Thursday, June 29, 2017, 10:14 AM EDT
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Area Forecast Discussion
Valid At
Wed, Dec 31, 7:00pm EST
FXUS65 KSLC 290926
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
326 AM MDT Thu Jun 29 2017

.SYNOPSIS...High pressure will return today and tomorrow. A 
weakening trough will cross namely northern Utah Sunday prior to 
high pressure rebuilding once again early next week.

&&

.SHORT TERM (THROUGH 12Z SATURDAY)...
Water Vapor Satellite shows a trough over the Northern Rockies. 
400-200mb MDCARS wind observations place a 60-100kt cyclonic jet 
from the Pacific Northwest into the Great Basin where it merges 
with a westerly subtropical jet. GOES/SLC 00Z RAOB/HRRR indicate 
that precipitable water values vary from 0.15"-0.25" southern and 
central mountains to 0.30"-0.60" most valleys.

Cooler and a little bit more humid today and tomorrow behind the
cold front. Breezy northwest winds where downslope flow is
enhanced, generally far northwest Utah and eastern valleys.

Trough to our north exits to the east through tomorrow promoting
rising heights. SREF show meager instability at best through 
tomorrow.

.LONG TERM (AFTER 12Z SATURDAY)...
A stretched out low-amplitude trough is moving into the Great 
Basin and will translate eastward through the remainder of the 
weekend. Weak falling heights ahead of this trough, along with 
weak cooling aloft is advertised by forecast models. Dry and 
stable conditions will be present behind this trough. Any 
instability looks to be confined primarily to high terrain, and 
weak at that. Have kept very light mention of convection in the 
mountains through the weekend. 

Very modest cooling at the mid-levels will rebound by Monday as the 
shortwave progresses eastward and heights once again build in across 
the Great Basin with 700mb temperatures warming above 14C across our 
county warning area. High pressure will build over the region and be 
the dominating feature, or so one model thinks. The ECMWF however 
has other ideas. By late Wednesday, the ECMWF has a deepening upper 
level trough off the Pacific Northwest coast carving through the 
Northern Rockies and up through Canada, all while the GFS still 
thinks the ridge is the main feature. As that feature is forecast by 
the EC, the southern tier does not seem to make many ripples across 
Utah and southern Wyoming, if anything some minor cooling.

With this mostly dry and stable airmass in place, temperatures will 
continue to run warm or hot across the state, some 10-15 degrees 
above seasonal normal. Mostly dry, with some afternoon instability 
convection possible though not looking too favorable, any mention of 
activity was limited to afternoon time and terrain based. 

&&

.AVIATION...
Conditions at KSLC terminal will remain at VFR through 
the valid TAF period. Northerly winds will persist through the 
morning, with a period of light and variable possible before 
returning to northerly by 16z. Expecting the same conditions this 
evening, predominantly northerly with a brief period of light and 
variable or southerly, though short duration.

&&

.FIRE WEATHER...
ERC values have risen to between the above their 90th percentile 
across southern and central Utah, with a few reporting stations 
above their 97th percentile. Far northeast Utah remains below 50th
percentile, but the remainder of northern Utah is climbing above 
the 50th percentile.

Cooler and not quite as bone dry today behind the cold front.
However RH will remain in the 5-10% range and areas that are
favored in northwest flow downslope winds such as the eastern
valleys will see critical fire weather conditions. Haines will be
a 6 across southern and parts of central Utah today, decreasing a
bit for tomorrow. Lighter and more northerly flow tomorrow due to
high pressure building in.

A ridge builds for Saturday, increasing Haines Index to 6 again, 
along with a warming and drying trend. There could be some 
isolated showers and thunderstorms in the mountains each afternoon
and evening this weekend.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Red Flag Warning until 10 PM MDT this evening for UTZ482-484-488-
     489-493-494-496-498.

WY...None.
&&

$$

SHORT TERM/FIRE WEATHER...Rogowski
LONG TERM/AVIATION...Dewey

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

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