Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 260149 AAB

Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
849 PM CDT Mon Sep 25 2017

.NEAR TERM...(Tonight)
Issued at 845 PM CDT Mon Sep 25 2017

An increasingly sheared cut-off low is still evident in GOES-16
Water Vapor bands and in model analyses to our S-SW. This feature
continues to produce mainly mid-level clouds to our SW in central
Mississippi. However, clouds have largely cleared out of the HUN
forecast area and surface flow has become lgt/variable. With the loss
of deep mixing, dew point temperatures have climbed this evening,
while temperatures have fallen steadily. Most dew point depressions
are around 2-4 degrees F, and given a continuation of ideal
radiational cooling conditions, fog is likely again tonight. Slight
dry air advection from the east may tend to hinder the
intensity/coverage of the fog a little. However, fog climatology and
the utilization of the crossover method suggests fog development
again late tonight, especially in the eastern valleys. Patchy fog may
also occur in parts of southern middle TN (especially near the Elk
River), Wheeler/Wilson Lakes, and southern parts of Sand Mountain.

.SHORT TERM...(Tuesday through Wednesday night)
Issued at 155 PM CDT Mon Sep 25 2017

Weak ridging is building over the area today and the subsidence
associated with it will result in a dry forecast for the short-term.
Not much of a change is expected in the conditions for Tuesday or
Wednesday with highs in the mid to upper 80s and lows in the lower
60s. Winds remain below 10 mph both days but begin to shift to the
north on Wednesday in response to a surface high over the Plains
states. There isn`t much of a change in the surface conditions with
these northerly winds just yet. It won`t be until Thursday/Friday
before we see a change in temps. Think Tuesday will likely be the
last day we see fog for awhile.

.LONG TERM...(Thursday through Sunday)
Issued at 155 PM CDT Mon Sep 25 2017

An almost stationary cold front will be stretched out from the OK/TX
area NE into the OH Valley to start Thursday. Then a trough moving
out of central Canada will drop into the Great Lakes and push this
front through the area. Some guidance continues to waver a little bit
in whether or not there will be enough lift and lingering moisture
for a few isolated showers to develop Thursday. But based on
soundings and the overall pattern have kept the forecast dry for

The cold front will finally bring some fall like weather to the TN
Valley with highs in the low to mid 70s and overnight lows in the 50s
for much of the area and upper 40s for the cooler spots. We remain in
the northerly flow through the weekend and highs should remain in the
mid 70s. As we head into early next week model solutions begin to
diverge and ensembles show a good deal of spread. The 00z guidance
had a trough moving across the northern half of the CONUS with a
potentially cut-off low over the area. However, it appears that the
12z guidance keeps the trough to the north but builds a ridge over
the area for next week. So, due to the uncertainty kept the forecast
dry and started to nudge temps up as winds begin to shift to the


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 630 PM CDT Mon Sep 25 2017

VFR conditions likely at KHSV over the next 24 hours. At KMSL, patchy
fog is expected to develop around 10Z and linger through about
12Z...similar to other recent mornings. The intensity is still
difficult to forecast at this time as some drier air will gradually
filter into the area overnight. However, dry air advection will be
from the east (farther from the KMSL location), and conditions
favorable for patchy fog development will still be in place
otherwise. Nevertheless, prevailing MVFR vis appears most likely
currently given temp/dewpoint factors.




LONG TERM...Stumpf

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