS FRONT WILL BE THE
MODEST CAA IN WAKE OF PASSAGE WHICH WILL DROP TEMPS TO NEAR OR
SLIGHTLY BELOW SEASONAL NORMS THROUGH MIDWEEK. CONTINUE TO EXPECT
LIGHT FROST FOR THE NORTHERN MOUNTAIN VALLEYS COME TUESDAY
MORNING.
LONG TERM (AFTER 00Z THURSDAY)
A DRY WEST TO NORTHWEST FLOW IS
EXPECTED TO PERSIST THURSDAY INTO FRIDAY MORNING WITH THE FORECAST
AREA IN BETWEEN A TROUGH OVER THE NORTH CENTRAL UNITED STATES AND A
LOW OVER THE PACIFIC. THIS WILL RESULT IN A STEADY WARMING TREND IN
TEMPERATURES WITH NO PRECIPITATION ANTICIPATED. MAXES BY FRIDAY ARE
EXPECTED TO BE 5-7F ABOVE SEASONAL NORMALS ACROSS THE FORECAST AREA.
GLOBAL MODELS INDICATE THAT THE PACIFIC LOW WILL MOVE ONSHORE AND
EVENTUALLY GRAZE NORTHERN UTAH SATURDAY INTO SUNDAY AS IT OPENS UP
AND WEAKENS, BRINGING ANOTHER COLD FRONT THROUGH. MODELS OVERALL ARE
TRENDING WEAKER WITH THIS SYSTEM, THOUGH THE GFS STILL SHOWS IT AS A
BIT STRONGER THAN THE EC. HAVE KEPT SOME POPS IN FOR SATURDAY
AFTERNOON INTO SUNDAY, BUT OVERALL HAVE TRENDED DOWNWARD GIVEN THE
CURRENT LOOK OF THE FORECAST MODELS.
AVIATION
VFR CONDITIONS ARE EXPECTED TO PREVAIL AT SLC THROUGH
THE TAF PERIOD WILL CEILINGS REMAINING ABOVE 7K FT AND ANY STORMS
STAYING TO THE SOUTH AND/OR EAST OF THE TERMINAL. NORTHERLY WINDS
CURRENTLY IN PLACE ARE EXPECTED TO MAINTAIN THEMSELVES THROUGH THE
PERIOD, AND MAY BE STRONG/GUSTY AT TIMES THIS AFTERNOON/EVENING
BEFORE SPEEDS DIMINISH AFTER MIDNIGHT.
FIRE WEATHER
MODEST MID LEVEL MOISTURE IS BECOMING
ESTABLISHED ACROSS THE AREA IN ADVANCE OF AN APPROACHING FRONT
THAT IS NOW MOVING INTO FAR NORTHWESTERN UTAH. A CHANCE OF SHOWERS
AND ISOLATED STORMS REMAINS IN PLACE FROM WEST-CENTRAL UTAH INTO
NORTHEASTERN UTAH FOCUSED BETWEEN 1700-2100 TONIGHT, BUT WITH THE
DRY BOUNDARY LAYER IN PLACE MINIMAL RAINFALL IS EXPECTED WITH
CELLS MORE GUSTY THAN ANYTHING. THE COLD FRONT WILL SAG INTO
CENTRAL UTAH TONIGHT, THEN SOUTHERN UTAH MONDAY BRINGING A WIND
SWITCH TO WEST-NORTHWEST. IN WAKE OF FRONTAL PASSAGE, GUSTY WEST
TO NORTHWEST DOWNSLOPING WINDS ARE EXPECTED FROM THE SOUTHERN
UINTAS SOUTH ACROSS THE UINTA BASIN AND INTO CASTLE COUNTRY.
ALTHOUGH WINDS WILL BE TRENDING DOWN ACROSS THE WESTERN VALLEYS
AND NORTHERN MOUNTAINS MONDAY, ISOLATED CRITICAL WINDS/RH REMAIN
LIKELY IN THE BEAR RIVER VALLEY AND IS POSSIBLE IN SOME OF THE
CANYON AREAS IN THE WASATCH.
FIRE WEATHER CONCERNS WILL BECOME LIMITED BY TUESDAY...LIKELY
THROUGH FRIDAY AS A DRY WEST-NORTHWEST FLOW BECOMES ESTABLISHED.
COOL THROUGH MIDWEEK WITH GRADUAL WARMING LATE WEEK. THE NEXT
POTENTIAL SIGNIFICANT FIRE WEATHER PERIOD LOOKS TO COME NEXT
WEEKEND.
SLC WATCHES/WARNINGS/ADVISORIES
UT...RED FLAG WARNING UNTIL 8 PM MDT MONDAY FOR UTZ481>484.
RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING FOR UTZ479-480-492.
RED FLAG WARNING FROM NOON TO 8 PM MDT MONDAY FOR UTZ489.
WY...RED FLAG WARNING UNTIL 8 PM MDT MONDAY FOR WYZ277.
MERRILL/TRAPHAGAN/CARR
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY
FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page